workspacesView: Support horizontal layout

Just as we did for the workspace switcher popup, support workspaces
being laid out in a single row in the window picker.

Note that this takes care of the various workspace switch actions in
the overview (scrolling, panning, touch(pad) gestures) as well as the
switch animation, but not of the overview's workspace switcher component.

There are currently no plans to support other layouts there, as the
component is inherently vertical (in fact, it was the whole reason for
switching the layout in the first place).

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/575

js/ui/workspacesView.js

@@ -189,26 +189,32 @@ var WorkspacesView = class extends WorkspacesViewBase {
 
             Tweener.removeTweens(workspace.actor);
 
-            let y = (w - active) * this._fullGeometry.height;
+            let params = {};
+            if (workspaceManager.layout_rows == -1)
+                params.y = (w - active) * this._fullGeometry.height;
+            else if (this.actor.text_direction == Clutter.TextDirection.RTL)
+                params.x = (active - w) * this._fullGeometry.width;
+            else
+                params.x = (w - active) * this._fullGeometry.width;
 
             if (showAnimation) {
-                let params = { y: y,
+                let tweenParams = Object.assign(params, {
                     time: WORKSPACE_SWITCH_TIME,
                     transition: 'easeOutQuad'
-                             };
+                });
                 // we have to call _updateVisibility() once before the
                 // animation and once afterwards - it does not really
                 // matter which tween we use, so we pick the first one ...
                 if (w == 0) {
                     this._updateVisibility();
-                    params.onComplete = () => {
+                    tweenParams.onComplete = () => {
                         this._animating = false;
                         this._updateVisibility();
                     };
                 }
-                Tweener.addTween(workspace.actor, params);
+                Tweener.addTween(workspace.actor, tweenParams);
             } else {
-                workspace.actor.set_position(0, y);
+                workspace.actor.set(params);
                 if (w == 0)
                     this._updateVisibility();
             }
@@ -346,16 +352,18 @@ var WorkspacesView = class extends WorkspacesViewBase {
             metaWorkspace.activate(global.get_current_time());
         }
 
+        if (adj.upper == 1)
+            return;
+
         let last = this._workspaces.length - 1;
+
+        if (workspaceManager.layout_rows == -1) {
             let firstWorkspaceY = this._workspaces[0].actor.y;
             let lastWorkspaceY = this._workspaces[last].actor.y;
             let workspacesHeight = lastWorkspaceY - firstWorkspaceY;
 
-        if (adj.upper == 1)
-            return;
-
             let currentY = firstWorkspaceY;
-        let newY =  - adj.value / (adj.upper - 1) * workspacesHeight;
+            let newY = -adj.value / (adj.upper - 1) * workspacesHeight;
 
             let dy = newY - currentY;
 
@@ -363,6 +371,21 @@ var WorkspacesView = class extends WorkspacesViewBase {
                 this._workspaces[i].actor.visible = Math.abs(i - adj.value) <= 1;
                 this._workspaces[i].actor.y += dy;
             }
+        } else {
+            let firstWorkspaceX = this._workspaces[0].actor.x;
+            let lastWorkspaceX = this._workspaces[last].actor.x;
+            let workspacesWidth = lastWorkspaceX - firstWorkspaceX;
+
+            let currentX = firstWorkspaceX;
+            let newX = -adj.value / (adj.upper - 1) * workspacesWidth;
+
+            let dx = newX - currentX;
+
+            for (let i = 0; i < this._workspaces.length; i++) {
+                this._workspaces[i].actor.visible = Math.abs(i - adj.value) <= 1;
+                this._workspaces[i].actor.x += dx;
+            }
+        }
     }
 };
 Signals.addSignalMethods(WorkspacesView.prototype);
@@ -509,7 +532,12 @@ var WorkspacesDisplay = class {
     _onPan(action) {
         let [dist, dx, dy] = action.get_motion_delta(0);
         let adjustment = this._scrollAdjustment;
+        if (global.workspace_manager.layout_rows == -1)
             adjustment.value -= (dy / this.actor.height) * adjustment.page_size;
+        else if (this.actor.text_direction == Clutter.TextDirection.RTL)
+            adjustment.value += (dx / this.actor.width) * adjustment.page_size;
+        else
+            adjustment.value -= (dx / this.actor.width) * adjustment.page_size;
         return false;
     }
 
@@ -541,7 +569,12 @@ var WorkspacesDisplay = class {
         let workspaceManager = global.workspace_manager;
         let active = workspaceManager.get_active_workspace_index();
         let adjustment = this._scrollAdjustment;
+        if (workspaceManager.layout_rows == -1)
             adjustment.value = (active - yRel / this.actor.height) * adjustment.page_size;
+        else if (this.actor.text_direction == Clutter.TextDirection.RTL)
+            adjustment.value = (active + xRel / this.actor.width) * adjustment.page_size;
+        else
+            adjustment.value = (active - xRel / this.actor.width) * adjustment.page_size;
     }
 
     _onSwitchWorkspaceActivated(action, direction) {
@@ -765,6 +798,12 @@ var WorkspacesDisplay = class {
         case Clutter.ScrollDirection.DOWN:
             ws = activeWs.get_neighbor(Meta.MotionDirection.DOWN);
             break;
+        case Clutter.ScrollDirection.LEFT:
+            ws = activeWs.get_neighbor(Meta.MotionDirection.LEFT);
+            break;
+        case Clutter.ScrollDirection.RIGHT:
+            ws = activeWs.get_neighbor(Meta.MotionDirection.RIGHT);
+            break;
         default:
             return Clutter.EVENT_PROPAGATE;
         }