PrintPreview - DoubleBuffered

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PrintPreview - DoubleBuffered

Postby thecocce » February 18th, 2014, 1:03 pm

Hi all, i have a problem with TThumbnailPreview component.
If the container form prop DoubleBuffered is set to true all the thumbnails are shown as black rectangles.

Is there a workaround about this problem?

Thanks in advance
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Re: PrintPreview - DoubleBuffered

Postby arhangelsoft » February 18th, 2014, 7:29 pm

Hi, I think this is a internal VCL problem.

Drop TToolBar on Form, set doublebuffered to true, in run-time or even design-tim, u will see your problem again. All TToolButton's will view as black squares.
I have this bug on Delphi XE4 with all updates.
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Re: PrintPreview - DoubleBuffered

Postby Kambiz » February 18th, 2014, 8:45 pm

All of print preview components have their own double buffering mechanism. For this reason setting DoubleBuffered to true does nothing but decreasing the performance.
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Re: PrintPreview - DoubleBuffered

Postby thecocce » February 24th, 2014, 8:51 am

Ok, but is there a workaround about this problem?
Is not just a decrease of performances, the component doesn't work.
If i need to use Doublebuffer for other component in a form i can't use PrintPreview.

Thanks in advance
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Re: PrintPreview - DoubleBuffered

Postby Kambiz » March 1st, 2014, 1:24 pm

Which version of Delphi?

I have only Delphi 7 and in this version I see no issues.

Anyway, instead of using double buffered form, only set the DoubleBuffered property of the control that needs it. If there are many controls needing double buffering and they change all tohether, put them on a panel and set DoubleBuffered property of the panel.
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