From the todo:

Hanging Tooltips solved!

It appeared to be that an active button remained in that state when
another region/editor became active. It then kept the button-activate
state, and therefore also the optional tooltip.

This only happened on fast moves, when a mousemove event was not passed
on anymore to the previously active subwindow.

It has been solved with a new notifier (SWINACTIVE), which gets sent on
new active regions. The screen listener then calls uiFreeActiveButtons()
to find out if buttons were still active somewhere else.

source/blender/editors/include/ED_screen.h

@@ -95,14 +95,14 @@ void	ED_area_swapspace(struct bContext *C, ScrArea *sa1, ScrArea *sa2);
 void	ED_screens_initialize(struct wmWindowManager *wm);
 void	ED_screen_draw(struct wmWindow *win);
 void	ED_screen_refresh(struct wmWindowManager *wm, struct wmWindow *win);
-void	ED_screen_do_listen(struct wmWindow *win, struct wmNotifier *note);
+void	ED_screen_do_listen(struct bContext *C, struct wmNotifier *note);
 bScreen *ED_screen_duplicate(struct wmWindow *win, struct bScreen *sc);
 bScreen *ED_screen_add(struct wmWindow *win, struct Scene *scene, const char *name);
 void	ED_screen_set(struct bContext *C, struct bScreen *sc);
 void	ED_screen_delete(struct bContext *C, struct bScreen *sc);
 void	ED_screen_set_scene(struct bContext *C, struct Scene *scene);
 void	ED_screen_delete_scene(struct bContext *C, struct Scene *scene);
-void	ED_screen_set_subwinactive(struct wmWindow *win, struct wmEvent *event);
+void	ED_screen_set_subwinactive(struct bContext *C, struct wmEvent *event);
 void	ED_screen_exit(struct bContext *C, struct wmWindow *window, struct bScreen *screen);
 void	ED_screen_animation_timer(struct bContext *C, int redraws, int refresh, int sync, int enable);
 void	ED_screen_animation_timer_update(struct bScreen *screen, int redraws, int refresh);

source/blender/editors/include/UI_interface.h

@@ -322,6 +322,7 @@ void uiBlockSetEmboss(uiBlock *block, char dt);
 void uiFreeBlock(const struct bContext *C, uiBlock *block);
 void uiFreeBlocks(const struct bContext *C, struct ListBase *lb);
 void uiFreeInactiveBlocks(const struct bContext *C, struct ListBase *lb);
+void uiFreeActiveButtons(const struct bContext *C, struct bScreen *screen);
 
 void uiBlockSetRegion(uiBlock *block, struct ARegion *region);
 

source/blender/editors/interface/interface_handlers.c

@@ -144,11 +144,11 @@ typedef struct uiHandleButtonData {
 	float dragf, dragfstart;
 	CBData *dragcbd;
 
-	/* menu open */
+	/* menu open (watch uiFreeActiveButtons) */
 	uiPopupBlockHandle *menu;
 	int menuretval;
 	
-	/* search box */
+	/* search box (watch uiFreeActiveButtons) */
 	ARegion *searchbox;
 
 	/* post activate */
@@ -4595,6 +4595,27 @@ int ui_button_is_active(ARegion *ar)
 	return (ui_but_find_activated(ar) != NULL);
 }
 
+/* is called by notifier */
+void uiFreeActiveButtons(const bContext *C, bScreen *screen)
+{
+	ScrArea *sa= screen->areabase.first;
+	
+	for(;sa; sa= sa->next) {
+		ARegion *ar= sa->regionbase.first;
+		for(;ar; ar= ar->next) {
+			uiBut *but= ui_but_find_activated(ar);
+			if(but) {
+				uiHandleButtonData *data= but->active;
+				
+				if(data->menu==NULL && data->searchbox==NULL)
+					ui_button_active_free(C, but);
+			}
+		}
+	}
+}
+
+
+
 /* returns TRUE if highlighted button allows drop of names */
 /* called in region context */
 int UI_but_active_drop_name(bContext *C)

source/blender/editors/screen/screen_edit.c

@@ -960,8 +960,9 @@ static void region_cursor_set(wmWindow *win, int swinid)
 	}
 }
 
-void ED_screen_do_listen(wmWindow *win, wmNotifier *note)
+void ED_screen_do_listen(bContext *C, wmNotifier *note)
 {
+	wmWindow *win= CTX_wm_window(C);
 	
 	/* generic notes */
 	switch(note->category) {
@@ -973,8 +974,11 @@ void ED_screen_do_listen(wmWindow *win, wmNotifier *note)
 			win->screen->do_draw= 1;
 			break;
 		case NC_SCREEN:
+			if(note->data==ND_SUBWINACTIVE)
+				uiFreeActiveButtons(C, win->screen);
 			if(note->action==NA_EDITED)
 				win->screen->do_draw= win->screen->do_refresh= 1;
+			break;
 		case NC_SCENE:
 			if(note->data==ND_MODE)
 				region_cursor_set(win, note->swinid);				
@@ -1217,8 +1221,10 @@ static void screen_cursor_set(wmWindow *win, wmEvent *event)
 
 /* called in wm_event_system.c. sets state vars in screen, cursors */
 /* event type is mouse move */
-void ED_screen_set_subwinactive(wmWindow *win, wmEvent *event)
+void ED_screen_set_subwinactive(bContext *C, wmEvent *event)
 {
+	wmWindow *win= CTX_wm_window(C);
+	
 	if(win->screen) {
 		bScreen *scr= win->screen;
 		ScrArea *sa;
@@ -1264,6 +1270,7 @@ void ED_screen_set_subwinactive(wmWindow *win, wmEvent *event)
 		}
 		else if(oldswin!=scr->subwinactive) {
 			region_cursor_set(win, scr->subwinactive);
+			WM_event_add_notifier(C, NC_SCREEN|ND_SUBWINACTIVE, scr);
 		}
 	}
 }

source/blender/windowmanager/WM_types.h

@@ -179,6 +179,7 @@ typedef struct wmNotifier {
 #define ND_EDITOR_CHANGED	(6<<16) /*sent to new editors after switching to them*/
 #define ND_SCREENSET		(7<<16)
 #define ND_SKETCH			(8<<16)
+#define ND_SUBWINACTIVE		(9<<16)
 
 	/* NC_SCENE Scene */
 #define ND_SCENEBROWSE		(1<<16)

source/blender/windowmanager/intern/wm_event_system.c

@@ -270,7 +270,7 @@ void wm_event_do_notifiers(bContext *C)
 				CTX_wm_window_set(C, win);
 
 				/* printf("notifier win %d screen %s cat %x\n", win->winid, win->screen->id.name+2, note->category); */
-				ED_screen_do_listen(win, note);
+				ED_screen_do_listen(C, note);
 
 				for(ar=win->screen->regionbase.first; ar; ar= ar->next) {
 					ED_region_do_listen(ar, note);
@@ -1741,7 +1741,7 @@ void wm_event_do_handlers(bContext *C)
 			/* XXX to solve, here screen handlers? */
 			if(event->type==MOUSEMOVE) {
 				/* state variables in screen, cursors, also used in wm_draw.c */
-				ED_screen_set_subwinactive(win, event);	
+				ED_screen_set_subwinactive(C, event);	
 				/* for regions having custom cursors */
 				wm_paintcursor_test(C, event);
 			}