1 files changed, 85 insertions, 0 deletions
diff --git a/devtools/client/inspector/rules/models/user-properties.js b/devtools/client/inspector/rules/models/user-properties.js
new file mode 100644
index 0000000000..381b800e59
--- /dev/null
+++ b/devtools/client/inspector/rules/models/user-properties.js
@@ -0,0 +1,85 @@
+/* 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/. */
+
+"use strict";
+
+/**
+ * Store of CSSStyleDeclarations mapped to properties that have been changed by
+ * the user.
+ */
+class UserProperties {
+  constructor() {
+    this.map = new Map();
+  }
+
+  /**
+   * Get a named property for a given CSSStyleDeclaration.
+   *
+   * @param {CSSStyleDeclaration} style
+   *        The CSSStyleDeclaration against which the property is mapped.
+   * @param {String} name
+   *        The name of the property to get.
+   * @param {String} value
+   *        Default value.
+   * @return {String}
+   *        The property value if it has previously been set by the user, null
+   *        otherwise.
+   */
+  getProperty(style, name, value) {
+    const key = this.getKey(style);
+    const entry = this.map.get(key, null);
+
+    if (entry && name in entry) {
+      return entry[name];
+    }
+    return value;
+  }
+
+  /**
+   * Set a named property for a given CSSStyleDeclaration.
+   *
+   * @param {CSSStyleDeclaration} style
+   *        The CSSStyleDeclaration against which the property is to be mapped.
+   * @param {String} name
+   *        The name of the property to set.
+   * @param {String} userValue
+   *        The value of the property to set.
+   */
+  setProperty(style, name, userValue) {
+    const key = this.getKey(style, name);
+    const entry = this.map.get(key, null);
+
+    if (entry) {
+      entry[name] = userValue;
+    } else {
+      const props = {};
+      props[name] = userValue;
+      this.map.set(key, props);
+    }
+  }
+
+  /**
+   * Check whether a named property for a given CSSStyleDeclaration is stored.
+   *
+   * @param {CSSStyleDeclaration} style
+   *        The CSSStyleDeclaration against which the property would be mapped.
+   * @param {String} name
+   *        The name of the property to check.
+   */
+  contains(style, name) {
+    const key = this.getKey(style, name);
+    const entry = this.map.get(key, null);
+    return !!entry && name in entry;
+  }
+
+  getKey(style, name) {
+    return style.actorID + ":" + name;
+  }
+
+  clear() {
+    this.map.clear();
+  }
+}
+
+module.exports = UserProperties;