Drawing problems

Drawing problems

Post by Ian » Tue, 24 Jun 2003 00:36:05



Hi,
    I'm drawing on an image canvas, (i.e. Canvas->MoveTo(X,Y) and
Canvas->LineTo(X,Y))  and have a couple of problems-
1. The drawing seems a little slow. I am drawing perhaps a few thousand
lines, and it takes maybe a quarter of a second. Is there a quicker way?

2. If the form with the image on which I am drawing looses focus, then
regains it, all of the drawing is lost. How can I prevent this from
happening?

Many thanks.

--
======================================
Ian Belchamber
mobile: +44(0)7802 416525

 
 
 

Drawing problems

Post by Maynard Philbroo » Tue, 24 Jun 2003 01:13:33


if your using the canvas from the form it is only painting to the video
cards memory.
 you need to write to a bitmap to  keep your work and then paint it to the
canvas
 on a onPaint event.
  how ever all is not lost..
 Timage has a screen canvas and contains a bitmap for you.
 drop a timage on the form and use the canvas of that instead.
  in short your actually drawing to the picture.bitmap.canvas that is
contained
 in Timage,  but timage overriders the canvas to always insure that an
 invalidate message is sent to windows after your drawing to force it to
 paint the contents of the bitmap to the forms surface.

> Hi,
>     I'm drawing on an image canvas, (i.e. Canvas->MoveTo(X,Y) and
> Canvas->LineTo(X,Y))  and have a couple of problems-
> 1. The drawing seems a little slow. I am drawing perhaps a few thousand
> lines, and it takes maybe a quarter of a second. Is there a quicker way?

> 2. If the form with the image on which I am drawing looses focus, then
> regains it, all of the drawing is lost. How can I prevent this from
> happening?

> Many thanks.

> --
> ======================================
> Ian Belchamber
> mobile: +44(0)7802 416525


 
 
 

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thanks
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