action dispatcher: Introduce global pseudo focus while navigating

The action dispatcher would only allow actions to operate on tiled windows.

However some actions, like cycleWindowWidth, are able to operate on eg. scratch
windows, while it at the same time wants context between repeated cycles.

To solve this we add an explicitly tracked pseduo focus to the dispatcher.
Actions can now return a MetaWindow which then becomes the new focus.

This should pave the way for us to integrate eg. alt-tab with the dispatcher.

keybindings.js

@@ -250,13 +250,15 @@ function impliedOptions(options) {
 }
 
 /**
- * handler: function(metaWindow, space, {binding, display, screen}) -> ignored
+ * handler: function(metaWindow, space, {binding, display, screen}) -> metaWindow | null
  * options: {
  *   opensMinimap:      true|false Start navigation and open the minimap
  *   opensNavigator:    true|false Start navigation (eg. Esc will restore selected space and window)
  *   activeInNavigator: true|false Action is available during navigation
  *   ...
  * }
+ * The optionally returned window determines pseudo focus while navigating. Ie.
+ * the next action will operate on this window.
  */
 function registerAction(actionName, handler, options) {
     options = impliedOptions(options)

navigator.js

@@ -57,6 +57,8 @@ var ActionDispatcher = class {
 
         this.contexts = new Map();
 
+        this.focus = display.focus_window;
+
         this.actor.connect('key-press-event', this._keyPressEvent.bind(this));
         this.actor.connect('key-release-event', this._keyReleaseEvent.bind(this));
 
@@ -151,7 +153,10 @@ var ActionDispatcher = class {
 
         let action = Keybindings.byId(mutterActionId);
         let space = Tiling.spaces.selectedSpace;
-        let metaWindow = space.selectedWindow;
+        // Make sure the window is alive
+        if (this.focus && !this.focus.get_compositor_private())
+            this.focus = space.selectedWindow;
+        let metaWindow = this.focus;
 
         if (this.lastAction !== action) {
             this.contexts.delete(action);
@@ -164,7 +169,10 @@ var ActionDispatcher = class {
             if (action.options.opensMinimap) {
                 this.navigator._showMinimap(space);
             }
-            action.handler(metaWindow, space, {navigator: this.navigator, context});
+            let focus = action.handler(metaWindow, space, {navigator: this.navigator, context});
+            if (focus && focus.constructor.name.match('MetaWindow')) {
+                this.focus = focus;
+            }
             if (space !== Tiling.spaces.selectedSpace) {
                 this.navigator.minimaps.forEach(m => typeof(m) === 'number' ?
                                                 Mainloop.source_remove(m) : m.hide());

tiling.js

@@ -704,13 +704,13 @@ class Space extends Array {
 
         let metaWindow = this.getWindow(index, row);
         ensureViewport(metaWindow, this);
-        return true;
+        return metaWindow;
     }
 
-    switchLeft() { this.switch(Meta.MotionDirection.LEFT) }
-    switchRight() { this.switch(Meta.MotionDirection.RIGHT) }
-    switchUp() { this.switch(Meta.MotionDirection.UP) }
-    switchDown() { this.switch(Meta.MotionDirection.DOWN) }
+    switchLeft() { return this.switch(Meta.MotionDirection.LEFT) }
+    switchRight() { return this.switch(Meta.MotionDirection.RIGHT) }
+    switchUp() { return this.switch(Meta.MotionDirection.UP) }
+    switchDown() { return this.switch(Meta.MotionDirection.DOWN) }
     switch(direction) {
         let space = this;
         let index = space.selectedIndex();
@@ -747,6 +747,7 @@ class Space extends Array {
 
         let metaWindow = space.getWindow(index, row);
         ensureViewport(metaWindow, space);
+        return metaWindow;
     }
 
     positionOf(metaWindow) {
@@ -1448,7 +1449,7 @@ class Spaces extends Map {
         let currentSpace = this.monitors.get(monitor);
         let i = display.get_monitor_neighbor_index(monitor.index, direction);
         if (i === -1)
-            return;
+            return null;
         let newMonitor = Main.layoutManager.monitors[i];
         let space = this.monitors.get(newMonitor);
 
@@ -1478,6 +1479,7 @@ class Spaces extends Map {
         } else {
             space.workspace.activate(global.get_current_time());
         }
+        return focus;
     }
 
     switchWorkspace(wm, fromIndex, toIndex) {
@@ -1662,6 +1664,7 @@ class Spaces extends Map {
                              });
 
         });
+        return newSpace.selectedWindow;
     }
 
     animateToSpace(to, from, callback) {
@@ -2824,11 +2827,11 @@ function barf(metaWindow) {
 }
 
 function selectPreviousSpace(mw, space) {
-    spaces.selectSpace(Meta.MotionDirection.DOWN);
+    return spaces.selectSpace(Meta.MotionDirection.DOWN);
 }
 
 function selectPreviousSpaceBackwards(mw, space) {
-    spaces.selectSpace(Meta.MotionDirection.UP);
+    return spaces.selectSpace(Meta.MotionDirection.UP);
 }
 
 function movePreviousSpace(mw, space) {