classic: Add 'horizontal-workspaces' extension

Vertical workspaces are another defining characteristics of GNOME 3,
and thus rather un-classic. That switch was driven by the overall
layout of the overview, and now that we disable the overview in
GNOME Classic, we can just return to the traditional workspace
layout as well.

Add a small extension that does just that.

https://gitlab.gnome.org/GNOME/gnome-shell-extensions/merge_requests/72

extensions/horizontal-workspaces/extension.js

@@ -0,0 +1,38 @@
+/* exported init */
+const { Meta } = imports.gi;
+
+const { ThumbnailsBox } = imports.ui.workspaceThumbnail;
+
+class Extension {
+    constructor() {
+        this._origUpdateSwitcherVisibility =
+            ThumbnailsBox.prototype._updateSwitcherVisibility;
+    }
+
+    enable() {
+        global.workspace_manager.override_workspace_layout(
+            Meta.DisplayCorner.TOPLEFT,
+            false,
+            1,
+            -1);
+
+        ThumbnailsBox.prototype._updateSwitcherVisibility = function() {
+            this.hide();
+        };
+    }
+
+    disable() {
+        global.workspace_manager.override_workspace_layout(
+            Meta.DisplayCorner.TOPLEFT,
+            false,
+            -1,
+            1);
+
+        ThumbnailsBox.prototype._updateSwitcherVisibility =
+            this._origUpdateSwitcherVisibility;
+    }
+}
+
+function init() {
+    return new Extension();
+}

extensions/horizontal-workspaces/meson.build

@@ -0,0 +1,5 @@
+extension_data += configure_file(
+  input: metadata_name + '.in',
+  output: metadata_name,
+  configuration: metadata_conf
+)

extensions/horizontal-workspaces/metadata.json.in

@@ -0,0 +1,10 @@
+{
+"extension-id": "@extension_id@",
+"uuid": "@uuid@",
+"settings-schema": "@gschemaname@",
+"gettext-domain": "@gettext_domain@",
+"name": "Horizontal workspaces",
+"description": "Use a horizontal workspace layout",
+"shell-version": [ "@shell_current@" ],
+"url": "@url@"
+}

extensions/horizontal-workspaces/stylesheet.css

@@ -0,0 +1 @@
+/* This extensions requires no special styling */

meson.build

@@ -33,6 +33,7 @@ uuid_suffix = '@gnome-shell-extensions.gcampax.github.com'
 
 classic_extensions = [
   'apps-menu',
+  'horizontal-workspaces',
   'places-menu',
   'launch-new-instance',
   'window-list'