Added initial version of Chrome screensharing extension.

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

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

.gitignore

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+dist/
+nextcloud-spreed-screensharing-*.zip

Makefile

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+VERSION := $(shell node -e "fs=require('fs');console.log(JSON.parse(fs.readFileSync(process.argv[1])).version)" ./extension/manifest.json)
+
+all:
+	@echo "Version: $(VERSION) - use \"make zip\" to build ..."
+
+dist:
+	@mkdir -p dist
+	@cp -r extension dist
+
+zip: dist
+	cd dist && zip ../nextcloud-spreed-screensharing-$(VERSION).zip extension/*
+
+.PHONY: dist

README.md

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+# Chrome extension to support screensharing in the Nextcloud Spreed app
+
+Based on the getScreenMedia example from
+https://github.com/HenrikJoreteg/getScreenMedia/tree/master/chrome-extension-sample
+
+
+## Installation
+
+See https://developer.chrome.com/extensions/getstarted#unpacked for further
+information on how to load the unpacked extension.

extension/background.js

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+/* global chrome, Promise */
+
+/**
+ * @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/>.
+ *
+ */
+
+(function() {
+
+    var priority = 100;
+
+    chrome.runtime.onMessage.addListener(function(msg, sender, sendResponse) {
+        switch (msg.type) {
+        case 'init-nc-screensharing':
+            var data = msg.data;
+            var details = chrome.app.getDetails();
+            if (data.extension) {
+                // Existing extension data. Checking id.
+                if (details.id !== data.extension.id) {
+                    // Different extension. Check prio.
+                    if (data.extension.priority && data.extension.priority >= priority) {
+                        // Existing extension has same or higher priority - skip ourselves.
+                        console.log('Refusing to initialize as other extension with same or higher priority found.', data.extension);
+                        return;
+                    } else {
+                        console.log('Refusing to initialize as other extension is already initialized', data.extension);
+                        return;
+                    }
+                }
+            }
+            console.log('Initializing screensharing extension ...', sender.tab.id, data);
+            sendResponse({
+                id: details.id,
+                version: details.version,
+                priority: priority
+            });
+            // Embed our script.
+            chrome.tabs.executeScript(sender.tab.id, {
+                file: 'content.js',
+                runAt: 'document_end'
+            });
+            break;
+        }
+    });
+
+    var ExtensionApi = function(port) {
+        this.port = port;
+    };
+
+    ExtensionApi.prototype.getScreen = function(resolve, reject, msg) {
+        var pending = chrome.desktopCapture.chooseDesktopMedia(['screen', 'window'], this.port.sender.tab, function(id) {
+            var response = {
+                'type': 'gotScreen',
+                'id': msg.id
+            };
+            if (chrome.runtime.lastError) {
+                response.sourceId = '';
+                response.error = chrome.runtime.lastError;
+            } else {
+                response.sourceId = id;
+            }
+            resolve(response);
+        });
+        if (!pending) {
+            return;
+        }
+
+        return {
+            'type': 'getScreenPending',
+            'id': msg.id
+        };
+    };
+
+    ExtensionApi.prototype.call = function(msg) {
+        var api = this;
+        var promise = new Promise(function(resolve, reject) {
+            var f = api[msg.type];
+            if (!f) {
+                reject('action ' + msg.type + ' not found');
+                return;
+            }
+            var response = f.bind(api)(resolve, reject, msg);
+            if (response) {
+                response.answer = true;
+                api.port.postMessage(response);
+            }
+        });
+        promise.then(function(result) {
+            result.answer = true;
+            api.port.postMessage(result);
+        }, function(err) {
+            if (typeof(err) === 'string') {
+                err = {
+                    'error': err
+                };
+            }
+            api.port.postMessage(err);
+        });
+    };
+
+    chrome.runtime.onConnect.addListener(function(port) {
+        var tab = port.sender.tab;
+        var api = new ExtensionApi(port);
+        console.log('Extension connected:', tab.id);
+        port.onMessage.addListener(function(msg) {
+            if (msg.answer) {
+                return;
+            }
+
+            msg.answer = true;
+            api.call(msg);
+        });
+    });
+
+    // Bootstrap directly after install so pages need not be refreshed.
+    chrome.runtime.onInstalled.addListener(function(details) {
+        switch (details.reason) {
+        case 'install':
+        case 'update':
+            console.log('Extension updated or installed', details);
+            chrome.windows.getAll({populate: true}, function(windows) {
+                windows.forEach(function(window) {
+                    window.tabs.forEach(function(tab) {
+                        if (tab.url.match(/https:\/\//gi)) {
+                            chrome.tabs.executeScript(tab.id, {
+                                file: 'detector.js',
+                                runAt: 'document_end'
+                            });
+                        }
+                    });
+                });
+            });
+        }
+    });
+
+})();

extension/content.js

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+/* global chrome */
+
+/**
+ * @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/>.
+ *
+ */
+
+(function() {
+
+    var port = chrome.runtime.connect();
+
+    // Forward message from Nextcloud Spreed app to the extension.
+    window.addEventListener('message', function(event) {
+        var msg = event.data;
+        if (event.source === window && !msg.answer) {
+            port.postMessage(msg);
+        }
+    });
+
+    // Forward message from the extension to the Nextcloud Spreed app.
+    port.onMessage.addListener(function(msg) {
+        window.postMessage(msg, window.document.URL);
+    });
+
+})();

extension/detector.js

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+/* global chrome */
+
+/**
+ * @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/>.
+ *
+ */
+
+(function(document) {
+
+	function hasClass(element, cls) {
+		return (' ' + element.className + ' ').indexOf(' ' + cls + ' ') > -1;
+	}
+
+	// Only add extension if the page is running the Nextcloud Spreed app.
+	var nc = document.getElementById('app');
+	if (!nc || !hasClass(nc, 'nc-enable-screensharing-extension')) {
+		return;
+	}
+
+	var extension = nc.getAttribute('data-chromeExtensionData');
+	if (extension) {
+		try {
+			extension = JSON.parse(extension);
+		} catch (e) {
+			return;
+		}
+	}
+
+	console.log('Detected Nextcloud Spreed app.');
+	var msg = {
+		type: 'init-nc-screensharing',
+		data: {
+			extension: extension || null
+		}
+	};
+
+	chrome.runtime.sendMessage(null, msg, null, function(data) {
+		console.log('Initialized extension', data);
+		nc.setAttribute('data-chromeExtensionData', JSON.stringify(data));
+	});
+
+}(document));

extension/manifest.json

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+{
+  "name": "Nextcloud Screensharing",
+  "description": "Screensharing utility for the Nextcloud Spreed app.",
+  "author": "Joachim Bauch <bauch@struktur.de>",
+  "homepage_url": "https://nextcloud.com",
+  "version": "0.0.1",
+  "manifest_version": 2,
+  "minimum_chrome_version": "34",
+  "icons": {
+  },
+  "permissions": [
+    "tabs",
+    "desktopCapture",
+    "https://*/*"
+  ],
+  "background": {
+    "scripts": ["background.js"],
+    "persistent": false
+  },
+  "content_scripts": [
+    {
+      "js": ["detector.js"],
+      "matches": ["https://*/*"],
+      "run_at": "document_end",
+      "all_frames": true
+    }
+  ]
+}