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Editorial Team
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Asked: 2026-05-20T12:06:18+00:00

I’m currently writing an custom control which has to hold child control and have

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I’m currently writing an custom control which has to hold child control and have to support scrolling and autorisze.
Autoscrolling is not possible because my control is fully selfpainted an only a part of the control should be scrolled.

Now the the repainting of the Controls is extrem slow, especialy with textbox and buttoncontrols with systempainting. Deactivating systempainting (TextBox.BorderStyle = Borderstyle.Fixed) helps, but the control should also support this. Using SetRedraw and updating the controls afterward doesn’t help, because the textbox systemdraw is ignored and the textbox looks ugly. Refreshing my whole control or using `RedrawWindow slows the painting down again.

i also already tried to suspend my control and child controls layout without success.

Does anybody know how to speedup the childcontrol painting like AutoScrolling.

My CustomControl has the Style ControlStyles.AllPaintingInWmPaint | ControlStyles.SupportsTransparentBackColor | ControlStyles.OptimizedDoubleBuffer.

The ChildControl bound is changed on (MyControl)Resize and (ScrollBar)OnValueChanged.

Using a Timer helps a little, but i don’t know if this is realy the right solution.

EDIT :
I have found the problem, aufter reactivating SetRedraw and Refresh, OnPaint fires 38 times with 37 Controls. Is the any workaround?

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1 Answer

  1. Editorial Team

    I was able to speed it up, by adding a custom flag which tells me if the OnPaint is fired by my control or by a child control. If my control fires the event i draw my controls content to a bitmap and just blit it for the childcontrols.

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