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, 23 insertions, 17 deletions

diff --git a/source/blender/editors/interface/interface_anim.c b/source/blender/editors/interface/interface_anim.c
index 8d12a1dd1ad..cc58082cb02 100644
--- a/source/blender/editors/interface/interface_anim.c
+++ b/source/blender/editors/interface/interface_anim.c
@@ -120,35 +120,41 @@ void ui_but_anim_flag(uiBut *but, const AnimationEvalContext *anim_eval_context)
   }
 }
 
-static uiBut *ui_but_anim_decorate_find_attached_button(uiBut *but_decorate)
+static uiBut *ui_but_anim_decorate_find_attached_button(uiButDecorator *but_decorate)
 {
   uiBut *but_iter = NULL;
 
-  BLI_assert(UI_but_is_decorator(but_decorate));
-  BLI_assert(but_decorate->rnasearchpoin.data && but_decorate->rnasearchprop);
+  BLI_assert(UI_but_is_decorator(&but_decorate->but));
+  BLI_assert(but_decorate->rnapoin.data && but_decorate->rnaprop);
 
-  LISTBASE_CIRCULAR_BACKWARD_BEGIN (&but_decorate->block->buttons, but_iter, but_decorate->prev) {
-    if (but_iter != but_decorate &&
-        ui_but_rna_equals_ex(but_iter,
-                             &but_decorate->rnasearchpoin,
-                             but_decorate->rnasearchprop,
-                             POINTER_AS_INT(but_decorate->custom_data))) {
+  LISTBASE_CIRCULAR_BACKWARD_BEGIN (
+      &but_decorate->but.block->buttons, but_iter, but_decorate->but.prev) {
+    if (but_iter != (uiBut *)but_decorate &&
+        ui_but_rna_equals_ex(
+            but_iter, &but_decorate->rnapoin, but_decorate->rnaprop, but_decorate->rnaindex)) {
       return but_iter;
     }
   }
-  LISTBASE_CIRCULAR_BACKWARD_END(&but_decorate->block->buttons, but_iter, but_decorate->prev);
+  LISTBASE_CIRCULAR_BACKWARD_END(
+      &but_decorate->but.block->buttons, but_iter, but_decorate->but.prev);
 
   return NULL;
 }
 
-void ui_but_anim_decorate_update_from_flag(uiBut *but)
+void ui_but_anim_decorate_update_from_flag(uiButDecorator *decorator_but)
 {
-  const uiBut *but_anim = ui_but_anim_decorate_find_attached_button(but);
+  if (!decorator_but->rnapoin.data || !decorator_but->rnaprop) {
+    /* Nothing to do. */
+    return;
+  }
+
+  const uiBut *but_anim = ui_but_anim_decorate_find_attached_button(decorator_but);
+  uiBut *but = &decorator_but->but;
 
   if (!but_anim) {
     printf("Could not find button with matching property to decorate (%s.%s)\n",
-           RNA_struct_identifier(but->rnasearchpoin.type),
-           RNA_property_identifier(but->rnasearchprop));
+           RNA_struct_identifier(decorator_but->rnapoin.type),
+           RNA_property_identifier(decorator_but->rnaprop));
     return;
   }
 
@@ -325,7 +331,7 @@ void ui_but_anim_paste_driver(bContext *C)
 void ui_but_anim_decorate_cb(bContext *C, void *arg_but, void *UNUSED(arg_dummy))
 {
   wmWindowManager *wm = CTX_wm_manager(C);
-  uiBut *but_decorate = arg_but;
+  uiButDecorator *but_decorate = arg_but;
   uiBut *but_anim = ui_but_anim_decorate_find_attached_button(but_decorate);
 
   if (!but_anim) {
@@ -333,7 +339,7 @@ void ui_but_anim_decorate_cb(bContext *C, void *arg_but, void *UNUSED(arg_dummy)
   }
 
   /* FIXME(campbell), swapping active pointer is weak. */
-  SWAP(struct uiHandleButtonData *, but_anim->active, but_decorate->active);
+  SWAP(struct uiHandleButtonData *, but_anim->active, but_decorate->but.active);
   wm->op_undo_depth++;
 
   if (but_anim->flag & UI_BUT_DRIVEN) {
@@ -357,6 +363,6 @@ void ui_but_anim_decorate_cb(bContext *C, void *arg_but, void *UNUSED(arg_dummy)
     WM_operator_properties_free(&props_ptr);
   }
 
-  SWAP(struct uiHandleButtonData *, but_anim->active, but_decorate->active);
+  SWAP(struct uiHandleButtonData *, but_anim->active, but_decorate->but.active);
   wm->op_undo_depth--;
 }