QMacNativeWidget Class

Detailed Description

The QMacNativeWidget class provides a widget for macOS that provides a way to put Qt widgets into Cocoa hierarchies.

On macOS, there is a difference between a window and view; normally expressed as widgets in Qt. Qt makes assumptions about its parent-child hierarchy that make it complex to put an arbitrary Qt widget into a hierarchy of "normal" views from Apple frameworks. QMacNativeWidget bridges the gap between views and windows and makes it possible to put a hierarchy of Qt widgets into a non-Qt window or view.

QMacNativeWidget pretends it is a window (i.e. isWindow() will return true), but it cannot be shown on its own. It needs to be put into a window when it is created or later through a native call.

QMacNativeWidget works for either Carbon or Cocoa depending on how Qt was configured. If Qt is using Carbon, QMacNativeWidget will embed into Carbon hierarchies. If Qt is using Cocoa, QMacNativeWidget embeds into Cocoa hierarchies.

Here is an example of putting a QPushButton into a NSWindow:

      NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
      NSWindow *window = [[NSWindow alloc] initWithContentRect:NSMakeRect(200, app.desktop()->height() - 200, 239, 200)
                          styleMask:NSTitledWindowMask | NSClosableWindowMask
                                    | NSMiniaturizableWindowMask | NSResizableWindowMask
                          backing:NSBackingStoreBuffered defer:NO];

      QMacNativeWidget *nativeWidget = new QMacNativeWidget();
      nativeWidget->move(0, 0);
      nativeWidget->setPalette(QPalette(Qt::red));
      nativeWidget->setAutoFillBackground(true);
      QVBoxLayout *layout = new QVBoxLayout();
      QPushButton *pushButton = new QPushButton("An Embedded Qt Button!", nativeWidget);
      pushButton->setAttribute(Qt::WA_LayoutUsesWidgetRect); // Don't use the layout rect calculated from QMacStyle.
      layout->addWidget(pushButton);
      nativeWidget->setLayout(layout);

      // Adjust Cocoa layouts
      NSView *nativeWidgetView = reinterpret_cast<NSView *>(nativeWidget->winId());
      NSView *contentView = [window contentView];
      [contentView setAutoresizesSubviews:YES];
      [nativeWidgetView setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
      [nativeWidgetView setAutoresizesSubviews:YES];
      NSView *pushButtonView = reinterpret_cast<NSView *>(pushButton->winId());
      [pushButtonView setAutoresizingMask:NSViewWidthSizable];

      // Add the nativeWidget to the window.
      [contentView addSubview:nativeWidgetView positioned:NSWindowAbove relativeTo:nil];
      nativeWidget->show();
      pushButton->show();

      // Show the window.
      [window makeKeyAndOrderFront:window];
      [pool release];

Note that QMacNativeWidget requires knowledge of Carbon or Cocoa. All it does is get the Qt hierarchy into a window not owned by Qt. It is then up to the programmer to ensure it is placed correctly in the window and responds correctly to events.