Lion fullscreen support

Quote Qt5-feedback:

That is no big deal, code-wise: Basically it boils down to setting a "window
flag" NSWindowCollectionBehaviorFullScreenPrimary. In my own code I did this
within a *.mm ("objective C++") file, with OS X API calls such as:

NSView *nsview = (NSView *) mainWindow.winId();
NSWindow *nswindow = [nsview window];
[nswindow setCollectionBehavior:NSWindowCollectionBehaviorFullScreenPrimary];

And that's it! Almost. It adds this "fullscreen" icon to your window title bar
with which you can toggle into/from fullscreen.

If you want to control this from your own code - e.g. from a separate "Window"
or "View" menu entry - you can call the following OSX API. Inside some slot:

QMainWindow *mainWindow = ...;
NSView *nsview = (NSView *) mainWindow->winId();
NSWindow *nswindow = [nsview window];
[nswindow toggleFullScreen:nil]; // That's the magic here!

The following code is useful to figure out the "fullscreen" state:

QMainWindow *mainWindow = ...;
NSView *nsview = (NSView *) mainWindow->winId();
NSWindow *nswindow = [nsview window];
NSUInteger masks = [nswindow styleMask];
bool result = masks & NSFullScreenWindowMask;

A few #ifdefs here (#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7 is
your friend), a few runtime checks there, and my code compiles and runs on both
OS X 10.6 and 10.7 (on 10.6 off course the fallback is the available
QWidget::showFullScreen mechanism).

So my wish here would be that "Qt does all that for me" That is when my Qt
application runs on Lion (runtime checks!) it would default to the "Lion
fullscreen mode" upon QWidget::showFullScreen(), or optionally use the existing
fullscreen approach when some additional Qt style flag would be set (like
"PlatformFullScreen" vs "QtFullScreen" or whatever...).

However with a Qt 4.7.3 (and also with Qt 4.8 Beta I think) I had some issue
with the "native" (or "unified") toolbar, especially when trying to toggle the
visibility of the toolbar: sometimes the toolbar was not properly restored
("invisible"), even though the Qt API claimed it was "visible". And it somewhat
flickers when going from "fullscreen" back to "normal" (well, it's more like
some "animation" which makes it first invisible and then visible again).

I tried to hack around this by setting the "visible" state explicitly. Also
calling setUnifiedTitleAndToolBarOnMac() when changing state seemed to help a
little.

What I absolutely did not manage was something like "Show toolbar in normal
view, but hide it when going fullscreen - show it again when going to normal
view again". After toogling back and forth all of a sudden the toolbar would not
show up, or only a few pixel height toolbar was visible etc.

I think in general that "unified toolbar" code should be looked at again when
testing "Lion fullscreen support"...