input: add a weston_pointer_clear_focus() helper function

Valgrind has shown that in at least one place (default_grab_pointer_focus)
we're testing uninitialized values coming out of weston_compositor_pick_view.

This is happening when default_grab_pointer_focus is called when there is
nothing on the view list, and during the first repaint when only the black
surface with no input region exists.

This patch adds a function to clear pointer focus and also set the sx,sy
co-ordinates to a sentinel value we shouldn't compute with.

Assertions are added to make sure any time pointer focus is set to NULL
these values are used.

weston_compositor_pick_view() now returns these values too.

Now the values are always initialized, even when no view exists, and
they're initialized in such a way that actually doing computation
with them should fail in an obvious way, but we can compare them
safely for equality.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

desktop-shell/exposay.c

@@ -589,9 +589,7 @@ exposay_transition_active(struct desktop_shell *shell)
 	if (pointer) {
 		weston_pointer_start_grab(pointer,
 		                          &shell->exposay.grab_ptr);
-		weston_pointer_set_focus(pointer, NULL,
-				         pointer->x,
-					 pointer->y);
+		weston_pointer_clear_focus(pointer);
 	}
 	wl_list_for_each(shell_output, &shell->output_list, link) {
 		enum exposay_layout_state state;

desktop-shell/shell.c

@@ -3218,9 +3218,7 @@ popup_grab_focus(struct weston_pointer_grab *grab)
 	    wl_resource_get_client(view->surface->resource) == client) {
 		weston_pointer_set_focus(pointer, view, sx, sy);
 	} else {
-		weston_pointer_set_focus(pointer, NULL,
-					 wl_fixed_from_int(0),
-					 wl_fixed_from_int(0));
+		weston_pointer_clear_focus(pointer);
 	}
 }
 

src/compositor.c

@@ -1716,6 +1716,8 @@ weston_compositor_pick_view(struct weston_compositor *compositor,
 		return view;
 	}
 
+	*vx = wl_fixed_from_int(-1000000);
+	*vy = wl_fixed_from_int(-1000000);
 	return NULL;
 }
 
@@ -1760,10 +1762,7 @@ weston_view_unmap(struct weston_view *view)
 		if (keyboard && keyboard->focus == view->surface)
 			weston_keyboard_set_focus(keyboard, NULL);
 		if (pointer && pointer->focus == view)
-			weston_pointer_set_focus(pointer,
-						 NULL,
-						 wl_fixed_from_int(0),
-						 wl_fixed_from_int(0));
+			weston_pointer_clear_focus(pointer);
 		if (touch && touch->focus == view)
 			weston_touch_set_focus(touch, NULL);
 	}

src/compositor.h

@@ -374,6 +374,8 @@ weston_pointer_set_focus(struct weston_pointer *pointer,
 			 struct weston_view *view,
 			 wl_fixed_t sx, wl_fixed_t sy);
 void
+weston_pointer_clear_focus(struct weston_pointer *pointer);
+void
 weston_pointer_start_grab(struct weston_pointer *pointer,
 			  struct weston_pointer_grab *grab);
 void

src/data-device.c

@@ -591,8 +591,7 @@ weston_pointer_start_drag(struct weston_pointer *pointer,
 			      &drag->base.data_source_listener);
 	}
 
-	weston_pointer_set_focus(pointer, NULL,
-				 wl_fixed_from_int(0), wl_fixed_from_int(0));
+	weston_pointer_clear_focus(pointer);
 	weston_pointer_start_grab(pointer, &drag->grab);
 
 	return 0;

src/input.c

@@ -82,7 +82,7 @@ pointer_focus_view_destroyed(struct wl_listener *listener, void *data)
 		container_of(listener, struct weston_pointer,
 			     focus_view_listener);
 
-	weston_pointer_set_focus(pointer, NULL, 0, 0);
+	weston_pointer_clear_focus(pointer);
 }
 
 static void
@@ -92,7 +92,7 @@ pointer_focus_resource_destroyed(struct wl_listener *listener, void *data)
 		container_of(listener, struct weston_pointer,
 			     focus_resource_listener);
 
-	weston_pointer_set_focus(pointer, NULL, 0, 0);
+	weston_pointer_clear_focus(pointer);
 }
 
 static void
@@ -498,6 +498,9 @@ weston_pointer_create(struct weston_seat *seat)
 	wl_signal_add(&seat->compositor->output_destroyed_signal,
 		      &pointer->output_destroy_listener);
 
+	pointer->sx = wl_fixed_from_int(-1000000);
+	pointer->sy = wl_fixed_from_int(-1000000);
+
 	return pointer;
 }
 
@@ -628,6 +631,26 @@ seat_send_updated_caps(struct weston_seat *seat)
 	wl_signal_emit(&seat->updated_caps_signal, seat);
 }
 
+
+/** Clear the pointer focus
+ *
+ * \param pointer the pointer to clear focus for.
+ *
+ * This can be used to unset pointer focus and set the co-ordinates to the
+ * arbitrary values we use for the no focus case.
+ *
+ * There's no requirement to use this function.  For example, passing the
+ * results of a weston_compositor_pick_view() directly to
+ * weston_pointer_set_focus() will do the right thing when no view is found.
+ */
+WL_EXPORT void
+weston_pointer_clear_focus(struct weston_pointer *pointer)
+{
+	weston_pointer_set_focus(pointer, NULL,
+				 wl_fixed_from_int(-1000000),
+				 wl_fixed_from_int(-1000000));
+}
+
 WL_EXPORT void
 weston_pointer_set_focus(struct weston_pointer *pointer,
 			 struct weston_view *view,
@@ -699,6 +722,9 @@ weston_pointer_set_focus(struct weston_pointer *pointer,
 	pointer->sx = sx;
 	pointer->sy = sy;
 
+	assert(view || sx == wl_fixed_from_int(-1000000));
+	assert(view || sy == wl_fixed_from_int(-1000000));
+
 	wl_signal_emit(&pointer->focus_signal, pointer);
 }
 
@@ -2271,9 +2297,7 @@ weston_seat_release_pointer(struct weston_seat *seat)
 
 	seat->pointer_device_count--;
 	if (seat->pointer_device_count == 0) {
-		weston_pointer_set_focus(pointer, NULL,
-					 wl_fixed_from_int(0),
-					 wl_fixed_from_int(0));
+		weston_pointer_clear_focus(pointer);
 		weston_pointer_cancel_grab(pointer);
 
 		if (pointer->sprite)