Canvas never transparent

[_qt_user_]

Hi,

I'm trying to build a plot in a QWidget which has a background. I want to see through my plot the background of this widget.

I tried a lot of tips given by Uwe on this forum but I have never managed to have my plot fully transparent.

Here is what I tried :

With palette :

setAutoFillBackground( true );
QColor c( Qt::gray );
c.setAlpha( 50 );
QPalette pal;
pal.setColor( QPalette::Window, c );

canvas()->setPalette( pal );
canvas()->setAutoFillBackground( true );

with stylesheet :

setAutoFillBackground( true );
setStyleSheet("QwtPlot{ border: 0px; background: transparent;}");
canvas()->setStyleSheet("border: 0px; background: transparent;");
canvas()->setAutoFillBackground(false);

I must have some issues with the attribute and PaintAttribute but I can't find which one.
The best result I had was :
- axis fully transparent but canvas stays white
- all plot and canvas transparent through the parent widget itself (I can see the widgets under my parent's widget)

Thanks for your help

[_qt_user_]

Is it because my question is stupid that nobody answers? Or am I not clear?

Please I just need this to finish my interface !

[Spitfire]

It's quite simple - when you already know it

plot->canvas()->setPaintAttribute( QwtPlotCanvas::PaintPacked, false );
plot->canvas()->setPaintAttribute( QwtPlotCanvas::PaintCached, false );
plot->setCanvasBackground( Qt::transparent );

plot->canvas()->setPaintAttribute( QwtPlotCanvas::PaintPacked, false );
plot->canvas()->setPaintAttribute( QwtPlotCanvas::PaintCached, false );
plot->setCanvasBackground( Qt::transparent );

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Using this method you may get severe performance hit with large plots as caching is disabled, but I'm not sure if there's another way of doing it.

[Uwe]

When the background color is set to transparent you probably don't need to disable the PaintCached mode, what is the important one for the performance when using stuff like rubberbands.

Uwe

[Spitfire]

I've tested it against qwt5 and you need to disable both in there.
Not sure about qwt6 though.