- Qt 5.15
- Qt WebEngine
- Qt WebEngine Widgets Examples
- WebEngine StyleSheet Browser Example
- Qt 5.15.19 Reference Documentation

# WebEngine StyleSheet Browser Example

Demonstrates how to inject CSS into web pages using user scripts.

StyleSheet Browser demonstrates how to use the Qt WebEngine C++ classes to inject user stylesheets into web pages.

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

#### Working With Stylesheets

We use JavaScript to create and append CSS elements to the documents. After declaring the script source, QWebEnginePage::runJavaScript() can run it immediately and apply newly created styles on the current content of the web view. Encapsulating the script into a QWebEngineScript and adding it to the script collection of QWebEnginePage makes its effect permanent.

     void MainWindow::insertStyleSheet(const QString &name, const QString &source, bool immediately)
     {
         QWebEngineScript script;
         QString s = QString::fromLatin1("(function() {"\
                                         "    css = document.createElement('style');"\
                                         "    css.type = 'text/css';"\
                                         "    css.id = '%1';"\
                                         "    document.head.appendChild(css);"\
                                         "    css.innerText = '%2';"\
                                         "})()").arg(name).arg(source.simplified());
         if (immediately)
             ui->webEngineView->page()->runJavaScript(s, QWebEngineScript::ApplicationWorld);

         script.setName(name);
         script.setSourceCode(s);
         script.setInjectionPoint(QWebEngineScript::DocumentReady);
         script.setRunsOnSubFrames(true);
         script.setWorldId(QWebEngineScript::ApplicationWorld);
         ui->webEngineView->page()->scripts().insert(script);
     }

Removing stylesheets can be done similarly:

     void MainWindow::removeStyleSheet(const QString &name, bool immediately)
     {
         QString s = QString::fromLatin1("(function() {"\
                                         "    var element = document.getElementById('%1');"\
                                         "    element.outerHTML = '';"\
                                         "    delete element;"\
                                         "})()").arg(name);
         if (immediately)
             ui->webEngineView->page()->runJavaScript(s, QWebEngineScript::ApplicationWorld);

         QWebEngineScript script = ui->webEngineView->page()->scripts().findScript(name);
         ui->webEngineView->page()->scripts().remove(script);
     }

#### Files and Attributions

The example uses icons from the Tango Icon Library:

Tango Icon Library | Public Domain

Example project @ code.qt.io