QMacCocoaViewContainer Class

详细描述

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 frameworks offer functionality that is not currently available (or may never end up) in Qt. Using QMacCocoaViewContainer, it is possible to take an arbitrary NSView-derived class from Cocoa and put it in a Qt widgets hierarchy. Depending on the level of integration you need, you can use QMacCocoaViewContainer directly or subclass it to wrap more functionality of the underlying NSView.

It should be also noted that, at the Cocoa level, there is a difference between top-level windows and views (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 window. The best way to ensure this is to make sure QMacCocoaViewContainer's parent widget is not null.

If you are using QMacCocoaViewContainer as a subclass and are accessing Cocoa API, it is probably simpler to have your file end with .mm instead of .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 showing how to subclass QMacCocoaViewContainer to wrap an 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];
  }