[Lazarus] Optimize DBGrid speed
petr.kristan at epos.cz
Wed Jan 8 17:55:19 CET 2014
On Wed, Jan 08, 2014 at 02:35:08PM +0100, Hans-Peter Diettrich wrote:
> Petr Kristan schrieb:
> >In the beginning of Grid paint is Canvas.GetClipRect called to obtain area
> >which wee must redraw. This function directly calls WidgetSet.GetClipBox.
> >I find out difference betwen Win32 and gtk2 bahaviour of this func.
> >In gtk2 TGtk2WidgetSet.GetClipBox returns previously Invalidated area
> >(through DC.PaintRectangle = PS.rcPaint retrieved in BeginPaint)
> >But in win32 directly calls Windows.GetClipBox, but this func returns
> >whole grid area. Do not takes account on invalidated area retrieved in
> It may be a bug in the Win32 widgetset, invalidating the entire
> control area instead of only the affected cell, *or* some special
> handling of invalidated areas by Windows. I remember that Windows
> used to extend the UpdateRect to include *all* invalidated parts of
> the DC. This can lead to a big update area, when a single bit at the
> top left and at the bottom right of the DC was invalidated. This may
> have changed in the meantime, though.
My idea was wrong, I overlook something in debug logs.
Canvas.GetClipRect returns correct value.
Problem must be in another place.
First Paint has correct update rect, but then second Paint is called
on whole grid.
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