Fix enter/leave events on titlebars

This adds a global variable that tracks the drawable that is currently under the
mouse cursor. This new variable is then used so that we get consistent behavior
for enter/leave signals. Such signals are now also generated when a MotionNotify
event tells us that the pointer is now in a different titlebar.

Before this, it was possible that we did not generate a leave event on a
titlebar since the LeaveNotify contains the cursor position after the leave and
we did not manage to figure out which titlebar was left.

Signed-off-by: Uli Schlachter <psychon@znc.in>

event.c

@@ -411,6 +411,44 @@ event_handle_destroynotify(xcb_destroy_notify_event_t *ev)
             }
 }
 
+/** Record that the given drawable contains the pointer.
+ */
+static void
+event_drawable_under_mouse(lua_State *L, int ud)
+{
+    void *d;
+
+    lua_pushvalue(L, ud);
+    d = luaA_object_ref(L, -1);
+
+    if (d == globalconf.drawable_under_mouse)
+    {
+        /* Nothing to do */
+        luaA_object_unref(L, d);
+        return;
+    }
+
+    if (globalconf.drawable_under_mouse != NULL)
+    {
+        /* Emit leave on previous drawable */
+        luaA_object_push(L, globalconf.drawable_under_mouse);
+        luaA_object_emit_signal(L, -1, "mouse::leave", 0);
+        lua_pop(L, 1);
+
+        /* Unref the previous drawable */
+        luaA_object_unref(L, globalconf.drawable_under_mouse);
+        globalconf.drawable_under_mouse = NULL;
+    }
+    if (d != NULL)
+    {
+        /* Reference the drawable for leave event later */
+        globalconf.drawable_under_mouse = d;
+
+        /* Emit enter */
+        luaA_object_emit_signal(L, ud, "mouse::enter", 0);
+    }
+}
+
 /** The motion notify event handler.
  * \param ev The event.
  */
@@ -439,6 +477,7 @@ event_handle_motionnotify(xcb_motion_notify_event_t *ev)
         if (d)
         {
             luaA_object_push_item(L, -1, d);
+            event_drawable_under_mouse(L, -1);
             lua_pushnumber(L, x);
             lua_pushnumber(L, y);
             luaA_object_emit_signal(L, -3, "mouse::move", 2);
@@ -451,6 +490,7 @@ event_handle_motionnotify(xcb_motion_notify_event_t *ev)
     {
         luaA_object_push(L, w);
         luaA_object_push_item(L, -1, w->drawable);
+        event_drawable_under_mouse(L, -1);
         lua_pushnumber(L, ev->event_x);
         lua_pushnumber(L, ev->event_y);
         luaA_object_emit_signal(L, -3, "mouse::move", 2);
@@ -465,7 +505,6 @@ static void
 event_handle_leavenotify(xcb_leave_notify_event_t *ev)
 {
     lua_State *L = globalconf_get_lua_State();
-    drawin_t *drawin;
     client_t *c;
 
     globalconf.timestamp = ev->time;
@@ -477,23 +516,11 @@ event_handle_leavenotify(xcb_leave_notify_event_t *ev)
     {
         luaA_object_push(L, c);
         luaA_object_emit_signal(L, -1, "mouse::leave", 0);
-        drawable_t *d = client_get_drawable(c, ev->event_x, ev->event_y);
-        if (d)
-        {
-            luaA_object_push_item(L, -1, d);
-            luaA_object_emit_signal(L, -1, "mouse::leave", 0);
-            lua_pop(L, 1);
-        }
-        lua_pop(L, 1);
     }
 
-    if((drawin = drawin_getbywin(ev->event)))
+    lua_pushnil(L);
-    {
+    event_drawable_under_mouse(L, -1);
-        luaA_object_push(L, drawin);
+    lua_pop(L, 1);
-        luaA_object_push_item(L, -1, drawin->drawable);
-        luaA_object_emit_signal(L, -1, "mouse::leave", 0);
-        lua_pop(L, 2);
-    }
 }
 
 /** The enter notify event handler.
@@ -515,7 +542,7 @@ event_handle_enternotify(xcb_enter_notify_event_t *ev)
     {
         luaA_object_push(L, drawin);
         luaA_object_push_item(L, -1, drawin->drawable);
-        luaA_object_emit_signal(L, -1, "mouse::enter", 0);
+        event_drawable_under_mouse(L, -1);
         lua_pop(L, 2);
     }
 
@@ -527,7 +554,7 @@ event_handle_enternotify(xcb_enter_notify_event_t *ev)
         if (d)
         {
             luaA_object_push_item(L, -1, d);
-            luaA_object_emit_signal(L, -1, "mouse::enter", 0);
+            event_drawable_under_mouse(L, -1);
             lua_pop(L, 1);
         }
         lua_pop(L, 1);

globalconf.h

@@ -108,6 +108,8 @@ typedef struct
     int keygrabber;
     /** The mouse pointer grabber function */
     int mousegrabber;
+    /** The drawable that currently contains the pointer */
+    drawable_t *drawable_under_mouse;
     /** Input focus information */
     struct
     {