Canvas Draw function failing every now and again....

Canvas Draw function failing every now and again....

Post by Giant Slot » Thu, 30 Nov 2000 04:00:00



We're writing bitmaps out to a high speed printer and every now and
then a bitmap doesn't get drawn.  Has anyone had this problem before?
We're drawing the same bitmaps over and over (In our test), but every
now and then it doesn't draw the bitmap.  It's a blank spot where the
bitmap should be.   We're using the Window BitBlt, thinking that would
be different than Draw, but they work the same.

Thanks for any help!

 
 
 

Canvas Draw function failing every now and again....

Post by Giant Slot » Thu, 30 Nov 2000 04:00:00


On Wed, 29 Nov 2000 08:51:47 -0600, Giant Sloth


>We're writing bitmaps out to a high speed printer and every now and
>then a bitmap doesn't get drawn.  Has anyone had this problem before?
>We're drawing the same bitmaps over and over (In our test), but every
>now and then it doesn't draw the bitmap.  It's a blank spot where the
>bitmap should be.   We're using the Window BitBlt, thinking that would
>be different than Draw, but they work the same.

>Thanks for any help!

We started checking the GetLastError and every now and then we also
get an Error 87, which is Invalid Parameters.  Our parameters all look
good....  Anyone have ideas?  Thank you

 
 
 

Canvas Draw function failing every now and again....

Post by Giant Slot » Thu, 30 Nov 2000 04:00:00


It turns out that Delphi was actually returning bad handles sometimes
in the Bitmap.Canvas.Handle call.  We did a Lock before and Unlock
aftewards and it seems to work fine now.  Go figure......
 
 
 

Canvas Draw function failing every now and again....

Post by Maynard Philbroo » Mon, 04 Dec 2000 04:00:00


Try checking for the Lock Count before doing  your draw.
you must be doing multithreading..

> We're writing bitmaps out to a high speed printer and every now and
> then a bitmap doesn't get drawn.  Has anyone had this problem before?
> We're drawing the same bitmaps over and over (In our test), but every
> now and then it doesn't draw the bitmap.  It's a blank spot where the
> bitmap should be.   We're using the Window BitBlt, thinking that would
> be different than Draw, but they work the same.

> Thanks for any help!

 
 
 

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