Cleanup: Remove interface region files to C++

Moves all `interface_region*` files to C++ except for the tooptip region
which is slightly more complicated. Also move a few other files as well.
This helps to simplify and speed up code, especially through the use
of better C++ data structures. This change builds on all platforms on
the buildbot.

13 files changed, 339 insertions, 331 deletions

diff --git a/source/blender/editors/include/UI_interface.h b/source/blender/editors/include/UI_interface.h
index 74797f91046..a4508cb5b6d 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -634,7 +634,7 @@ uiPopupMenu *UI_popup_menu_begin_ex(struct bContext *C,
  * Set the whole structure to work.
  */
 void UI_popup_menu_end(struct bContext *C, struct uiPopupMenu *pup);
-bool UI_popup_menu_end_or_cancel(struct bContext *C, struct uiPopupMenu *head);
+bool UI_popup_menu_end_or_cancel(struct bContext *C, struct uiPopupMenu *pup);
 struct uiLayout *UI_popup_menu_layout(uiPopupMenu *pup);
 
 void UI_popup_menu_reports(struct bContext *C, struct ReportList *reports) ATTR_NONNULL();
@@ -1595,13 +1595,15 @@ typedef enum {
 } eButLabelAlign;
 
 /* Return info for uiDefAutoButsRNA */
-typedef enum {
+typedef enum eAutoPropButsReturn {
   /* Returns when no buttons were added */
   UI_PROP_BUTS_NONE_ADDED = 1 << 0,
   /* Returned when any property failed the custom check callback (check_prop) */
   UI_PROP_BUTS_ANY_FAILED_CHECK = 1 << 1,
 } eAutoPropButsReturn;
 
+ENUM_OPERATORS(eAutoPropButsReturn, UI_PROP_BUTS_ANY_FAILED_CHECK);
+
 uiBut *uiDefAutoButR(uiBlock *block,
                      struct PointerRNA *ptr,
                      struct PropertyRNA *prop,
diff --git a/source/blender/editors/interface/CMakeLists.txt b/source/blender/editors/interface/CMakeLists.txt
index 100be2c10c9..a1ee5c38838 100644
--- a/source/blender/editors/interface/CMakeLists.txt
+++ b/source/blender/editors/interface/CMakeLists.txt
@@ -46,17 +46,17 @@ set(SRC
   interface_layout.c
   interface_ops.c
   interface_panel.c
-  interface_query.c
-  interface_region_color_picker.c
-  interface_region_hud.c
-  interface_region_menu_pie.c
-  interface_region_menu_popup.c
-  interface_region_popover.c
-  interface_region_popup.c
+  interface_query.cc
+  interface_region_color_picker.cc
+  interface_region_hud.cc
+  interface_region_menu_pie.cc
+  interface_region_menu_popup.cc
+  interface_region_popover.cc
+  interface_region_popup.cc
   interface_region_search.cc
   interface_region_tooltip.c
-  interface_regions.c
-  interface_style.c
+  interface_regions.cc
+  interface_style.cc
   interface_template_asset_view.cc
   interface_template_attribute_search.cc
   interface_template_list.cc
@@ -64,7 +64,7 @@ set(SRC
   interface_template_search_operator.c
   interface_templates.c
   interface_undo.c
-  interface_utils.c
+  interface_utils.cc
   interface_view.cc
   interface_widgets.c
   resources.c
diff --git a/source/blender/editors/interface/interface_intern.h b/source/blender/editors/interface/interface_intern.h
index a7a2409ef17..e619b14fb69 100644
--- a/source/blender/editors/interface/interface_intern.h
+++ b/source/blender/editors/interface/interface_intern.h
@@ -214,8 +214,8 @@ struct uiBut {
   BIFIconID icon;
   /** Copied from the #uiBlock.emboss */
   eUIEmbossType emboss;
-  /** direction in a pie menu, used for collision detection (RadialDirection) */
-  signed char pie_dir;
+  /** direction in a pie menu, used for collision detection. */
+  RadialDirection pie_dir;
   /** could be made into a single flag */
   bool changed;
   /** so buttons can support unit systems which are not RNA */
@@ -954,7 +954,7 @@ void ui_pie_menu_level_create(uiBlock *block,
                               const EnumPropertyItem *items,
                               int totitem,
                               wmOperatorCallContext context,
-                              int flag);
+                              wmOperatorCallContext flag);
 
 /* interface_region_popup.c */
 
diff --git a/source/blender/editors/interface/interface_query.c b/source/blender/editors/interface/interface_query.cc
index 4703367671d..2767a184619 100644
--- a/source/blender/editors/interface/interface_query.c
+++ b/source/blender/editors/interface/interface_query.cc
@@ -61,7 +61,7 @@ bool ui_but_is_toggle(const uiBut *but)
 bool ui_but_is_interactive(const uiBut *but, const bool labeledit)
 {
   /* NOTE: #UI_BTYPE_LABEL is included for highlights, this allows drags. */
-  if ((but->type == UI_BTYPE_LABEL) && but->dragpoin == NULL) {
+  if ((but->type == UI_BTYPE_LABEL) && but->dragpoin == nullptr) {
     return false;
   }
   if (ELEM(but->type, UI_BTYPE_ROUNDBOX, UI_BTYPE_SEPR, UI_BTYPE_SEPR_LINE, UI_BTYPE_LISTBOX)) {
@@ -119,12 +119,12 @@ bool ui_but_has_array_value(const uiBut *but)
                PROP_COORDS));
 }
 
-static wmOperatorType *g_ot_tool_set_by_id = NULL;
+static wmOperatorType *g_ot_tool_set_by_id = nullptr;
 bool UI_but_is_tool(const uiBut *but)
 {
   /* very evil! */
-  if (but->optype != NULL) {
-    if (g_ot_tool_set_by_id == NULL) {
+  if (but->optype != nullptr) {
+    if (g_ot_tool_set_by_id == nullptr) {
       g_ot_tool_set_by_id = WM_operatortype_find("WM_OT_tool_set_by_id", false);
     }
     if (but->optype == g_ot_tool_set_by_id) {
@@ -198,7 +198,7 @@ bool ui_but_contains_pt(const uiBut *but, float mx, float my)
 
 bool ui_but_contains_rect(const uiBut *but, const rctf *rect)
 {
-  return BLI_rctf_isect(&but->rect, rect, NULL);
+  return BLI_rctf_isect(&but->rect, rect, nullptr);
 }
 
 bool ui_but_contains_point_px(const uiBut *but, const ARegion *region, const int xy[2])
@@ -260,7 +260,7 @@ static uiBut *ui_but_find(const ARegion *region,
     }
   }
 
-  return NULL;
+  return nullptr;
 }
 
 uiBut *ui_but_find_mouse_over_ex(const ARegion *region,
@@ -269,10 +269,10 @@ uiBut *ui_but_find_mouse_over_ex(const ARegion *region,
                                  const uiButFindPollFn find_poll,
                                  const void *find_custom_data)
 {
-  uiBut *butover = NULL;
+  uiBut *butover = nullptr;
 
   if (!ui_region_contains_point_px(region, xy)) {
-    return NULL;
+    return nullptr;
   }
   LISTBASE_FOREACH (uiBlock *, block, &region->uiblocks) {
     float mx = xy[0], my = xy[1];
@@ -310,20 +310,20 @@ uiBut *ui_but_find_mouse_over_ex(const ARegion *region,
 
 uiBut *ui_but_find_mouse_over(const ARegion *region, const wmEvent *event)
 {
-  return ui_but_find_mouse_over_ex(region, event->xy, event->modifier & KM_CTRL, NULL, NULL);
+  return ui_but_find_mouse_over_ex(region, event->xy, event->modifier & KM_CTRL, nullptr, nullptr);
 }
 
 uiBut *ui_but_find_rect_over(const struct ARegion *region, const rcti *rect_px)
 {
   if (!ui_region_contains_rect_px(region, rect_px)) {
-    return NULL;
+    return nullptr;
   }
 
   /* Currently no need to expose this at the moment. */
   const bool labeledit = true;
   rctf rect_px_fl;
   BLI_rctf_rcti_copy(&rect_px_fl, rect_px);
-  uiBut *butover = NULL;
+  uiBut *butover = nullptr;
 
   LISTBASE_FOREACH (uiBlock *, block, &region->uiblocks) {
     rctf rect_block;
@@ -343,7 +343,7 @@ uiBut *ui_but_find_rect_over(const struct ARegion *region, const rcti *rect_px)
     /* CLIP_EVENTS prevents the event from reaching other blocks */
     if (block->flag & UI_BLOCK_CLIP_EVENTS) {
       /* check if mouse is inside block */
-      if (BLI_rctf_isect(&block->rect, &rect_block, NULL)) {
+      if (BLI_rctf_isect(&block->rect, &rect_block, nullptr)) {
         break;
       }
     }
@@ -354,7 +354,7 @@ uiBut *ui_but_find_rect_over(const struct ARegion *region, const rcti *rect_px)
 uiBut *ui_list_find_mouse_over_ex(const ARegion *region, const int xy[2])
 {
   if (!ui_region_contains_point_px(region, xy)) {
-    return NULL;
+    return nullptr;
   }
   LISTBASE_FOREACH (uiBlock *, block, &region->uiblocks) {
     float mx = xy[0], my = xy[1];
@@ -366,14 +366,14 @@ uiBut *ui_list_find_mouse_over_ex(const ARegion *region, const int xy[2])
     }
   }
 
-  return NULL;
+  return nullptr;
 }
 
 uiBut *ui_list_find_mouse_over(const ARegion *region, const wmEvent *event)
 {
-  if (event == NULL) {
+  if (event == nullptr) {
     /* If there is no info about the mouse, just act as if there is nothing underneath it. */
-    return NULL;
+    return nullptr;
   }
   return ui_list_find_mouse_over_ex(region, event->xy);
 }
@@ -382,10 +382,10 @@ uiList *UI_list_find_mouse_over(const ARegion *region, const wmEvent *event)
 {
   uiBut *list_but = ui_list_find_mouse_over(region, event);
   if (!list_but) {
-    return NULL;
+    return nullptr;
   }
 
-  return list_but->custom_data;
+  return static_cast<uiList *>(list_but->custom_data);
 }
 
 static bool ui_list_contains_row(const uiBut *listbox_but, const uiBut *listrow_but)
@@ -398,7 +398,7 @@ static bool ui_list_contains_row(const uiBut *listbox_but, const uiBut *listrow_
 
 static bool ui_but_is_listbox_with_row(const uiBut *but, const void *customdata)
 {
-  const uiBut *row_but = customdata;
+  const uiBut *row_but = static_cast<const uiBut *>(customdata);
   return (but->type == UI_BTYPE_LISTBOX) && ui_list_contains_row(but, row_but);
 }
 
@@ -414,7 +414,7 @@ static bool ui_but_is_listrow(const uiBut *but, const void *UNUSED(customdata))
 
 uiBut *ui_list_row_find_mouse_over(const ARegion *region, const int xy[2])
 {
-  return ui_but_find_mouse_over_ex(region, xy, false, ui_but_is_listrow, NULL);
+  return ui_but_find_mouse_over_ex(region, xy, false, ui_but_is_listrow, nullptr);
 }
 
 struct ListRowFindIndexData {
@@ -424,19 +424,18 @@ struct ListRowFindIndexData {
 
 static bool ui_but_is_listrow_at_index(const uiBut *but, const void *customdata)
 {
-  const struct ListRowFindIndexData *find_data = customdata;
+  const ListRowFindIndexData *find_data = static_cast<const ListRowFindIndexData *>(customdata);
 
-  return ui_but_is_listrow(but, NULL) && ui_list_contains_row(find_data->listbox, but) &&
+  return ui_but_is_listrow(but, nullptr) && ui_list_contains_row(find_data->listbox, but) &&
          (but->hardmax == find_data->index);
 }
 
 uiBut *ui_list_row_find_from_index(const ARegion *region, const int index, uiBut *listbox)
 {
   BLI_assert(listbox->type == UI_BTYPE_LISTBOX);
-  struct ListRowFindIndexData data = {
-      .index = index,
-      .listbox = listbox,
-  };
+  ListRowFindIndexData data = {};
+  data.index = index;
+  data.listbox = listbox;
   return ui_but_find(region, ui_but_is_listrow_at_index, &data);
 }
 
@@ -447,7 +446,7 @@ static bool ui_but_is_treerow(const uiBut *but, const void *UNUSED(customdata))
 
 uiBut *ui_tree_row_find_mouse_over(const ARegion *region, const int xy[2])
 {
-  return ui_but_find_mouse_over_ex(region, xy, false, ui_but_is_treerow, NULL);
+  return ui_but_find_mouse_over_ex(region, xy, false, ui_but_is_treerow, nullptr);
 }
 
 static bool ui_but_is_active_treerow(const uiBut *but, const void *customdata)
@@ -462,7 +461,7 @@ static bool ui_but_is_active_treerow(const uiBut *but, const void *customdata)
 
 uiBut *ui_tree_row_find_active(const ARegion *region)
 {
-  return ui_but_find(region, ui_but_is_active_treerow, NULL);
+  return ui_but_find(region, ui_but_is_active_treerow, nullptr);
 }
 
 /** \} */
@@ -479,7 +478,7 @@ uiBut *ui_but_prev(uiBut *but)
       return but;
     }
   }
-  return NULL;
+  return nullptr;
 }
 
 uiBut *ui_but_next(uiBut *but)
@@ -490,7 +489,7 @@ uiBut *ui_but_next(uiBut *but)
       return but;
     }
   }
-  return NULL;
+  return nullptr;
 }
 
 uiBut *ui_but_first(uiBlock *block)
@@ -500,21 +499,19 @@ uiBut *ui_but_first(uiBlock *block)
       return but;
     }
   }
-  return NULL;
+  return nullptr;
 }
 
 uiBut *ui_but_last(uiBlock *block)
 {
-  uiBut *but;
-
-  but = block->buttons.last;
+  uiBut *but = static_cast<uiBut *>(block->buttons.last);
   while (but) {
     if (ui_but_is_editable(but)) {
       return but;
     }
     but = but->prev;
   }
-  return NULL;
+  return nullptr;
 }
 
 bool ui_but_is_cursor_warp(const uiBut *but)
@@ -550,7 +547,7 @@ size_t ui_but_drawstr_len_without_sep_char(const uiBut *but)
 {
   if (but->flag & UI_BUT_HAS_SEP_CHAR) {
     const char *str_sep = strrchr(but->drawstr, UI_SEP_CHAR);
-    if (str_sep != NULL) {
+    if (str_sep != nullptr) {
       return (str_sep - but->drawstr);
     }
   }
@@ -565,12 +562,12 @@ size_t ui_but_drawstr_without_sep_char(const uiBut *but, char *str, size_t str_m
 
 size_t ui_but_tip_len_only_first_line(const uiBut *but)
 {
-  if (but->tip == NULL) {
+  if (but->tip == nullptr) {
     return 0;
   }
 
   const char *str_sep = strchr(but->tip, '\n');
-  if (str_sep != NULL) {
+  if (str_sep != nullptr) {
     return (str_sep - but->tip);
   }
   return strlen(but->tip);
@@ -590,7 +587,7 @@ uiBut *ui_block_active_but_get(const uiBlock *block)
     }
   }
 
-  return NULL;
+  return nullptr;
 }
 
 bool ui_block_is_menu(const uiBlock *block)
@@ -622,12 +619,12 @@ static const uiBut *ui_but_next_non_separator(const uiBut *but)
       return but;
     }
   }
-  return NULL;
+  return nullptr;
 }
 
 bool UI_block_is_empty_ex(const uiBlock *block, const bool skip_title)
 {
-  const uiBut *but = block->buttons.first;
+  const uiBut *but = static_cast<const uiBut *>(block->buttons.first);
   if (skip_title) {
     /* Skip the first label, since popups often have a title,
      * we may want to consider the block empty in this case. */
@@ -636,7 +633,7 @@ bool UI_block_is_empty_ex(const uiBlock *block, const bool skip_title)
       but = but->next;
     }
   }
-  return (ui_but_next_non_separator(but) == NULL);
+  return (ui_but_next_non_separator(but) == nullptr);
 }
 
 bool UI_block_is_empty(const uiBlock *block)
@@ -647,7 +644,7 @@ bool UI_block_is_empty(const uiBlock *block)
 bool UI_block_can_add_separator(const uiBlock *block)
 {
   if (ui_block_is_menu(block) && !ui_block_is_pie_menu(block)) {
-    const uiBut *but = block->buttons.last;
+    const uiBut *but = static_cast<const uiBut *>(block->buttons.last);
     return (but && !ELEM(but->type, UI_BTYPE_SEPR_LINE, UI_BTYPE_SEPR));
   }
   return true;
@@ -662,7 +659,7 @@ bool UI_block_can_add_separator(const uiBlock *block)
 uiBlock *ui_block_find_mouse_over_ex(const ARegion *region, const int xy[2], bool only_clip)
 {
   if (!ui_region_contains_point_px(region, xy)) {
-    return NULL;
+    return nullptr;
   }
   LISTBASE_FOREACH (uiBlock *, block, &region->uiblocks) {
     if (only_clip) {
@@ -676,7 +673,7 @@ uiBlock *ui_block_find_mouse_over_ex(const ARegion *region, const int xy[2], boo
       return block;
     }
   }
-  return NULL;
+  return nullptr;
 }
 
 uiBlock *ui_block_find_mouse_over(const ARegion *region, const wmEvent *event, bool only_clip)
@@ -699,7 +696,7 @@ uiBut *ui_region_find_active_but(ARegion *region)
     }
   }
 
-  return NULL;
+  return nullptr;
 }
 
 uiBut *ui_region_find_first_but_test_flag(ARegion *region, int flag_include, int flag_exclude)
@@ -712,7 +709,7 @@ uiBut *ui_region_find_first_but_test_flag(ARegion *region, int flag_include, int
     }
   }
 
-  return NULL;
+  return nullptr;
 }
 
 /** \} */
@@ -752,7 +749,7 @@ bool ui_region_contains_rect_px(const ARegion *region, const rcti *rect_px)
 {
   rcti winrct;
   ui_region_winrct_get_no_margin(region, &winrct);
-  if (!BLI_rcti_isect(&winrct, rect_px, NULL)) {
+  if (!BLI_rcti_isect(&winrct, rect_px, nullptr)) {
     return false;
   }
 
@@ -761,7 +758,7 @@ bool ui_region_contains_rect_px(const ARegion *region, const rcti *rect_px)
     const View2D *v2d = &region->v2d;
     rcti rect_region;
     ui_window_to_region_rcti(region, &rect_region, rect_px);
-    if (!BLI_rcti_isect(&v2d->mask, &rect_region, NULL) ||
+    if (!BLI_rcti_isect(&v2d->mask, &rect_region, nullptr) ||
         UI_view2d_rect_in_scrollers(region, &region->v2d, rect_px)) {
       return false;
     }
@@ -787,7 +784,7 @@ ARegion *ui_screen_region_find_mouse_over_ex(bScreen *screen, const int xy[2])
       return region;
     }
   }
-  return NULL;
+  return nullptr;
 }
 
 ARegion *ui_screen_region_find_mouse_over(bScreen *screen, const wmEvent *event)
@@ -803,7 +800,7 @@ ARegion *ui_screen_region_find_mouse_over(bScreen *screen, const wmEvent *event)
 
 void ui_interface_tag_script_reload_queries(void)
 {
-  g_ot_tool_set_by_id = NULL;
+  g_ot_tool_set_by_id = nullptr;
 }
 
 /** \} */
diff --git a/source/blender/editors/interface/interface_region_color_picker.c b/source/blender/editors/interface/interface_region_color_picker.cc
index 9fb6f538191..ab0a6039cdc 100644
--- a/source/blender/editors/interface/interface_region_color_picker.c
+++ b/source/blender/editors/interface/interface_region_color_picker.cc
@@ -7,9 +7,9 @@
  * Color Picker Region & Color Utils
  */
 
-#include <stdarg.h>
-#include <stdlib.h>
-#include <string.h>
+#include <cstdarg>
+#include <cstdlib>
+#include <cstring>
 
 #include "MEM_guardedalloc.h"
 
@@ -168,7 +168,7 @@ static void ui_color_picker_update_hsv(ColorPicker *cpicker,
 void ui_but_hsv_set(uiBut *but)
 {
   float rgb_perceptual[3];
-  ColorPicker *cpicker = but->custom_data;
+  ColorPicker *cpicker = static_cast<ColorPicker *>(but->custom_data);
   float *hsv_perceptual = cpicker->hsv_perceptual;
 
   ui_color_picker_hsv_to_rgb(hsv_perceptual, rgb_perceptual);
@@ -255,7 +255,8 @@ static void ui_colorpicker_rgba_update_cb(bContext *UNUSED(C), void *bt1, void *
 
   if (prop) {
     RNA_property_float_get_array(&ptr, prop, rgb_scene_linear);
-    ui_update_color_picker_buts_rgb(but, but->block, but->custom_data, rgb_scene_linear);
+    ui_update_color_picker_buts_rgb(
+        but, but->block, static_cast<ColorPicker *>(but->custom_data), rgb_scene_linear);
   }
 
   if (popup) {
@@ -268,7 +269,7 @@ static void ui_colorpicker_hsv_update_cb(bContext *UNUSED(C), void *bt1, void *U
   uiBut *but = (uiBut *)bt1;
   uiPopupBlockHandle *popup = but->block->handle;
   float rgb_scene_linear[3];
-  ColorPicker *cpicker = but->custom_data;
+  ColorPicker *cpicker = static_cast<ColorPicker *>(but->custom_data);
 
   ui_color_picker_hsv_to_rgb(cpicker->hsv_scene_linear, rgb_scene_linear);
   ui_update_color_picker_buts_rgb(but, but->block, cpicker, rgb_scene_linear);
@@ -282,7 +283,7 @@ static void ui_colorpicker_hex_rna_cb(bContext *UNUSED(C), void *bt1, void *hexc
 {
   uiBut *but = (uiBut *)bt1;
   uiPopupBlockHandle *popup = but->block->handle;
-  ColorPicker *cpicker = but->custom_data;
+  ColorPicker *cpicker = static_cast<ColorPicker *>(but->custom_data);
   char *hexcol = (char *)hexcl;
   float rgb[3];
 
@@ -307,7 +308,7 @@ static void ui_popup_close_cb(bContext *UNUSED(C), void *bt1, void *UNUSED(arg))
   uiPopupBlockHandle *popup = but->block->handle;
 
   if (popup) {
-    ColorPicker *cpicker = but->custom_data;
+    ColorPicker *cpicker = static_cast<ColorPicker *>(but->custom_data);
     BLI_assert(cpicker->is_init);
     popup->menuretval = (equals_v3v3(cpicker->hsv_perceptual, cpicker->hsv_perceptual_init) ?
                              UI_RETURN_CANCEL :
@@ -315,7 +316,7 @@ static void ui_popup_close_cb(bContext *UNUSED(C), void *bt1, void *UNUSED(arg))
   }
 }
 
-static void ui_colorpicker_hide_reveal(uiBlock *block, enum ePickerType colormode)
+static void ui_colorpicker_hide_reveal(uiBlock *block, ePickerType colormode)
 {
   /* tag buttons */
   LISTBASE_FOREACH (uiBut *, bt, &block->buttons) {
@@ -337,9 +338,9 @@ static void ui_colorpicker_hide_reveal(uiBlock *block, enum ePickerType colormod
 
 static void ui_colorpicker_create_mode_cb(bContext *UNUSED(C), void *bt1, void *UNUSED(arg))
 {
-  uiBut *bt = bt1;
+  uiBut *bt = static_cast<uiBut *>(bt1);
   const short colormode = ui_but_value_get(bt);
-  ui_colorpicker_hide_reveal(bt->block, colormode);
+  ui_colorpicker_hide_reveal(bt->block, (ePickerType)colormode);
 }
 
 #define PICKER_H (7.5f * U.widget_unit)
@@ -374,7 +375,7 @@ static void ui_colorpicker_circle(uiBlock *block,
                       0.0,
                       0,
                       TIP_("Color"));
-  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, nullptr);
   bt->custom_data = cpicker;
 
   /* value */
@@ -396,7 +397,7 @@ static void ui_colorpicker_circle(uiBlock *block,
                                              0,
                                              "Lightness");
     hsv_but->gradient_type = UI_GRAD_L_ALT;
-    UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, NULL);
+    UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, nullptr);
   }
   else {
     hsv_but = (uiButHSVCube *)uiDefButR_prop(block,
@@ -416,7 +417,7 @@ static void ui_colorpicker_circle(uiBlock *block,
                                              0,
                                              TIP_("Value"));
     hsv_but->gradient_type = UI_GRAD_V_ALT;
-    UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, NULL);
+    UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, nullptr);
   }
   hsv_but->but.custom_data = cpicker;
 }
@@ -449,7 +450,7 @@ static void ui_colorpicker_square(uiBlock *block,
                                            0,
                                            TIP_("Color"));
   hsv_but->gradient_type = type;
-  UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, NULL);
+  UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, nullptr);
   hsv_but->but.custom_data = cpicker;
 
   /* value */
@@ -469,8 +470,8 @@ static void ui_colorpicker_square(uiBlock *block,
                                            0,
                                            0,
                                            TIP_("Value"));
-  hsv_but->gradient_type = type + 3;
-  UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, NULL);
+  hsv_but->gradient_type = (eButGradientType)(type + 3);
+  UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, nullptr);
   hsv_but->but.custom_data = cpicker;
 }
 
@@ -547,7 +548,7 @@ static void ui_block_colorpicker(uiBlock *block,
                  "");
   UI_but_flag_disable(bt, UI_BUT_UNDO);
   UI_but_drawflag_disable(bt, UI_BUT_TEXT_LEFT);
-  UI_but_func_set(bt, ui_colorpicker_create_mode_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_create_mode_cb, bt, nullptr);
   bt->custom_data = cpicker;
   bt = uiDefButC(block,
                  UI_BTYPE_ROW,
@@ -565,7 +566,7 @@ static void ui_block_colorpicker(uiBlock *block,
                  "");
   UI_but_flag_disable(bt, UI_BUT_UNDO);
   UI_but_drawflag_disable(bt, UI_BUT_TEXT_LEFT);
-  UI_but_func_set(bt, ui_colorpicker_create_mode_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_create_mode_cb, bt, nullptr);
   bt->custom_data = cpicker;
   bt = uiDefButC(block,
                  UI_BTYPE_ROW,
@@ -583,7 +584,7 @@ static void ui_block_colorpicker(uiBlock *block,
                  "");
   UI_but_flag_disable(bt, UI_BUT_UNDO);
   UI_but_drawflag_disable(bt, UI_BUT_TEXT_LEFT);
-  UI_but_func_set(bt, ui_colorpicker_create_mode_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_create_mode_cb, bt, nullptr);
   bt->custom_data = cpicker;
   UI_block_align_end(block);
 
@@ -598,10 +599,10 @@ static void ui_block_colorpicker(uiBlock *block,
                        yco,
                        UI_UNIT_X,
                        UI_UNIT_Y,
-                       NULL);
+                       nullptr);
     UI_but_flag_disable(bt, UI_BUT_UNDO);
     UI_but_drawflag_disable(bt, UI_BUT_ICON_LEFT);
-    UI_but_func_set(bt, ui_popup_close_cb, bt, NULL);
+    UI_but_func_set(bt, ui_popup_close_cb, bt, nullptr);
     bt->custom_data = cpicker;
   }
 
@@ -625,7 +626,7 @@ static void ui_block_colorpicker(uiBlock *block,
                       0,
                       3,
                       TIP_("Red"));
-  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, nullptr);
   bt->custom_data = cpicker;
   bt = uiDefButR_prop(block,
                       UI_BTYPE_NUM_SLIDER,
@@ -643,7 +644,7 @@ static void ui_block_colorpicker(uiBlock *block,
                       0,
                       3,
                       TIP_("Green"));
-  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, nullptr);
   bt->custom_data = cpicker;
   bt = uiDefButR_prop(block,
                       UI_BTYPE_NUM_SLIDER,
@@ -661,7 +662,7 @@ static void ui_block_colorpicker(uiBlock *block,
                       0,
                       3,
                       TIP_("Blue"));
-  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, nullptr);
   bt->custom_data = cpicker;
 
   /* Could use:
@@ -686,7 +687,7 @@ static void ui_block_colorpicker(uiBlock *block,
                  3,
                  TIP_("Hue"));
   UI_but_flag_disable(bt, UI_BUT_UNDO);
-  UI_but_func_set(bt, ui_colorpicker_hsv_update_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_hsv_update_cb, bt, nullptr);
   bt->custom_data = cpicker;
   bt = uiDefButF(block,
                  UI_BTYPE_NUM_SLIDER,
@@ -703,7 +704,7 @@ static void ui_block_colorpicker(uiBlock *block,
                  3,
                  TIP_("Saturation"));
   UI_but_flag_disable(bt, UI_BUT_UNDO);
-  UI_but_func_set(bt, ui_colorpicker_hsv_update_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_hsv_update_cb, bt, nullptr);
   bt->custom_data = cpicker;
   if (U.color_picker_type == USER_CP_CIRCLE_HSL) {
     bt = uiDefButF(block,
@@ -740,7 +741,7 @@ static void ui_block_colorpicker(uiBlock *block,
   UI_but_flag_disable(bt, UI_BUT_UNDO);
 
   bt->hardmax = hardmax; /* not common but rgb  may be over 1.0 */
-  UI_but_func_set(bt, ui_colorpicker_hsv_update_cb, bt, NULL);
+  UI_but_func_set(bt, ui_colorpicker_hsv_update_cb, bt, nullptr);
   bt->custom_data = cpicker;
 
   UI_block_align_end(block);
@@ -762,7 +763,7 @@ static void ui_block_colorpicker(uiBlock *block,
                         0,
                         3,
                         TIP_("Alpha"));
-    UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, NULL);
+    UI_but_func_set(bt, ui_colorpicker_rgba_update_cb, bt, nullptr);
     bt->custom_data = cpicker;
   }
   else {
@@ -809,14 +810,14 @@ static void ui_block_colorpicker(uiBlock *block,
            yco - UI_UNIT_Y,
            butwidth,
            UI_UNIT_Y,
-           NULL,
+           nullptr,
            0.0,
            0.0,
            0,
            0,
            "");
 
-  ui_colorpicker_hide_reveal(block, colormode);
+  ui_colorpicker_hide_reveal(block, (ePickerType)colormode);
 }
 
 static int ui_colorpicker_small_wheel_cb(const bContext *UNUSED(C),
@@ -834,9 +835,9 @@ static int ui_colorpicker_small_wheel_cb(const bContext *UNUSED(C),
 
   if (add != 0.0f) {
     LISTBASE_FOREACH (uiBut *, but, &block->buttons) {
-      if (but->type == UI_BTYPE_HSVCUBE && but->active == NULL) {
+      if (but->type == UI_BTYPE_HSVCUBE && but->active == nullptr) {
         uiPopupBlockHandle *popup = block->handle;
-        ColorPicker *cpicker = but->custom_data;
+        ColorPicker *cpicker = static_cast<ColorPicker *>(but->custom_data);
         float *hsv_perceptual = cpicker->hsv_perceptual;
 
         float rgb_perceptual[3];
@@ -865,7 +866,7 @@ static int ui_colorpicker_small_wheel_cb(const bContext *UNUSED(C),
 
 uiBlock *ui_block_func_COLOR(bContext *C, uiPopupBlockHandle *handle, void *arg_but)
 {
-  uiBut *but = arg_but;
+  uiBut *but = static_cast<uiBut *>(arg_but);
   uiBlock *block;
   bool show_picker = true;
 
@@ -901,7 +902,7 @@ uiBlock *ui_block_func_COLOR(bContext *C, uiPopupBlockHandle *handle, void *arg_
 
 ColorPicker *ui_block_colorpicker_create(struct uiBlock *block)
 {
-  ColorPicker *cpicker = MEM_callocN(sizeof(ColorPicker), "color_picker");
+  ColorPicker *cpicker = MEM_cnew<ColorPicker>(__func__);
   BLI_addhead(&block->color_pickers.list, cpicker);
 
   return cpicker;
diff --git a/source/blender/editors/interface/interface_region_hud.c b/source/blender/editors/interface/interface_region_hud.cc
index 4d72cd5382c..d6166694a4a 100644
--- a/source/blender/editors/interface/interface_region_hud.c
+++ b/source/blender/editors/interface/interface_region_hud.cc
@@ -7,7 +7,7 @@
  * Floating Persistent Region
  */
 
-#include <string.h>
+#include <cstring>
 
 #include "MEM_guardedalloc.h"
 
@@ -49,7 +49,7 @@ struct HudRegionData {
 static bool last_redo_poll(const bContext *C, short region_type)
 {
   wmOperator *op = WM_operator_last_redo(C);
-  if (op == NULL) {
+  if (op == nullptr) {
     return false;
   }
 
@@ -60,7 +60,8 @@ static bool last_redo_poll(const bContext *C, short region_type)
      * wrong context.
      */
     ScrArea *area = CTX_wm_area(C);
-    ARegion *region_op = (region_type != -1) ? BKE_area_find_region_type(area, region_type) : NULL;
+    ARegion *region_op = (region_type != -1) ? BKE_area_find_region_type(area, region_type) :
+                                               nullptr;
     ARegion *region_prev = CTX_wm_region(C);
     CTX_wm_region_set((bContext *)C, region_op);
 
@@ -90,9 +91,9 @@ static bool hud_panel_operator_redo_poll(const bContext *C, PanelType *UNUSED(pt
 {
   ScrArea *area = CTX_wm_area(C);
   ARegion *region = BKE_area_find_region_type(area, RGN_TYPE_HUD);
-  if (region != NULL) {
-    struct HudRegionData *hrd = region->regiondata;
-    if (hrd != NULL) {
+  if (region != nullptr) {
+    HudRegionData *hrd = static_cast<HudRegionData *>(region->regiondata);
+    if (hrd != nullptr) {
       return last_redo_poll(C, hrd->regionid);
     }
   }
@@ -108,7 +109,7 @@ static void hud_panel_operator_redo_draw_header(const bContext *C, Panel *panel)
 static void hud_panel_operator_redo_draw(const bContext *C, Panel *panel)
 {
   wmOperator *op = WM_operator_last_redo(C);
-  if (op == NULL) {
+  if (op == nullptr) {
     return;
   }
   if (!WM_operator_check_ui_enabled(C, op->type->name)) {
@@ -120,9 +121,7 @@ static void hud_panel_operator_redo_draw(const bContext *C, Panel *panel)
 
 static void hud_panels_register(ARegionType *art, int space_type, int region_type)
 {
-  PanelType *pt;
-
-  pt = MEM_callocN(sizeof(PanelType), __func__);
+  PanelType *pt = MEM_cnew<PanelType>(__func__);
   strcpy(pt->idname, "OPERATOR_PT_redo");
   strcpy(pt->label, N_("Redo"));
   strcpy(pt->translation_context, BLT_I18NCONTEXT_DEFAULT_BPYRNA);
@@ -155,8 +154,8 @@ static void hud_region_free(ARegion *region)
 
 static void hud_region_layout(const bContext *C, ARegion *region)
 {
-  struct HudRegionData *hrd = region->regiondata;
-  if (hrd == NULL || !last_redo_poll(C, hrd->regionid)) {
+  HudRegionData *hrd = static_cast<HudRegionData *>(region->regiondata);
+  if (hrd == nullptr || !last_redo_poll(C, hrd->regionid)) {
     ED_region_tag_redraw(region);
     hud_region_hide(region);
     return;
@@ -205,19 +204,17 @@ static void hud_region_draw(const bContext *C, ARegion *region)
   GPU_clear_color(0.0f, 0.0f, 0.0f, 0.0f);
 
   if ((region->flag & RGN_FLAG_HIDDEN) == 0) {
-    ui_draw_menu_back(NULL,
-                      NULL,
-                      &(rcti){
-                          .xmax = region->winx,
-                          .ymax = region->winy,
-                      });
+    rcti reset_rect = {};
+    reset_rect.xmax = region->winx;
+    reset_rect.ymax = region->winy;
+    ui_draw_menu_back(nullptr, nullptr, &reset_rect);
     ED_region_panels_draw(C, region);
   }
 }
 
 ARegionType *ED_area_type_hud(int space_type)
 {
-  ARegionType *art = MEM_callocN(sizeof(ARegionType), __func__);
+  ARegionType *art = MEM_cnew<ARegionType>(__func__);
   art->regionid = RGN_TYPE_HUD;
   art->keymapflag = ED_KEYMAP_UI | ED_KEYMAP_VIEW2D;
   art->layout = hud_region_layout;
@@ -238,7 +235,7 @@ ARegionType *ED_area_type_hud(int space_type)
 
 static ARegion *hud_region_add(ScrArea *area)
 {
-  ARegion *region = MEM_callocN(sizeof(ARegion), "area region");
+  ARegion *region = MEM_cnew<ARegion>(__func__);
   ARegion *region_win = BKE_area_find_region_type(area, RGN_TYPE_WINDOW);
   if (region_win) {
     BLI_insertlinkbefore(&area->regionbase, region_win, region);
@@ -288,7 +285,7 @@ void ED_area_type_hud_ensure(bContext *C, ScrArea *area)
   ED_area_type_hud_clear(wm, area);
 
   ARegionType *art = BKE_regiontype_from_id(area->type, RGN_TYPE_HUD);
-  if (art == NULL) {
+  if (art == nullptr) {
     return;
   }
 
@@ -301,9 +298,9 @@ void ED_area_type_hud_ensure(bContext *C, ScrArea *area)
   }
 
   bool init = false;
-  const bool was_hidden = region == NULL || region->visible == false;
+  const bool was_hidden = region == nullptr || region->visible == false;
   ARegion *region_op = CTX_wm_region(C);
-  BLI_assert((region_op == NULL) || (region_op->regiontype != RGN_TYPE_HUD));
+  BLI_assert((region_op == nullptr) || (region_op->regiontype != RGN_TYPE_HUD));
   if (!last_redo_poll(C, region_op ? region_op->regiontype : -1)) {
     if (region) {
       ED_region_tag_redraw(region);
@@ -312,7 +309,7 @@ void ED_area_type_hud_ensure(bContext *C, ScrArea *area)
     return;
   }
 
-  if (region == NULL) {
+  if (region == nullptr) {
     init = true;
     region = hud_region_add(area);
     region->type = art;
@@ -332,9 +329,9 @@ void ED_area_type_hud_ensure(bContext *C, ScrArea *area)
   }
 
   {
-    struct HudRegionData *hrd = region->regiondata;
-    if (hrd == NULL) {
-      hrd = MEM_callocN(sizeof(*hrd), __func__);
+    HudRegionData *hrd = static_cast<HudRegionData *>(region->regiondata);
+    if (hrd == nullptr) {
+      hrd = MEM_cnew<HudRegionData>(__func__);
       region->regiondata = hrd;
     }
     if (region_op) {
@@ -355,10 +352,10 @@ void ED_area_type_hud_ensure(bContext *C, ScrArea *area)
   ED_region_tag_redraw(region);
 
   /* Reset zoom level (not well supported). */
-  region->v2d.cur = region->v2d.tot = (rctf){
-      .xmax = region->winx,
-      .ymax = region->winy,
-  };
+  rctf reset_rect = {};
+  reset_rect.xmax = region->winx;
+  reset_rect.ymax = region->winy;
+  region->v2d.cur = region->v2d.tot = reset_rect;
   region->v2d.minzoom = 1.0f;
   region->v2d.maxzoom = 1.0f;
 
@@ -373,10 +370,7 @@ void ED_area_type_hud_ensure(bContext *C, ScrArea *area)
     if (was_hidden) {
       region->winx = region->v2d.winx;
       region->winy = region->v2d.winy;
-      region->v2d.cur = region->v2d.tot = (rctf){
-          .xmax = region->winx,
-          .ymax = region->winy,
-      };
+      region->v2d.cur = region->v2d.tot = reset_rect;
     }
     CTX_wm_region_set((bContext *)C, region_prev);
   }
diff --git a/source/blender/editors/interface/interface_region_menu_pie.c b/source/blender/editors/interface/interface_region_menu_pie.cc
index 74e128f3098..586aeef44fd 100644
--- a/source/blender/editors/interface/interface_region_menu_pie.c
+++ b/source/blender/editors/interface/interface_region_menu_pie.cc
@@ -7,9 +7,9 @@
  * Pie Menu Region
  */
 
-#include <stdarg.h>
-#include <stdlib.h>
-#include <string.h>
+#include <cstdarg>
+#include <cstdlib>
+#include <cstring>
 
 #include "MEM_guardedalloc.h"
 
@@ -51,7 +51,7 @@ struct uiPieMenu {
 static uiBlock *ui_block_func_PIE(bContext *UNUSED(C), uiPopupBlockHandle *handle, void *arg_pie)
 {
   uiBlock *block;
-  uiPieMenu *pie = arg_pie;
+  uiPieMenu *pie = static_cast<uiPieMenu *>(arg_pie);
   int minwidth, width, height;
 
   minwidth = UI_MENU_WIDTH_MIN;
@@ -89,14 +89,13 @@ static float ui_pie_menu_title_width(const char *name, int icon)
 uiPieMenu *UI_pie_menu_begin(struct bContext *C, const char *title, int icon, const wmEvent *event)
 {
   const uiStyle *style = UI_style_get_dpi();
-  uiPieMenu *pie;
   short event_type;
 
   wmWindow *win = CTX_wm_window(C);
 
-  pie = MEM_callocN(sizeof(*pie), "pie menu");
+  uiPieMenu *pie = MEM_cnew<uiPieMenu>(__func__);
 
-  pie->block_radial = UI_block_begin(C, NULL, __func__, UI_EMBOSS);
+  pie->block_radial = UI_block_begin(C, nullptr, __func__, UI_EMBOSS);
   /* may be useful later to allow spawning pies
    * from old positions */
   /* pie->block_radial->flag |= UI_BLOCK_POPUP_MEMORY; */
@@ -153,7 +152,7 @@ uiPieMenu *UI_pie_menu_begin(struct bContext *C, const char *title, int icon, co
                              0,
                              w,
                              UI_UNIT_Y,
-                             NULL,
+                             nullptr,
                              0.0,
                              0.0,
                              0,
@@ -170,7 +169,7 @@ uiPieMenu *UI_pie_menu_begin(struct bContext *C, const char *title, int icon, co
                      0,
                      w,
                      UI_UNIT_Y,
-                     NULL,
+                     nullptr,
                      0.0,
                      0.0,
                      0,
@@ -191,7 +190,7 @@ void UI_pie_menu_end(bContext *C, uiPieMenu *pie)
   wmWindow *window = CTX_wm_window(C);
   uiPopupBlockHandle *menu;
 
-  menu = ui_popup_block_create(C, NULL, NULL, NULL, ui_block_func_PIE, pie, NULL);
+  menu = ui_popup_block_create(C, nullptr, nullptr, nullptr, ui_block_func_PIE, pie, nullptr);
   menu->popup = true;
   menu->towardstime = PIL_check_seconds_timer();
 
@@ -212,7 +211,7 @@ int UI_pie_menu_invoke(struct bContext *C, const char *idname, const wmEvent *ev
   uiLayout *layout;
   MenuType *mt = WM_menutype_find(idname, true);
 
-  if (mt == NULL) {
+  if (mt == nullptr) {
     printf("%s: named menu \"%s\" not found\n", __func__, idname);
     return OPERATOR_CANCELLED;
   }
@@ -263,7 +262,7 @@ int UI_pie_menu_invoke_from_rna_enum(struct bContext *C,
   uiPieMenu *pie;
   uiLayout *layout;
 
-  RNA_pointer_create(NULL, &RNA_Context, C, &ctx_ptr);
+  RNA_pointer_create(nullptr, &RNA_Context, C, &ctx_ptr);
 
   if (!RNA_path_resolve(&ctx_ptr, path, &r_ptr, &r_prop)) {
     return OPERATOR_CANCELLED;
@@ -280,7 +279,7 @@ int UI_pie_menu_invoke_from_rna_enum(struct bContext *C,
   layout = UI_pie_menu_layout(pie);
 
   layout = uiLayoutRadial(layout);
-  uiItemFullR(layout, &r_ptr, r_prop, RNA_NO_INDEX, 0, UI_ITEM_R_EXPAND, NULL, 0);
+  uiItemFullR(layout, &r_ptr, r_prop, RNA_NO_INDEX, 0, UI_ITEM_R_EXPAND, nullptr, 0);
 
   UI_pie_menu_end(C, pie);
 
@@ -304,7 +303,7 @@ int UI_pie_menu_invoke_from_rna_enum(struct bContext *C,
  * - Julian (Feb 2016)
  * \{ */
 
-typedef struct PieMenuLevelData {
+ struct PieMenuLevelData {
   char title[UI_MAX_NAME_STR]; /* parent pie title, copied for level */
   int icon;                    /* parent pie icon, copied for level */
   int totitem;                 /* total count of *remaining* items */
@@ -314,7 +313,7 @@ typedef struct PieMenuLevelData {
   const char *propname;
   IDProperty *properties;
   wmOperatorCallContext context, flag;
-} PieMenuLevelData;
+} ;
 
 /**
  * Invokes a new pie menu for a new level.
@@ -362,17 +361,17 @@ void ui_pie_menu_level_create(uiBlock *block,
                               const EnumPropertyItem *items,
                               int totitem,
                               wmOperatorCallContext context,
-                              int flag)
+                              wmOperatorCallContext flag)
 {
   const int totitem_parent = PIE_MAX_ITEMS - 1;
   const int totitem_remain = totitem - totitem_parent;
   const size_t array_size = sizeof(EnumPropertyItem) * totitem_remain;
 
   /* used as but->func_argN so freeing is handled elsewhere */
-  EnumPropertyItem *remaining = MEM_mallocN(array_size + sizeof(EnumPropertyItem),
-                                            "pie_level_item_array");
+  EnumPropertyItem *remaining = static_cast<EnumPropertyItem *>(
+      MEM_mallocN(array_size + sizeof(EnumPropertyItem), "pie_level_item_array"));
   memcpy(remaining, items + totitem_parent, array_size);
-  /* A NULL terminating sentinel element is required. */
+  /* A nullptr terminating sentinel element is required. */
   memset(&remaining[totitem_remain], 0, sizeof(EnumPropertyItem));
 
   /* yuk, static... issue is we can't reliably free this without doing dangerous changes */
@@ -395,7 +394,7 @@ void ui_pie_menu_level_create(uiBlock *block,
                                 0,
                                 UI_UNIT_X * 3,
                                 UI_UNIT_Y,
-                                NULL,
+                                nullptr,
                                 0.0f,
                                 0.0f,
                                 0.0f,
diff --git a/source/blender/editors/interface/interface_region_menu_popup.c b/source/blender/editors/interface/interface_region_menu_popup.cc
index 7d8f4315710..e843a275d08 100644
--- a/source/blender/editors/interface/interface_region_menu_popup.c
+++ b/source/blender/editors/interface/interface_region_menu_popup.cc
@@ -7,9 +7,9 @@
  * PopUp Menu Region
  */
 
-#include <stdarg.h>
-#include <stdlib.h>
-#include <string.h>
+#include <cstdarg>
+#include <cstdlib>
+#include <cstring>
 
 #include "MEM_guardedalloc.h"
 
@@ -50,7 +50,7 @@ bool ui_but_menu_step_poll(const uiBut *but)
   BLI_assert(but->type == UI_BTYPE_MENU);
 
   /* currently only RNA buttons */
-  return ((but->menu_step_func != NULL) ||
+  return ((but->menu_step_func != nullptr) ||
           (but->rnaprop && RNA_property_type(but->rnaprop) == PROP_ENUM));
 }
 
@@ -58,12 +58,16 @@ int ui_but_menu_step(uiBut *but, int direction)
 {
   if (ui_but_menu_step_poll(but)) {
     if (but->menu_step_func) {
-      return but->menu_step_func(but->block->evil_C, direction, but->poin);
+      return but->menu_step_func(
+          static_cast<bContext *>(but->block->evil_C), direction, but->poin);
     }
 
     const int curval = RNA_property_enum_get(&but->rnapoin, but->rnaprop);
-    return RNA_property_enum_step(
-        but->block->evil_C, &but->rnapoin, but->rnaprop, curval, direction);
+    return RNA_property_enum_step(static_cast<bContext *>(but->block->evil_C),
+                                  &but->rnapoin,
+                                  but->rnaprop,
+                                  curval,
+                                  direction);
   }
 
   printf("%s: cannot cycle button '%s'\n", __func__, but->str);
@@ -85,7 +89,7 @@ static uint ui_popup_string_hash(const char *str, const bool use_sep)
 {
   /* sometimes button contains hotkey, sometimes not, strip for proper compare */
   int hash;
-  const char *delimit = use_sep ? strrchr(str, UI_SEP_CHAR) : NULL;
+  const char *delimit = use_sep ? strrchr(str, UI_SEP_CHAR) : nullptr;
 
   if (delimit) {
     hash = BLI_ghashutil_strhash_n(str, delimit - str);
@@ -102,7 +106,7 @@ uint ui_popup_menu_hash(const char *str)
   return BLI_ghashutil_strhash(str);
 }
 
-/* but == NULL read, otherwise set */
+/* but == nullptr read, otherwise set */
 static uiBut *ui_popup_menu_memory__internal(uiBlock *block, uiBut *but)
 {
   static uint mem[256];
@@ -114,13 +118,13 @@ static uiBut *ui_popup_menu_memory__internal(uiBlock *block, uiBut *but)
   if (first) {
     /* init */
     memset(mem, -1, sizeof(mem));
-    first = 0;
+    first = false;
   }
 
   if (but) {
     /* set */
     mem[hash_mod] = ui_popup_string_hash(but->str, but->flag & UI_BUT_HAS_SEP_CHAR);
-    return NULL;
+    return nullptr;
   }
 
   /* get */
@@ -131,12 +135,12 @@ static uiBut *ui_popup_menu_memory__internal(uiBlock *block, uiBut *but)
     }
   }
 
-  return NULL;
+  return nullptr;
 }
 
 uiBut *ui_popup_menu_memory_get(uiBlock *block)
 {
-  return ui_popup_menu_memory__internal(block, NULL);
+  return ui_popup_menu_memory__internal(block, nullptr);
 }
 
 void ui_popup_menu_memory_set(uiBlock *block, uiBut *but)
@@ -166,7 +170,7 @@ struct uiPopupMenu {
 static uiBlock *ui_block_func_POPUP(bContext *C, uiPopupBlockHandle *handle, void *arg_pup)
 {
   uiBlock *block;
-  uiPopupMenu *pup = arg_pup;
+  uiPopupMenu *pup = static_cast<uiPopupMenu *>(arg_pup);
   int minwidth, width, height;
   char direction;
   bool flip;
@@ -174,7 +178,7 @@ static uiBlock *ui_block_func_POPUP(bContext *C, uiPopupBlockHandle *handle, voi
   if (pup->menu_func) {
     pup->block->handle = handle;
     pup->menu_func(C, pup->layout, pup->menu_arg);
-    pup->block->handle = NULL;
+    pup->block->handle = nullptr;
   }
 
   /* Find block minimum width. */
@@ -229,7 +233,7 @@ static uiBlock *ui_block_func_POPUP(bContext *C, uiPopupBlockHandle *handle, voi
   if (pup->popup) {
     int offset[2];
 
-    uiBut *but_activate = NULL;
+    uiBut *but_activate = nullptr;
     UI_block_flag_enable(block, UI_BLOCK_LOOP | UI_BLOCK_NUMSELECT);
     UI_block_theme_style_set(block, UI_BLOCK_THEME_STYLE_POPUP);
     UI_block_direction_set(block, direction);
@@ -309,10 +313,9 @@ uiPopupBlockHandle *ui_popup_menu_create(
   wmWindow *window = CTX_wm_window(C);
   const uiStyle *style = UI_style_get_dpi();
   uiPopupBlockHandle *handle;
-  uiPopupMenu *pup;
 
-  pup = MEM_callocN(sizeof(uiPopupMenu), __func__);
-  pup->block = UI_block_begin(C, NULL, __func__, UI_EMBOSS_PULLDOWN);
+  uiPopupMenu *pup = MEM_cnew<uiPopupMenu>(__func__);
+  pup->block = UI_block_begin(C, nullptr, __func__, UI_EMBOSS_PULLDOWN);
   pup->block->flag |= UI_BLOCK_NUMSELECT; /* default menus to numselect */
   pup->layout = UI_block_layout(
       pup->block, UI_LAYOUT_VERTICAL, UI_LAYOUT_MENU, 0, 0, 200, 0, UI_MENU_PADDING, style);
@@ -348,7 +351,7 @@ uiPopupBlockHandle *ui_popup_menu_create(
   pup->menu_func = menu_func;
   pup->menu_arg = arg;
 
-  handle = ui_popup_block_create(C, butregion, but, NULL, ui_block_func_POPUP, pup, NULL);
+  handle = ui_popup_block_create(C, butregion, but, nullptr, ui_block_func_POPUP, pup, nullptr);
 
   if (!but) {
     handle->popup = true;
@@ -374,10 +377,10 @@ uiPopupMenu *UI_popup_menu_begin_ex(bContext *C,
                                     int icon)
 {
   const uiStyle *style = UI_style_get_dpi();
-  uiPopupMenu *pup = MEM_callocN(sizeof(uiPopupMenu), "popup menu");
+  uiPopupMenu *pup = MEM_cnew<uiPopupMenu>(__func__);
   uiBut *but;
 
-  pup->block = UI_block_begin(C, NULL, block_name, UI_EMBOSS_PULLDOWN);
+  pup->block = UI_block_begin(C, nullptr, block_name, UI_EMBOSS_PULLDOWN);
   pup->block->flag |= UI_BLOCK_POPUP_MEMORY | UI_BLOCK_IS_FLIP;
   pup->block->puphash = ui_popup_menu_hash(title);
   pup->layout = UI_block_layout(
@@ -389,7 +392,7 @@ uiPopupMenu *UI_popup_menu_begin_ex(bContext *C,
   uiLayoutSetOperatorContext(pup->layout, WM_OP_EXEC_REGION_WIN);
 
   /* create in advance so we can let buttons point to retval already */
-  pup->block->handle = MEM_callocN(sizeof(uiPopupBlockHandle), "uiPopupBlockHandle");
+  pup->block->handle = MEM_cnew<uiPopupBlockHandle>(__func__);
 
   /* create title button */
   if (title[0]) {
@@ -406,7 +409,7 @@ uiPopupMenu *UI_popup_menu_begin_ex(bContext *C,
                        0,
                        200,
                        UI_UNIT_Y,
-                       NULL,
+                       nullptr,
                        0.0,
                        0.0,
                        0,
@@ -415,7 +418,7 @@ uiPopupMenu *UI_popup_menu_begin_ex(bContext *C,
     }
     else {
       but = uiDefBut(
-          pup->block, UI_BTYPE_LABEL, 0, title, 0, 0, 200, UI_UNIT_Y, NULL, 0.0, 0.0, 0, 0, "");
+          pup->block, UI_BTYPE_LABEL, 0, title, 0, 0, 200, UI_UNIT_Y, nullptr, 0.0, 0.0, 0, 0, "");
       but->drawflag = UI_BUT_TEXT_LEFT;
     }
 
@@ -440,8 +443,8 @@ void UI_popup_menu_end(bContext *C, uiPopupMenu *pup)
 {
   wmWindow *window = CTX_wm_window(C);
   uiPopupBlockHandle *menu;
-  uiBut *but = NULL;
-  ARegion *butregion = NULL;
+  uiBut *but = nullptr;
+  ARegion *butregion = nullptr;
 
   pup->popup = true;
   pup->mx = window->eventstate->xy[0];
@@ -452,7 +455,7 @@ void UI_popup_menu_end(bContext *C, uiPopupMenu *pup)
     butregion = pup->butregion;
   }
 
-  menu = ui_popup_block_create(C, butregion, but, NULL, ui_block_func_POPUP, pup, NULL);
+  menu = ui_popup_block_create(C, butregion, but, nullptr, ui_block_func_POPUP, pup, nullptr);
   menu->popup = true;
 
   UI_popup_handlers_add(C, &window->modalhandlers, menu, 0);
@@ -467,7 +470,7 @@ bool UI_popup_menu_end_or_cancel(bContext *C, uiPopupMenu *pup)
     UI_popup_menu_end(C, pup);
     return true;
   }
-  UI_block_layout_resolve(pup->block, NULL, NULL);
+  UI_block_layout_resolve(pup->block, nullptr, nullptr);
   MEM_freeN(pup->block->handle);
   UI_block_free(C, pup->block);
   MEM_freeN(pup);
@@ -487,7 +490,7 @@ uiLayout *UI_popup_menu_layout(uiPopupMenu *pup)
 
 void UI_popup_menu_reports(bContext *C, ReportList *reports)
 {
-  uiPopupMenu *pup = NULL;
+  uiPopupMenu *pup = nullptr;
   uiLayout *layout;
 
   if (!CTX_wm_window(C)) {
@@ -502,7 +505,7 @@ void UI_popup_menu_reports(bContext *C, ReportList *reports)
       continue;
     }
 
-    if (pup == NULL) {
+    if (pup == nullptr) {
       char title[UI_MAX_DRAW_STR];
       BLI_snprintf(title, sizeof(title), "%s: %s", IFACE_("Report"), report->typestr);
       /* popup_menu stuff does just what we need (but pass meaningful block name) */
@@ -540,7 +543,7 @@ int UI_popup_menu_invoke(bContext *C, const char *idname, ReportList *reports)
   uiLayout *layout;
   MenuType *mt = WM_menutype_find(idname, true);
 
-  if (mt == NULL) {
+  if (mt == nullptr) {
     BKE_reportf(reports, RPT_ERROR, "Menu \"%s\" not found", idname);
     return OPERATOR_CANCELLED;
   }
@@ -572,7 +575,7 @@ void UI_popup_block_invoke_ex(
   wmWindow *window = CTX_wm_window(C);
   uiPopupBlockHandle *handle;
 
-  handle = ui_popup_block_create(C, NULL, NULL, func, NULL, arg, arg_free);
+  handle = ui_popup_block_create(C, nullptr, nullptr, func, nullptr, arg, arg_free);
   handle->popup = true;
 
   /* It can be useful to disable refresh (even though it will work)
@@ -580,7 +583,8 @@ void UI_popup_block_invoke_ex(
   handle->can_refresh = can_refresh;
 
   UI_popup_handlers_add(C, &window->modalhandlers, handle, 0);
-  UI_block_active_only_flagged_buttons(C, handle->region, handle->region->uiblocks.first);
+  UI_block_active_only_flagged_buttons(
+      C, handle->region, static_cast<uiBlock *>(handle->region->uiblocks.first));
   WM_event_add_mousemove(window);
 }
 
@@ -599,7 +603,7 @@ void UI_popup_block_ex(bContext *C,
   wmWindow *window = CTX_wm_window(C);
   uiPopupBlockHandle *handle;
 
-  handle = ui_popup_block_create(C, NULL, NULL, func, NULL, arg, NULL);
+  handle = ui_popup_block_create(C, nullptr, nullptr, func, nullptr, arg, nullptr);
   handle->popup = true;
   handle->retvalue = 1;
   handle->can_refresh = true;
@@ -611,7 +615,8 @@ void UI_popup_block_ex(bContext *C,
   // handle->opcontext = opcontext;
 
   UI_popup_handlers_add(C, &window->modalhandlers, handle, 0);
-  UI_block_active_only_flagged_buttons(C, handle->region, handle->region->uiblocks.first);
+  UI_block_active_only_flagged_buttons(
+      C, handle->region, static_cast<uiBlock *>(handle->region->uiblocks.first));
   WM_event_add_mousemove(window);
 }
 
@@ -621,7 +626,7 @@ void uiPupBlockOperator(bContext *C, uiBlockCreateFunc func, wmOperator *op, wmO
   wmWindow *window = CTX_wm_window(C);
   uiPopupBlockHandle *handle;
 
-  handle = ui_popup_block_create(C, NULL, NULL, func, NULL, op, NULL);
+  handle = ui_popup_block_create(C, nullptr, nullptr, func, nullptr, op, nullptr);
   handle->popup = 1;
   handle->retvalue = 1;
   handle->can_refresh = true;
@@ -638,7 +643,7 @@ void uiPupBlockOperator(bContext *C, uiBlockCreateFunc func, wmOperator *op, wmO
 
 void UI_popup_block_close(bContext *C, wmWindow *win, uiBlock *block)
 {
-  /* if loading new .blend while popup is open, window will be NULL */
+  /* if loading new .blend while popup is open, window will be nullptr */
   if (block->handle) {
     if (win) {
       const bScreen *screen = WM_window_get_active_screen(win);
diff --git a/source/blender/editors/interface/interface_region_popover.c b/source/blender/editors/interface/interface_region_popover.cc
index 7c7c9e887dd..2e10261a4f7 100644
--- a/source/blender/editors/interface/interface_region_popover.c
+++ b/source/blender/editors/interface/interface_region_popover.cc
@@ -80,7 +80,7 @@ static void ui_popover_create_block(bContext *C, uiPopover *pup, wmOperatorCallC
 
   const uiStyle *style = UI_style_get_dpi();
 
-  pup->block = UI_block_begin(C, NULL, __func__, UI_EMBOSS);
+  pup->block = UI_block_begin(C, nullptr, __func__, UI_EMBOSS);
   UI_block_flag_enable(pup->block, UI_BLOCK_KEEP_OPEN | UI_BLOCK_POPOVER);
 #ifdef USE_UI_POPOVER_ONCE
   if (pup->is_once) {
@@ -104,7 +104,7 @@ static void ui_popover_create_block(bContext *C, uiPopover *pup, wmOperatorCallC
 
 static uiBlock *ui_block_func_POPOVER(bContext *C, uiPopupBlockHandle *handle, void *arg_pup)
 {
-  uiPopover *pup = arg_pup;
+  uiPopover *pup = static_cast<uiPopover *>(arg_pup);
 
   /* Create UI block and layout now if it wasn't done between begin/end. */
   if (!pup->layout) {
@@ -113,10 +113,10 @@ static uiBlock *ui_block_func_POPOVER(bContext *C, uiPopupBlockHandle *handle, v
     if (pup->menu_func) {
       pup->block->handle = handle;
       pup->menu_func(C, pup->layout, pup->menu_arg);
-      pup->block->handle = NULL;
+      pup->block->handle = nullptr;
     }
 
-    pup->layout = NULL;
+    pup->layout = nullptr;
   }
 
   /* Setup and resolve UI layout for block. */
@@ -185,10 +185,10 @@ static uiBlock *ui_block_func_POPOVER(bContext *C, uiPopupBlockHandle *handle, v
     block->minbounds = UI_MENU_WIDTH_MIN;
 
     if (!handle->refresh) {
-      uiBut *but = NULL;
-      uiBut *but_first = NULL;
+      uiBut *but = nullptr;
+      uiBut *but_first = nullptr;
       LISTBASE_FOREACH (uiBut *, but_iter, &block->buttons) {
-        if ((but_first == NULL) && ui_but_is_editable(but_iter)) {
+        if ((but_first == nullptr) && ui_but_is_editable(but_iter)) {
           but_first = but_iter;
         }
         if (but_iter->flag & (UI_SELECT | UI_SELECT_DRAW)) {
@@ -219,8 +219,8 @@ static uiBlock *ui_block_func_POPOVER(bContext *C, uiPopupBlockHandle *handle, v
 
 static void ui_block_free_func_POPOVER(void *arg_pup)
 {
-  uiPopover *pup = arg_pup;
-  if (pup->keymap != NULL) {
+  uiPopover *pup = static_cast<uiPopover *>(arg_pup);
+  if (pup->keymap != nullptr) {
     wmWindow *window = pup->window;
     WM_event_remove_keymap_handler(&window->modalhandlers, pup->keymap);
   }
@@ -235,7 +235,7 @@ uiPopupBlockHandle *ui_popover_panel_create(
   const PanelType *panel_type = (PanelType *)arg;
 
   /* Create popover, buttons are created from callback. */
-  uiPopover *pup = MEM_callocN(sizeof(uiPopover), __func__);
+  uiPopover *pup = MEM_cnew<uiPopover>(__func__);
   pup->but = but;
 
   /* FIXME: maybe one day we want non panel popovers? */
@@ -262,7 +262,7 @@ uiPopupBlockHandle *ui_popover_panel_create(
   /* Create popup block. */
   uiPopupBlockHandle *handle;
   handle = ui_popup_block_create(
-      C, butregion, but, NULL, ui_block_func_POPOVER, pup, ui_block_free_func_POPOVER);
+      C, butregion, but, nullptr, ui_block_func_POPOVER, pup, ui_block_free_func_POPOVER);
   handle->can_refresh = true;
 
   /* Add handlers. If attached to a button, the button will already
@@ -286,7 +286,7 @@ int UI_popover_panel_invoke(bContext *C, const char *idname, bool keep_open, Rep
 {
   uiLayout *layout;
   PanelType *pt = WM_paneltype_find(idname, true);
-  if (pt == NULL) {
+  if (pt == nullptr) {
     BKE_reportf(reports, RPT_ERROR, "Panel \"%s\" not found", idname);
     return OPERATOR_CANCELLED;
   }
@@ -296,23 +296,23 @@ int UI_popover_panel_invoke(bContext *C, const char *idname, bool keep_open, Rep
     return (OPERATOR_CANCELLED | OPERATOR_PASS_THROUGH);
   }
 
-  uiBlock *block = NULL;
+  uiBlock *block = nullptr;
   if (keep_open) {
     uiPopupBlockHandle *handle = ui_popover_panel_create(
-        C, NULL, NULL, ui_item_paneltype_func, pt);
-    uiPopover *pup = handle->popup_create_vars.arg;
+        C, nullptr, nullptr, ui_item_paneltype_func, pt);
+    uiPopover *pup = static_cast<uiPopover *>(handle->popup_create_vars.arg);
     block = pup->block;
   }
   else {
     uiPopover *pup = UI_popover_begin(C, U.widget_unit * pt->ui_units_x, false);
     layout = UI_popover_layout(pup);
     UI_paneltype_draw(C, pt, layout);
-    UI_popover_end(C, pup, NULL);
+    UI_popover_end(C, pup, nullptr);
     block = pup->block;
   }
 
   if (block) {
-    uiPopupBlockHandle *handle = block->handle;
+    uiPopupBlockHandle *handle = static_cast<uiPopupBlockHandle *>(block->handle);
     UI_block_active_only_flagged_buttons(C, handle->region, block);
   }
   return OPERATOR_INTERFACE;
@@ -326,20 +326,20 @@ int UI_popover_panel_invoke(bContext *C, const char *idname, bool keep_open, Rep
 
 uiPopover *UI_popover_begin(bContext *C, int ui_menu_width, bool from_active_button)
 {
-  uiPopover *pup = MEM_callocN(sizeof(uiPopover), "popover menu");
+  uiPopover *pup = MEM_cnew<uiPopover>(__func__);
   if (ui_menu_width == 0) {
     ui_menu_width = U.widget_unit * UI_POPOVER_WIDTH_UNITS;
   }
   pup->ui_size_x = ui_menu_width;
 
-  ARegion *butregion = NULL;
-  uiBut *but = NULL;
+  ARegion *butregion = nullptr;
+  uiBut *but = nullptr;
 
   if (from_active_button) {
     butregion = CTX_wm_region(C);
     but = UI_region_active_but_get(butregion);
-    if (but == NULL) {
-      butregion = NULL;
+    if (but == nullptr) {
+      butregion = nullptr;
     }
   }
 
@@ -350,14 +350,14 @@ uiPopover *UI_popover_begin(bContext *C, int ui_menu_width, bool from_active_but
   ui_popover_create_block(C, pup, WM_OP_EXEC_REGION_WIN);
 
   /* create in advance so we can let buttons point to retval already */
-  pup->block->handle = MEM_callocN(sizeof(uiPopupBlockHandle), "uiPopupBlockHandle");
+  pup->block->handle = MEM_cnew<uiPopupBlockHandle>(__func__);
 
   return pup;
 }
 
 static void popover_keymap_fn(wmKeyMap *UNUSED(keymap), wmKeyMapItem *UNUSED(kmi), void *user_data)
 {
-  uiPopover *pup = user_data;
+  uiPopover *pup = static_cast<uiPopover *>(user_data);
   pup->block->handle->menuretval = UI_RETURN_OK;
 }
 
@@ -376,8 +376,13 @@ void UI_popover_end(bContext *C, uiPopover *pup, wmKeyMap *keymap)
     WM_event_set_keymap_handler_post_callback(pup->keymap_handler, popover_keymap_fn, pup);
   }
 
-  handle = ui_popup_block_create(
-      C, pup->butregion, pup->but, NULL, ui_block_func_POPOVER, pup, ui_block_free_func_POPOVER);
+  handle = ui_popup_block_create(C,
+                                 pup->butregion,
+                                 pup->but,
+                                 nullptr,
+                                 ui_block_func_POPOVER,
+                                 pup,
+                                 ui_block_free_func_POPOVER);
 
   /* Add handlers. */
   UI_popup_handlers_add(C, &window->modalhandlers, handle, 0);
diff --git a/source/blender/editors/interface/interface_region_popup.c b/source/blender/editors/interface/interface_region_popup.cc
index 2f2556225b5..74c228e3338 100644
--- a/source/blender/editors/interface/interface_region_popup.c
+++ b/source/blender/editors/interface/interface_region_popup.cc
@@ -7,9 +7,9 @@
  * PopUp Region (Generic)
  */
 
-#include <stdarg.h>
-#include <stdlib.h>
-#include <string.h>
+#include <cstdarg>
+#include <cstdlib>
+#include <cstring>
 
 #include "MEM_guardedalloc.h"
 
@@ -120,7 +120,7 @@ static void ui_popup_block_position(wmWindow *window,
   short dir1 = 0, dir2 = 0;
 
   if (!handle->refresh) {
-    bool left = 0, right = 0, top = 0, down = 0;
+    bool left = false, right = false, top = false, down = false;
 
     const int win_x = WM_window_pixels_x(window);
     const int win_y = WM_window_pixels_y(window);
@@ -131,24 +131,24 @@ static void ui_popup_block_position(wmWindow *window,
 
     /* check if there's space at all */
     if (butrct.xmin - max_size_x + center_x > 0.0f) {
-      left = 1;
+      left = true;
     }
     if (butrct.xmax + max_size_x - center_x < win_x) {
-      right = 1;
+      right = true;
     }
     if (butrct.ymin - max_size_y + center_y > 0.0f) {
-      down = 1;
+      down = true;
     }
     if (butrct.ymax + max_size_y - center_y < win_y) {
-      top = 1;
+      top = true;
     }
 
     if (top == 0 && down == 0) {
       if (butrct.ymin - max_size_y < win_y - butrct.ymax - max_size_y) {
-        top = 1;
+        top = true;
       }
       else {
-        down = 1;
+        down = true;
       }
     }
 
@@ -335,7 +335,7 @@ static void ui_popup_block_position(wmWindow *window,
   }
 
   /* Keep a list of these, needed for pull-down menus. */
-  uiSafetyRct *saferct = MEM_callocN(sizeof(uiSafetyRct), "uiSafetyRct");
+  uiSafetyRct *saferct = MEM_cnew<uiSafetyRct>(__func__);
   saferct->parent = butrct;
   saferct->safety = block->safety;
   BLI_freelistN(&block->saferct);
@@ -520,7 +520,7 @@ static void ui_popup_block_remove(bContext *C, uiPopupBlockHandle *handle)
   CTX_wm_window_set(C, win);
   ui_region_temp_remove(C, screen, handle->region);
 
-  /* Reset context (area and region were NULL'ed when changing context window). */
+  /* Reset context (area and region were nullptr'ed when changing context window). */
   CTX_wm_window_set(C, ctx_win);
   CTX_wm_area_set(C, ctx_area);
   CTX_wm_region_set(C, ctx_region);
@@ -548,10 +548,10 @@ uiBlock *ui_popup_block_refresh(bContext *C,
   const uiBlockHandleCreateFunc handle_create_func = handle->popup_create_vars.handle_create_func;
   void *arg = handle->popup_create_vars.arg;
 
-  uiBlock *block_old = region->uiblocks.first;
+  uiBlock *block_old = static_cast<uiBlock *>(region->uiblocks.first);
   uiBlock *block;
 
-  handle->refresh = (block_old != NULL);
+  handle->refresh = (block_old != nullptr);
 
   BLI_assert(!handle->refresh || handle->can_refresh);
 
@@ -573,7 +573,7 @@ uiBlock *ui_popup_block_refresh(bContext *C,
 
   /* ensure we don't use mouse coords here! */
 #ifdef DEBUG
-  window->eventstate = NULL;
+  window->eventstate = nullptr;
 #endif
 
   if (block->handle) {
@@ -588,7 +588,7 @@ uiBlock *ui_popup_block_refresh(bContext *C,
   region->regiondata = handle;
 
   /* set UI_BLOCK_NUMSELECT before UI_block_end() so we get alphanumeric keys assigned */
-  if (but == NULL) {
+  if (but == nullptr) {
     block->flag |= UI_BLOCK_POPUP;
   }
 
@@ -596,7 +596,7 @@ uiBlock *ui_popup_block_refresh(bContext *C,
   UI_block_theme_style_set(block, UI_BLOCK_THEME_STYLE_POPUP);
 
   /* defer this until blocks are translated (below) */
-  block->oldblock = NULL;
+  block->oldblock = nullptr;
 
   if (!block->endblock) {
     UI_block_end_ex(
@@ -610,9 +610,8 @@ uiBlock *ui_popup_block_refresh(bContext *C,
     handle->direction = block->direction;
   }
   else {
-    uiSafetyRct *saferct;
     /* Keep a list of these, needed for pull-down menus. */
-    saferct = MEM_callocN(sizeof(uiSafetyRct), "uiSafetyRct");
+    uiSafetyRct *saferct = MEM_cnew<uiSafetyRct>(__func__);
     saferct->safety = block->safety;
     BLI_addhead(&block->saferct, saferct);
   }
@@ -760,7 +759,6 @@ uiPopupBlockHandle *ui_popup_block_create(bContext *C,
   static ARegionType type;
   ARegion *region;
   uiBlock *block;
-  uiPopupBlockHandle *handle;
 
   /* disable tooltips from buttons below */
   if (activebut) {
@@ -770,7 +768,7 @@ uiPopupBlockHandle *ui_popup_block_create(bContext *C,
   WM_cursor_set(window, WM_CURSOR_DEFAULT);
 
   /* create handle */
-  handle = MEM_callocN(sizeof(uiPopupBlockHandle), "uiPopupBlockHandle");
+  uiPopupBlockHandle *handle = MEM_cnew<uiPopupBlockHandle>(__func__);
 
   /* store context for operator */
   handle->ctx_area = CTX_wm_area(C);
@@ -782,7 +780,7 @@ uiPopupBlockHandle *ui_popup_block_create(bContext *C,
   handle->popup_create_vars.arg = arg;
   handle->popup_create_vars.arg_free = arg_free;
   handle->popup_create_vars.but = but;
-  handle->popup_create_vars.butregion = but ? butregion : NULL;
+  handle->popup_create_vars.butregion = but ? butregion : nullptr;
   copy_v2_v2_int(handle->popup_create_vars.event_xy, window->eventstate->xy);
 
   /* don't allow by default, only if popup type explicitly supports it */
@@ -816,7 +814,7 @@ void ui_popup_block_free(bContext *C, uiPopupBlockHandle *handle)
   /* If this popup is created from a popover which does NOT have keep-open flag set,
    * then close the popover too. We could extend this to other popup types too. */
   ARegion *region = handle->popup_create_vars.butregion;
-  if (region != NULL) {
+  if (region != nullptr) {
     LISTBASE_FOREACH (uiBlock *, block, &region->uiblocks) {
       if (block->handle && (block->flag & UI_BLOCK_POPOVER) &&
           (block->flag & UI_BLOCK_KEEP_OPEN) == 0) {
diff --git a/source/blender/editors/interface/interface_regions.c b/source/blender/editors/interface/interface_regions.cc
index ea6d293e52f..1a2c1f7919c 100644
--- a/source/blender/editors/interface/interface_regions.c
+++ b/source/blender/editors/interface/interface_regions.cc
@@ -25,7 +25,7 @@
 
 ARegion *ui_region_temp_add(bScreen *screen)
 {
-  ARegion *region = MEM_callocN(sizeof(ARegion), __func__);
+  ARegion *region = MEM_cnew<ARegion>(__func__);
   BLI_addtail(&screen->regionbase, region);
 
   region->regiontype = RGN_TYPE_TEMPORARY;
@@ -45,6 +45,6 @@ void ui_region_temp_remove(bContext *C, bScreen *screen, ARegion *region)
   }
 
   ED_region_exit(C, region);
-  BKE_area_region_free(NULL, region); /* NULL: no spacetype */
+  BKE_area_region_free(nullptr, region); /* nullptr: no spacetype */
   BLI_freelinkN(&screen->regionbase, region);
 }
diff --git a/source/blender/editors/interface/interface_style.c b/source/blender/editors/interface/interface_style.cc
index 76023f3033f..b4e97f8a396 100644
--- a/source/blender/editors/interface/interface_style.c
+++ b/source/blender/editors/interface/interface_style.cc
@@ -5,11 +5,11 @@
  * \ingroup edinterface
  */
 
-#include <limits.h>
-#include <math.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
+#include <climits>
+#include <cmath>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
 
 #include "MEM_guardedalloc.h"
 
@@ -57,7 +57,7 @@
 
 static uiStyle *ui_style_new(ListBase *styles, const char *name, short uifont_id)
 {
-  uiStyle *style = MEM_callocN(sizeof(uiStyle), "new style");
+  uiStyle *style = MEM_cnew<uiStyle>(__func__);
 
   BLI_addtail(styles, style);
   BLI_strncpy(style->name, name, MAX_STYLE_NAME);
@@ -108,14 +108,14 @@ static uiStyle *ui_style_new(ListBase *styles, const char *name, short uifont_id
 
 static uiFont *uifont_to_blfont(int id)
 {
-  uiFont *font = U.uifonts.first;
+  uiFont *font = static_cast<uiFont *>(U.uifonts.first);
 
   for (; font; font = font->next) {
     if (font->uifont_id == id) {
       return font;
     }
   }
-  return U.uifonts.first;
+  return static_cast<uiFont *>(U.uifonts.first);
 }
 
 /* *************** draw ************************ */
@@ -198,7 +198,7 @@ void UI_fontstyle_draw(const uiFontStyle *fs,
                        const uchar col[4],
                        const struct uiFontStyleDraw_Params *fs_params)
 {
-  UI_fontstyle_draw_ex(fs, rect, str, str_len, col, fs_params, NULL, NULL, NULL);
+  UI_fontstyle_draw_ex(fs, rect, str, str_len, col, fs_params, nullptr, nullptr, nullptr);
 }
 
 void UI_fontstyle_draw_rotated(const uiFontStyle *fs,
@@ -284,17 +284,13 @@ void UI_fontstyle_draw_simple_backdrop(const uiFontStyle *fs,
     const float decent = BLF_descender(fs->uifont_id);
     const float margin = height / 4.0f;
 
+    rctf rect;
+    rect.xmin = x - margin;
+    rect.xmax = x + width + margin;
+    rect.ymin = (y + decent) - margin;
+    rect.ymax = (y + decent) + height + margin;
     UI_draw_roundbox_corner_set(UI_CNR_ALL);
-    UI_draw_roundbox_4fv(
-        &(const rctf){
-            .xmin = x - margin,
-            .xmax = x + width + margin,
-            .ymin = (y + decent) - margin,
-            .ymax = (y + decent) + height + margin,
-        },
-        true,
-        margin,
-        col_bg);
+    UI_draw_roundbox_4fv(&rect, true, margin, col_bg);
   }
 
   BLF_position(fs->uifont_id, x, y, 0.0f);
@@ -307,12 +303,12 @@ void UI_fontstyle_draw_simple_backdrop(const uiFontStyle *fs,
 const uiStyle *UI_style_get(void)
 {
 #if 0
-  uiStyle *style = NULL;
+  uiStyle *style = nullptr;
   /* offset is two struct uiStyle pointers */
   style = BLI_findstring(&U.uistyles, "Unifont Style", sizeof(style) * 2);
-  return (style != NULL) ? style : U.uistyles.first;
+  return (style != nullptr) ? style : U.uistyles.first;
 #else
-  return U.uistyles.first;
+  return static_cast<const uiStyle *>(U.uistyles.first);
 #endif
 }
 
@@ -378,7 +374,7 @@ int UI_fontstyle_height_max(const uiFontStyle *fs)
 
 void uiStyleInit(void)
 {
-  const uiStyle *style = U.uistyles.first;
+  const uiStyle *style = static_cast<uiStyle *>(U.uistyles.first);
 
   /* recover from uninitialized dpi */
   if (U.dpi == 0) {
@@ -400,11 +396,11 @@ void uiStyleInit(void)
     blf_mono_font_render = -1;
   }
 
-  uiFont *font_first = U.uifonts.first;
+  uiFont *font_first = static_cast<uiFont *>(U.uifonts.first);
 
   /* default builtin */
-  if (font_first == NULL) {
-    font_first = MEM_callocN(sizeof(uiFont), "ui font");
+  if (font_first == nullptr) {
+    font_first = MEM_cnew<uiFont>(__func__);
     BLI_addtail(&U.uifonts, font_first);
   }
 
@@ -439,7 +435,7 @@ void uiStyleInit(void)
     }
   }
 
-  if (style == NULL) {
+  if (style == nullptr) {
     style = ui_style_new(&U.uistyles, "Default Style", UIFONT_DEFAULT);
   }
 
diff --git a/source/blender/editors/interface/interface_utils.c b/source/blender/editors/interface/interface_utils.cc
index 728d42a9353..b796f07c24b 100644
--- a/source/blender/editors/interface/interface_utils.c
+++ b/source/blender/editors/interface/interface_utils.cc
@@ -5,17 +5,16 @@
  * \ingroup edinterface
  */
 
-#include <ctype.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
+#include <cctype>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
 
 #include "DNA_object_types.h"
 #include "DNA_screen_types.h"
 
 #include "ED_screen.h"
 
-#include "BLI_alloca.h"
 #include "BLI_listbase.h"
 #include "BLI_math.h"
 #include "BLI_string.h"
@@ -55,12 +54,12 @@ uiBut *uiDefAutoButR(uiBlock *block,
                      int width,
                      int height)
 {
-  uiBut *but = NULL;
+  uiBut *but = nullptr;
 
   switch (RNA_property_type(prop)) {
     case PROP_BOOLEAN: {
       if (RNA_property_array_check(prop) && index == -1) {
-        return NULL;
+        return nullptr;
       }
 
       if (icon && name && name[0] == '\0') {
@@ -79,7 +78,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                  0,
                                  -1,
                                  -1,
-                                 NULL);
+                                 nullptr);
       }
       else if (icon) {
         but = uiDefIconTextButR_prop(block,
@@ -98,7 +97,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                      0,
                                      -1,
                                      -1,
-                                     NULL);
+                                     nullptr);
       }
       else {
         but = uiDefButR_prop(block,
@@ -116,7 +115,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                              0,
                              -1,
                              -1,
-                             NULL);
+                             nullptr);
       }
       break;
     }
@@ -139,10 +138,10 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                0,
                                0,
                                0,
-                               NULL);
+                               nullptr);
         }
         else {
-          return NULL;
+          return nullptr;
         }
       }
       else if (RNA_property_subtype(prop) == PROP_PERCENTAGE ||
@@ -162,11 +161,25 @@ uiBut *uiDefAutoButR(uiBlock *block,
                              0,
                              -1,
                              -1,
-                             NULL);
+                             nullptr);
       }
       else {
-        but = uiDefButR_prop(
-            block, UI_BTYPE_NUM, 0, name, x, y, width, height, ptr, prop, index, 0, 0, 0, 0, NULL);
+        but = uiDefButR_prop(block,
+                             UI_BTYPE_NUM,
+                             0,
+                             name,
+                             x,
+                             y,
+                             width,
+                             height,
+                             ptr,
+                             prop,
+                             index,
+                             0,
+                             0,
+                             0,
+                             0,
+                             nullptr);
       }
 
       if (RNA_property_flag(prop) & PROP_TEXTEDIT_UPDATE) {
@@ -191,14 +204,14 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                  0,
                                  -1,
                                  -1,
-                                 NULL);
+                                 nullptr);
       }
       else if (icon) {
         but = uiDefIconTextButR_prop(block,
                                      UI_BTYPE_MENU,
                                      0,
                                      icon,
-                                     NULL,
+                                     nullptr,
                                      x,
                                      y,
                                      width,
@@ -210,7 +223,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                      0,
                                      -1,
                                      -1,
-                                     NULL);
+                                     nullptr);
       }
       else {
         but = uiDefButR_prop(block,
@@ -228,7 +241,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                              0,
                              -1,
                              -1,
-                             NULL);
+                             nullptr);
       }
       break;
     case PROP_STRING:
@@ -248,7 +261,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                  0,
                                  -1,
                                  -1,
-                                 NULL);
+                                 nullptr);
       }
       else if (icon) {
         but = uiDefIconTextButR_prop(block,
@@ -267,7 +280,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                      0,
                                      -1,
                                      -1,
-                                     NULL);
+                                     nullptr);
       }
       else {
         but = uiDefButR_prop(block,
@@ -285,7 +298,7 @@ uiBut *uiDefAutoButR(uiBlock *block,
                              0,
                              -1,
                              -1,
-                             NULL);
+                             nullptr);
       }
 
       if (RNA_property_flag(prop) & PROP_TEXTEDIT_UPDATE) {
@@ -319,20 +332,21 @@ uiBut *uiDefAutoButR(uiBlock *block,
                                    0,
                                    -1,
                                    -1,
-                                   NULL);
-      ui_but_add_search(but, ptr, prop, NULL, NULL);
+                                   nullptr);
+      ui_but_add_search(but, ptr, prop, nullptr, nullptr);
       break;
     }
     case PROP_COLLECTION: {
       char text[256];
       BLI_snprintf(
           text, sizeof(text), IFACE_("%d items"), RNA_property_collection_length(ptr, prop));
-      but = uiDefBut(block, UI_BTYPE_LABEL, 0, text, x, y, width, height, NULL, 0, 0, 0, 0, NULL);
+      but = uiDefBut(
+          block, UI_BTYPE_LABEL, 0, text, x, y, width, height, nullptr, 0, 0, 0, 0, nullptr);
       UI_but_flag_enable(but, UI_BUT_DISABLED);
       break;
     }
     default:
-      but = NULL;
+      but = nullptr;
       break;
   }
 
@@ -414,7 +428,7 @@ eAutoPropButsReturn uiDefAutoButsRNA(uiLayout *layout,
       case UI_BUT_LABEL_ALIGN_NONE:
       default:
         col = layout;
-        name = NULL; /* no smart label alignment, show default name with button */
+        name = nullptr; /* no smart label alignment, show default name with button */
         break;
     }
 
@@ -440,7 +454,7 @@ eAutoPropButsReturn uiDefAutoButsRNA(uiLayout *layout,
 
 /* *** RNA collection search menu *** */
 
-typedef struct CollItemSearch {
+struct CollItemSearch {
   struct CollItemSearch *next, *prev;
   void *data;
   char *name;
@@ -449,7 +463,7 @@ typedef struct CollItemSearch {
   bool is_id;
   int name_prefix_offset;
   uint has_sep_char : 1;
-} CollItemSearch;
+};
 
 static bool add_collection_search_item(CollItemSearch *cis,
                                        const bool requires_exact_data_name,
@@ -462,10 +476,11 @@ static bool add_collection_search_item(CollItemSearch *cis,
    * name prefix for showing the library status. */
   int name_prefix_offset = cis->name_prefix_offset;
   if (!has_id_icon && cis->is_id && !requires_exact_data_name) {
-    cis->iconid = UI_icon_from_library(cis->data);
+    cis->iconid = UI_icon_from_library(static_cast<const ID *>(cis->data));
     /* No need to re-allocate, string should be shorter than before (lib status prefix is
      * removed). */
-    BKE_id_full_name_ui_prefix_get(name_buf, cis->data, false, UI_SEP_CHAR, &name_prefix_offset);
+    BKE_id_full_name_ui_prefix_get(
+        name_buf, static_cast<const ID *>(cis->data), false, UI_SEP_CHAR, &name_prefix_offset);
     BLI_assert(strlen(name_buf) <= MEM_allocN_len(cis->name));
     strcpy(cis->name, name_buf);
   }
@@ -478,15 +493,12 @@ static bool add_collection_search_item(CollItemSearch *cis,
                             name_prefix_offset);
 }
 
-void ui_rna_collection_search_update_fn(const struct bContext *C,
-                                        void *arg,
-                                        const char *str,
-                                        uiSearchItems *items,
-                                        const bool is_first)
+void ui_rna_collection_search_update_fn(
+    const bContext *C, void *arg, const char *str, uiSearchItems *items, const bool is_first)
 {
-  uiRNACollectionSearch *data = arg;
+  uiRNACollectionSearch *data = static_cast<uiRNACollectionSearch *>(arg);
   const int flag = RNA_property_flag(data->target_prop);
-  ListBase *items_list = MEM_callocN(sizeof(ListBase), "items_list");
+  ListBase *items_list = MEM_cnew<ListBase>("items_list");
   const bool is_ptr_target = (RNA_property_type(data->target_prop) == PROP_POINTER);
   /* For non-pointer properties, UI code acts entirely based on the item's name. So the name has to
    * match the RNA name exactly. So only for pointer properties, the name can be modified to add
@@ -497,7 +509,7 @@ void ui_rna_collection_search_update_fn(const struct bContext *C,
   char *name;
   bool has_id_icon = false;
 
-  StringSearch *search = skip_filter ? NULL : BLI_string_search_new();
+  StringSearch *search = skip_filter ? nullptr : BLI_string_search_new();
 
   /* build a temporary list of relevant items first */
   int item_index = 0;
@@ -522,18 +534,17 @@ void ui_rna_collection_search_update_fn(const struct bContext *C,
     const bool is_id = itemptr.type && RNA_struct_is_ID(itemptr.type);
 
     if (is_id) {
-      iconid = ui_id_icon_get(C, itemptr.data, false);
+      iconid = ui_id_icon_get(C, static_cast<ID *>(itemptr.data), false);
       if (!ELEM(iconid, 0, ICON_BLANK1)) {
         has_id_icon = true;
       }
 
       if (requires_exact_data_name) {
-        name = RNA_struct_name_get_alloc(&itemptr, name_buf, sizeof(name_buf), NULL);
+        name = RNA_struct_name_get_alloc(&itemptr, name_buf, sizeof(name_buf), nullptr);
       }
       else {
-        const ID *id = itemptr.data;
-        BKE_id_full_name_ui_prefix_get(
-            name_buf, itemptr.data, true, UI_SEP_CHAR, &name_prefix_offset);
+        const ID *id = static_cast<ID *>(itemptr.data);
+        BKE_id_full_name_ui_prefix_get(name_buf, id, true, UI_SEP_CHAR, &name_prefix_offset);
         BLI_STATIC_ASSERT(sizeof(name_buf) >= MAX_ID_FULL_NAME_UI,
                           "Name string buffer should be big enough to hold full UI ID name");
         name = name_buf;
@@ -541,11 +552,11 @@ void ui_rna_collection_search_update_fn(const struct bContext *C,
       }
     }
     else {
-      name = RNA_struct_name_get_alloc(&itemptr, name_buf, sizeof(name_buf), NULL);
+      name = RNA_struct_name_get_alloc(&itemptr, name_buf, sizeof(name_buf), nullptr);
     }
 
     if (name) {
-      CollItemSearch *cis = MEM_callocN(sizeof(CollItemSearch), "CollectionItemSearch");
+      CollItemSearch *cis = MEM_cnew<CollItemSearch>(__func__);
       cis->data = itemptr.data;
       cis->name = BLI_strdup(name);
       cis->index = item_index;
@@ -597,7 +608,7 @@ void ui_rna_collection_search_update_fn(const struct bContext *C,
 
 int UI_icon_from_id(const ID *id)
 {
-  if (id == NULL) {
+  if (id == nullptr) {
     return ICON_NONE;
   }
 
@@ -608,7 +619,7 @@ int UI_icon_from_id(const ID *id)
     if (ob->type == OB_EMPTY) {
       return ICON_EMPTY_DATA;
     }
-    return UI_icon_from_id(ob->data);
+    return UI_icon_from_id(static_cast<const ID *>(ob->data));
   }
 
   /* otherwise get it through RNA, creating the pointer
@@ -761,7 +772,7 @@ bool UI_but_online_manual_id(const uiBut *but, char *r_str, size_t maxlength)
   return false;
 }
 
-bool UI_but_online_manual_id_from_active(const struct bContext *C, char *r_str, size_t maxlength)
+bool UI_but_online_manual_id_from_active(const bContext *C, char *r_str, size_t maxlength)
 {
   uiBut *but = UI_context_active_but_get(C);
 
@@ -861,7 +872,7 @@ void UI_but_ensure_in_view(const bContext *C, ARegion *region, const uiBut *but)
  * Modal Button Store API.
  *
  * Store for modal operators & handlers to register button pointers
- * which are maintained while drawing or NULL when removed.
+ * which are maintained while drawing or nullptr when removed.
  *
  * This is needed since button pointers are continuously freed and re-allocated.
  *
@@ -880,7 +891,7 @@ struct uiButStoreElem {
 
 uiButStore *UI_butstore_create(uiBlock *block)
 {
-  uiButStore *bs_handle = MEM_callocN(sizeof(uiButStore), __func__);
+  uiButStore *bs_handle = MEM_cnew<uiButStore>(__func__);
 
   bs_handle->block = block;
   BLI_addtail(&block->butstore, bs_handle);
@@ -899,7 +910,7 @@ void UI_butstore_free(uiBlock *block, uiButStore *bs_handle)
    * Ideally we would manage moving the 'uiButStore', keeping a correct state.
    * All things considered this is the most straightforward fix - Campbell.
    */
-  if (block != bs_handle->block && bs_handle->block != NULL) {
+  if (block != bs_handle->block && bs_handle->block != nullptr) {
     block = bs_handle->block;
   }
 
@@ -912,7 +923,7 @@ void UI_butstore_free(uiBlock *block, uiButStore *bs_handle)
 
 bool UI_butstore_is_valid(uiButStore *bs)
 {
-  return (bs->block != NULL);
+  return (bs->block != nullptr);
 }
 
 bool UI_butstore_is_registered(uiBlock *block, uiBut *but)
@@ -930,7 +941,7 @@ bool UI_butstore_is_registered(uiBlock *block, uiBut *but)
 
 void UI_butstore_register(uiButStore *bs_handle, uiBut **but_p)
 {
-  uiButStoreElem *bs_elem = MEM_callocN(sizeof(uiButStoreElem), __func__);
+  uiButStoreElem *bs_elem = MEM_cnew<uiButStoreElem>(__func__);
   BLI_assert(*but_p);
   bs_elem->but_p = but_p;
 
@@ -968,9 +979,9 @@ bool UI_butstore_register_update(uiBlock *block, uiBut *but_dst, const uiBut *bu
 void UI_butstore_clear(uiBlock *block)
 {
   LISTBASE_FOREACH (uiButStore *, bs_handle, &block->butstore) {
-    bs_handle->block = NULL;
+    bs_handle->block = nullptr;
     LISTBASE_FOREACH (uiButStoreElem *, bs_elem, &bs_handle->items) {
-      *bs_elem->but_p = NULL;
+      *bs_elem->but_p = nullptr;
     }
   }
 }
@@ -984,14 +995,14 @@ void UI_butstore_update(uiBlock *block)
     }
   }
 
-  if (LIKELY(block->butstore.first == NULL)) {
+  if (LIKELY(block->butstore.first == nullptr)) {
     return;
   }
 
   /* warning, loop-in-loop, in practice we only store <10 buttons at a time,
    * so this isn't going to be a problem, if that changes old-new mapping can be cached first */
   LISTBASE_FOREACH (uiButStore *, bs_handle, &block->butstore) {
-    BLI_assert(ELEM(bs_handle->block, NULL, block) ||
+    BLI_assert(ELEM(bs_handle->block, nullptr, block) ||
                (block->oldblock && block->oldblock == bs_handle->block));
 
     if (bs_handle->block == block->oldblock) {
@@ -1001,7 +1012,7 @@ void UI_butstore_update(uiBlock *block)
         if (*bs_elem->but_p) {
           uiBut *but_new = ui_but_find_new(block, *bs_elem->but_p);
 
-          /* can be NULL if the buttons removed,
+          /* can be nullptr if the buttons removed,
            * NOTE: we could allow passing in a callback when buttons are removed
            * so the caller can cleanup */
           *bs_elem->but_p = but_new;