UI: ignore events in empty region overlap areas

- Resizable areas use 2D view bounds.
- Header uses the button bounds.
- A margin is added to avoid clicking between buttons.
- Region resize edges clamp to the 2D view bounds.

Resovles T61554

4 files changed, 115 insertions, 15 deletions

diff --git a/source/blender/editors/interface/interface_handlers.c b/source/blender/editors/interface/interface_handlers.c
index 8125a42d3be..608ef69c4cc 100644
--- a/source/blender/editors/interface/interface_handlers.c
+++ b/source/blender/editors/interface/interface_handlers.c
@@ -7692,6 +7692,11 @@ uiBut *UI_region_active_but_get(ARegion *ar)
   return ui_context_button_active(ar, NULL);
 }
 
+uiBut *UI_region_but_find_rect_over(const ARegion *ar, const rcti *rect_px)
+{
+  return ui_but_find_rect_over(ar, rect_px);
+}
+
 /**
  * Version of #UI_context_active_but_get that also returns RNA property info.
  * Helper function for insert keyframe, reset to default, etc operators.
diff --git a/source/blender/editors/interface/interface_intern.h b/source/blender/editors/interface/interface_intern.h
index d6f18b4cd87..4af7fdd779f 100644
--- a/source/blender/editors/interface/interface_intern.h
+++ b/source/blender/editors/interface/interface_intern.h
@@ -903,6 +903,7 @@ void ui_but_pie_dir(RadialDirection dir, float vec[2]);
 bool ui_but_is_cursor_warp(const uiBut *but) ATTR_WARN_UNUSED_RESULT;
 
 bool ui_but_contains_pt(const uiBut *but, float mx, float my) ATTR_WARN_UNUSED_RESULT;
+bool ui_but_contains_rect(const uiBut *but, const rctf *rect);
 bool ui_but_contains_point_px_icon(const uiBut *but,
                                    struct ARegion *ar,
                                    const struct wmEvent *event) ATTR_WARN_UNUSED_RESULT;
@@ -918,6 +919,8 @@ uiBut *ui_but_find_mouse_over_ex(struct ARegion *ar,
                                  const bool labeledit) ATTR_WARN_UNUSED_RESULT;
 uiBut *ui_but_find_mouse_over(struct ARegion *ar,
                               const struct wmEvent *event) ATTR_WARN_UNUSED_RESULT;
+uiBut *ui_but_find_rect_over(const struct ARegion *ar,
+                             const rcti *rect_px) ATTR_WARN_UNUSED_RESULT;
 
 uiBut *ui_list_find_mouse_over_ex(struct ARegion *ar, int x, int y) ATTR_WARN_UNUSED_RESULT;
 
@@ -936,6 +939,7 @@ bool ui_block_is_popup_any(const uiBlock *block) ATTR_WARN_UNUSED_RESULT;
 uiBut *ui_region_find_first_but_test_flag(struct ARegion *ar, int flag_include, int flag_exclude);
 uiBut *ui_region_find_active_but(struct ARegion *ar) ATTR_WARN_UNUSED_RESULT;
 bool ui_region_contains_point_px(const struct ARegion *ar, int x, int y) ATTR_WARN_UNUSED_RESULT;
+bool ui_region_contains_rect_px(const struct ARegion *ar, const rcti *rect_px);
 
 /* interface_context_menu.c */
 bool ui_popup_context_menu_for_button(struct bContext *C, uiBut *but);
diff --git a/source/blender/editors/interface/interface_query.c b/source/blender/editors/interface/interface_query.c
index 9129bbddf69..db60e967d6d 100644
--- a/source/blender/editors/interface/interface_query.c
+++ b/source/blender/editors/interface/interface_query.c
@@ -201,6 +201,11 @@ bool ui_but_contains_pt(const uiBut *but, float mx, float my)
   return BLI_rctf_isect_pt(&but->rect, mx, my);
 }
 
+bool ui_but_contains_rect(const uiBut *but, const rctf *rect)
+{
+  return BLI_rctf_isect(&but->rect, rect, NULL);
+}
+
 bool ui_but_contains_point_px(const uiBut *but, const ARegion *ar, int x, int y)
 {
   uiBlock *block = but->block;
@@ -301,6 +306,44 @@ uiBut *ui_but_find_mouse_over(ARegion *ar, const wmEvent *event)
   return ui_but_find_mouse_over_ex(ar, event->x, event->y, event->ctrl != 0);
 }
 
+uiBut *ui_but_find_rect_over(const struct ARegion *ar, const rcti *rect_px)
+{
+  if (!ui_region_contains_rect_px(ar, rect_px)) {
+    return NULL;
+  }
+
+  /* Currently no need to expose this at the moment. */
+  bool labeledit = true;
+  rctf rect_px_fl;
+  BLI_rctf_rcti_copy(&rect_px_fl, rect_px);
+  uiBut *butover = NULL;
+
+  for (uiBlock *block = ar->uiblocks.first; block; block = block->next) {
+    rctf rect_block;
+    ui_window_to_block_rctf(ar, block, &rect_block, &rect_px_fl);
+
+    for (uiBut *but = block->buttons.last; but; but = but->prev) {
+      if (ui_but_is_interactive(but, labeledit)) {
+        /* No pie menu support. */
+        BLI_assert(but->pie_dir == UI_RADIAL_NONE);
+        if (ui_but_contains_rect(but, &rect_block)) {
+          butover = but;
+          break;
+        }
+      }
+    }
+
+    /* 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)) {
+        break;
+      }
+    }
+  }
+  return butover;
+}
+
 uiBut *ui_list_find_mouse_over_ex(ARegion *ar, int x, int y)
 {
   uiBlock *block;
@@ -485,17 +528,13 @@ uiBut *ui_region_find_first_but_test_flag(ARegion *ar, int flag_include, int fla
 /** \} */
 
 /* -------------------------------------------------------------------- */
-/** \name Region (#ARegion) State
+/** \name Region (#ARegion) Spatial
  * \{ */
 
 bool ui_region_contains_point_px(const ARegion *ar, int x, int y)
 {
   rcti winrct;
-
-  /* scale down area rect to exclude shadow */
   ui_region_winrct_get_no_margin(ar, &winrct);
-
-  /* check if the mouse is in the region */
   if (!BLI_rcti_isect_pt(&winrct, x, y)) {
     return false;
   }
@@ -507,14 +546,9 @@ bool ui_region_contains_point_px(const ARegion *ar, int x, int y)
    */
   if (ar->v2d.mask.xmin != ar->v2d.mask.xmax) {
     const View2D *v2d = &ar->v2d;
-    int mx, my;
+    int mx = x, my = y;
 
-    /* convert window coordinates to region coordinates */
-    mx = x;
-    my = y;
     ui_window_to_region(ar, &mx, &my);
-
-    /* check if in the rect */
     if (!BLI_rcti_isect_pt(&v2d->mask, mx, my) ||
         UI_view2d_mouse_in_scrollers(ar, &ar->v2d, x, y)) {
       return false;
@@ -524,4 +558,26 @@ bool ui_region_contains_point_px(const ARegion *ar, int x, int y)
   return true;
 }
 
+bool ui_region_contains_rect_px(const ARegion *ar, const rcti *rect_px)
+{
+  rcti winrct;
+  ui_region_winrct_get_no_margin(ar, &winrct);
+  if (!BLI_rcti_isect(&winrct, rect_px, NULL)) {
+    return false;
+  }
+
+  /* See comment in 'ui_region_contains_point_px' */
+  if (ar->v2d.mask.xmin != ar->v2d.mask.xmax) {
+    const View2D *v2d = &ar->v2d;
+    rcti rect_region;
+    ui_window_to_region_rcti(ar, &rect_region, rect_px);
+    if (!BLI_rcti_isect(&v2d->mask, &rect_region, NULL) ||
+        UI_view2d_rect_in_scrollers(ar, &ar->v2d, rect_px)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
 /** \} */
diff --git a/source/blender/editors/interface/view2d.c b/source/blender/editors/interface/view2d.c
index 4e53e59d7c0..096ea230bbe 100644
--- a/source/blender/editors/interface/view2d.c
+++ b/source/blender/editors/interface/view2d.c
@@ -2626,13 +2626,14 @@ void UI_view2d_offset(struct View2D *v2d, float xfac, float yfac)
 char UI_view2d_mouse_in_scrollers_ex(
     const ARegion *ar, const View2D *v2d, int x, int y, int *r_scroll)
 {
-  int co[2];
-  int scroll = view2d_scroll_mapped(v2d->scroll);
+  const int scroll = view2d_scroll_mapped(v2d->scroll);
   *r_scroll = scroll;
 
   /* clamp x,y to region-coordinates first */
-  co[0] = x - ar->winrct.xmin;
-  co[1] = y - ar->winrct.ymin;
+  const int co[2] = {
+      x - ar->winrct.xmin,
+      y - ar->winrct.ymin,
+  };
 
   /* check if within scrollbars */
   if (scroll & V2D_SCROLL_HORIZONTAL) {
@@ -2650,12 +2651,46 @@ char UI_view2d_mouse_in_scrollers_ex(
   return 0;
 }
 
+char UI_view2d_rect_in_scrollers_ex(const ARegion *ar,
+                                    const View2D *v2d,
+                                    const rcti *rect,
+                                    int *r_scroll)
+{
+  const int scroll = view2d_scroll_mapped(v2d->scroll);
+  *r_scroll = scroll;
+
+  /* clamp x,y to region-coordinates first */
+  rcti rect_region = *rect;
+  BLI_rcti_translate(&rect_region, -ar->winrct.xmin, ar->winrct.ymin);
+
+  /* check if within scrollbars */
+  if (scroll & V2D_SCROLL_HORIZONTAL) {
+    if (IN_2D_HORIZ_SCROLL_RECT(v2d, &rect_region)) {
+      return 'h';
+    }
+  }
+  if (scroll & V2D_SCROLL_VERTICAL) {
+    if (IN_2D_VERT_SCROLL_RECT(v2d, &rect_region)) {
+      return 'v';
+    }
+  }
+
+  /* not found */
+  return 0;
+}
+
 char UI_view2d_mouse_in_scrollers(const ARegion *ar, const View2D *v2d, int x, int y)
 {
   int scroll_dummy = 0;
   return UI_view2d_mouse_in_scrollers_ex(ar, v2d, x, y, &scroll_dummy);
 }
 
+char UI_view2d_rect_in_scrollers(const ARegion *ar, const View2D *v2d, const rcti *rect)
+{
+  int scroll_dummy = 0;
+  return UI_view2d_rect_in_scrollers_ex(ar, v2d, rect, &scroll_dummy);
+}
+
 /* ******************* view2d text drawing cache ******************** */
 
 typedef struct View2DString {