Board index » cppbuilder » TImage flicker

2006-10-21 12:10:55 AM
cppbuilder67
Hi,
I have:
void __fastcall TPreplot::ImageMouseMove(TObject *Sender, TShiftState
Shift, int X, int Y)
{
if(Panning)
{
Image->Align = alNone;
Image->Top += Y - OrigY;
Image->Left += X - OrigX;
return;
}
}
when the image pans it flickers. How can I stop the flickering?
Cheers,
Paul
 

: TForm(Owner)
{
// ...
DoubleBuffered = true;
// ...
}
--
Best Regards,
Vladimir Stefanovic
 

this has no effect
Vladimir Stefanovic wrote:

{smallsort}

Try Image->Canvas->Brush->Style=bsClear
"Paul Dowd" < XXXX@XXXXX.COM >ha scritto nel messaggio

Paul Dowd < XXXX@XXXXX.COM >wrote:
That causes the TImage to repaint twice with event and if you
have the Stretched property set to true it's even slower.
Since Window's can handle moving a large area without flicker,
it has to be your technique. Please explain exactly what you're
trying to accomplish. I'd bet that you can acomplish it with a
TBitmap or two instead of using a TImage.
~ JD
 

in place of setting Left and top with 2 different lines (=>2 different
calls) you can use Image->SetBounds ... I think
"JD" < XXXX@XXXXX.COM >ha scritto nel messaggio

Hi all,
After trying your various suggestions I have come to the conclusion that
the problem is just the refresh rate of the monitor.
Many thanks
Paul
Paul Dowd wrote:

Hi,
I actually posted a message saying that perhaps the problem was the
screen refresh rate, this is not the case.
I am trying to produce an image that can be zoomed in on by drawing a
rectangle on it and then panned by dragging using the mouse, similar to,
say, a PDF document. I have achieved all this but the flickering is
still a problem. How could I do this using a TBitmap instead of a TImage?
Paul

Paul Dowd < XXXX@XXXXX.COM >wrote:
Canvas because each time it's content changes, it needs to
redraw.
that requires all of the painting. If you want to get rid of
the flicker, your code must eliminate the need to constantly
repaint the image.
The easiest way for you at this point is to use a second TImage
that is transparent and overlays the other TImage exactly. Set
it's Transparent property to true and fill it's Canvas with
the same color (bottom/left pixel determines the transparent
color). Should take you about 5 minutes to fix it.
~ JD
 

No,
The problem likely is the internal invalidate.
To get rid of it you should intercept the OnPaint event and draw the image
using Canvas->Draw(x,y,Bitmap) without using Invalidate.
"Paul Dowd" < XXXX@XXXXX.COM >ha scritto nel messaggio

Paul Dowd wrote:
web.archive.org/web/20040213233900/www.bcbdev.com/faqs/faq34.htm
H^2
 

Harold,
This article is great - problem solved! Many thanks,
Paul
Harold Howe [TeamB] wrote: