[Mesa-dev] [PATCH 2/2] wglinfo: query and report multisample information

[Jose Fonseca]

----- Original Message -----
> On 06/09/2014 07:22 AM, Jose Fonseca wrote:
> > I don't think that OpenGL ICD should advertise multi-sample formats via the
> > standard DescribePixelFormat.
> > http://www.opengl.org/registry/specs/ARB/wgl_pixel_format.txt states:
> >
> >      Indices are assigned to pixel formats in the following order:
> >
> >      1. Accelerated pixel formats that are displayable
> >
> >      2. Accelerated pixel formats that are displayable and which have
> >         extended attributes
> >
> >      3. Generic pixel formats
> >
> >      4. Accelerated pixel formats that are non displayable
> >
> >      ChoosePixelFormat will never select pixel formats from either group
> >      2 or group 4. Each pixel format in group 2 is required to appear
> >      identical to some pixel format in group 1 when queried by
> >      DescribePixelFormat. Consequently, ChoosePixelFormat will always
> >      select a format from group 1 when it might otherwise have selected a
> >      format from group 2. Pixel formats in group 4 cannot be accessed by
> >      ChoosePixelFormat at all.
> >
> > That is, IIUC, in order to discover multi-sampled formats one must get the
> > the number of pixel formats via
> > wglGetPixelFormatAttribivARB(WGL_NUMBER_PIXEL_FORMATS_ARB) instead of
> >
> >     numVisuals = DescribePixelFormat(hdc, 1, sizeof(PIXELFORMATDESCRIPTOR),
> >     NULL);
> >     if (numVisuals == 0)
> >        return;
> >
> > And I'm not even sure if it is OK to call DescribePixelFormat() with
> > extended pixel formats or if one must use exclusively
> > wglGetPixelFormatAttribivARB/wglGetPixelFormatAttribivARB.  You can see
> > how GLFW does it on
> > https://github.com/glfw/glfw/blob/master/src/wgl_context.c#L144
> 
> Nothing's ever easy on Windows. <sigh>

No. OPENGL32.DLL interface 

> The code as-is seems to work fine both on a Windows/nvidia host and in
> the guest but I'll try the changes you suggested...

Is wglinfo displaying multi-sampled pixelformats on NVIDIA as is?  If so then my interpretation might be wrong somehow.


Jose