WM: message bus replacement for property notifiers

Use dynamically generated message publish/subscribe
so buttons and manipulators update properly.

This resolves common glitches where manipulators weren't updating
as well as the UI when add-ons exposed properties which
hard coded listeners weren't checking for.

Python can also publish/scribe changes via `bpy.msgbus`.

See D2917

1 files changed, 7 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_screen.h b/source/blender/blenkernel/BKE_screen.h
index 8ba103b915e..6669f3103da 100644
--- a/source/blender/blenkernel/BKE_screen.h
+++ b/source/blender/blenkernel/BKE_screen.h
@@ -56,6 +56,7 @@ struct wmWindow;
 struct wmWindowManager;
 struct WorkSpace;
 struct GPUFXSettings;
+struct wmMsgBus;
 
 #include "BLI_compiler_attrs.h"
 
@@ -139,6 +140,12 @@ typedef struct ARegionType {
 	/* contextual changes should be handled here */
 	void (*listener)(struct bScreen *, struct ScrArea *, struct ARegion *,
 	                 struct wmNotifier *, const struct Scene *scene);
+	/* Optional callback to generate subscriptions. */
+	void (*message_subscribe)(
+	        const struct bContext *C,
+	        struct WorkSpace *workspace, struct Scene *scene,
+	        struct bScreen *sc, struct ScrArea *sa, struct ARegion *ar,
+	        struct wmMsgBus *mbus);
 
 	void (*free)(struct ARegion *);