[Qt-interest] Always on top, transparent window, no title - Mac OS X

[John Clayton]

Hi All,

I'd like to make an 'overlay' window on Mac OS X using Qt, that is  
transparent and has no title bar.  The window will be used to draw the  
outlines of other windows - so it needs to cover/overlay the entire  
area of all displays attached to the computer.  The outlines of other  
windows will be drawn using the standard QPainter calls.

I'd like to know what the best way is to achieve the following:
	- fully transparent window
	- that stays on top, always - "on top" meaning on the top of all  
other windows of any other app
	- can be drawn on
	- ignores mouse events entirely, mouse events *must* be delivered to  
apps underneath this window
	- spans the entire display(s)

I've presently got one solution that uses one QWidget per display -  
but I can't work out how to make sure that this one window stays on  
the very top, all the time.  It is transparent.  I set it up like this:

MarkerOverlay::MarkerOverlay(QWidget* parent) : super(parent) {
	setAutoFillBackground(true);
	
	QPalette pal = this->palette();	
	pal.setBrush(QPalette::Base, Qt::transparent);
	pal.setBrush(QPalette::Window, Qt::transparent);
	pal.setBrush(QPalette::Background, Qt::transparent);
	this->setPalette(pal);
	
	setWindowFlags(Qt::WindowStaysOnTopHint);
	setWindowFlags(Qt::CustomizeWindowHint);
	
	setAttribute(Qt::WA_TranslucentBackground, true);
	setAttribute(Qt::WA_DeleteOnClose, false);
	
	setFocusPolicy(Qt::NoFocus);
}

Is there a way to tell Qt to put windows on top of *everything* else,  
all the time?  I do know how to do this using the Cocoa windows  
(setWindowLevel: on the NSWindow instance).  Its trivial, I'd just  
like to know if there's a way to get this done using Qt.


Thanks.
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