workspacesView: Update zoom scale when controls are reallocated

The scale we zoom to in the "zoomed out" mode depends on the width of the
controls area. Once we rescale the workspaces dynamically, we'll need to
update the zoom scale as we add and remove workspaces.

https://bugzilla.gnome.org/show_bug.cgi?id=641879

js/ui/workspacesView.js

@@ -25,12 +25,12 @@ const MAX_WORKSPACES = 16;
 const CONTROLS_POP_IN_TIME = 0.1;
 
 
-function WorkspacesView(width, height, x, y, zoomScale, workspaces) {
+function WorkspacesView(width, height, x, y, workspaces) {
-    this._init(width, height, x, y, zoomScale, workspaces);
+    this._init(width, height, x, y, workspaces);
 }
 
 WorkspacesView.prototype = {
-    _init: function(width, height, x, y, zoomScale, workspaces) {
+    _init: function(width, height, x, y, workspaces) {
         this.actor = new St.Group({ style_class: 'workspaces-view' });
         this.actor.set_clip(x, y, width, height);
 
@@ -52,7 +52,7 @@ WorkspacesView.prototype = {
         this._height = height;
         this._x = x;
         this._y = y;
-        this._zoomScale = zoomScale;
+        this._zoomScale = 1.0;
         this._spacing = 0;
         this._activeWorkspaceX = 0; // x offset of active ws while dragging
         this._activeWorkspaceY = 0; // y offset of active ws while dragging
@@ -109,6 +109,32 @@ WorkspacesView.prototype = {
         this._swipeScrollEndId = 0;
     },
 
+    setZoomScale: function(zoomScale) {
+        if (zoomScale == this._zoomScale)
+            return;
+
+        this._zoomScale = zoomScale;
+        if (this._zoomOut) {
+            // If we are already zoomed out, then we have to reposition.
+            // Note that when shown initially zoomOut is false, so we
+            // won't trigger this.
+
+            // setZoomScale can be invoked when the workspaces view is
+            // reallocated. Since we just want to animate things to the
+            // new position it seems OK to call updateWorkspaceActors
+            // immediately - adding a tween doesn't immediately cause
+            // a new allocation. But hide/show of the window overlays we
+            // do around animation does, so we need to do it later.
+            // This can be removed when we fix things to not hide/show
+            // the window overlay.
+            Meta.later_add(Meta.LaterType.BEFORE_REDRAW,
+                           Lang.bind(this, function() {
+                                         this._computeWorkspacePositions();
+                                         this._updateWorkspaceActors(true);
+                                     }));
+        }
+    },
+
     _lookupWorkspaceForMetaWindow: function (metaWindow) {
         for (let i = 0; i < this._workspaces.length; i++) {
             if (this._workspaces[i].containsMetaWindow(metaWindow))
@@ -638,7 +664,6 @@ WorkspacesDisplay.prototype = {
         let totalWidth = totalAllocation.x2 - totalAllocation.x1;
         let totalHeight = totalAllocation.y2 - totalAllocation.y1;
 
-        let [controlsMin, controlsNatural] = this._controls.get_preferred_width(totalHeight);
         let controlsVisible = this._controls.get_theme_node().get_length('visible-width');
 
         totalWidth -= controlsVisible;
@@ -664,8 +689,8 @@ WorkspacesDisplay.prototype = {
         if (rtl)
             x += controlsVisible;
 
-        let zoomScale = (totalWidth - (controlsNatural - controlsVisible)) / totalWidth;
+        let newView = new WorkspacesView(width, height, x, y, this._workspaces);
-        let newView = new WorkspacesView(width, height, x, y, zoomScale, this._workspaces);
+        this._updateZoomScale();
 
         if (this.workspacesView)
             this.workspacesView.destroy();
@@ -779,6 +804,23 @@ WorkspacesDisplay.prototype = {
         childBox.y1 = 0;
         childBox.y2 = box.y2- box.y1;
         this._controls.allocate(childBox, flags);
+
+        this._updateZoomScale();
+    },
+
+    _updateZoomScale: function() {
+        if (!this.workspacesView)
+            return;
+
+        let totalAllocation = this.actor.allocation;
+        let totalWidth = totalAllocation.x2 - totalAllocation.x1;
+        let totalHeight = totalAllocation.y2 - totalAllocation.y1;
+
+        let [controlsMin, controlsNatural] = this._controls.get_preferred_width(totalHeight);
+        let controlsVisible = this._controls.get_theme_node().get_length('visible-width');
+
+        let zoomScale = (totalWidth - controlsNatural) / (totalWidth - controlsVisible);
+        this.workspacesView.setZoomScale(zoomScale);
     },
 
     _onRestacked: function() {