Bug 1821821 - Enable about:messagepreview in release and beta. r=emcminn,omc-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D173569

Author: aminomancer

browser/components/about/AboutRedirector.cpp

@@ -106,13 +106,11 @@ static const RedirEntry kRedirMap[] = {
          nsIAboutModule::URI_CAN_LOAD_IN_PRIVILEGEDABOUT_PROCESS |
          nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
          nsIAboutModule::ALLOW_SCRIPT},
-#ifdef NIGHTLY_BUILD
     {"messagepreview",
      "chrome://browser/content/messagepreview/messagepreview.html",
      nsIAboutModule::URI_MUST_LOAD_IN_CHILD |
          nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
          nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::HIDE_FROM_ABOUTABOUT},
-#endif
     {"pocket-saved", "chrome://pocket/content/panels/saved.html",
      nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
          nsIAboutModule::URI_MUST_LOAD_IN_CHILD | nsIAboutModule::ALLOW_SCRIPT |

browser/components/messagepreview/actors/AboutMessagePreviewChild.sys.mjs

@@ -2,6 +2,8 @@
  * 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/. */
 
+import { AppConstants } from "resource://gre/modules/AppConstants.sys.mjs";
+
 export class AboutMessagePreviewChild extends JSWindowActorChild {
   handleEvent(event) {
     console.log(`Received page event ${event.type}`);
@@ -12,14 +14,45 @@ export class AboutMessagePreviewChild extends JSWindowActorChild {
   }
 
   exportFunctions() {
-    const window = this.contentWindow;
+    if (this.contentWindow) {
+      for (const name of ["MPShowMessage", "MPIsEnabled", "MPShouldShowHint"]) {
+        Cu.exportFunction(this[name].bind(this), this.contentWindow, {
+          defineAs: name,
+        });
+      }
+    }
+  }
 
-    Cu.exportFunction(this.MPShowMessage.bind(this), window, {
-      defineAs: "MPShowMessage",
-    });
+  /**
+   * Check if the Message Preview feature is enabled. This reflects the value of
+   * the pref `browser.newtabpage.activity-stream.asrouter.devtoolsEnabled`.
+   *
+   * @returns {boolean}
+   */
+  MPIsEnabled() {
+    return Services.prefs.getBoolPref(
+      "browser.newtabpage.activity-stream.asrouter.devtoolsEnabled",
+      false
+    );
   }
 
+  /**
+   * Route a message to the parent process to be displayed with the relevant
+   * messaging surface.
+   *
+   * @param {object} message
+   */
   MPShowMessage(message) {
     this.sendAsyncMessage(`MessagePreview:SHOW_MESSAGE`, message);
   }
+
+  /**
+   * Check if a hint should be shown about how to enable Message Preview. The
+   * hint is only displayed in local/unofficial builds.
+   *
+   * @returns {boolean}
+   */
+  MPShouldShowHint() {
+    return !this.MPIsEnabled() && !AppConstants.MOZILLA_OFFICIAL;
+  }
 }

browser/components/messagepreview/jar.mn

@@ -3,9 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 browser.jar:
-#ifdef NIGHTLY_BUILD
     content/browser/messagepreview/messagepreview.html
     content/browser/messagepreview/messagepreview.js
     content/browser/messagepreview/limelight.svg
     content/browser/messagepreview/messagepreview.css
-#endif

browser/components/messagepreview/limelight.svg

@@ -10,15 +10,24 @@ html,
 body {
   height: 100%;
   width: 100%;
+}
+
+body {
   background: url(chrome://browser/content/messagepreview/limelight.svg)
     center/contain no-repeat;
-  -moz-context-properties: fill;
+  -moz-context-properties: fill, fill-opacity;
   fill: var(--in-content-icon-color);
-  filter: opacity(0.1);
+  fill-opacity: 0.2;
+}
+
+.hint-box {
+  display: flex;
+  align-items: center;
+  justify-content: center;
 }
 
-@media (prefers-color-scheme: dark) {
-  body {
-    filter: none;
-  }
+.hint {
+  max-width: 40em;
+  font-size: 1.2em;
+  text-align: center;
 }

browser/components/messagepreview/messagepreview.css

@@ -2,7 +2,7 @@
  * 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/. */
 
-/* global MPShowMessage */
+/* global MPShowMessage, MPIsEnabled, MPShouldShowHint */
 
 "use strict";
 
@@ -17,8 +17,23 @@ function decodeMessageFromUrl() {
   return null;
 }
 
+function showHint() {
+  document.body.classList.add("hint-box");
+  document.body.innerHTML = `<div class="hint">Message preview is not enabled. Enable it in about:config by setting <code>browser.newtabpage.activity-stream.asrouter.devtoolsEnabled</code> to true.</div>`;
+}
+
 const message = decodeMessageFromUrl();
 
 if (message) {
-  MPShowMessage(message);
+  // If message preview is enabled, show the message.
+  if (MPIsEnabled()) {
+    MPShowMessage(message);
+  } else if (MPShouldShowHint()) {
+    // If running in a local build, show a hint about how to enable preview.
+    if (document.body) {
+      showHint();
+    } else {
+      document.addEventListener("DOMContentLoaded", showHint, { once: true });
+    }
+  }
 }