Added initial version of Firefox screensharing addon.

This is required to support screensharing in Firefox for the Nextcloud Spreed
app (see nextcloud/spreed#227).

Signed-off-by: Joachim Bauch <bauch@struktur.de>

.gitignore

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+dist/

Makefile

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+SRC := ./extension
+DIST := ./dist
+ZIP := $(shell which zip)
+
+PACKAGE_NAME := nextcloud-spreed-screensharing
+PACKAGE_VERSION := $(shell  echo `sed -rn -e 's/<em:version>(.*)<\/em:version>/\1/p' $(SRC)/install.rdf` | sed -rn -e 's/^ *//p')
+
+build:
+	rm -rf $(DIST); \
+	mkdir -p $(DIST); \
+	cd $(SRC); \
+	find . -type f -print | $(ZIP) ../$(DIST)/$(PACKAGE_NAME)-$(PACKAGE_VERSION).xpi -@

README.md

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+# Firefox addon to support screensharing in the Nextcloud Spreed app
+
+## Installation
+
+See https://developer.mozilla.org/en-US/docs/Tools/about:debugging#Add-ons for
+further information on how to load the extension.

extension/bootstrap.js

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+/**
+ * Nextcloud Firefox extension.
+ *
+ * @author Joachim Bauch <bauch@struktur.de>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/* https://developer.mozilla.org/en-US/Add-ons/Bootstrapped_extensions */
+/* https://developer.mozilla.org/en-US/docs/Extensions/bootstrap.js */
+/* https://github.com/HenrikJoreteg/getScreenMedia/blob/master/firefox-extension-sample/bootstrap.js */
+
+/* https://developer.mozilla.org/en-US/Add-ons/Bootstrapped_extensions#Reason_constants */
+var APP_STARTUP = 1;
+var APP_SHUTDOWN = 2;
+var ADDON_ENABLE = 3;
+var ADDON_DISABLE = 4;
+var ADDON_INSTALL = 5;
+var ADDON_UNINSTALL = 6;
+var ADDON_UPGRADE = 7;
+var ADDON_DOWNGRADE = 8;
+var NAMESPACE = 'nextcloud-spreed';
+
+var START_SCREENSHARING_MESSAGE = 'webrtcStartScreensharing';
+var STOP_SCREENSHARING_MESSAGE = 'webrtcStopScreensharing';
+
+/**
+ * Extension api
+ * @returns {object}
+ */
+var api = (function() {
+	var SCREENSHARING_ADD_DOMAIN_EVENT = 'ExtensionAddDomain';
+	var SCREENSHARING_REMOVE_DOMAIN_EVENT = 'ExtensionRemoveDomain';
+	var SCREENSHARING_ALLOWED_DOMAINS_PREF = 'media.getusermedia.screensharing.allowed_domains';
+
+	/* https://developer.mozilla.org/en-US/Add-ons/Working_with_multiprocess_Firefox#Porting_to_the_message_manager */
+	/* https://github.com/mdn/e10s-example-addons/tree/master/run-script-in-all-pages/ported-message-manager/src/chrome/content */
+	var globalMM = Components.classes["@mozilla.org/globalmessagemanager;1"].getService(Components.interfaces.nsIMessageListenerManager);
+
+	var preferences = Components.classes['@mozilla.org/preferences-service;1'].getService(Components.interfaces.nsIPrefBranch);
+	var hasBootstrapped = false;
+
+	var registeredDomains = {};
+
+	var unique_id = Date.now();
+
+	var extensionData = {
+		id: null,
+		version: null
+	};
+	/**
+	 * @param {Object} data Object holding extension information
+	 * @param {String} data.id The extension id
+	 * @param {String} data.version The current extension version
+	 */
+	var setExtensionData = function(data) {
+		if (data.id && data.version) {
+			extensionData.id = data.id;
+			extensionData.version = data.version;
+		} else {
+			throw new Error('Data object invalid and without relevant properties.');
+		}
+	};
+	var getExtensionData = function() {
+		return extensionData;
+	};
+	/**
+	 * Append domains to the Firefox list of allowed screensharing domains
+	 * @param {array} domains List of domains to append to allowed screensharing domains
+	 * @param {boolean} force If a domain already exists append it anyway to current domain list
+	 */
+	var insertDomains = function(addDomains, force) {
+		var domainsToAppend = [];
+		var domains = preferences.getCharPref(SCREENSHARING_ALLOWED_DOMAINS_PREF).split(',');
+		// Prevent inserting a domain that is already part of the list
+		for (var i = 0; i < addDomains.length; i++) {
+			if (force || domains.indexOf(addDomains[i]) < 0) {
+				domainsToAppend.push(addDomains[i]);
+				console.log(NAMESPACE,'Adding domain', addDomains[i]);
+			} else {
+				console.log(NAMESPACE,'Domain exists', addDomains[i]);
+			}
+		}
+		if (domains.length > 0 || domainsToAppend.length > 0) {
+			preferences.setCharPref(SCREENSHARING_ALLOWED_DOMAINS_PREF, domains.concat(domainsToAppend).join(','));
+		} else {
+			throw new Error('No screensharing domains');
+		}
+	};
+	/**
+	 * Remove domains from the Firefox list of allowed screensharing domains
+	 * @param {array} domains List of domains to remove from allowed screensharing domains
+	 */
+	var removeDomains = function(deleteDomains) {
+		var domains = preferences.getCharPref(SCREENSHARING_ALLOWED_DOMAINS_PREF).split(',');
+		var modified = false;
+		for (var i = 0; i < deleteDomains.length; i++) {
+			var x = domains.lastIndexOf(deleteDomains[i]);
+			if (x >= 0) {
+				console.log(NAMESPACE,'Removed domain', deleteDomains[i], 'at index', x);
+				domains.splice(x, 1);
+				modified = true;
+			}
+		}
+		if (modified) {
+			preferences.setCharPref(SCREENSHARING_ALLOWED_DOMAINS_PREF, domains.join(','));
+		}
+	};
+	var insertDynamicDomain = function(domain) {
+		if (domain) {
+			if (registeredDomains.hasOwnProperty(domain)) {
+				registeredDomains[domain] += 1;
+				return;
+			}
+			registeredDomains[domain] = 1;
+			console.log(NAMESPACE, "Insert", domain);
+			insertDomains([domain], true);
+		} else {
+			throw new Error('Domain argument undefined.');
+		}
+	};
+	var removeDynamicDomain = function(domain) {
+		if (domain) {
+			if (!registeredDomains.hasOwnProperty(domain)) {
+				return;
+			}
+			registeredDomains[domain] -= 1;
+			if (registeredDomains[domain] > 0) {
+				return;
+			}
+			delete registeredDomains[domain];
+			console.log(NAMESPACE, "Remove", domain);
+			removeDomains([domain]);
+		} else {
+			throw new Error('Domain argument undefined.');
+		}
+	};
+
+	var addDomainListener = function(event) {
+		if (!event || !event.data || !event.data.host) {
+			return;
+		}
+
+		console.log(NAMESPACE, "Add domain", event.data.host);
+		insertDynamicDomain(event.data.host);
+	};
+
+	var removeDomainListener = function(event) {
+		if (!event || !event.data || !event.data.host) {
+			return;
+		}
+
+		console.log(NAMESPACE, "Remove domain", event.data.host);
+		removeDynamicDomain(event.data.host);
+	};
+
+	var syncExtensionData = function() {
+		return getExtensionData();
+	};
+
+	var logMessage = function(event) {
+		var args = event.data || [];
+		args.splice(0, 0, NAMESPACE);
+		console.log.apply(console, args);
+	};
+
+	var bootstrap = function(data) {
+		if (hasBootstrapped) {
+			// Ensure we are not loading scripts more than once into a tab.
+			return;
+		}
+
+		console.log(NAMESPACE, "bootstrap");
+		setExtensionData({id: data.id, version: data.version});
+		globalMM.addMessageListener(NAMESPACE + ':ExtensionDataSync', syncExtensionData);
+		globalMM.addMessageListener(NAMESPACE + ':log', logMessage);
+		globalMM.addMessageListener(NAMESPACE + ':' + START_SCREENSHARING_MESSAGE, addDomainListener);
+		globalMM.addMessageListener(NAMESPACE + ':' + STOP_SCREENSHARING_MESSAGE, removeDomainListener, true);
+		globalMM.loadFrameScript("chrome://nextcloud-screensharing/content/framescript.js", true);
+		globalMM.broadcastAsyncMessage(NAMESPACE + ':startup', {'unique_id': unique_id});
+		hasBootstrapped = true;
+		console.log(NAMESPACE, "bootstrap done");
+	};
+
+	var teardown = function() {
+		if (!hasBootstrapped) {
+			return;
+		}
+
+		console.log(NAMESPACE, "teardown");
+		globalMM.broadcastAsyncMessage(NAMESPACE + ':teardown', {'unique_id': unique_id});
+		globalMM.removeDelayedFrameScript('chrome://nextcloud-screensharing/content/framescript.js');
+		globalMM.removeMessageListener(NAMESPACE + ':ExtensionDataSync', syncExtensionData);
+		globalMM.removeMessageListener(NAMESPACE + ':log', logMessage);
+		globalMM.removeMessageListener(NAMESPACE + ':' + START_SCREENSHARING_MESSAGE, addDomainListener);
+		globalMM.removeMessageListener(NAMESPACE + ':' + STOP_SCREENSHARING_MESSAGE, removeDomainListener, true);
+		hasBootstrapped = false;
+		console.log(NAMESPACE, "teardown done");
+	};
+
+	return {
+		bootstrap: bootstrap,
+		teardown: teardown
+	};
+})();
+
+function startup(data, reason) {
+	api.bootstrap(data);
+}
+
+function shutdown(data, reason) {
+	api.teardown();
+}
+
+function install(data, reason) {}
+
+function uninstall(data, reason) {}

extension/chrome.manifest

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+# Only certain instructions are supported in bootstrapped extensions
+# See https://developer.mozilla.org/en/docs/Chrome_Registration#Instructions_supported_in_bootstrapped_add_ons
+
+# https://developer.mozilla.org/en/docs/Chrome_Registration#content-instruction
+content nextcloud-screensharing chrome/