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, 32 insertions, 26 deletions

diff --git a/source/blender/editors/uvedit/uvedit_buttons.c b/source/blender/editors/uvedit/uvedit_buttons.c
index edfbfd0cdc3..f9949f6b671 100644
--- a/source/blender/editors/uvedit/uvedit_buttons.c
+++ b/source/blender/editors/uvedit/uvedit_buttons.c
@@ -175,33 +175,39 @@ static void uvedit_vertex_buttons(const bContext *C, uiBlock *block)
       digits = 2;
     }
 
+    uiBut *but;
+
     UI_block_align_begin(block);
-    uiDefButF(block,
-              UI_BTYPE_NUM,
-              B_UVEDIT_VERTEX,
-              IFACE_("X:"),
-              0,
-              0,
-              width,
-              UI_UNIT_Y,
-              &uvedit_old_center[0],
-              UNPACK2(range_xy[0]),
-              step,
-              digits,
-              "");
-    uiDefButF(block,
-              UI_BTYPE_NUM,
-              B_UVEDIT_VERTEX,
-              IFACE_("Y:"),
-              width,
-              0,
-              width,
-              UI_UNIT_Y,
-              &uvedit_old_center[1],
-              UNPACK2(range_xy[1]),
-              step,
-              digits,
-              "");
+    but = uiDefButF(block,
+                    UI_BTYPE_NUM,
+                    B_UVEDIT_VERTEX,
+                    IFACE_("X:"),
+                    0,
+                    0,
+                    width,
+                    UI_UNIT_Y,
+                    &uvedit_old_center[0],
+                    UNPACK2(range_xy[0]),
+                    0,
+                    0,
+                    "");
+    UI_but_number_step_size_set(but, step);
+    UI_but_number_precision_set(but, digits);
+    but = uiDefButF(block,
+                    UI_BTYPE_NUM,
+                    B_UVEDIT_VERTEX,
+                    IFACE_("Y:"),
+                    width,
+                    0,
+                    width,
+                    UI_UNIT_Y,
+                    &uvedit_old_center[1],
+                    UNPACK2(range_xy[1]),
+                    0,
+                    0,
+                    "");
+    UI_but_number_step_size_set(but, step);
+    UI_but_number_precision_set(but, digits);
     UI_block_align_end(block);
   }