UI: Make uiBut safe for non-trivial construction

No user-visible changes expected.

Essentially, this makes it possible to use C++ types like `std::function`
inside `uiBut`. This has plenty of benefits, for example this should help
significantly reducing unsafe `void *` use (since a `std::function` can hold
arbitrary data while preserving types).

----

I wanted to use a non-trivially-constructible C++ type (`std::function`) inside
`uiBut`. But this would mean we can't use `MEM_cnew()` like allocation anymore.

Rather than writing worse code, allow non-trivial construction for `uiBut`.
Member-initializing all members is annoying since there are so many, but rather
safe than sorry. As we use more C++ types (e.g. convert callbacks to use
`std::function`), this should become less since they initialize properly on
default construction.

Also use proper C++ inheritance for `uiBut` subtypes, the old way to allocate
based on size isn't working anymore.

Differential Revision: https://developer.blender.org/D17164

Reviewed by: Hans Goudey

source/blender/editors/include/UI_interface.h

@@ -322,6 +322,8 @@ enum {
  * - bit  9-15: button type (now 6 bits, 64 types)
  */
 typedef enum {
+  UI_BUT_POIN_NONE = 0,
+
   UI_BUT_POIN_CHAR = 32,
   UI_BUT_POIN_SHORT = 64,
   UI_BUT_POIN_INT = 96,

source/blender/editors/interface/interface.cc

@@ -3474,7 +3474,7 @@ static void ui_but_free(const bContext *C, uiBut *but)
 
   BLI_assert(UI_butstore_is_registered(but->block, but) == false);
 
-  MEM_freeN(but);
+  MEM_delete(but);
 }
 
 void UI_block_free(const bContext *C, uiBlock *block)
@@ -3975,89 +3975,57 @@ void ui_block_cm_to_display_space_v3(uiBlock *block, float pixel[3])
   IMB_colormanagement_scene_linear_to_display_v3(pixel, display);
 }
 
-static void ui_but_alloc_info(const eButType type,
+/**
-                              size_t *r_alloc_size,
+ * Factory function: Allocate button and set #uiBut.type.
-                              const char **r_alloc_str,
+ */
-                              bool *r_has_custom_type)
+static uiBut *ui_but_new(const eButType type)
 {
-  size_t alloc_size;
+  uiBut *but = nullptr;
-  const char *alloc_str;
-  bool has_custom_type = true;
 
   switch (type) {
     case UI_BTYPE_NUM:
-      alloc_size = sizeof(uiButNumber);
+      but = MEM_new<uiButNumber>("uiButNumber");
-      alloc_str = "uiButNumber";
       break;
     case UI_BTYPE_COLOR:
-      alloc_size = sizeof(uiButColor);
+      but = MEM_new<uiButColor>("uiButColor");
-      alloc_str = "uiButColor";
       break;
     case UI_BTYPE_DECORATOR:
-      alloc_size = sizeof(uiButDecorator);
+      but = MEM_new<uiButDecorator>("uiButDecorator");
-      alloc_str = "uiButDecorator";
       break;
     case UI_BTYPE_TAB:
-      alloc_size = sizeof(uiButTab);
+      but = MEM_new<uiButTab>("uiButTab");
-      alloc_str = "uiButTab";
       break;
     case UI_BTYPE_SEARCH_MENU:
-      alloc_size = sizeof(uiButSearch);
+      but = MEM_new<uiButSearch>("uiButSearch");
-      alloc_str = "uiButSearch";
       break;
     case UI_BTYPE_PROGRESS_BAR:
-      alloc_size = sizeof(uiButProgressbar);
+      but = MEM_new<uiButProgressbar>("uiButProgressbar");
-      alloc_str = "uiButProgressbar";
       break;
     case UI_BTYPE_HSVCUBE:
-      alloc_size = sizeof(uiButHSVCube);
+      but = MEM_new<uiButHSVCube>("uiButHSVCube");
-      alloc_str = "uiButHSVCube";
       break;
     case UI_BTYPE_COLORBAND:
-      alloc_size = sizeof(uiButColorBand);
+      but = MEM_new<uiButColorBand>("uiButColorBand");
-      alloc_str = "uiButColorBand";
       break;
     case UI_BTYPE_CURVE:
-      alloc_size = sizeof(uiButCurveMapping);
+      but = MEM_new<uiButCurveMapping>("uiButCurveMapping");
-      alloc_str = "uiButCurveMapping";
       break;
     case UI_BTYPE_CURVEPROFILE:
-      alloc_size = sizeof(uiButCurveProfile);
+      but = MEM_new<uiButCurveProfile>("uiButCurveProfile");
-      alloc_str = "uiButCurveProfile";
       break;
     case UI_BTYPE_HOTKEY_EVENT:
-      alloc_size = sizeof(uiButHotkeyEvent);
+      but = MEM_new<uiButHotkeyEvent>("uiButHotkeyEvent");
-      alloc_str = "uiButHotkeyEvent";
       break;
     case UI_BTYPE_VIEW_ITEM:
-      alloc_size = sizeof(uiButViewItem);
+      but = MEM_new<uiButViewItem>("uiButViewItem");
-      alloc_str = "uiButViewItem";
       break;
     default:
-      alloc_size = sizeof(uiBut);
+      but = MEM_new<uiBut>("uiBut");
-      alloc_str = "uiBut";
-      has_custom_type = false;
       break;
   }
 
-  if (r_alloc_size) {
+  but->type = type;
-    *r_alloc_size = alloc_size;
+  return but;
-  }
-  if (r_alloc_str) {
-    *r_alloc_str = alloc_str;
-  }
-  if (r_has_custom_type) {
-    *r_has_custom_type = has_custom_type;
-  }
-}
-
-static uiBut *ui_but_alloc(const eButType type)
-{
-  size_t alloc_size;
-  const char *alloc_str;
-  ui_but_alloc_info(type, &alloc_size, &alloc_str, nullptr);
-
-  return static_cast<uiBut *>(MEM_callocN(alloc_size, alloc_str));
 }
 
 uiBut *ui_but_change_type(uiBut *but, eButType new_type)
@@ -4067,25 +4035,19 @@ uiBut *ui_but_change_type(uiBut *but, eButType new_type)
     return but;
   }
 
-  size_t alloc_size;
-  const char *alloc_str;
   uiBut *insert_after_but = but->prev;
-  bool new_has_custom_type, old_has_custom_type;
 
   /* Remove old button address */
   BLI_remlink(&but->block->buttons, but);
 
-  ui_but_alloc_info(but->type, nullptr, nullptr, &old_has_custom_type);
-  ui_but_alloc_info(new_type, &alloc_size, &alloc_str, &new_has_custom_type);
-
-  if (new_has_custom_type || old_has_custom_type) {
   const uiBut *old_but_ptr = but;
   /* Button may have pointer to a member within itself, this will have to be updated. */
   const bool has_str_ptr_to_self = but->str == but->strdata;
   const bool has_poin_ptr_to_self = but->poin == (char *)but;
 
-    but = static_cast<uiBut *>(MEM_recallocN_id(but, alloc_size, alloc_str));
+  /* Copy construct button with the new type. */
-    but->type = new_type;
+  but = ui_but_new(new_type);
+  *but = *old_but_ptr;
   if (has_str_ptr_to_self) {
     but->str = but->strdata;
   }
@@ -4106,7 +4068,8 @@ uiBut *ui_but_change_type(uiBut *but, eButType new_type)
     UI_editsource_but_replace(old_but_ptr, but);
   }
 #endif
-  }
+
+  MEM_delete(old_but_ptr);
 
   return but;
 }
@@ -4152,14 +4115,11 @@ static uiBut *ui_def_but(uiBlock *block,
     }
   }
 
-  uiBut *but = ui_but_alloc((eButType)(type & BUTTYPE));
+  uiBut *but = ui_but_new((eButType)(type & BUTTYPE));
 
-  but->type = (eButType)(type & BUTTYPE);
   but->pointype = (eButPointerType)(type & UI_BUT_POIN_TYPES);
   but->bit = type & UI_BUT_POIN_BIT;
   but->bitnr = type & 31;
-  but->icon = ICON_NONE;
-  but->iconadd = 0;
 
   but->retval = retval;
 
@@ -4180,7 +4140,6 @@ static uiBut *ui_def_but(uiBlock *block,
 
   but->disabled_info = block->lockstr;
   but->emboss = block->emboss;
-  but->pie_dir = UI_RADIAL_NONE;
 
   but->block = block; /* pointer back, used for front-buffer status, and picker. */
 
@@ -6310,7 +6269,7 @@ void UI_but_func_search_set(uiBut *but,
 
   if (search_exec_fn) {
 #ifdef DEBUG
-    if (search_but->but.func) {
+    if (but->func) {
       /* watch this, can be cause of much confusion, see: T47691 */
       printf("%s: warning, overwriting button callback with search function callback!\n",
              __func__);

source/blender/editors/interface/interface_anim.cc

@@ -113,41 +113,38 @@ void ui_but_anim_flag(uiBut *but, const AnimationEvalContext *anim_eval_context)
   }
 }
 
-static uiBut *ui_but_anim_decorate_find_attached_button(uiButDecorator *but_decorate)
+static uiBut *ui_but_anim_decorate_find_attached_button(uiButDecorator *but)
 {
   uiBut *but_iter = nullptr;
 
-  BLI_assert(UI_but_is_decorator(&but_decorate->but));
+  BLI_assert(UI_but_is_decorator(but));
-  BLI_assert(but_decorate->rnapoin.data && but_decorate->rnaprop);
+  BLI_assert(but->decorated_rnapoin.data && but->decorated_rnaprop);
 
-  LISTBASE_CIRCULAR_BACKWARD_BEGIN (
+  LISTBASE_CIRCULAR_BACKWARD_BEGIN (uiBut *, &but->block->buttons, but_iter, but->prev) {
-      uiBut *, &but_decorate->but.block->buttons, but_iter, but_decorate->but.prev) {
+    if (but_iter != but &&
-    if (but_iter != (uiBut *)but_decorate &&
         ui_but_rna_equals_ex(
-            but_iter, &but_decorate->rnapoin, but_decorate->rnaprop, but_decorate->rnaindex)) {
+            but_iter, &but->decorated_rnapoin, but->decorated_rnaprop, but->decorated_rnaindex)) {
       return but_iter;
     }
   }
-  LISTBASE_CIRCULAR_BACKWARD_END(
+  LISTBASE_CIRCULAR_BACKWARD_END(uiBut *, &but->block->buttons, but_iter, but->prev);
-      uiBut *, &but_decorate->but.block->buttons, but_iter, but_decorate->but.prev);
 
   return nullptr;
 }
 
-void ui_but_anim_decorate_update_from_flag(uiButDecorator *decorator_but)
+void ui_but_anim_decorate_update_from_flag(uiButDecorator *but)
 {
-  if (!decorator_but->rnapoin.data || !decorator_but->rnaprop) {
+  if (!but->decorated_rnapoin.data || !but->decorated_rnaprop) {
     /* Nothing to do. */
     return;
   }
 
-  const uiBut *but_anim = ui_but_anim_decorate_find_attached_button(decorator_but);
+  const uiBut *but_anim = ui_but_anim_decorate_find_attached_button(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(decorator_but->rnapoin.type),
+           RNA_struct_identifier(but->decorated_rnapoin.type),
-           RNA_property_identifier(decorator_but->rnaprop));
+           RNA_property_identifier(but->decorated_rnaprop));
     return;
   }
 
@@ -326,7 +323,7 @@ void ui_but_anim_decorate_cb(bContext *C, void *arg_but, void * /*arg_dummy*/)
   }
 
   /* FIXME(@campbellbarton): swapping active pointer is weak. */
-  std::swap(but_anim->active, but_decorate->but.active);
+  std::swap(but_anim->active, but_decorate->active);
   wm->op_undo_depth++;
 
   if (but_anim->flag & UI_BUT_DRIVEN) {
@@ -350,6 +347,6 @@ void ui_but_anim_decorate_cb(bContext *C, void *arg_but, void * /*arg_dummy*/)
     WM_operator_properties_free(&props_ptr);
   }
 
-  std::swap(but_anim->active, but_decorate->but.active);
+  std::swap(but_anim->active, but_decorate->active);
   wm->op_undo_depth--;
 }

source/blender/editors/interface/interface_context_menu.cc

@@ -934,7 +934,7 @@ bool ui_popup_context_menu_for_button(bContext *C, uiBut *but, const wmEvent *ev
     uiButViewItem *view_item_but = (uiButViewItem *)ui_view_item_find_mouse_over(region,
                                                                                  event->xy);
     if (view_item_but) {
-      BLI_assert(view_item_but->but.type == UI_BTYPE_VIEW_ITEM);
+      BLI_assert(view_item_but->type == UI_BTYPE_VIEW_ITEM);
       UI_view_item_context_menu_build(C, view_item_but->view_item, uiLayoutColumn(layout, false));
       uiItemS(layout);
     }

source/blender/editors/interface/interface_handlers.cc

@@ -4752,7 +4752,7 @@ static int ui_do_but_VIEW_ITEM(bContext *C,
                                const wmEvent *event)
 {
   uiButViewItem *view_item_but = (uiButViewItem *)but;
-  BLI_assert(view_item_but->but.type == UI_BTYPE_VIEW_ITEM);
+  BLI_assert(view_item_but->type == UI_BTYPE_VIEW_ITEM);
 
   if (data->state == BUTTON_STATE_HIGHLIGHT) {
     if (event->type == LEFTMOUSE) {
@@ -4961,14 +4961,13 @@ static float ui_numedit_apply_snap(int temp,
   return temp;
 }
 
-static bool ui_numedit_but_NUM(uiButNumber *number_but,
+static bool ui_numedit_but_NUM(uiButNumber *but,
                                uiHandleButtonData *data,
                                int mx,
                                const bool is_motion,
                                const enum eSnapType snap,
                                float fac)
 {
-  uiBut *but = &number_but->but;
   float deler, tempf;
   int lvalue, temp;
   bool changed = false;
@@ -4990,13 +4989,13 @@ static bool ui_numedit_but_NUM(uiButNumber *number_but,
 
     const float log_min = (scale_type == PROP_SCALE_LOG) ?
                               max_ff(max_ff(softmin, UI_PROP_SCALE_LOG_MIN),
-                                     powf(10, -number_but->precision) * 0.5f) :
+                                     powf(10, -but->precision) * 0.5f) :
                               0;
 
     /* Mouse location isn't screen clamped to the screen so use a linear mapping
      * 2px == 1-int, or 1px == 1-ClickStep */
     if (is_float) {
-      fac *= 0.01f * number_but->step_size;
+      fac *= 0.01f * but->step_size;
       switch (scale_type) {
         case PROP_SCALE_LINEAR: {
           tempf = float(data->startvalue) + float(mx - data->dragstartx) * fac;
@@ -5170,7 +5169,7 @@ static bool ui_numedit_but_NUM(uiButNumber *number_but,
       }
       case PROP_SCALE_LOG: {
         const float log_min = max_ff(max_ff(softmin, UI_PROP_SCALE_LOG_MIN),
-                                     powf(10.0f, -number_but->precision) * 0.5f);
+                                     powf(10.0f, -but->precision) * 0.5f);
         const float base = softmax / log_min;
         tempf = powf(base, data->dragf) * log_min;
         if (tempf <= log_min) {
@@ -6148,8 +6147,8 @@ static bool ui_numedit_but_UNITVEC(
 static void ui_palette_set_active(uiButColor *color_but)
 {
   if (color_but->is_pallete_color) {
-    Palette *palette = (Palette *)color_but->but.rnapoin.owner_id;
+    Palette *palette = (Palette *)color_but->rnapoin.owner_id;
-    PaletteColor *color = static_cast<PaletteColor *>(color_but->but.rnapoin.data);
+    PaletteColor *color = static_cast<PaletteColor *>(color_but->rnapoin.data);
     palette->active_color = BLI_findindex(&palette->colors, color);
   }
 }

source/blender/editors/interface/interface_intern.hh

@@ -152,24 +152,25 @@ enum {
 #define PIE_MAX_ITEMS 8
 
 struct uiBut {
-  uiBut *next, *prev;
+  uiBut *next = nullptr, *prev = nullptr;
 
   /** Pointer back to the layout item holding this button. */
-  uiLayout *layout;
+  uiLayout *layout = nullptr;
-  int flag, drawflag;
+  int flag = 0;
-  eButType type;
+  int drawflag = 0;
-  eButPointerType pointype;
+  eButType type = eButType(0);
-  short bit, bitnr, retval, strwidth, alignnr;
+  eButPointerType pointype = UI_BUT_POIN_NONE;
-  short ofs, pos, selsta, selend;
+  short bit = 0, bitnr = 0, retval = 0, strwidth = 0, alignnr = 0;
+  short ofs = 0, pos = 0, selsta = 0, selend = 0;
 
-  char *str;
+  char *str = nullptr;
-  char strdata[UI_MAX_NAME_STR];
+  char strdata[UI_MAX_NAME_STR] = "";
-  char drawstr[UI_MAX_DRAW_STR];
+  char drawstr[UI_MAX_DRAW_STR] = "";
 
-  rctf rect; /* block relative coords */
+  rctf rect = {}; /* block relative coords */
 
-  char *poin;
+  char *poin = nullptr;
-  float hardmin, hardmax, softmin, softmax;
+  float hardmin = 0, hardmax = 0, softmin = 0, softmax = 0;
 
   /* both these values use depends on the button type
    * (polymorphic struct or union would be nicer for this stuff) */
@@ -180,7 +181,7 @@ struct uiBut {
    * - UI_BTYPE_SCROLL:       Use as scroll size.
    * - UI_BTYPE_SEARCH_MENU:  Use as number or rows.
    */
-  float a1;
+  float a1 = 0;
 
   /**
    * For #uiBut.type:
@@ -188,210 +189,195 @@ struct uiBut {
    * - UI_BTYPE_LABEL:        If `(a1 == 1.0f)` use a2 as a blending factor.
    * - UI_BTYPE_SEARCH_MENU:  Use as number or columns.
    */
-  float a2;
+  float a2 = 0;
 
-  uchar col[4];
+  uchar col[4] = {0};
 
   /** See \ref UI_but_func_identity_compare_set(). */
-  uiButIdentityCompareFunc identity_cmp_func;
+  uiButIdentityCompareFunc identity_cmp_func = nullptr;
 
-  uiButHandleFunc func;
+  uiButHandleFunc func = nullptr;
-  void *func_arg1;
+  void *func_arg1 = nullptr;
-  void *func_arg2;
+  void *func_arg2 = nullptr;
 
-  uiButHandleNFunc funcN;
+  uiButHandleNFunc funcN = nullptr;
-  void *func_argN;
+  void *func_argN = nullptr;
 
-  bContextStore *context;
+  bContextStore *context = nullptr;
 
-  uiButCompleteFunc autocomplete_func;
+  uiButCompleteFunc autocomplete_func = nullptr;
-  void *autofunc_arg;
+  void *autofunc_arg = nullptr;
 
-  uiButHandleRenameFunc rename_func;
+  uiButHandleRenameFunc rename_func = nullptr;
-  void *rename_arg1;
+  void *rename_arg1 = nullptr;
-  void *rename_orig;
+  void *rename_orig = nullptr;
 
   /** Run an action when holding the button down. */
-  uiButHandleHoldFunc hold_func;
+  uiButHandleHoldFunc hold_func = nullptr;
-  void *hold_argN;
+  void *hold_argN = nullptr;
 
-  const char *tip;
+  const char *tip = nullptr;
-  uiButToolTipFunc tip_func;
+  uiButToolTipFunc tip_func = nullptr;
-  void *tip_arg;
+  void *tip_arg = nullptr;
-  uiFreeArgFunc tip_arg_free;
+  uiFreeArgFunc tip_arg_free = nullptr;
 
   /** info on why button is disabled, displayed in tooltip */
-  const char *disabled_info;
+  const char *disabled_info = nullptr;
 
-  BIFIconID icon;
+  BIFIconID icon = ICON_NONE;
   /** Copied from the #uiBlock.emboss */
-  eUIEmbossType emboss;
+  eUIEmbossType emboss = UI_EMBOSS;
   /** direction in a pie menu, used for collision detection. */
-  RadialDirection pie_dir;
+  RadialDirection pie_dir = UI_RADIAL_NONE;
   /** could be made into a single flag */
-  bool changed;
+  bool changed = false;
   /** so buttons can support unit systems which are not RNA */
-  uchar unit_type;
+  uchar unit_type = 0;
-  short iconadd;
+  short iconadd = 0;
 
   /** #UI_BTYPE_BLOCK data */
-  uiBlockCreateFunc block_create_func;
+  uiBlockCreateFunc block_create_func = nullptr;
 
   /** #UI_BTYPE_PULLDOWN / #UI_BTYPE_MENU data */
-  uiMenuCreateFunc menu_create_func;
+  uiMenuCreateFunc menu_create_func = nullptr;
 
-  uiMenuStepFunc menu_step_func;
+  uiMenuStepFunc menu_step_func = nullptr;
 
   /* RNA data */
-  PointerRNA rnapoin;
+  PointerRNA rnapoin = {};
-  PropertyRNA *rnaprop;
+  PropertyRNA *rnaprop = nullptr;
-  int rnaindex;
+  int rnaindex = 0;
 
   /* Operator data */
-  wmOperatorType *optype;
+  wmOperatorType *optype = nullptr;
-  PointerRNA *opptr;
+  PointerRNA *opptr = nullptr;
-  wmOperatorCallContext opcontext;
+  wmOperatorCallContext opcontext = WM_OP_INVOKE_DEFAULT;
 
   /** When non-zero, this is the key used to activate a menu items (`a-z` always lower case). */
-  uchar menu_key;
+  uchar menu_key = 0;
 
-  ListBase extra_op_icons; /** #uiButExtraOpIcon */
+  ListBase extra_op_icons = {nullptr, nullptr}; /** #uiButExtraOpIcon */
 
   /* Drag-able data, type is WM_DRAG_... */
-  char dragtype;
+  char dragtype = WM_DRAG_ID;
-  short dragflag;
+  short dragflag = 0;
-  void *dragpoin;
+  void *dragpoin = nullptr;
-  ImBuf *imb;
+  ImBuf *imb = nullptr;
-  float imb_scale;
+  float imb_scale = 0;
 
   /** Active button data (set when the user is hovering or interacting with a button). */
-  uiHandleButtonData *active;
+  uiHandleButtonData *active = nullptr;
 
   /** Custom button data (borrowed, not owned). */
-  void *custom_data;
+  void *custom_data = nullptr;
 
-  char *editstr;
+  char *editstr = nullptr;
-  double *editval;
+  double *editval = nullptr;
-  float *editvec;
+  float *editvec = nullptr;
 
-  uiButPushedStateFunc pushed_state_func;
+  uiButPushedStateFunc pushed_state_func = nullptr;
-  const void *pushed_state_arg;
+  const void *pushed_state_arg = nullptr;
 
   /** Little indicator (e.g., counter) displayed on top of some icons. */
-  IconTextOverlay icon_overlay_text;
+  IconTextOverlay icon_overlay_text = {};
 
   /* pointer back */
-  uiBlock *block;
+  uiBlock *block = nullptr;
+
+  uiBut() = default;
+  /** Performs a mostly shallow copy for now. Only contained C++ types are deep copied. */
+  uiBut(const uiBut &other) = default;
+  /** Mostly shallow copy, just like copy constructor above. */
+  uiBut &operator=(const uiBut &other) = default;
 };
 
 /** Derived struct for #UI_BTYPE_NUM */
-struct uiButNumber {
+struct uiButNumber : public uiBut {
-  uiBut but;
+  float step_size = 0;
-
+  float precision = 0;
-  float step_size;
-  float precision;
 };
 
 /** Derived struct for #UI_BTYPE_COLOR */
-struct uiButColor {
+struct uiButColor : public uiBut {
-  uiBut but;
+  bool is_pallete_color = false;
-
+  int palette_color_index = -1;
-  bool is_pallete_color;
-  int palette_color_index;
 };
 
 /** Derived struct for #UI_BTYPE_TAB */
-struct uiButTab {
+struct uiButTab : public uiBut {
-  uiBut but;
+  struct MenuType *menu = nullptr;
-  struct MenuType *menu;
 };
 
 /** Derived struct for #UI_BTYPE_SEARCH_MENU */
-struct uiButSearch {
+struct uiButSearch : public uiBut {
-  uiBut but;
+  uiButSearchCreateFn popup_create_fn = nullptr;
+  uiButSearchUpdateFn items_update_fn = nullptr;
+  uiButSearchListenFn listen_fn = nullptr;
 
-  uiButSearchCreateFn popup_create_fn;
+  void *item_active = nullptr;
-  uiButSearchUpdateFn items_update_fn;
-  uiButSearchListenFn listen_fn;
 
-  void *item_active;
+  void *arg = nullptr;
+  uiFreeArgFunc arg_free_fn = nullptr;
 
-  void *arg;
+  uiButSearchContextMenuFn item_context_menu_fn = nullptr;
-  uiFreeArgFunc arg_free_fn;
+  uiButSearchTooltipFn item_tooltip_fn = nullptr;
 
-  uiButSearchContextMenuFn item_context_menu_fn;
+  const char *item_sep_string = nullptr;
-  uiButSearchTooltipFn item_tooltip_fn;
 
-  const char *item_sep_string;
+  PointerRNA rnasearchpoin = {};
-
+  PropertyRNA *rnasearchprop = nullptr;
-  PointerRNA rnasearchpoin;
-  PropertyRNA *rnasearchprop;
 
   /**
    * The search box only provides suggestions, it does not force
    * the string to match one of the search items when applying.
    */
-  bool results_are_suggestions;
+  bool results_are_suggestions = false;
 };
 
-/** Derived struct for #UI_BTYPE_DECORATOR */
+/** Derived struct for #UI_BTYPE_DECORATOR
-struct uiButDecorator {
+ * Decorators have own RNA data, using the normal #uiBut RNA members has many side-effects.
-  uiBut but;
+ */
-
+struct uiButDecorator : public uiBut {
-  struct PointerRNA rnapoin;
+  struct PointerRNA decorated_rnapoin = {};
-  struct PropertyRNA *rnaprop;
+  struct PropertyRNA *decorated_rnaprop = nullptr;
-  int rnaindex;
+  int decorated_rnaindex = -1;
 };
 
 /** Derived struct for #UI_BTYPE_PROGRESS_BAR. */
-struct uiButProgressbar {
+struct uiButProgressbar : public uiBut {
-  uiBut but;
-
   /* 0..1 range */
-  float progress;
+  float progress = 0;
 };
 
-struct uiButViewItem {
+struct uiButViewItem : public uiBut {
-  uiBut but;
-
   /* C-Handle to the view item this button was created for. */
-  uiViewItemHandle *view_item;
+  uiViewItemHandle *view_item = nullptr;
 };
 
 /** Derived struct for #UI_BTYPE_HSVCUBE. */
-struct uiButHSVCube {
+struct uiButHSVCube : public uiBut {
-  uiBut but;
+  eButGradientType gradient_type = UI_GRAD_SV;
-
-  eButGradientType gradient_type;
 };
 
 /** Derived struct for #UI_BTYPE_COLORBAND. */
-struct uiButColorBand {
+struct uiButColorBand : public uiBut {
-  uiBut but;
+  ColorBand *edit_coba = nullptr;
-
-  ColorBand *edit_coba;
 };
 
 /** Derived struct for #UI_BTYPE_CURVEPROFILE. */
-struct uiButCurveProfile {
+struct uiButCurveProfile : public uiBut {
-  uiBut but;
+  struct CurveProfile *edit_profile = nullptr;
-
-  struct CurveProfile *edit_profile;
 };
 
 /** Derived struct for #UI_BTYPE_CURVE. */
-struct uiButCurveMapping {
+struct uiButCurveMapping : public uiBut {
-  uiBut but;
+  struct CurveMapping *edit_cumap = nullptr;
-
+  eButGradientType gradient_type = UI_GRAD_SV;
-  struct CurveMapping *edit_cumap;
-  eButGradientType gradient_type;
 };
 
 /** Derived struct for #UI_BTYPE_HOTKEY_EVENT. */
-struct uiButHotkeyEvent {
+struct uiButHotkeyEvent : public uiBut {
-  uiBut but;
+  short modifier_key = 0;
-
-  short modifier_key;
 };
 
 /**

source/blender/editors/interface/interface_layout.cc

@@ -3139,7 +3139,7 @@ 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++) {
-    uiButDecorator *decorator_but = (uiButDecorator *)uiDefIconBut(block,
+    uiButDecorator *but = (uiButDecorator *)uiDefIconBut(block,
                                                          UI_BTYPE_DECORATOR,
                                                          0,
                                                          ICON_DOT,
@@ -3154,13 +3154,13 @@ void uiItemDecoratorR_prop(uiLayout *layout, PointerRNA *ptr, PropertyRNA *prop,
                                                          0.0,
                                                          TIP_("Animate property"));
 
-    UI_but_func_set(&decorator_but->but, ui_but_anim_decorate_cb, decorator_but, nullptr);
+    UI_but_func_set(but, ui_but_anim_decorate_cb, but, nullptr);
-    decorator_but->but.flag |= UI_BUT_UNDO | UI_BUT_DRAG_LOCK;
+    but->flag |= UI_BUT_UNDO | UI_BUT_DRAG_LOCK;
-    /* Reusing RNA search members, setting actual RNA data has many side-effects. */
+    /* Decorators have own RNA data, using the normal #uiBut RNA members has many side-effects. */
-    decorator_but->rnapoin = *ptr;
+    but->decorated_rnapoin = *ptr;
-    decorator_but->rnaprop = prop;
+    but->decorated_rnaprop = prop;
     /* ui_def_but_rna() sets non-array buttons to have a RNA index of 0. */
-    decorator_but->rnaindex = (!is_array || is_expand) ? i : index;
+    but->decorated_rnaindex = (!is_array || is_expand) ? i : index;
   }
 }
 

source/blender/editors/interface/interface_ops.cc

@@ -1658,8 +1658,8 @@ static void ui_editsource_active_but_set(uiBut *but)
 {
   BLI_assert(ui_editsource_info == nullptr);
 
-  ui_editsource_info = MEM_cnew<uiEditSourceStore>(__func__);
+  ui_editsource_info = MEM_new<uiEditSourceStore>(__func__);
-  memcpy(&ui_editsource_info->but_orig, but, sizeof(uiBut));
+  ui_editsource_info->but_orig = *but;
 
   ui_editsource_info->hash = BLI_ghash_ptr_new(__func__);
 }

source/blender/editors/interface/interface_region_color_picker.cc

@@ -397,7 +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, nullptr);
+    UI_but_func_set(hsv_but, ui_colorpicker_rgba_update_cb, hsv_but, nullptr);
   }
   else {
     hsv_but = (uiButHSVCube *)uiDefButR_prop(block,
@@ -417,9 +417,9 @@ 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, nullptr);
+    UI_but_func_set(hsv_but, ui_colorpicker_rgba_update_cb, hsv_but, nullptr);
   }
-  hsv_but->but.custom_data = cpicker;
+  hsv_but->custom_data = cpicker;
 }
 
 static void ui_colorpicker_square(uiBlock *block,
@@ -450,8 +450,8 @@ 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, nullptr);
+  UI_but_func_set(hsv_but, ui_colorpicker_rgba_update_cb, hsv_but, nullptr);
-  hsv_but->but.custom_data = cpicker;
+  hsv_but->custom_data = cpicker;
 
   /* value */
   hsv_but = (uiButHSVCube *)uiDefButR_prop(block,
@@ -471,8 +471,8 @@ static void ui_colorpicker_square(uiBlock *block,
                                            0,
                                            TIP_("Value"));
   hsv_but->gradient_type = (eButGradientType)(type + 3);
-  UI_but_func_set(&hsv_but->but, ui_colorpicker_rgba_update_cb, &hsv_but->but, nullptr);
+  UI_but_func_set(hsv_but, ui_colorpicker_rgba_update_cb, hsv_but, nullptr);
-  hsv_but->but.custom_data = cpicker;
+  hsv_but->custom_data = cpicker;
 }
 
 /* a HS circle, V slider, rgb/hsv/hex sliders */

source/blender/editors/interface/interface_region_search.cc

@@ -433,17 +433,17 @@ bool ui_searchbox_event(
 
 /** Wrap #uiButSearchUpdateFn callback. */
 static void ui_searchbox_update_fn(bContext *C,
-                                   uiButSearch *search_but,
+                                   uiButSearch *but,
                                    const char *str,
                                    uiSearchItems *items)
 {
   /* While the button is in text editing mode (searchbox open), remove tooltips on every update. */
-  if (search_but->but.editstr) {
+  if (but->editstr) {
     wmWindow *win = CTX_wm_window(C);
     WM_tooltip_clear(C, win);
   }
-  const bool is_first_search = !search_but->but.changed;
+  const bool is_first_search = !but->changed;
-  search_but->items_update_fn(C, search_but->arg, str, items, is_first_search);
+  but->items_update_fn(C, but->arg, str, items, is_first_search);
 }
 
 void ui_searchbox_update(bContext *C, ARegion *region, uiBut *but, const bool reset)
@@ -464,7 +464,7 @@ void ui_searchbox_update(bContext *C, ARegion *region, uiBut *but, const bool re
     data->active = -1;
 
     /* On init, find and center active item. */
-    const bool is_first_search = !search_but->but.changed;
+    const bool is_first_search = !but->changed;
     if (is_first_search && search_but->items_update_fn && search_but->item_active) {
       data->items.active = search_but->item_active;
       ui_searchbox_update_fn(C, search_but, but->editstr, &data->items);
@@ -704,12 +704,11 @@ static void ui_searchbox_region_listen_fn(const wmRegionListenerParams *params)
 
 static ARegion *ui_searchbox_create_generic_ex(bContext *C,
                                                ARegion *butregion,
-                                               uiButSearch *search_but,
+                                               uiButSearch *but,
                                                const bool use_shortcut_sep)
 {
   wmWindow *win = CTX_wm_window(C);
   const uiStyle *style = UI_style_get();
-  uiBut *but = &search_but->but;
   const float aspect = but->block->aspect;
   const int margin = UI_POPUP_MARGIN;
 
@@ -726,8 +725,8 @@ static ARegion *ui_searchbox_create_generic_ex(bContext *C,
 
   /* Create search-box data. */
   uiSearchboxData *data = MEM_cnew<uiSearchboxData>(__func__);
-  data->search_arg = search_but->arg;
+  data->search_arg = but->arg;
-  data->search_listener = search_but->listen_fn;
+  data->search_listener = but->listen_fn;
 
   /* Set font, get the bounding-box. */
   data->fstyle = style->widget; /* copy struct */
@@ -751,7 +750,7 @@ static ARegion *ui_searchbox_create_generic_ex(bContext *C,
   if (but->optype != nullptr || use_shortcut_sep) {
     data->use_shortcut_sep = true;
   }
-  data->sep_string = search_but->item_sep_string;
+  data->sep_string = but->item_sep_string;
 
   /* compute position */
   if (but->block->flag & UI_BLOCK_SEARCH_MENU) {
@@ -1013,10 +1012,8 @@ ARegion *ui_searchbox_create_menu(bContext *C, ARegion *butregion, uiButSearch *
   return region;
 }
 
-void ui_but_search_refresh(uiButSearch *search_but)
+void ui_but_search_refresh(uiButSearch *but)
 {
-  uiBut *but = &search_but->but;
-
   /* possibly very large lists (such as ID datablocks) only
    * only validate string RNA buts (not pointers) */
   if (but->rnaprop && RNA_property_type(but->rnaprop) != PROP_STRING) {
@@ -1033,9 +1030,9 @@ void ui_but_search_refresh(uiButSearch *search_but)
     items->names[i] = (char *)MEM_callocN(but->hardmax + 1, __func__);
   }
 
-  ui_searchbox_update_fn((bContext *)but->block->evil_C, search_but, but->drawstr, items);
+  ui_searchbox_update_fn((bContext *)but->block->evil_C, but, but->drawstr, items);
 
-  if (!search_but->results_are_suggestions) {
+  if (!but->results_are_suggestions) {
     /* Only red-alert when we are sure of it, this can miss cases when >10 matches. */
     if (items->totitem == 0) {
       UI_but_flag_enable(but, UI_BUT_REDALERT);

source/blender/editors/interface/interface_templates.cc

@@ -1677,12 +1677,12 @@ static void template_ID_tabs(const bContext *C,
                                                0.0f,
                                                0.0f,
                                                "");
-    UI_but_funcN_set(&tab->but, template_ID_set_property_exec_fn, MEM_dupallocN(template_id), id);
+    UI_but_funcN_set(tab, template_ID_set_property_exec_fn, MEM_dupallocN(template_id), id);
-    UI_but_drag_set_id(&tab->but, id);
+    UI_but_drag_set_id(tab, id);
-    tab->but.custom_data = (void *)id;
+    tab->custom_data = (void *)id;
     tab->menu = mt;
 
-    UI_but_drawflag_enable(&tab->but, but_align);
+    UI_but_drawflag_enable(tab, but_align);
   }
 
   BLI_freelistN(&ordered);
@@ -5639,7 +5639,7 @@ void uiTemplateColorPicker(uiLayout *layout,
           hsv_but->gradient_type = UI_GRAD_HV;
           break;
       }
-      but = &hsv_but->but;
+      but = hsv_but;
       break;
 
     /* user default */
@@ -5785,7 +5785,7 @@ void uiTemplateColorPicker(uiLayout *layout,
         break;
     }
 
-    hsv_but->but.custom_data = cpicker;
+    hsv_but->custom_data = cpicker;
   }
 }
 
@@ -6286,7 +6286,7 @@ void uiTemplateRunningJobs(uiLayout *layout, bContext *C)
                                                                             nullptr);
 
       but_progress->progress = progress;
-      UI_but_func_tooltip_set(&but_progress->but, progress_tooltip_func, tip_arg, MEM_freeN);
+      UI_but_func_tooltip_set(but_progress, progress_tooltip_func, tip_arg, MEM_freeN);
     }
 
     if (!wm->is_interface_locked) {

source/blender/editors/interface/interface_widgets.cc

@@ -3152,7 +3152,7 @@ void ui_hsvcube_pos_from_vals(
     case UI_GRAD_V_ALT:
       x = 0.5f;
       /* exception only for value strip - use the range set in but->min/max */
-      y = (hsv[2] - hsv_but->but.softmin) / (hsv_but->but.softmax - hsv_but->but.softmin);
+      y = (hsv[2] - hsv_but->softmin) / (hsv_but->softmax - hsv_but->softmin);
       break;
   }
 

source/blender/editors/interface/views/grid_view.cc

@@ -130,7 +130,7 @@ void AbstractGridViewItem::add_grid_tile_button(uiBlock &block)
                                              "");
 
   view_item_but_->view_item = reinterpret_cast<uiViewItemHandle *>(this);
-  UI_but_func_set(&view_item_but_->but, grid_tile_click_fn, view_item_but_, nullptr);
+  UI_but_func_set(view_item_but_, grid_tile_click_fn, view_item_but_, nullptr);
 }
 
 void AbstractGridViewItem::on_activate()

source/blender/editors/interface/views/tree_view.cc

@@ -136,7 +136,7 @@ void AbstractTreeViewItem::add_treerow_button(uiBlock &block)
       &block, UI_BTYPE_VIEW_ITEM, 0, "", 0, 0, UI_UNIT_X * 10, UI_UNIT_Y, nullptr, 0, 0, 0, 0, "");
 
   view_item_but_->view_item = reinterpret_cast<uiViewItemHandle *>(this);
-  UI_but_func_set(&view_item_but_->but, tree_row_click_fn, view_item_but_, nullptr);
+  UI_but_func_set(view_item_but_, tree_row_click_fn, view_item_but_, nullptr);
 }
 
 void AbstractTreeViewItem::add_indent(uiLayout &row) const
@@ -322,8 +322,8 @@ bool AbstractTreeViewItem::is_hovered() const
   /* The new layout hasn't finished construction yet, so the final state of the button is unknown.
    * Get the matching button from the previous redraw instead. */
   uiButViewItem *old_item_but = ui_block_view_find_matching_view_item_but_in_old_block(
-      view_item_but_->but.block, this_item_handle);
+      view_item_but_->block, this_item_handle);
-  return old_item_but && (old_item_but->but.flag & UI_ACTIVE);
+  return old_item_but && (old_item_but->flag & UI_ACTIVE);
 }
 
 bool AbstractTreeViewItem::is_collapsed() const