🚀 go-pugleaf

Oliver,
You are ABSOLUTELY right. Canvas is a pain in thread  :-(
I just found out that it wasn't the (only) problem that the unfinished image
is copied. It's simply the CopyRect gets crazy. Before, I was moving some
windows around while my program was running. Therefore I assumed that the
OnPaint came in place. But then I found out that also happens even I just
move the mouse pointer around, which is not triggering the OnPaint event at
all. The funny thing is if I leave my program running without any movement
the graphic is fine. Luckily, I found someone has experienced the same thing
:-)

I used to use WinAPI to draw. But then I thought that's the time of Win3.x
and it's no long up-to-date :-) So, I tried the BCB lib.
Can you give me any advice to convert my CopyRect to WinAPI? Is there a
similar function and with binary operation (CopyMode)?
Since I also plan to compile my program with Kylix for Linux (maybe one day)
:-)  shouldn't I avoid to use too many WinAPI's, what do you think?
Should I have a look in SDL (www.libsdl.org)? Will I have the same problem
with SDL?


Vielen Dank
Phuoc Can HUA


"Oliver Rutsch" <nospam@sympatec.com> wrote in message
news:1046770772.980524@post.sympatec.net...
> Hi Phuoc,
> [...]
> >
>
> Normally you should use the Canvas->Lock(), Canvas->Unlock() and
> Canvas->TryLock() for this purpose. If you don't trust it, you can also
> use a TCriticalSection (i think the VCL locking functions are using
> critical sections internally, too) for your locking mechanism. Although
> you can use a semaphore for this purpose, it is more likely designed for
> instance or resource counters from different processes (global sync
> object like a named mutex).
> But as I wrote before I don't think that it will help to solve your
> problem. I tried every known locking mechanism in the Paint() function
> of my component and nothing helped. The Canvas->Handle sometimes got
> invalid (the VCL throws NO exception in that case, it just does
> something stupid...) and then you're lost. Using the Win32 API functions
> for drawing looks like a bad idea, but once started it is not too much
> work, because you have a lot of functions you can use nearly in the same
> way as the Canvas does.
> Again, the GUI functions of the VCL are not designed for multithreading,
> so I would check if it is really neccessary to use multithreaded visual
> components. Keep your main thread free to update your user interface and
> start some worker threads for the rest.
>
> Hope that helps.
>
> Bye,
>
> --
> Dipl. Ing. Oliver Rutsch
> EMail: orutsch at sympatec.com
> Sympatec GmbH Germany
>