UI Code Quality: Use derived structs for search buttons and decorators

The current on-size-fits-all `uiBut` creates quite a mess, where it's
hard to reason about which members are free for use, under which
conditions they are used and how.
`uiBut` also has members that aren't used at times, violating the "don't
pay for what you don't use" principle.

To address this, we want to move to typed buttons, where `uiBut` is just
a base struct and each type extends it as needed. That structures data
better and type specific data is only available if it's actually used by
a button type.

Two trade-offs:
* Many casts to the derived type have to be done.
* Sometimes we change the button type after it's created. So I had to
  add logic to reallocate the button for use with the new, possibly
  derived struct. Ideally that wouldn't be needed, but for now that's
  what we have.

Part of T74432.

Differential Revision: https://developer.blender.org/D7610

Reviewed by: Brecht Van Lommel, Campbell Barton

1 files changed, 72 insertions, 44 deletions

diff --git a/source/blender/editors/interface/interface_layout.c b/source/blender/editors/interface/interface_layout.c
index 98408156f4b..888cacb64eb 100644
--- a/source/blender/editors/interface/interface_layout.c
+++ b/source/blender/editors/interface/interface_layout.c
@@ -2278,7 +2278,7 @@ void uiItemFullR(uiLayout *layout,
   /* property with separate label */
   else if (type == PROP_ENUM || type == PROP_STRING || type == PROP_POINTER) {
     but = ui_item_with_label(layout, block, name, icon, ptr, prop, index, 0, 0, w, h, flag);
-    ui_but_add_search(but, ptr, prop, NULL, NULL);
+    but = ui_but_add_search(but, ptr, prop, NULL, NULL);
 
     if (layout->redalert) {
       UI_but_flag_enable(but, UI_BUT_REDALERT);
@@ -2651,7 +2651,10 @@ static void ui_rna_collection_search_arg_free_fn(void *ptr)
   MEM_freeN(ptr);
 }
 
-void ui_but_add_search(
+/**
+ * \note May reallocate \a but, so the possibly new address is returned.
+ */
+uiBut *ui_but_add_search(
     uiBut *but, PointerRNA *ptr, PropertyRNA *prop, PointerRNA *searchptr, PropertyRNA *searchprop)
 {
   StructRNA *ptype;
@@ -2669,11 +2672,13 @@ void ui_but_add_search(
   /* turn button into search button */
   if (searchprop) {
     uiRNACollectionSearch *coll_search = MEM_mallocN(sizeof(*coll_search), __func__);
+    uiButSearch *search_but;
 
-    but->type = UI_BTYPE_SEARCH_MENU;
+    but = ui_but_change_type(but, UI_BTYPE_SEARCH_MENU);
+    search_but = (uiButSearch *)but;
+    search_but->rnasearchpoin = *searchptr;
+    search_but->rnasearchprop = searchprop;
     but->hardmax = MAX2(but->hardmax, 256.0f);
-    but->rnasearchpoin = *searchptr;
-    but->rnasearchprop = searchprop;
     but->drawflag |= UI_BUT_ICON_LEFT | UI_BUT_TEXT_LEFT;
     if (RNA_property_is_unlink(prop)) {
       but->flag |= UI_BUT_VALUE_CLEAR;
@@ -2707,6 +2712,8 @@ void ui_but_add_search(
      * so other code might have already set but->type to search menu... */
     but->flag |= UI_BUT_DISABLED;
   }
+
+  return but;
 }
 
 void uiItemPointerR_prop(uiLayout *layout,
@@ -2939,29 +2946,28 @@ void uiItemMContents(uiLayout *layout, const char *menuname)
 void uiItemDecoratorR_prop(uiLayout *layout, PointerRNA *ptr, PropertyRNA *prop, int index)
 {
   uiBlock *block = layout->root->block;
-  uiBut *but = NULL;
-
   uiLayout *col;
+
   UI_block_layout_set_current(block, layout);
   col = uiLayoutColumn(layout, false);
   col->space = 0;
   col->emboss = UI_EMBOSS_NONE;
 
   if (ELEM(NULL, ptr, prop) || !RNA_property_animateable(ptr, prop)) {
-    but = uiDefIconBut(block,
-                       UI_BTYPE_BUT,
-                       0,
-                       ICON_BLANK1,
-                       0,
-                       0,
-                       UI_UNIT_X,
-                       UI_UNIT_Y,
-                       NULL,
-                       0.0,
-                       0.0,
-                       0.0,
-                       0.0,
-                       "");
+    uiBut *but = uiDefIconBut(block,
+                              UI_BTYPE_DECORATOR,
+                              0,
+                              ICON_BLANK1,
+                              0,
+                              0,
+                              UI_UNIT_X,
+                              UI_UNIT_Y,
+                              NULL,
+                              0.0,
+                              0.0,
+                              0.0,
+                              0.0,
+                              "");
     but->flag |= UI_BUT_DISABLED;
     return;
   }
@@ -2971,27 +2977,28 @@ void uiItemDecoratorR_prop(uiLayout *layout, PointerRNA *ptr, PropertyRNA *prop,
 
   /* Loop for the array-case, but only do in case of an expanded array. */
   for (int i = 0; i < (is_expand ? RNA_property_array_length(ptr, prop) : 1); i++) {
-    but = uiDefIconBut(block,
-                       UI_BTYPE_BUT,
-                       0,
-                       ICON_DOT,
-                       0,
-                       0,
-                       UI_UNIT_X,
-                       UI_UNIT_Y,
-                       NULL,
-                       0.0,
-                       0.0,
-                       0.0,
-                       0.0,
-                       TIP_("Animate property"));
-    UI_but_func_set(but, ui_but_anim_decorate_cb, but, NULL);
-    but->flag |= UI_BUT_UNDO | UI_BUT_DRAG_LOCK;
+    uiButDecorator *decorator_but = (uiButDecorator *)uiDefIconBut(block,
+                                                                   UI_BTYPE_DECORATOR,
+                                                                   0,
+                                                                   ICON_DOT,
+                                                                   0,
+                                                                   0,
+                                                                   UI_UNIT_X,
+                                                                   UI_UNIT_Y,
+                                                                   NULL,
+                                                                   0.0,
+                                                                   0.0,
+                                                                   0.0,
+                                                                   0.0,
+                                                                   TIP_("Animate property"));
+
+    UI_but_func_set(&decorator_but->but, ui_but_anim_decorate_cb, decorator_but, NULL);
+    decorator_but->but.flag |= UI_BUT_UNDO | UI_BUT_DRAG_LOCK;
     /* Reusing RNA search members, setting actual RNA data has many side-effects. */
-    but->rnasearchpoin = *ptr;
-    but->rnasearchprop = prop;
+    decorator_but->rnapoin = *ptr;
+    decorator_but->rnaprop = prop;
     /* ui_def_but_rna() sets non-array buttons to have a RNA index of 0. */
-    but->custom_data = POINTER_FROM_INT((!is_array || is_expand) ? i : index);
+    decorator_but->rnaindex = (!is_array || is_expand) ? i : index;
   }
 }
 
@@ -4819,8 +4826,6 @@ void ui_layout_list_set_labels_active(uiLayout *layout)
 
 uiLayout *uiLayoutListBox(uiLayout *layout,
                           uiList *ui_list,
-                          PointerRNA *ptr,
-                          PropertyRNA *prop,
                           PointerRNA *actptr,
                           PropertyRNA *actprop)
 {
@@ -4829,8 +4834,6 @@ uiLayout *uiLayoutListBox(uiLayout *layout,
 
   but->custom_data = ui_list;
 
-  but->rnasearchpoin = *ptr;
-  but->rnasearchprop = prop;
   but->rnapoin = *actptr;
   but->rnaprop = actprop;
 
@@ -5407,6 +5410,7 @@ void ui_layout_add_but(uiLayout *layout, uiBut *but)
   else {
     BLI_addtail(&layout->items, bitem);
   }
+  but->layout = layout;
 
   if (layout->context) {
     but->context = layout->context;
@@ -5418,6 +5422,30 @@ void ui_layout_add_but(uiLayout *layout, uiBut *but)
   }
 }
 
+bool ui_layout_replace_but_ptr(uiLayout *layout, const void *old_but_ptr, uiBut *new_but)
+{
+  ListBase *child_list = layout->child_items_layout ? &layout->child_items_layout->items :
+                                                      &layout->items;
+
+  LISTBASE_FOREACH (uiItem *, item, child_list) {
+    if (item->type == ITEM_BUTTON) {
+      uiButtonItem *bitem = (uiButtonItem *)item;
+
+      if (bitem->but == old_but_ptr) {
+        bitem->but = new_but;
+        return true;
+      }
+    }
+    else {
+      if (ui_layout_replace_but_ptr((uiLayout *)item, old_but_ptr, new_but)) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
 void uiLayoutSetFixedSize(uiLayout *layout, bool fixed_size)
 {
   if (fixed_size) {