QDialog w/ transparent background

[LarryDobson]

I know. I know.
This question has been answered 100 times.
I know. I know.
I read them all.
None of the answers work for me.
I need a dialog with a transparent client area.
All of my attempts have failed.
When I attempt to mask it out, the rest (decorations) of the dialog goes gray.
I no longer have a titlebar, frame or buttons.
Putting a transparent label on it, only shows the background of the QDialog.
This seems like it should be easy...
Please help,
TIA,
Larry

[jpn]

I know. I know.
This question has been answered 100 times.
I know. I know.
I read them all.
None of the answers work for me.

Not even this? Pay attention to the parts where coordinates are being mapped from global coordinate system to widget's own coordinate system.

I need a dialog with a transparent client area.

Please be more specific. What is a transparent client area?

All of my attempts have failed.
When I attempt to mask it out, the rest (decorations) of the dialog goes gray.
I no longer have a titlebar, frame or buttons.

How are you applying the mask? Are you calculating a region? Or are you using QPixmap::mask()?

Putting a transparent label on it, only shows the background of the QDialog.

Child widgets are transparent since Qt 4.1 by default. A top level widget, however, can only be set transparent as a whole by QWidget::setWindowOpacity() (read notes in the docs), or parts of it can be made completely hidden by applying a mask. Note that any child widget intersecting a masked area becomes invisible too (over the masked area).

[LarryDobson]

Hello J-P,
I had tried your solution.
This left the caption bar and frame gray (with strange beveling).
Without the ability to move or resize.
I appreciate the help though.

"Please be more specific. What is a transparent client area?"

See geometry() // contents of dialog -vs- caption bar and frame

Very close target!
Client are is transparent, but, frame and Caption bar are gray.
Larry

[LarryDobson]

Got it!
Here is the solution...

void resizeEvent(QResizeEvent *e)
{
	QDialog::resizeEvent(e);
 
	// grab the geometry
	QRect fg = frameGeometry();
	QRect rg = geometry();
 
	// get some reusable values
	int nCaptionHeight	= rg.top()	- fg.top();
	int nFrameWidth		= rg.left()	- fg.left();
 
	// map the global coords to local for the frame
	fg.moveTo(mapFromGlobal(fg.topLeft()));
 
	// create a rectangle for the frame
	QRect rectFrame(fg.left() - nFrameWidth,
				fg.top() - nCaptionHeight,
				fg.width() + ( nFrameWidth * 2 ),
				fg.height() + ( nCaptionHeight + nFrameWidth ) );
 
	// create a region from the frame rectangle
	QRegion regionFrame( rectFrame );
 
	// map the global coords to local for the client area
	rg.moveTo(mapFromGlobal(rg.topLeft()));
 
	// move the rect to 0,0
	rg.moveTo( QPoint(0,0) );
 
	// create a region from the client rect
	QRegion regionClient( rg );
 
	// set a mask to be the frame region minus the client region
	setMask( regionFrame - regionClient );
}

void resizeEvent(QResizeEvent *e)
{
	QDialog::resizeEvent(e);

	// grab the geometry
	QRect fg = frameGeometry();
	QRect rg = geometry();

	// get some reusable values
	int nCaptionHeight	= rg.top()	- fg.top();
	int nFrameWidth		= rg.left()	- fg.left();

	// map the global coords to local for the frame
	fg.moveTo(mapFromGlobal(fg.topLeft()));

	// create a rectangle for the frame
	QRect rectFrame(fg.left() - nFrameWidth,
				fg.top() - nCaptionHeight,
				fg.width() + ( nFrameWidth * 2 ),
				fg.height() + ( nCaptionHeight + nFrameWidth ) );

	// create a region from the frame rectangle
	QRegion regionFrame( rectFrame );
		
	// map the global coords to local for the client area
	rg.moveTo(mapFromGlobal(rg.topLeft()));

	// move the rect to 0,0
	rg.moveTo( QPoint(0,0) );

	// create a region from the client rect
	QRegion regionClient( rg );

	// set a mask to be the frame region minus the client region
	setMask( regionFrame - regionClient );
}

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You will probably recognize some of this code from this thread.
Many thanks to J-P Nurmi for laying the foundation...
It just took a bit to figure out that my problem was the math (e.g. negative numbers to allow the caption bar (since QPoint(0,0) is the upper left corner of the client area).
Thanks again JPN

This is what I was looking for...

[high_flyer]

does this works with semi transparency as well?
EDIT: after thinking about it a bit, I think it should - so:
(in this case) QDialog gets tsetWindowOpacity() to wanted degree of opacity
The rest as in the suggested above code.
This way we get a semi opaque non square resizeable dialog.
At least in theory.

[LarryDobson]

does this works with semi transparency as well?
EDIT: after thinking about it a bit, I think it should - so:
(in this case) QDialog gets tsetWindowOpacity() to wanted degree of opacity
The rest as in the suggested above code.
This way we get a semi opaque non square resizeable dialog.
At least in theory.

In Theory...

"non square" ??? making the dialog semi-tranparent will not effect the corners.

[wysota]

"non square" ??? making the dialog semi-tranparent will not effect the corners.

No, but setMask() will.