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diff --git a/mobile/android/docs/geckoview/consumer/web-extensions.rst b/mobile/android/docs/geckoview/consumer/web-extensions.rst new file mode 100644 index 0000000000..f4b7b2a179 --- /dev/null +++ b/mobile/android/docs/geckoview/consumer/web-extensions.rst @@ -0,0 +1,403 @@ +.. -*- Mode: rst; fill-column: 80; -*- + +============================ +Interacting with Web content +============================ + +Interacting with Web content and WebExtensions +============================================== + +GeckoView allows embedder applications to register and run +`WebExtensions <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions>`_ +in a GeckoView instance. Extensions are the preferred way to interact +with Web content. + +.. contents:: :local: + +Running extensions in GeckoView +------------------------------- + +Extensions bundled with applications can be provided in a folder in the +``/assets`` section of the APK. Like ordinary extensions, every +extension bundled with GeckoView requires a +`manifest.json <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json>`_ +file. + +To locate files bundled with the APK, GeckoView provides a shorthand +``resource://android/`` that points to the root of the APK. + +E.g. ``resource://android/assets/messaging/`` will point to the +``/assets/messaging/`` folder present in the APK. + +Note: Every installed extension will need an +`id <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/browser_specific_settings>`_ +and +`version <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/version>`_ +specified in the ``manifest.json`` file. + +To install a bundled extension in GeckoView, simply call +`WebExtensionController.installBuiltIn <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtensionController.html#installBuiltIn(java.lang.String)>`_. + +.. code:: java + + runtime.getWebExtensionController() + .installBuiltIn("resource://android/assets/messaging/") + +Note that the lifetime of the extension is not tied with the lifetime of +the +`GeckoRuntime <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/GeckoRuntime.html>`_ +instance. The extension persists even when your app is restarted. +Installing at every start up is fine, but it could be slow. To avoid +installing multiple times you can use ``WebExtensionRuntime.ensureBuiltIn``, +which will only install if the extension is not installed yet. + +.. code:: java + + runtime.getWebExtensionController() + .ensureBuiltIn("resource://android/assets/messaging/", "messaging@example.com") + .accept( + extension -> Log.i("MessageDelegate", "Extension installed: " + extension), + e -> Log.e("MessageDelegate", "Error registering WebExtension", e) + ); + +Communicating with Web Content +------------------------------ + +GeckoView allows bidirectional communication with Web pages through +extensions. + +When using GeckoView, `native +messaging <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_messaging#Exchanging_messages>`_ +can be used for communicating to and from the browser. + +- `runtime.sendNativeMessage <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/sendNativeMessage>`_ + for one-off messages. +- `runtime.connectNative <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/connectNative>`_ + for connection-based messaging. + +Note: these APIs are only available when the ``geckoViewAddons`` +`permission <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/permissions>`_ +is present in the ``manifest.json`` file of the extension. + +One-off messages +~~~~~~~~~~~~~~~~ + +The easiest way to send messages from a `content +script <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Content_scripts>`_ +or a `background +script <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Anatomy_of_a_WebExtension#Background_scripts>`_ +is using +`runtime.sendNativeMessage <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/sendNativeMessage>`_. + +Note: Ordinarily, native extensions would use a `native +manifest <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_messaging#App_manifest>`_ +to define what native app identifier to use. For GeckoView this is *not* +needed, the ``nativeApp`` parameter in ``setMessageDelegate`` will be +use to determine what native app string is used. + +Messaging Example +~~~~~~~~~~~~~~~~~ + +To receive messages from the background script, call +`setMessageDelegate <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtension.html#setMessageDelegate(org.mozilla.geckoview.WebExtension.MessageDelegate,java.lang.String)>`_ +on the +`WebExtension <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtension.html>`_ +object. + +.. code:: java + + extension.setMessageDelegate(messageDelegate, "browser"); + +`SessionController.setMessageDelegate <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtension.SessionController.html#setMessageDelegate(org.mozilla.geckoview.WebExtension,org.mozilla.geckoview.WebExtension.MessageDelegate,java.lang.String)>`_ +allows the app to receive messages from content scripts. + +.. code:: java + + session.getWebExtensionController() + .setMessageDelegate(extension, messageDelegate, "browser"); + +Note: the ``"browser"`` parameter in the code above determines what +native app id the extension can use to send native messages. + +Note: extension can only send messages from content scripts if +explicitly authorized by the app by adding +``nativeMessagingFromContent`` in the manifest.json file, e.g. + +.. code:: + + "permissions": [ + "nativeMessaging", + "nativeMessagingFromContent", + "geckoViewAddons" + ] + +Example +~~~~~~~ + +Let’s set up an activity that registers an extension located in the +``/assets/messaging/`` folder of the APK. This activity will set up a +`MessageDelegate <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtension.MessageDelegate.html>`_ +that will be used to communicate with Web Content. + +You can find the full example here: +`MessagingExample <https://searchfox.org/mozilla-central/source/mobile/android/examples/messaging_example>`_. + +Activity.java +^^^^^^^^^^^^^ + +.. code:: java + + WebExtension.MessageDelegate messageDelegate = new WebExtension.MessageDelegate() { + @Nullable + public GeckoResult<Object> onMessage(final @NonNull String nativeApp, + final @NonNull Object message, + final @NonNull WebExtension.MessageSender sender) { + // The sender object contains information about the session that + // originated this message and can be used to validate that the message + // has been sent from the expected location. + + // Be careful when handling the type of message as it depends on what + // type of object was sent from the WebExtension script. + if (message instanceof JSONObject) { + // Do something with message + } + return null; + } + }; + + // Let's make sure the extension is installed + runtime.getWebExtensionController() + .ensureBuiltIn(EXTENSION_LOCATION, "messaging@example.com").accept( + // Set delegate that will receive messages coming from this extension. + extension -> session.getWebExtensionController() + .setMessageDelegate(extension, messageDelegate, "browser"), + // Something bad happened, let's log an error + e -> Log.e("MessageDelegate", "Error registering extension", e) + ); + + +Now add the ``geckoViewAddons``, ``nativeMessaging`` and +``nativeMessagingFromContent`` permissions to your ``manifest.json`` +file. + +/assets/messaging/manifest.json +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code:: json + + { + "manifest_version": 2, + "name": "messaging", + "version": "1.0", + "description": "Example messaging web extension.", + "browser_specific_settings": { + "gecko": { + "id": "messaging@example.com" + } + }, + "content_scripts": [ + { + "matches": ["*://*.twitter.com/*"], + "js": ["messaging.js"] + } + ], + "permissions": [ + "nativeMessaging", + "nativeMessagingFromContent", + "geckoViewAddons" + ] + } + +And finally, write a content script that will send a message to the app +when a certain event occurs. For example, you could send a message +whenever a `WPA +manifest <https://developer.mozilla.org/en-US/docs/Web/Manifest>`_ is +found on the page. Note that our ``nativeApp`` identifier used for +``sendNativeMessage`` is the same as the one used in the +``setMessageDelegate`` call in `Activity.java <#activityjava>`_. + +/assets/messaging/messaging.js +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code:: javascript + + let manifest = document.querySelector("head > link[rel=manifest]"); + if (manifest) { + fetch(manifest.href) + .then(response => response.json()) + .then(json => { + let message = {type: "WPAManifest", manifest: json}; + browser.runtime.sendNativeMessage("browser", message); + }); + } + +You can handle this message in the ``onMessage`` method in the +``messageDelegate`` `above <#activityjava>`_. + +.. code:: java + + @Nullable + public GeckoResult<Object> onMessage(final @NonNull String nativeApp, + final @NonNull Object message, + final @NonNull WebExtension.MessageSender sender) { + if (message instanceof JSONObject) { + JSONObject json = (JSONObject) message; + try { + if (json.has("type") && "WPAManifest".equals(json.getString("type"))) { + JSONObject manifest = json.getJSONObject("manifest"); + Log.d("MessageDelegate", "Found WPA manifest: " + manifest); + } + } catch (JSONException ex) { + Log.e("MessageDelegate", "Invalid manifest", ex); + } + } + return null; + } + +Note that, in the case of content scripts, ``sender.session`` will be a +reference to the ``GeckoSession`` instance from which the message +originated. For background scripts, ``sender.session`` will always be +``null``. + +Also note that the type of ``message`` will depend on what was sent from +the extension. + +The type of ``message`` will be ``JSONObject`` when the extension sends +a javascript object, but could also be a primitive type if the extension +sends one, e.g. for + +.. code:: javascript + + runtime.browser.sendNativeMessage("browser", "Hello World!"); + +the type of ``message`` will be ``java.util.String``. + +Connection-based messaging +-------------------------- + +For more complex scenarios or for when you want to send messages *from* +the app to the extension, +`runtime.connectNative <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/connectNative>`_ +is the appropriate API to use. + +``connectNative`` returns a +`runtime.Port <https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/Port>`_ +that can be used to send messages to the app. On the app side, +implementing +`MessageDelegate#onConnect <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtension.MessageDelegate.html#onConnect(org.mozilla.geckoview.WebExtension.Port)>`_ +will allow you to receive a +`Port <https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtension.Port.html>`_ +object that can be used to receive and send messages to the extension. + +The following example can be found +`here <https://searchfox.org/mozilla-central/source/mobile/android/examples/port_messaging_example>`_. + +For this example, the extension side will do the following: + +- open a port on the background script using ``connectNative`` +- listen on the port and log to console every message received +- send a message immediately after opening the port. + +/assets/messaging/background.js +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. code:: javascript + + // Establish connection with app + let port = browser.runtime.connectNative("browser"); + port.onMessage.addListener(response => { + // Let's just echo the message back + port.postMessage(`Received: ${JSON.stringify(response)}`); + }); + port.postMessage("Hello from WebExtension!"); + +On the app side, following the `above <#activityjava>`_ example, +``onConnect`` will be storing the ``Port`` object in a member variable +and then using it when needed. + +.. code:: java + + private WebExtension.Port mPort; + + @Override + protected void onCreate(Bundle savedInstanceState) { + // ... initialize GeckoView + + // This delegate will handle all communications from and to a specific Port + // object + WebExtension.PortDelegate portDelegate = new WebExtension.PortDelegate() { + public WebExtension.Port port = null; + + public void onPortMessage(final @NonNull Object message, + final @NonNull WebExtension.Port port) { + // This method will be called every time a message is sent from the + // extension through this port. For now, let's just log a + // message. + Log.d("PortDelegate", "Received message from WebExtension: " + + message); + } + + public void onDisconnect(final @NonNull WebExtension.Port port) { + // After this method is called, this port is not usable anymore. + if (port == mPort) { + mPort = null; + } + } + }; + + // This delegate will handle requests to open a port coming from the + // extension + WebExtension.MessageDelegate messageDelegate = new WebExtension.MessageDelegate() { + @Nullable + public void onConnect(final @NonNull WebExtension.Port port) { + // Let's store the Port object in a member variable so it can be + // used later to exchange messages with the WebExtension. + mPort = port; + + // Registering the delegate will allow us to receive messages sent + // through this port. + mPort.setDelegate(portDelegate); + } + }; + + runtime.getWebExtensionController() + .ensureBuiltIn("resource://android/assets/messaging/", "messaging@example.com") + .accept( + // Register message delegate for background script + extension -> extension.setMessageDelegate(messageDelegate, "browser"), + e -> Log.e("MessageDelegate", "Error registering WebExtension", e) + ); + + // ... other + } + +For example, let’s send a message to the extension every time the user +long presses on a key on the virtual keyboard, e.g. on the back button. + +.. code:: java + + @Override + public boolean onKeyLongPress(int keyCode, KeyEvent event) { + if (mPort == null) { + // No extension registered yet, let's ignore this message + return false; + } + + JSONObject message = new JSONObject(); + try { + message.put("keyCode", keyCode); + message.put("event", KeyEvent.keyCodeToString(event.getKeyCode())); + } catch (JSONException ex) { + throw new RuntimeException(ex); + } + + mPort.postMessage(message); + return true; + } + +This allows bidirectional communication between the app and the +extension. + +.. _GeckoRuntime: https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/GeckoRuntime.html +.. _runtime.sendNativeMessage: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/sendNativeMessage +.. _WebExtension: https://mozilla.github.io/geckoview/javadoc/mozilla-central/org/mozilla/geckoview/WebExtension.html |