Jesse Allen wrote :
On 11/3/06, Bertrand Coconnier bcoconni@club-internet.fr wrote:
Hi,
After investigating a bit in the Wine code, it seems that the flickering bug of WoW in OpenGL mode is due to wglGetPbufferDCARB that returns a DC which type is OBJ_MEMDC while it should return a DC which type is OBJ_DC. And since in the current git tree, the DC type of a Pbuffer is OBJ_MEMDC then the code located in lines 1394-1395 of dlls/winex11.drv/opengl.c is executed : the Pbuffer is copied to the screen each time the GL context is made current to the Pbuffer hence the flickering (WoW bounds the GL context alternatively to the screen and to the Pbuffer). The expected behaviour is not to copy the Pbuffer content to the screen since WoW does it itself.
The easiest workaround for this bug would be to make X11DRV_wglGetPbufferDCARB to return the Pbuffer's object->hdc (this fixes the flickering bug). However, I have made some tests with Windows XP and it appears that wglGetPbufferDCARB returns a HDC different from the HDC passed when wglCreatePbufferARB was called. So such a patch would be a dirty hack not a real fix.
http://oss.sgi.com/projects/ogl-sample/registry/ARB/wgl_pbuffer.txt
"To create a device context for the pbuffer, call
HDC wglGetPbufferDCARB(HPBUFFERARB hPbuffer);
where <hPbuffer> is a handle returned from a previous call to wglCreatePbufferARB. A device context is returned by wglGetPbufferDCARB which can be used to associate a rendering context with the pbuffer. Any rendering context created with a wglCreateContext that is "compatible" with the <iPixelFormat> may be used to render into the pbuffer."
So yes, it's supposed to return a new one.
So I can understand better, what are these set to when you run your program on both windows and linux?
type1 = GetObjectType(hDC); type2 = GetObjectType(pBufferHDC);Jesse
Under Windows XP : type1 == OBJ_DC type2 == OBJ_DC
Under Wine : type1 == OBJ_DC type2 == OBJ_MEMDC /* should be OBJ_DC since pBuffers are supposed to be located in Video Memory or whatever its name */
And since device contexts of Wine's pBuffers are OBJ_MEMDC, the following code in X11DRV_wglMakeCurrent is executed (line 1392 of dlls/winex11.drv/opengl.c) :
if(ret && type == OBJ_MEMDC) { ctx->do_escape = TRUE; pglDrawBuffer(GL_FRONT_LEFT); }
the content of the Pbuffer's DC is copied to the color buffer by Wine while it should not (there is no reason for some memory data to be copied to the color buffer when a GL context is made current to a Pbuffer).
Bertrand.