UI Code Quality: Use derived struct for hot-key buttons

`uiBut` contained a variable that was only used for these hot-key
buttons. This may also help getting rid of the `UI_BUT_IMMEDIATE` flag,
which is also only used for this button type. We are running out of
available bits for flags, so this would be useful.

Continuing the work from 49f088e2d093. Part of T74432.

1 files changed, 5 insertions, 2 deletions

diff --git a/source/blender/editors/interface/interface_handlers.c b/source/blender/editors/interface/interface_handlers.c
index 2c408619fe7..b2271abdd34 100644
--- a/source/blender/editors/interface/interface_handlers.c
+++ b/source/blender/editors/interface/interface_handlers.c
@@ -4501,10 +4501,13 @@ static int ui_do_but_HOTKEYEVT(bContext *C,
                                uiHandleButtonData *data,
                                const wmEvent *event)
 {
+  uiButHotkeyEvent *hotkey_but = (uiButHotkeyEvent *)but;
+  BLI_assert(but->type == UI_BTYPE_HOTKEY_EVENT);
+
   if (data->state == BUTTON_STATE_HIGHLIGHT) {
     if (ELEM(event->type, LEFTMOUSE, EVT_PADENTER, EVT_RETKEY) && event->val == KM_PRESS) {
       but->drawstr[0] = 0;
-      but->modifier_key = 0;
+      hotkey_but->modifier_key = 0;
       button_activate_state(C, but, BUTTON_STATE_WAIT_KEY_EVENT);
       return WM_UI_HANDLER_BREAK;
     }
@@ -4538,7 +4541,7 @@ static int ui_do_but_HOTKEYEVT(bContext *C,
     }
 
     /* always set */
-    but->modifier_key = event->modifier;
+    hotkey_but->modifier_key = event->modifier;
 
     ui_but_update(but);
     ED_region_tag_redraw(data->region);