On 24/05/2011 13:06, Matthias Melcher wrote:
>
>
> Maybe the overlay API was not available when this was written. Seriously
> though, the overlay stuff is about 10 years old, and I seriously doubt that
> any of this is still current. If the OP really needs overlay panes under
> Cygwin, I would recommend to change the flag and test the results. If it
> works well (which is hard to test, because different graphics cards and
> drivers will behave differently) we should consider a patch for 1.3.1 or
> later.
>
Possibly, and I was digging into it because I have found an overlay glitch -
which I have resolved now. It seems like a bug of Intel's GL driver for Windows
7
(and possibly Vista), other graphics (ATI/AMD, nVidia, or even Intel on XP)
work fine.
The bug is weird as the ortho_context (which is only used to copy back buffer
to front to emulate overlay) does not like repetitive setting of
glReadBuffer(GL_BACK); glDrawBuffer(GL_FRONT); in which case overlay is not
displayed :-(. It also does not like glRasterPos2i(0,0), which was commented
out in
1.1.x (and is uncommented in 1.3, I have put the comment back again...)
My resolution to it is setting it only once when this context is created. As
this context is used only for the back/front buffer copy and never changes
(apart
from viewport), the new code should be correct (and should be also slightly
faster). Here is what I did:
ORIGINAL CODE, Fl_Fl_Window.cxx staring at line 372:
if (orthoinit) ortho_context = fl_create_gl_context(this, g);
fl_set_gl_context(this, ortho_context);
if (orthoinit || !save_valid || ortho_window != this) {
glDisable(GL_DEPTH_TEST);
glReadBuffer(GL_BACK);
glDrawBuffer(GL_FRONT);
glLoadIdentity();
glViewport(0, 0, w(), h());
glOrtho(0, w(), 0, h(), -1, 1);
glRasterPos2i(0,0);
ortho_window = this;
}
glCopyPixels(0,0,w(),h(),GL_COLOR);
make_current(); // set current context back to draw overlay
NEW CODE which suppresses the bug:
if (orthoinit){
ortho_context = fl_create_gl_context(this, g);
fl_set_gl_context(this, ortho_context);
glDisable(GL_DEPTH_TEST);
glReadBuffer(GL_BACK);
glDrawBuffer(GL_FRONT);
glLoadIdentity();
}else
fl_set_gl_context(this, ortho_context);
if (orthoinit || !save_valid || ortho_window != this) {
glViewport(0, 0, w(), h());
glOrtho(0, w(), 0, h(), -1, 1);
// glRasterPos2i(0,0); // <- commenting it out again...
ortho_window = this;
}
glCopyPixels(0,0,w(),h(),GL_COLOR);
make_current(); // set current context back to draw overlay
After that, everything seems to work fine.
Shall I fill an STR?
R.
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