qwebchannel.js Example File | Qt WebEngine 5.8

Qt 5.8 | Qt WebEngine | WebEngine Markdown Editor Example | qwebchannel.js Example File

Qt 5.8.0 Reference Documentation

# qwebchannel.js Example File

webenginewidgets/markdowneditor/resources/qwebchannel.js

      /****************************************************************************
      **
      ** Copyright (C) 2016 The Qt Company Ltd.
      ** Copyright (C) 2014 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Milian Wolff <milian.wolff@kdab.com>
      ** Contact: https://www.qt.io/licensing/
      **
      ** This file is part of the QtWebChannel module of the Qt Toolkit.
      **
      ** $QT_BEGIN_LICENSE:BSD$
      ** Commercial License Usage
      ** Licensees holding valid commercial Qt licenses may use this file in
      ** accordance with the commercial license agreement provided with the
      ** Software or, alternatively, in accordance with the terms contained in
      ** a written agreement between you and The Qt Company. For licensing terms
      ** and conditions see https://www.qt.io/terms-conditions. For further
      ** information use the contact form at https://www.qt.io/contact-us.
      **
      ** BSD License Usage
      ** Alternatively, you may use this file under the terms of the BSD license
      ** as follows:
      **
      ** "Redistribution and use in source and binary forms, with or without
      ** modification, are permitted provided that the following conditions are
      ** met:
      **   * Redistributions of source code must retain the above copyright
      **     notice, this list of conditions and the following disclaimer.
      **   * Redistributions in binary form must reproduce the above copyright
      **     notice, this list of conditions and the following disclaimer in
      **     the documentation and/or other materials provided with the
      **     distribution.
      **   * Neither the name of The Qt Company Ltd nor the names of its
      **     contributors may be used to endorse or promote products derived
      **     from this software without specific prior written permission.
      **
      **
      ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
      **
      ** $QT_END_LICENSE$
      **
      ****************************************************************************/

      "use strict";

      var QWebChannelMessageTypes = {
          signal: 1,
          propertyUpdate: 2,
          init: 3,
          idle: 4,
          debug: 5,
          invokeMethod: 6,
          connectToSignal: 7,
          disconnectFromSignal: 8,
          setProperty: 9,
          response: 10,
      };

      var QWebChannel = function(transport, initCallback)
      {
          if (typeof transport !== "object" || typeof transport.send !== "function") {
              console.error("The QWebChannel expects a transport object with a send function and onmessage callback property." +
                            " Given is: transport: " + typeof(transport) + ", transport.send: " + typeof(transport.send));
              return;
          }

          var channel = this;
          this.transport = transport;

          this.send = function(data)
          {
              if (typeof(data) !== "string") {
                  data = JSON.stringify(data);
              }
              channel.transport.send(data);
          }

          this.transport.onmessage = function(message)
          {
              var data = message.data;
              if (typeof data === "string") {
                  data = JSON.parse(data);
              }
              switch (data.type) {
                  case QWebChannelMessageTypes.signal:
                      channel.handleSignal(data);
                      break;
                  case QWebChannelMessageTypes.response:
                      channel.handleResponse(data);
                      break;
                  case QWebChannelMessageTypes.propertyUpdate:
                      channel.handlePropertyUpdate(data);
                      break;
                  default:
                      console.error("invalid message received:", message.data);
                      break;
              }
          }

          this.execCallbacks = {};
          this.execId = 0;
          this.exec = function(data, callback)
          {
              if (!callback) {
                  // if no callback is given, send directly
                  channel.send(data);
                  return;
              }
              if (channel.execId === Number.MAX_VALUE) {
                  // wrap
                  channel.execId = Number.MIN_VALUE;
              }
              if (data.hasOwnProperty("id")) {
                  console.error("Cannot exec message with property id: " + JSON.stringify(data));
                  return;
              }
              data.id = channel.execId++;
              channel.execCallbacks[data.id] = callback;
              channel.send(data);
          };

          this.objects = {};

          this.handleSignal = function(message)
          {
              var object = channel.objects[message.object];
              if (object) {
                  object.signalEmitted(message.signal, message.args);
              } else {
                  console.warn("Unhandled signal: " + message.object + "::" + message.signal);
              }
          }

          this.handleResponse = function(message)
          {
              if (!message.hasOwnProperty("id")) {
                  console.error("Invalid response message received: ", JSON.stringify(message));
                  return;
              }
              channel.execCallbacks[message.id](message.data);
              delete channel.execCallbacks[message.id];
          }

          this.handlePropertyUpdate = function(message)
          {
              for (var i in message.data) {
                  var data = message.data[i];
                  var object = channel.objects[data.object];
                  if (object) {
                      object.propertyUpdate(data.signals, data.properties);
                  } else {
                      console.warn("Unhandled property update: " + data.object + "::" + data.signal);
                  }
              }
              channel.exec({type: QWebChannelMessageTypes.idle});
          }

          this.debug = function(message)
          {
              channel.send({type: QWebChannelMessageTypes.debug, data: message});
          };

          channel.exec({type: QWebChannelMessageTypes.init}, function(data) {
              for (var objectName in data) {
                  var object = new QObject(objectName, data[objectName], channel);
              }
              // now unwrap properties, which might reference other registered objects
              for (var objectName in channel.objects) {
                  channel.objects[objectName].unwrapProperties();
              }
              if (initCallback) {
                  initCallback(channel);
              }
              channel.exec({type: QWebChannelMessageTypes.idle});
          });
      };

      function QObject(name, data, webChannel)
      {
          this.__id__ = name;
          webChannel.objects[name] = this;

          // List of callbacks that get invoked upon signal emission
          this.__objectSignals__ = {};

          // Cache of all properties, updated when a notify signal is emitted
          this.__propertyCache__ = {};

          var object = this;

          // ----------------------------------------------------------------------

          this.unwrapQObject = function(response)
          {
              if (response instanceof Array) {
                  // support list of objects
                  var ret = new Array(response.length);
                  for (var i = 0; i < response.length; ++i) {
                      ret[i] = object.unwrapQObject(response[i]);
                  }
                  return ret;
              }
              if (!response
                  || !response["__QObject*__"]
                  || response.id === undefined) {
                  return response;
              }

              var objectId = response.id;
              if (webChannel.objects[objectId])
                  return webChannel.objects[objectId];

              if (!response.data) {
                  console.error("Cannot unwrap unknown QObject " + objectId + " without data.");
                  return;
              }

              var qObject = new QObject( objectId, response.data, webChannel );
              qObject.destroyed.connect(function() {
                  if (webChannel.objects[objectId] === qObject) {
                      delete webChannel.objects[objectId];
                      // reset the now deleted QObject to an empty {} object
                      // just assigning {} though would not have the desired effect, but the
                      // below also ensures all external references will see the empty map
                      // NOTE: this detour is necessary to workaround QTBUG-40021
                      var propertyNames = [];
                      for (var propertyName in qObject) {
                          propertyNames.push(propertyName);
                      }
                      for (var idx in propertyNames) {
                          delete qObject[propertyNames[idx]];
                      }
                  }
              });
              // here we are already initialized, and thus must directly unwrap the properties
              qObject.unwrapProperties();
              return qObject;
          }

          this.unwrapProperties = function()
          {
              for (var propertyIdx in object.__propertyCache__) {
                  object.__propertyCache__[propertyIdx] = object.unwrapQObject(object.__propertyCache__[propertyIdx]);
              }
          }

          function addSignal(signalData, isPropertyNotifySignal)
          {
              var signalName = signalData[0];
              var signalIndex = signalData[1];
              object[signalName] = {
                  connect: function(callback) {
                      if (typeof(callback) !== "function") {
                          console.error("Bad callback given to connect to signal " + signalName);
                          return;
                      }

                      object.__objectSignals__[signalIndex] = object.__objectSignals__[signalIndex] || [];
                      object.__objectSignals__[signalIndex].push(callback);

                      if (!isPropertyNotifySignal && signalName !== "destroyed") {
                          // only required for "pure" signals, handled separately for properties in propertyUpdate
                          // also note that we always get notified about the destroyed signal
                          webChannel.exec({
                              type: QWebChannelMessageTypes.connectToSignal,
                              object: object.__id__,
                              signal: signalIndex
                          });
                      }
                  },
                  disconnect: function(callback) {
                      if (typeof(callback) !== "function") {
                          console.error("Bad callback given to disconnect from signal " + signalName);
                          return;
                      }
                      object.__objectSignals__[signalIndex] = object.__objectSignals__[signalIndex] || [];
                      var idx = object.__objectSignals__[signalIndex].indexOf(callback);
                      if (idx === -1) {
                          console.error("Cannot find connection of signal " + signalName + " to " + callback.name);
                          return;
                      }
                      object.__objectSignals__[signalIndex].splice(idx, 1);
                      if (!isPropertyNotifySignal && object.__objectSignals__[signalIndex].length === 0) {
                          // only required for "pure" signals, handled separately for properties in propertyUpdate
                          webChannel.exec({
                              type: QWebChannelMessageTypes.disconnectFromSignal,
                              object: object.__id__,
                              signal: signalIndex
                          });
                      }
                  }
              };
          }

          /**
           * Invokes all callbacks for the given signalname. Also works for property notify callbacks.
           */
          function invokeSignalCallbacks(signalName, signalArgs)
          {
              var connections = object.__objectSignals__[signalName];
              if (connections) {
                  connections.forEach(function(callback) {
                      callback.apply(callback, signalArgs);
                  });
              }
          }

          this.propertyUpdate = function(signals, propertyMap)
          {
              // update property cache
              for (var propertyIndex in propertyMap) {
                  var propertyValue = propertyMap[propertyIndex];
                  object.__propertyCache__[propertyIndex] = propertyValue;
              }

              for (var signalName in signals) {
                  // Invoke all callbacks, as signalEmitted() does not. This ensures the
                  // property cache is updated before the callbacks are invoked.
                  invokeSignalCallbacks(signalName, signals[signalName]);
              }
          }

          this.signalEmitted = function(signalName, signalArgs)
          {
              invokeSignalCallbacks(signalName, signalArgs);
          }

          function addMethod(methodData)
          {
              var methodName = methodData[0];
              var methodIdx = methodData[1];
              object[methodName] = function() {
                  var args = [];
                  var callback;
                  for (var i = 0; i < arguments.length; ++i) {
                      if (typeof arguments[i] === "function")
                          callback = arguments[i];
                      else
                          args.push(arguments[i]);
                  }

                  webChannel.exec({
                      "type": QWebChannelMessageTypes.invokeMethod,
                      "object": object.__id__,
                      "method": methodIdx,
                      "args": args
                  }, function(response) {
                      if (response !== undefined) {
                          var result = object.unwrapQObject(response);
                          if (callback) {
                              (callback)(result);
                          }
                      }
                  });
              };
          }

          function bindGetterSetter(propertyInfo)
          {
              var propertyIndex = propertyInfo[0];
              var propertyName = propertyInfo[1];
              var notifySignalData = propertyInfo[2];
              // initialize property cache with current value
              // NOTE: if this is an object, it is not directly unwrapped as it might
              // reference other QObject that we do not know yet
              object.__propertyCache__[propertyIndex] = propertyInfo[3];

              if (notifySignalData) {
                  if (notifySignalData[0] === 1) {
                      // signal name is optimized away, reconstruct the actual name
                      notifySignalData[0] = propertyName + "Changed";
                  }
                  addSignal(notifySignalData, true);
              }

              Object.defineProperty(object, propertyName, {
                  configurable: true,
                  get: function () {
                      var propertyValue = object.__propertyCache__[propertyIndex];
                      if (propertyValue === undefined) {
                          // This shouldn't happen
                          console.warn("Undefined value in property cache for property \"" + propertyName + "\" in object " + object.__id__);
                      }

                      return propertyValue;
                  },
                  set: function(value) {
                      if (value === undefined) {
                          console.warn("Property setter for " + propertyName + " called with undefined value!");
                          return;
                      }
                      object.__propertyCache__[propertyIndex] = value;
                      webChannel.exec({
                          "type": QWebChannelMessageTypes.setProperty,
                          "object": object.__id__,
                          "property": propertyIndex,
                          "value": value
                      });
                  }
              });

          }

          // ----------------------------------------------------------------------

          data.methods.forEach(addMethod);

          data.properties.forEach(bindGetterSetter);

          data.signals.forEach(function(signal) { addSignal(signal, false); });

          for (var name in data.enums) {
              object[name] = data.enums[name];
          }
      }

      //required for use with nodejs
      if (typeof module === 'object') {
          module.exports = {
              QWebChannel: QWebChannel
          };
      }