Flicker when custom drawing on a double buffered TTreeView

Question

When listening to the AdvancedCustomDraw event of a TTreeView event this way:

if Stage = cdPrePaint then begin
    // modify some Sender.Canvas properties and let it draw itself
end else if Stage = cdPostPaint then begin
    // draw 'something extra' using a separate TControlCanvas
    TControlCanvas.TextOut(SomeRect, 'Hello');
end;

... it seems that when I enable DoubleBuffered the control decides not to copy the 'something extra' to the offscreen buffer. This means that as long as I don't disturb the window in question, all is fine. When I do, the 'something extra' is only visible in random parts of the window.

What am I missing here?

Sounds like the simple solution is to switch `DoubleBuffered` to `False`. Why can't you do that? — David Heffernan, Feb 02 '13 at 19:09
@DavidHeffernan well, that makes erasing visible when resizing the control in question. And that's what I am trying to prevent. — Orwell, Feb 02 '13 at 21:15
That's easy to do. Just add the extended window style `WS_EX_COMPOSITED` whilst in the sizing loop. Personally I have made flicker free Delphi apps, flicker free during resize, without `DoubleBuffered`, a property which I regard to be evil. More details at my answer here: http://stackoverflow.com/questions/8058745/tlabel-and-tgroupbox-captions-flicker-on-resize — David Heffernan, Feb 02 '13 at 21:19

score 4 · Accepted Answer · edited May 23 '17 at 12:09

Since your comment gave me carte blanche to suggest an alternative solution, here's what I would do:

Stop using DoubleBuffered. It leads to lots of visual oddities in lots of controls. I personally avoid it like the plague.
Solve your flickering problem by adding the WS_EX_COMPOSITED extended window style to your control. This window style can be a bit of a performance drag and I'd recommend that you only add this during the sizing loop, which is when you need it. I describe how to do that in my answer here: TLabel and TGroupbox Captions Flicker on Resize.

Flicker when custom drawing on a double buffered TTreeView

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