1 files changed, 86 insertions, 0 deletions
diff --git a/devtools/client/projecteditor/lib/helpers/event.js b/devtools/client/projecteditor/lib/helpers/event.js
new file mode 100644
index 000000000..74b4adb04
--- /dev/null
+++ b/devtools/client/projecteditor/lib/helpers/event.js
@@ -0,0 +1,86 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This file wraps EventEmitter objects to provide functions to forget
+ * all events bound on a certain object.
+ */
+
+const { Class } = require("sdk/core/heritage");
+
+/**
+ * The Scope object is used to keep track of listeners.
+ * This object is not exported.
+ */
+var Scope = Class({
+  on: function (target, event, handler) {
+    this.listeners = this.listeners || [];
+    this.listeners.push({
+      target: target,
+      event: event,
+      handler: handler
+    });
+    target.on(event, handler);
+  },
+
+  off: function (t, e, h) {
+    if (!this.listeners) return;
+    this.listeners = this.listeners.filter(({ target, event, handler }) => {
+      return !(target === t && event === e && handler === h);
+    });
+    target.off(event, handler);
+  },
+
+  clear: function (clearTarget) {
+    if (!this.listeners) return;
+    this.listeners = this.listeners.filter(({ target, event, handler }) => {
+      if (target === clearTarget) {
+        target.off(event, handler);
+        return false;
+      }
+      return true;
+    });
+  },
+
+  destroy: function () {
+    if (!this.listeners) return;
+    this.listeners.forEach(({ target, event, handler }) => {
+      target.off(event, handler);
+    });
+    this.listeners = undefined;
+  }
+});
+
+var scopes = new WeakMap();
+function scope(owner) {
+  if (!scopes.has(owner)) {
+    let scope = new Scope(owner);
+    scopes.set(owner, scope);
+    return scope;
+  }
+  return scopes.get(owner);
+}
+exports.scope = scope;
+
+exports.on = function on(owner, target, event, handler) {
+  if (!target) return;
+  scope(owner).on(target, event, handler);
+};
+
+exports.off = function off(owner, target, event, handler) {
+  if (!target) return;
+  scope(owner).off(target, event, handler);
+};
+
+exports.forget = function forget(owner, target) {
+  scope(owner).clear(target);
+};
+
+exports.done = function done(owner) {
+  scope(owner).destroy();
+  scopes.delete(owner);
+};
+