UI Code Quality: Use "params" struct for area and region callbacks

These functions with many arguments can be unwieldy. Aside from the obvious issues
with rewriting the list of arguments and the opportunities for error and frustration
that presents, the long list of arguments make these systems hard to change. So when
an argument should be added, someone might skip that and add some hack instead.

So, as proposed in T73586#1037210, this patch instead uses a "params" struct for
each of these callbacks.

- Use param argument for `ARegionType.listener`
    - Remove unused window field in region listener
- Use param argument for `SpaceType.listener`
- Use params struct for `ARegionType.message_subscribe`

Differential Revision: https://developer.blender.org/D9750

3 files changed, 23 insertions, 5 deletions

diff --git a/source/blender/windowmanager/gizmo/WM_gizmo_api.h b/source/blender/windowmanager/gizmo/WM_gizmo_api.h
index 70ddae4d724..cf1a7628267 100644
--- a/source/blender/windowmanager/gizmo/WM_gizmo_api.h
+++ b/source/blender/windowmanager/gizmo/WM_gizmo_api.h
@@ -301,7 +301,7 @@ void WM_gizmomap_draw(struct wmGizmoMap *gzmap,
 void WM_gizmomap_add_handlers(struct ARegion *region, struct wmGizmoMap *gzmap);
 bool WM_gizmomap_select_all(struct bContext *C, struct wmGizmoMap *gzmap, const int action);
 bool WM_gizmomap_cursor_set(const struct wmGizmoMap *gzmap, struct wmWindow *win);
-void WM_gizmomap_message_subscribe(struct bContext *C,
+void WM_gizmomap_message_subscribe(const struct bContext *C,
                                    struct wmGizmoMap *gzmap,
                                    struct ARegion *region,
                                    struct wmMsgBus *mbus);
diff --git a/source/blender/windowmanager/gizmo/intern/wm_gizmo_map.c b/source/blender/windowmanager/gizmo/intern/wm_gizmo_map.c
index 479768c3536..12c6eb46c12 100644
--- a/source/blender/windowmanager/gizmo/intern/wm_gizmo_map.c
+++ b/source/blender/windowmanager/gizmo/intern/wm_gizmo_map.c
@@ -1156,7 +1156,7 @@ ListBase *wm_gizmomap_groups_get(wmGizmoMap *gzmap)
   return &gzmap->groups;
 }
 
-void WM_gizmomap_message_subscribe(bContext *C,
+void WM_gizmomap_message_subscribe(const bContext *C,
                                    wmGizmoMap *gzmap,
                                    ARegion *region,
                                    struct wmMsgBus *mbus)
diff --git a/source/blender/windowmanager/intern/wm_event_system.c b/source/blender/windowmanager/intern/wm_event_system.c
index 859336d0338..d08051dd5fb 100644
--- a/source/blender/windowmanager/intern/wm_event_system.c
+++ b/source/blender/windowmanager/intern/wm_event_system.c
@@ -543,13 +543,31 @@ void wm_event_do_notifiers(bContext *C)
         ED_screen_do_listen(C, note);
 
         LISTBASE_FOREACH (ARegion *, region, &screen->regionbase) {
-          ED_region_do_listen(win, NULL, region, note, scene);
+          wmRegionListenerParams region_params = {
+              .area = NULL,
+              .region = region,
+              .scene = scene,
+              .notifier = note,
+          };
+          ED_region_do_listen(&region_params);
         }
 
         ED_screen_areas_iter (win, screen, area) {
-          ED_area_do_listen(win, area, note, scene);
+          wmSpaceTypeListenerParams area_params = {
+              .window = win,
+              .area = area,
+              .notifier = note,
+              .scene = scene,
+          };
+          ED_area_do_listen(&area_params);
           LISTBASE_FOREACH (ARegion *, region, &area->regionbase) {
-            ED_region_do_listen(win, area, region, note, scene);
+            wmRegionListenerParams region_params = {
+                .area = area,
+                .region = region,
+                .scene = scene,
+                .notifier = note,
+            };
+            ED_region_do_listen(&region_params);
           }
         }
       }