shell: Replace set_margin with set_window_geometry

Currently, there is a fun flicker when toggling maximization or
fullscreen on a window in mutter or more sophisicated compositors
and WMs.

What happens is that the client want so go maximized, so we
calculate the size that we want the window to resize to (640x480),
and then add on its margins to find the buffer size (+10 = 660x500),
and then send out a configure event for that size. The client
renders to that size, realizes that it's maximized, and then
says "oh hey, my margins are actually 0 now!", and so the compositor
has to send out another configure event.

In order to fix this, make the the configure request correspond to
the window geometry we'd like the window to be at. At the same time,
replace set_margin with set_window_geometry, where we specify a rect
rather than a border around the window.

1 files changed, 41 insertions, 40 deletions

diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index fca1c007..593c7f3b 100644
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -171,9 +171,9 @@ struct shell_surface {
 	bool state_requested;
 
 	struct {
-		int left, right, top, bottom;
-	} margin, next_margin;
-	bool has_next_margin;
+		int32_t x, y, width, height;
+	} geometry, next_geometry;
+	bool has_set_geometry, has_next_geometry;
 
 	int focus_count;
 };
@@ -1554,14 +1554,12 @@ constrain_position(struct weston_move_grab *move, int *cx, int *cy)
 
 	panel_height = get_output_panel_height(shsurf->shell,
 					       shsurf->surface->output);
-	bottom = y + shsurf->surface->height - shsurf->margin.bottom;
+	bottom = y + shsurf->geometry.height;
 	if (bottom - panel_height < safety)
-		y = panel_height + safety -
-			shsurf->surface->height + shsurf->margin.bottom;
+		y = panel_height + safety - shsurf->geometry.height;
 
-	if (move->client_initiated &&
-	    y + shsurf->margin.top < panel_height)
-		y = panel_height - shsurf->margin.top;
+	if (move->client_initiated && y + shsurf->geometry.y < panel_height)
+		y = panel_height - shsurf->geometry.y;
 
 	*cx = x;
 	*cy = y;
@@ -1829,13 +1827,9 @@ surface_resize(struct shell_surface *shsurf,
 		return -1;
 
 	resize->edges = edges;
-	surface_subsurfaces_boundingbox(shsurf->surface, NULL, NULL,
-	                                &resize->width, &resize->height);
 
-	resize->width -= shsurf->margin.left;
-	resize->width -= shsurf->margin.right;
-	resize->height -= shsurf->margin.top;
-	resize->height -= shsurf->margin.bottom;
+	resize->width = shsurf->geometry.width;
+	resize->height = shsurf->geometry.height;
 
 	shsurf->resize_edges = edges;
 	shell_surface_state_changed(shsurf);
@@ -2130,14 +2124,14 @@ set_title(struct shell_surface *shsurf, const char *title)
 }
 
 static void
-set_margin(struct shell_surface *shsurf,
-	   int32_t left, int32_t right, int32_t top, int32_t bottom)
+set_window_geometry(struct shell_surface *shsurf,
+		    int32_t x, int32_t y, int32_t width, int32_t height)
 {
-	shsurf->next_margin.left = left;
-	shsurf->next_margin.right = right;
-	shsurf->next_margin.top = top;
-	shsurf->next_margin.bottom = bottom;
-	shsurf->has_next_margin = true;
+	shsurf->next_geometry.x = x;
+	shsurf->next_geometry.y = y;
+	shsurf->next_geometry.width = width;
+	shsurf->next_geometry.height = height;
+	shsurf->has_next_geometry = true;
 }
 
 static void
@@ -3399,19 +3393,6 @@ xdg_surface_set_parent(struct wl_client *client,
 }
 
 static void
-xdg_surface_set_margin(struct wl_client *client,
-			     struct wl_resource *resource,
-			     int32_t left,
-			     int32_t right,
-			     int32_t top,
-			     int32_t bottom)
-{
-	struct shell_surface *shsurf = wl_resource_get_user_data(resource);
-
-	set_margin(shsurf, left, right, top, bottom);
-}
-
-static void
 xdg_surface_set_app_id(struct wl_client *client,
 		       struct wl_resource *resource,
 		       const char *app_id)
@@ -3472,6 +3453,19 @@ xdg_surface_ack_configure(struct wl_client *client,
 }
 
 static void
+xdg_surface_set_window_geometry(struct wl_client *client,
+				struct wl_resource *resource,
+				int32_t x,
+				int32_t y,
+				int32_t width,
+				int32_t height)
+{
+	struct shell_surface *shsurf = wl_resource_get_user_data(resource);
+
+	set_window_geometry(shsurf, x, y, width, height);
+}
+
+static void
 xdg_surface_set_maximized(struct wl_client *client,
 			  struct wl_resource *resource)
 {
@@ -3542,13 +3536,13 @@ xdg_surface_set_minimized(struct wl_client *client,
 static const struct xdg_surface_interface xdg_surface_implementation = {
 	xdg_surface_destroy,
 	xdg_surface_set_parent,
-	xdg_surface_set_margin,
 	xdg_surface_set_title,
 	xdg_surface_set_app_id,
 	xdg_surface_show_window_menu,
 	xdg_surface_move,
 	xdg_surface_resize,
 	xdg_surface_ack_configure,
+	xdg_surface_set_window_geometry,
 	xdg_surface_set_maximized,
 	xdg_surface_unset_maximized,
 	xdg_surface_set_fullscreen,
@@ -5141,9 +5135,16 @@ shell_surface_configure(struct weston_surface *es, int32_t sx, int32_t sy)
 	if (es->width == 0)
 		return;
 
-	if (shsurf->has_next_margin) {
-		shsurf->margin = shsurf->next_margin;
-		shsurf->has_next_margin = false;
+	if (shsurf->has_next_geometry) {
+		shsurf->geometry = shsurf->next_geometry;
+		shsurf->has_next_geometry = false;
+		shsurf->has_set_geometry = true;
+	} else if (!shsurf->has_set_geometry) {
+		surface_subsurfaces_boundingbox(shsurf->surface,
+						&shsurf->geometry.x,
+						&shsurf->geometry.y,
+						&shsurf->geometry.width,
+						&shsurf->geometry.height);
 	}
 
 	if (shsurf->state_changed) {
@@ -6200,7 +6201,7 @@ module_init(struct weston_compositor *ec,
 	ec->shell_interface.move = shell_interface_move;
 	ec->shell_interface.resize = surface_resize;
 	ec->shell_interface.set_title = set_title;
-	ec->shell_interface.set_margin = set_margin;
+	ec->shell_interface.set_window_geometry = set_window_geometry;
 
 	weston_layer_init(&shell->fullscreen_layer, &ec->cursor_layer.link);
 	weston_layer_init(&shell->panel_layer, &shell->fullscreen_layer.link);