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  1. Qt
  2. QTBUG-94813

QWebChannel fails with condition (JS to C++)

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Not Evaluated
    • Resolution: Invalid
    • Affects Version/s: 5.15.2
    • Fix Version/s: None
    • Component/s: WebChannel, WebEngine, WebView
    • Labels:
      None
    • Environment:
      Windows / VS2019
    • Platform/s:
      Windows

      Description

      Hey,

      I'm doing some tests with QWebChannel interaction to include it in my application.

      I've try the following code and it works well :

      #include <QApplication>
      
      #include <QWebEngineView>
      #include <QWebChannel>
      #include <QFile>
      
      class JsInterface: public QObject
      {
          Q_OBJECT
      public:
          /// Log, for debugging
          Q_INVOKABLE void log(const QString& str) const
          {
              qDebug() << "LOG from JS: " << str;
          }
      };
      
      int main(int argc, char *argv[])
      {
          QApplication a(argc, argv);
      
          QWebEngineView * browser = new QWebEngineView;
      
          browser->resize(QSize(800,600));
          browser->show();
          browser->load(QUrl("http://www.wikipedia.org"));
      
          QWebChannel channel;
          JsInterface jsInterface;
          browser->page()->setWebChannel(&channel);
          channel.registerObject(QString("JsInterface"), &jsInterface);
      
          QObject::connect(browser, &QWebEngineView::loadFinished, [&browser](bool ok)
          {
              qDebug()<<"Load Finished " << ok;
      
              // TEST CODE HERE
              QString code = QStringLiteral(
              R"DELIM(
      
              var links = document.getElementsByTagName('a');
              for ( var i=0; i<links.length; ++i)
              {
                  links[i].style.backgroundColor = 'yellow';
              };
      
              )DELIM");
              browser->page()->runJavaScript(code);
      
              QFile apiFile(":/qtwebchannel/qwebchannel.js");
              if(!apiFile.open(QIODevice::ReadOnly))
                  qDebug()<< "Couldn't load Qt's QWebChannel API!";
      
              QString apiScript = QString::fromLatin1(apiFile.readAll());
              apiFile.close();
              browser->page()->runJavaScript(apiScript);
      
              QString code2 = QStringLiteral(
              R"DELIM(
              window.webChannel = new QWebChannel(qt.webChannelTransport, function( channel)
              {
                  var cpp = channel.objects.JsInterface;
                  cpp.log("Hello from JavaScript");
              });
      
              )DELIM");
              browser->page()->runJavaScript(code2);
          });
      
          return a.exec();
      }
      

      I've the output from the interface LOG from JS: Hello from JavaScript.

      But I've found something interesting. If I insert a condition, the QWebChannel seems to fail (JS to C++).

      This second example failed :

      #include <QApplication>
      
      #include <QWebEngineView>
      #include <QWebChannel>
      #include <QFile>
      
      class JsInterface: public QObject
      {
          Q_OBJECT
      public:
          /// Log, for debugging
          Q_INVOKABLE void log(const QString& str) const
          {
              qDebug() << "LOG from JS: " << str;
          }
      };
      
      
      int main(int argc, char *argv[])
      {
          QApplication a(argc, argv);
      
          bool testwebchannel_main = true;
      
          if ( testwebchannel_main )
          {
              QWebEngineView * browser = new QWebEngineView;
          
              browser->resize(QSize(800,600));
              browser->show();
              browser->load(QUrl("http://www.wikipedia.org"));
          
              QWebChannel channel;
              JsInterface jsInterface;
              browser->page()->setWebChannel(&channel);
              channel.registerObject(QString("JsInterface"), &jsInterface);
          
              QObject::connect(browser, &QWebEngineView::loadFinished, [&browser](bool ok)
              {
                  qDebug()<<"Load Finished " << ok;
          
                  // TEST CODE HERE
                  QString code = QStringLiteral(
                  R"DELIM(
          
                  var links = document.getElementsByTagName('a');
                  for ( var i=0; i<links.length; ++i)
                  {
                      links[i].style.backgroundColor = 'yellow';
                  };
          
                  )DELIM");
                  browser->page()->runJavaScript(code);
          
                  QFile apiFile(":/qtwebchannel/qwebchannel.js");
                  if(!apiFile.open(QIODevice::ReadOnly))
                      qDebug()<< "Couldn't load Qt's QWebChannel API!";
          
                  QString apiScript = QString::fromLatin1(apiFile.readAll());
                  apiFile.close();
                  browser->page()->runJavaScript(apiScript);
          
                  QString code2 = QStringLiteral(
                  R"DELIM(
                  window.webChannel = new QWebChannel(qt.webChannelTransport, function( channel)
                  {
                      var cpp = channel.objects.JsInterface;
                      cpp.log("Hello from JavaScript");
                  });
          
                  )DELIM");
                  browser->page()->runJavaScript(code2);
              });
          }
      
          return a.exec();
      }
      

      Any idea why it's appening ?

      Thanks in advance

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            Assignee:
            oyheskes Øystein Heskestad
            Reporter:
            blzt Bl Zt
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              Dates

              Created:
              Updated:
              Resolved:

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