UI Code Quality: Use derived struct for number buttons

For the man rationale behind this design, see 49f088e2d093. Further,
this removes users of uiBut.a1/uiBut.a2, which is a very ugly design
choice (hard to reason about).

Note that I had to do rather ugly, specific exceptions for the number
buttons in `ui_def_but_rna()`. But once all users of a1/a2 are removed,
this special handling shouldn't be needed anymore.
I also had to move a sanity check out of the button definition. It's now
moved into a new debug only sanity checking function executed when
finishing the layout definition (block end).

1 files changed, 3 insertions, 0 deletions

diff --git a/source/blender/editors/include/UI_interface.h b/source/blender/editors/include/UI_interface.h
index b23f8ae11c9..d5d489b1742 100644
--- a/source/blender/editors/include/UI_interface.h
+++ b/source/blender/editors/include/UI_interface.h
@@ -1602,6 +1602,9 @@ int UI_search_items_find_index(uiSearchItems *items, const char *name);
 
 void UI_but_node_link_set(uiBut *but, struct bNodeSocket *socket, const float draw_color[4]);
 
+void UI_but_number_step_size_set(uiBut *but, float step_size);
+void UI_but_number_precision_set(uiBut *but, float precision);
+
 void UI_block_func_handle_set(uiBlock *block, uiBlockHandleFunc func, void *arg);
 void UI_block_func_butmenu_set(uiBlock *block, uiMenuHandleFunc func, void *arg);
 void UI_block_func_set(uiBlock *block, uiButHandleFunc func, void *arg1, void *arg2);