Flickering bug for World of Warcraft

[Bertrand Coconnier]

Roderick Colenbrander wrote :
>> Roderick Colenbrander wrote :
>>
>>> Or perhaps a testcase isn't needed at all. I think the use of
>> CreateCompatibleDC in wglGetPbufferDCARB is incorrect. According to MSDN this
>> function creates a memory device context. Perhaps something like this works:
>>> HDC hdc = CreateDC(...);
>>> int format_orig = GetPixelFormat(hdc_orig);
>>> SetPixelFormat(hdc, format_orig);
>>> return hdc;
>> Thanks to your hints I could make the attached patch. It fixes the issue
>> on my 
>> side : wglGetPbufferDCARB returns a DC which type is OBJ_DC and WoW does
>> not 
>> flicker any more.
>>
>> Regards,
>>
>> Bertrand.
> 
> @@ -1869,16 +1869,18 @@ static HDC WINAPI X11DRV_wglGetPbufferDC
>  {
>      Wine_GLPBuffer* object = (Wine_GLPBuffer*) hPbuffer;
>      HDC hDC;
> +    int iPixelFormat;
> +    PIXELFORMATDESCRIPTOR  pfd;
>      if (NULL == object) {
>          SetLastError(ERROR_INVALID_HANDLE);
>          return NULL;
>      }
> -    hDC = CreateCompatibleDC(object->hdc);
>  
> -    /* The function wglGetPbufferDCARB returns a DC to which the pbuffer can be connected.
> -     * We only support one onscreen rendering format (the one from the main visual), so use that. */
> -    SetPixelFormat(hDC, 1, NULL);
> -    set_drawable(hDC, object->drawable); /* works ?? */
> +    hDC = CreateDCA("DISPLAY", NULL, NULL, NULL);
> +    iPixelFormat = GetPixelFormat(object->hdc);
> +    DescribePixelFormat(hDC, iPixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
> +    SetPixelFormat(hDC, iPixelFormat, &pfd);
> +
>      TRACE("(%p)->(%p)\n", hPbuffer, hDC);
>      return hDC;
>  }
> 
> I'm not sure if this is correct for all programs. Some more testing needs to be done in other programs that use pbuffers. The set_drawable line must have a purpose (though I like to get rid of it or atleast implement it without ExtEscape). And I'm also not sure if we need to retrieve the pixelformat of the 'parent hdc' as it is allways 1 though retrieving it is nicer.
> 
> Roderick

The patch fixes the bug whether the set_drawable is included or not. So I guess 
it does not hurt. I also dug in the wine-patches mailing list and it appeared 
that you included this line in your original patch (see 
http://www.winehq.org/pipermail/wine-patches/2006-September/030335.html) but 
infortunately you did not give any detail at the time about the reason of its 
inclusion. Yet it seems logical that the DC returned by wglGetPbufferDCARB is 
linked to the Pbuffer drawable rather than the window drawable.

About the retrival of the pixel format of the 'parent hdc', I agree that it is a 
bit overkill but once again it does not hurt and it may prevent bugs to occur if 
one day Wine will use more than one pixel format.

So what about this patch ?

@@ -1869,16 +1869,18 @@ static HDC WINAPI X11DRV_wglGetPbufferDC
  {
      Wine_GLPBuffer* object = (Wine_GLPBuffer*) hPbuffer;
      HDC hDC;
+    int iPixelFormat;
+    PIXELFORMATDESCRIPTOR  pfd;
      if (NULL == object) {
          SetLastError(ERROR_INVALID_HANDLE);
          return NULL;
      }
-    hDC = CreateCompatibleDC(object->hdc);

-    /* The function wglGetPbufferDCARB returns a DC to which the pbuffer can be 
connected.
-     * We only support one onscreen rendering format (the one from the main 
visual), so use that. */
-    SetPixelFormat(hDC, 1, NULL);
+    hDC = CreateDCA("DISPLAY", NULL, NULL, NULL);
+    iPixelFormat = GetPixelFormat(object->hdc);
+    DescribePixelFormat(hDC, iPixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
+    SetPixelFormat(hDC, iPixelFormat, &pfd);
      set_drawable(hDC, object->drawable); /* works ?? */
+
      TRACE("(%p)->(%p)\n", hPbuffer, hDC);
      return hDC;
  }

About testing, I don't have an app other than WoW that uses OpenGL (not to 
mention Pbuffers) so if some people out there could give this patch a try...

Bertrand.