windowManager: add animations for fullscreen and unfullscreen

We use the newly introduced feature from Mutter to hook up our own
fullscreen and unfullscreen animations.
To give the illusion of a transition as smooth as possible, we create a
snapshot of the current contents of the actor before its state is
changed, and crossfade between the two states while the size changes.

https://bugzilla.gnome.org/show_bug.cgi?id=707248

js/ui/windowManager.js

@@ -677,6 +677,7 @@ const WindowManager = new Lang.Class({
         this._minimizing = [];
         this._unminimizing = [];
         this._mapping = [];
+        this._resizing = [];
         this._destroying = [];
         this._movingWindow = null;
 
@@ -692,6 +693,7 @@ const WindowManager = new Lang.Class({
             this._minimizeWindowDone(shellwm, actor);
             this._mapWindowDone(shellwm, actor);
             this._destroyWindowDone(shellwm, actor);
+            this._sizeChangeWindowDone(shellwm, actor);
         }));
 
         this._shellwm.connect('switch-workspace', Lang.bind(this, this._switchWorkspace));
@@ -1218,9 +1220,105 @@ const WindowManager = new Lang.Class({
     },
 
     _sizeChangeWindow : function(shellwm, actor, whichChange, oldFrameRect, oldBufferRect) {
+        let types = [Meta.WindowType.NORMAL];
+        if (!this._shouldAnimateActor(actor, types)) {
+            shellwm.completed_size_change(actor);
+            return;
+        }
+
+        if (whichChange == Meta.SizeChange.FULLSCREEN)
+            this._fullscreenWindow(shellwm, actor, oldFrameRect, oldBufferRect);
+        else if (whichChange == Meta.SizeChange.UNFULLSCREEN)
+            this._unfullscreenWindow(shellwm, actor, oldFrameRect, oldBufferRect);
+        else
+            shellwm.completed_size_change(actor);
+    },
+
+    _fullscreenWindow: function(shellwm, actor, oldFrameRect, oldBufferRect) {
+        actor.translation_x = oldFrameRect.x;
+        actor.translation_y = oldFrameRect.y;
+        this._fullscreenAnimation(shellwm, actor, oldFrameRect);
+    },
+
+    _unfullscreenWindow: function(shellwm, actor, oldFrameRect, oldBufferRect) {
+        let targetRect = actor.meta_window.get_frame_rect();
+        actor.translation_x = -targetRect.x;
+        actor.translation_y = -targetRect.y;
+        this._fullscreenAnimation(shellwm, actor, oldFrameRect);
+    },
+
+    _fullscreenAnimation: function(shellwm, actor, oldFrameRect) {
+        this._resizing.push(actor);
+
+        // Position a clone of the window on top of the old position,
+        // while actor updates are frozen.
+        // Note that the MetaWindow has up to date sizing information for
+        // the new geometry already.
+        let targetRect = actor.meta_window.get_frame_rect();
+        let actorContent = Shell.util_get_content_for_window_actor(actor, oldFrameRect);
+        let actorClone = new St.Widget({ content: actorContent });
+        actorClone.set_offscreen_redirect(Clutter.OffscreenRedirect.ALWAYS);
+        actorClone.set_position(oldFrameRect.x, oldFrameRect.y);
+        actorClone.set_size(oldFrameRect.width, oldFrameRect.height);
+        Main.uiGroup.add_actor(actorClone);
+
+        actor.__fullscreenClone = actorClone;
+
+        let scaleX = targetRect.width / oldFrameRect.width;
+        let scaleY = targetRect.height / oldFrameRect.height;
+
+        // Now scale and fade out the clone
+        Tweener.addTween(actorClone,
+                         { x: targetRect.x,
+                           y: targetRect.y,
+                           scale_x: scaleX,
+                           scale_y: scaleY,
+                           opacity: 0,
+                           time: WINDOW_ANIMATION_TIME,
+                           transition: 'easeOutQuad'
+                         });
+
+        // Now set scale the actor to size it as the clone.
+        // Note that the caller of this function already set a translation
+        // on the actor.
+        actor.scale_x = 1 / scaleX;
+        actor.scale_y = 1 / scaleY;
+
+        // Scale it to its actual new size
+        Tweener.addTween(actor,
+                         { scale_x: 1.0,
+                           scale_y: 1.0,
+                           translation_x: 0,
+                           translation_y: 0,
+                           time: WINDOW_ANIMATION_TIME,
+                           transition: 'easeOutQuad',
+                           onComplete: this._sizeChangeWindowDone,
+                           onCompleteScope: this,
+                           onCompleteParams: [shellwm, actor]
+                         });
+
+        // Now unfreeze actor updates, to get it to the new size.
+        // It's important that we don't wait until the animation is completed to
+        // do this, otherwise our scale will be applied to the old texture size.
         shellwm.completed_size_change(actor);
     },
 
+    _sizeChangeWindowDone: function(shellwm, actor) {
+        if (this._removeEffect(this._resizing, actor)) {
+            Tweener.removeTweens(actor);
+            actor.scale_x = 1.0;
+            actor.scale_y = 1.0;
+            actor.translation_x = 0;
+            actor.translation_y = 0;
+
+            let actorClone = actor.__fullscreenClone;
+            if (actorClone) {
+                actorClone.destroy();
+                delete actor.__fullscreenClone;
+            }
+        }
+    },
+
     _hasAttachedDialogs: function(window, ignoreWindow) {
         var count = 0;
         window.foreach_transient(function(win) {

src/shell-util.c

@@ -13,6 +13,7 @@
 #include <gtk/gtk.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>
 #include <gdk/gdkx.h>
+#include <meta/meta-shaped-texture.h>
 
 #include <locale.h>
 #ifdef HAVE__NL_TIME_FIRST_WEEKDAY
@@ -403,3 +404,57 @@ shell_util_text_insert_keyval (ClutterActor *actor,
 
   clutter_actor_event (actor, &event, FALSE);
 }
+
+static gboolean
+canvas_draw_cb (ClutterContent *content,
+                cairo_t        *cr,
+                gint            width,
+                gint            height,
+                gpointer        user_data)
+{
+  cairo_surface_t *surface = user_data;
+
+  cairo_set_source_surface (cr, surface, 0, 0);
+  cairo_paint (cr);
+
+  return FALSE;
+}
+
+/**
+ * shell_util_get_content_for_window_actor:
+ * @window_actor: a #MetaWindowActor
+ * @window_rect: a #MetaRectangle
+ *
+ * Returns: (transfer full): a new #ClutterContent
+ */
+ClutterContent *
+shell_util_get_content_for_window_actor (MetaWindowActor *window_actor,
+                                         MetaRectangle   *window_rect)
+{
+  ClutterActor *texture;
+  ClutterContent *content;
+  cairo_surface_t *surface;
+  cairo_rectangle_int_t clip;
+  gfloat actor_x, actor_y;
+
+  texture = meta_window_actor_get_texture (window_actor);
+  clutter_actor_get_position (CLUTTER_ACTOR (window_actor), &actor_x, &actor_y);
+
+  clip.x = window_rect->x - (gint) actor_x;
+  clip.y = window_rect->y - (gint) actor_y;
+  clip.width = window_rect->width;
+  clip.height = window_rect->height;
+
+  surface = meta_shaped_texture_get_image (META_SHAPED_TEXTURE (texture),
+                                           &clip);
+
+  content = clutter_canvas_new ();
+  clutter_canvas_set_size (CLUTTER_CANVAS (content),
+                           clip.width, clip.height);
+  g_signal_connect (content, "draw",
+                    G_CALLBACK (canvas_draw_cb), surface);
+  clutter_content_invalidate (content);
+  cairo_surface_destroy (surface);
+
+  return content;
+}

src/shell-util.h

@@ -8,6 +8,7 @@
 #include <libsoup/soup.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>
 #include <meta/meta-cursor-tracker.h>
+#include <meta/meta-window-actor.h>
 
 G_BEGIN_DECLS
 
@@ -50,6 +51,9 @@ gboolean shell_util_need_background_refresh (void);
 void shell_util_text_insert_keyval (ClutterActor *actor,
                                     guint         keyval);
 
+ClutterContent * shell_util_get_content_for_window_actor (MetaWindowActor *window_actor,
+                                                          MetaRectangle   *window_rect);
+
 G_END_DECLS
 
 #endif /* __SHELL_UTIL_H__ */