QMacCocoaViewContainer Class

Detailed Description

The QMacCocoaViewContainer class provides a widget for macOS that can be used to wrap arbitrary Cocoa views (i.e., NSView subclasses) and insert them into Qt hierarchies.

While Qt offers a lot of classes for writing your application, Apple's Cocoa framework offers lots of functionality that is not currently in Qt or may never end up in Qt. Using QMacCocoaViewContainer, it is possible to put an arbitrary NSView-derived class from Cocoa and put it in a Qt hierarchy. Depending on how comfortable you are with using objective-C, you can use QMacCocoaViewContainer directly, or subclass it to wrap further functionality of the underlying NSView.

QMacCocoaViewContainer works regardless if Qt is built against Carbon or Cocoa. However, QCocoaContainerView requires macOS 10.5 or better to be used with Carbon.

It should be also noted that at the low level on macOS, there is a difference between windows (top-levels) and view (widgets that are inside a window). For this reason, make sure that the NSView that you are wrapping doesn't end up as a top-level. The best way to ensure this is to make sure you always have a parent and not set the parent to 0.

If you are using QMacCocoaViewContainer as a sub-class and are mixing and matching objective-C with C++ (a.k.a. objective-C++). It is probably simpler to have your file end with .mm than .cpp. Most Apple tools will correctly identify the source as objective-C++.

QMacCocoaViewContainer requires knowledge of how Cocoa works, especially in regard to its reference counting (retain/release) nature. It is noted in the functions below if there is any change in the reference count. Cocoa views often generate temporary objects that are released by an autorelease pool. If this is done outside of a running event loop, it is up to the developer to provide the autorelease pool.

The following is a snippet of subclassing QMacCocoaViewContainer to wrap a NSSearchField.

  SearchWidget::SearchWidget(QWidget *parent)
      : QMacCocoaViewContainer(0, parent)
  {
      // Many Cocoa objects create temporary autorelease objects,
      // so create a pool to catch them.
      NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

      // Create the NSSearchField, set it on the QCocoaViewContainer.
      NSSearchField *search = [[NSSearchField alloc] init];
      setCocoaView(search);

      // Use a Qt menu for the search field menu.
      QMenu *qtMenu = createMenu(this);
      NSMenu *nsMenu = qtMenu->macMenu(0);
      [[search cell] setSearchMenuTemplate:nsMenu];

      // Release our reference, since our super class takes ownership and we
      // don't need it anymore.
      [search release];

      // Clean up our pool as we no longer need it.
      [pool release];
  }