wasm: hellogl2 screen is black

We need to reset the OpenGL state in paintGL for the drawing
to work,

Also, disable the dock/add window functionality as it does not
work on webassembly.

Change-Id: I480d944bc2029a07d5d49f0a85c3754fbc8cd53c
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

examples/opengl/hellogl2/glwidget.cpp

@@ -7,6 +7,7 @@
 #include <QCoreApplication>
 #include <math.h>
 
+// Set from main
 bool GLWidget::m_transparent = false;
 
 GLWidget::GLWidget(QWidget *parent)
@@ -209,9 +210,11 @@ void GLWidget::setupVertexAttribs()
 
 void GLWidget::paintGL()
 {
+    glClearColor(0, 0, 0, m_transparent ? 0 : 1);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
     glEnable(GL_DEPTH_TEST);
     glEnable(GL_CULL_FACE);
+    setupVertexAttribs();
 
     m_world.setToIdentity();
     m_world.rotate(180.0f - (m_xRot / 16.0f), 1, 0, 0);

examples/opengl/hellogl2/main.cpp

@@ -42,6 +42,7 @@ int main(int argc, char *argv[])
 
     MainWindow mainWindow;
 
+    // Note: Transparency does not work for wasm
     GLWidget::setTransparent(parser.isSet(transparentOption));
     if (GLWidget::isTransparent()) {
         mainWindow.setAttribute(Qt::WA_TranslucentBackground);

examples/opengl/hellogl2/mainwindow.cpp

@@ -11,12 +11,13 @@
 
 MainWindow::MainWindow()
 {
+#ifndef Q_OS_WASM
     QMenu *menuWindow = menuBar()->addMenu(tr("&Window"));
     menuWindow->addAction(tr("Add new"), QKeySequence(Qt::CTRL | Qt::Key_N),
                           this, &MainWindow::onAddNew);
     menuWindow->addAction(tr("Quit"), QKeySequence(Qt::CTRL | Qt::Key_Q),
                           qApp, QApplication::closeAllWindows);
-
+#endif
     onAddNew();
 }
 

examples/opengl/hellogl2/window.cpp

@@ -45,10 +45,13 @@ Window::Window()
     container->addWidget(zSlider);
 
     mainLayout->addWidget(w);
+    dockBtn = nullptr;
+
+#ifndef Q_OS_WASM
     dockBtn = new QPushButton(tr("Undock"), this);
     connect(dockBtn, &QPushButton::clicked, this, &Window::dockUndock);
     mainLayout->addWidget(dockBtn);
-
+#endif
     xSlider->setValue(15 * 16);
     ySlider->setValue(345 * 16);
     zSlider->setValue(0 * 16);