jack3 wrote:
> Hi,
>
> Basically, my way is inherit a class glCanvas from GLWindow and override the
> function of draw_overlay and draw.
> then, I have a thread to continuely read image from network and call
> redraw_overlay.
That should be fine, I think a good way to do that would be
to make your own application loop (instead of calling Fl::run() in
main())
eg:
while ( 1 ) {
WaitForPixelData(); // wait for thread to be done putting
data into memory
yourwidget->redraw(); // tell fltk to schedule a redraw of your widget
Fl::wait(); // fltk redraws your widget
}
..or something to that effect.
Another approach would be to just call Fl:run(), and set up an
fltk timer to trigger the redraw()s, similar to this technique:
See: http://seriss.com/people/erco/fltk/#Animate
> Finally,draw_overlay should be called to refresh the image on the window.
> void VTGLCanvas::draw_overlay()
> {
> // the valid() property may be used to avoid reinitializing your
> // GL transformation for each redraw:
> if (!valid())
> {
> valid(1);
> glLoadIdentity();
> glViewport(0,0,w(),h());
> }
> glClearColor(0,0,0,0);
> glClear(GL_COLOR_BUFFER_BIT);
> CAVAutoLock lock(&m_CritSecData);
>
> glDrawPixels(m_nWidth,m_nHeight,GL_BGR_EXT,GL_UNSIGNED_BYTE,m_pFrameData);
> swap_buffers();
> }
>
Hmm, not sure why you're using draw_overlay() instead of draw().
I would think draw_overlay() puts a requirement on overlay hardware,
and is probably slow.
Try moving all your draw pixels code to draw() instead, and don't use
draw_overlay() at all.
I don't think you need to call swap_buffers().. FLTK's draw() function
should handle that. You /may/ need a glFlush() if you want to ensure
the glDrawPixels() function has finished before your lock gets released
at the closing brace (when the 'lock' instance goes out of scope)
Once that's working, focus on optimizing the glDrawPixels() transfer
flags so that the video data is moved as quickly as possible to the
screen.
Also, not sure why glClear() should need to be called each frame;
I would think just clearing both buffers during the !valid() section
should prevent the need to clear the screen each frame, unless your
width/height values are changing for the glDrawPixels() call, in which
case maybe only do the glClear() if the width/height values change.
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