Fix T86331: Preferences menu inaccessible until window resize

The RGN_TYPE_EXECUTE region was zero height - with the "Load & Save"
button drawing outside of those bounds - so it didn't respond to events.

This is because the region started off this size and does not change
with simply adding the buttons. Although it has RGN_FLAG_DYNAMIC_SIZE,
delayed reinit of regions is only currently supported on headers.

This gives the execute region an initial (minimum) vertical size but
also makes the region **hidden** by default.

- Showing Prefs as an editor among others it will show the header
  but not the execute region.

- Showing the Prefs in a popup window, hides the header region
  and shows the execute region.

Ref D10636

1 files changed, 5 insertions, 0 deletions

diff --git a/source/blender/editors/screen/screen_ops.c b/source/blender/editors/screen/screen_ops.c
index 797c3bcf132..5cd4e8c353b 100644
--- a/source/blender/editors/screen/screen_ops.c
+++ b/source/blender/editors/screen/screen_ops.c
@@ -4863,6 +4863,11 @@ static int userpref_show_exec(bContext *C, wmOperator *op)
     region->flag |= RGN_FLAG_HIDDEN;
     ED_region_visibility_change_update(C, area, region);
 
+    /* And also show the region with "Load & Save" buttons. */
+    region = BKE_area_find_region_type(area, RGN_TYPE_EXECUTE);
+    region->flag &= ~RGN_FLAG_HIDDEN;
+    ED_region_visibility_change_update(C, area, region);
+
     return OPERATOR_FINISHED;
   }
   BKE_report(op->reports, RPT_ERROR, "Failed to open window!");