Mega Code Archive
How to eliminate flickering without using LockWindowUpdate(Handle)
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Title: How to eliminate flickering without using LockWindowUpdate(Handle)?
Question: How to eliminate flickering without using LockWindowUpdate(Handle)?
Answer:
I have an application in which the user drags TImage descendants around on a
background image. When an image is dropped, I have to run through all the current images finding out where they are, and then arrange their z-order appropriately.
When I do this, there's significant flickering. I've tried calling
LockWindowUpdate(Handle) before the operation, then LockWindowUpdate(0) at the
end, but several repaint operations still seem to take place at once. I'd like
to be able to repaint the whole form once only, or failing that, limit the repaint to a specific area of the form (so that all my buttons etc, which aren't involved in any of this, don't have to flicker too).
var
FLockFormUpdatePile : integer;
procedure TForm1.LockFormUpdate;
begin
if FLockFormUpdatePile = 0 then
Perform(WM_SetRedraw, 0, 0);
inc(FLockFormUpdatePile);
end;
procedure TForm1.UnlockFormUpdate;
begin
dec(FLockFormUpdatePile);
if FLockFormUpdatePile = 0 then begin
Perform(WM_SetRedraw, 1, 0);
RedrawWindow(Handle, nil, 0, RDW_FRAME + RDW_INVALIDATE +
RDW_ALLCHILDREN + RDW_NOINTERNALPAINT);
end;
end;
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