view: unconditionally center views in output layout

Whatever type or dimensions of a view, position it at center of the
output layout. Then, if it is a primary view or if it extends the output
layout, send request to maximize it.
The client may or may not change the view dimensions after that.
If not, e.g. weston-flower, the view will be kept displayed at center
instead of to left.
If so, the view will expand from center to fill the whole output layout.

In order to update the view position, XDG shell surface commit is now
handled to check for dimension change.

view.c

@@ -52,36 +52,11 @@ view_activate(struct cg_view *view, bool activate)
 	view->impl->activate(view, activate);
 }
 
-static bool
+static inline bool
 view_extends_output_layout(struct cg_view *view, struct wlr_box *layout_box)
 {
-	int width, height;
-	view->impl->get_geometry(view, &width, &height);
-
-	return (layout_box->height < height || layout_box->width < width);
-}
-
-static void
-view_maximize(struct cg_view *view, struct wlr_box *layout_box)
-{
-	view->lx = layout_box->x;
-	view->ly = layout_box->y;
-
-	wlr_scene_node_set_position(&view->scene_tree->node, view->lx, view->ly);
-
-	view->impl->maximize(view, layout_box->width, layout_box->height);
-}
-
-static void
-view_center(struct cg_view *view, struct wlr_box *layout_box)
-{
-	int width, height;
-	view->impl->get_geometry(view, &width, &height);
-
-	view->lx = (layout_box->width - width) / 2;
-	view->ly = (layout_box->height - height) / 2;
-
-	wlr_scene_node_set_position(&view->scene_tree->node, view->lx, view->ly);
+	// View width and height are expected to be set before calling this function
+	return (layout_box->height < view->height || layout_box->width < view->width);
 }
 
 void
@@ -90,10 +65,16 @@ view_position(struct cg_view *view)
 	struct wlr_box layout_box;
 	wlr_output_layout_get_box(view->server->output_layout, NULL, &layout_box);
 
+	view->impl->get_geometry(view, &view->width, &view->height);
+
+	// If view dimensions are not the same as output layout ones, it will be centered first
+	view->lx = layout_box.x + (layout_box.width - view->width) / 2;
+	view->ly = layout_box.y + (layout_box.height - view->height) / 2;
+
+	wlr_scene_node_set_position(&view->scene_tree->node, view->lx, view->ly);
+
 	if (view_is_primary(view) || view_extends_output_layout(view, &layout_box)) {
-		view_maximize(view, &layout_box);
-	} else {
-		view_center(view, &layout_box);
+		view->impl->maximize(view, layout_box.width, layout_box.height);
 	}
 }
 

view.h

@@ -29,6 +29,7 @@ struct cg_view {
 
 	/* The view has a position in layout coordinates. */
 	int lx, ly;
+	int width, height;
 
 	enum cg_view_type type;
 	const struct cg_view_impl *impl;

xdg_shell.c

@@ -183,15 +183,34 @@ handle_xdg_shell_surface_unmap(struct wl_listener *listener, void *data)
 	struct cg_xdg_shell_view *xdg_shell_view = wl_container_of(listener, xdg_shell_view, unmap);
 	struct cg_view *view = &xdg_shell_view->view;
 
+	wl_list_remove(&xdg_shell_view->commit.link);
+
 	view_unmap(view);
 }
 
+static void
+handle_xdg_shell_surface_commit(struct wl_listener *listener, void *data)
+{
+	struct cg_xdg_shell_view *xdg_shell_view = wl_container_of(listener, xdg_shell_view, commit);
+	struct cg_view *view = &xdg_shell_view->view;
+
+	// Check if view dimensions have changed
+	int width, height;
+	get_geometry(view, &width, &height);
+	if (width != view->width || height != view->height) {
+		view_position(view);
+	}
+}
+
 static void
 handle_xdg_shell_surface_map(struct wl_listener *listener, void *data)
 {
 	struct cg_xdg_shell_view *xdg_shell_view = wl_container_of(listener, xdg_shell_view, map);
 	struct cg_view *view = &xdg_shell_view->view;
 
+	xdg_shell_view->commit.notify = handle_xdg_shell_surface_commit;
+	wl_signal_add(&xdg_shell_view->xdg_toplevel->base->surface->events.commit, &xdg_shell_view->commit);
+
 	view_map(view, xdg_shell_view->xdg_toplevel->base->surface);
 }
 

xdg_shell.h

@@ -15,6 +15,7 @@ struct cg_xdg_shell_view {
 	struct wl_listener unmap;
 	struct wl_listener map;
 	struct wl_listener request_fullscreen;
+	struct wl_listener commit;
 };
 
 struct cg_xdg_decoration {