🔧 Use factory to create shaders

src/ShaderFactory.js

@@ -0,0 +1,68 @@
+//////////////////////////////////////////////////////////////////////////////////////////
+//          )                                                   (                       //
+//       ( /(   (  (               )    (       (  (  (         )\ )    (  (            //
+//       )\()) ))\ )(   (         (     )\ )    )\))( )\  (    (()/( (  )\))(  (        //
+//      ((_)\ /((_|()\  )\ )      )\  '(()/(   ((_)()((_) )\ )  ((_)))\((_)()\ )\       //
+//      | |(_|_))( ((_)_(_/(    _((_))  )(_))  _(()((_|_)_(_/(  _| |((_)(()((_|(_)      //
+//      | '_ \ || | '_| ' \))  | '  \()| || |  \ V  V / | ' \)) _` / _ \ V  V (_-<      //
+//      |_.__/\_,_|_| |_||_|   |_|_|_|  \_, |   \_/\_/|_|_||_|\__,_\___/\_/\_//__/      //
+//                                 |__/                                                 //
+//                       Copyright (c) 2021 Simon Schneegans                            //
+//          Released under the GPLv3 or later. See LICENSE file for details.            //
+//////////////////////////////////////////////////////////////////////////////////////////
+
+'use strict';
+
+const GObject = imports.gi.GObject;
+
+const ExtensionUtils = imports.misc.extensionUtils;
+const Me             = imports.misc.extensionUtils.getCurrentExtension();
+
+//////////////////////////////////////////////////////////////////////////////////////////
+// This is the base class for all effects of Burn-My-Windows. It provides the logic     //
+// required for creating shader instances and reusing them as much as possible.         //
+//////////////////////////////////////////////////////////////////////////////////////////
+
+var ShaderFactory = class ShaderFactory {
+
+  // The _freeShaders array contains previously created shaders which are not currently in
+  // use.
+  constructor(nick, setupFunc) {
+    this._freeShaders = [];
+    this._nick        = nick;
+    this._setupFunc   = setupFunc;
+  }
+
+  // ---------------------------------------------------------------- API for extension.js
+
+  // This is called from extension.js whenever a window is opened or closed with this
+  // effect. It returns an instance of the shader class, trying to reuse previously
+  // created shaders. If a new shader instance is required, it calls this.createShader().
+  // This method must be defined be the derived class!
+  getShader() {
+    let shader;
+
+    if (this._freeShaders.length == 0) {
+
+      const typeName = `BurnMyWindowsShader_${this._nick}`;
+
+      if (GObject.type_from_name(typeName) == null) {
+        GObject.registerClass({GTypeName: typeName},
+                              class Shader extends Me.imports.src.Shader.Shader {});
+      }
+
+      shader = GObject.Object.new(GObject.type_from_name(typeName), {'nick': this._nick});
+
+      shader.returnToFactory = () => {
+        this._freeShaders.push(shader);
+      };
+
+      this._setupFunc(shader);
+
+    } else {
+      shader = this._freeShaders.pop();
+    }
+
+    return shader;
+  }
+}