| Summary: | No pixel formats with WGL_SWAP_UNDEFINED_ARB && WGL_DOUBLE_BUFFER_ARB=true | ||
|---|---|---|---|
| Product: | Mesa | Reporter: | Charles Huber <genpfault> |
| Component: | Mesa core | Assignee: | mesa-dev |
| Status: | RESOLVED NOTABUG | QA Contact: | mesa-dev |
| Severity: | major | ||
| Priority: | medium | CC: | brianp, jfonseca |
| Version: | 17.0 | ||
| Hardware: | x86 (IA32) | ||
| OS: | Windows (All) | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
| Attachments: | Init WGL & show number of matching pixel formats | ||
Created attachment 130833 [details]
Init WGL & show number of matching pixel formats
Hi Charles, I compiled your test program and ran it with Mesa in a Windows VM and wglChoosePixelFormatARB failed to find a pixel format. But I found the exact same failure when I ran it with NVIDIA's OpenGL driver on a Windows 7 system. I also used the wglinfo utility to examine the double buffered pixel formats offered with NVIDIA's driver. None of them use WGL_SWAP_UNDEFINED_ARB. They're all tagged with either WGL_SWAP_EXCHANGE_ARB or WGL_SWAP_COPY_ARB. I would expect that ANGLE is tested with NVIDIA's OpenGL driver, but I don't know how things could work with the ANGLE code I see. When you specify WGL_SWAP_METHOD_ARB = WGL_SWAP_UNDEFINED_ARB you're asking for a very specific type of implementation of wglSwapBuffers(). Any given Windows OpenGL driver is free to implement any of the three swap methods. AFAIK, none are required. Note that WGL_SWAP_UNDEFINED_ARB doesn't mean "don't care". Does ANGLE really require this specific type of buffer swap behavior? If not, the WGL_SWAP_METHOD_ARB attribute should simply be omitted. My guess is that the intent was to support eglChooseConfig()'s EGL_SWAP_BEHAVIOR_PRESERVED_BIT and eglSurfaceAttrib()'s EGL_BUFFER_PRESERVED/EGL_BUFFER_DESTROYED but currently GetDefaultPixelFormatAttributes()'s only caller unconditionally sets preservedSwap to false and always tries WGL_SWAP_UNDEFINED_ARB. I'll file a bug on ANGLE's tracker and see if they like the "if preservedSwap == false -> omit WGL_SWAP_METHOD_ARB entirely" idea. |
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I'm using llvmpipe on Windows 7 x64, though LLVM & Mesa are built for 32-bit. Requesting WGL_SWAP_UNDEFINED_ARB or WGL_SWAP_COPY_ARB in conjunction with WGL_DOUBLE_BUFFER_ARB = TRUE results in wglChoosePixelFormatARB() returning zero supported pixel formats. These attributes work: int pixel_attributes[] = { WGL_SUPPORT_OPENGL_ARB, TRUE, WGL_DOUBLE_BUFFER_ARB, TRUE, 0 }; These do not: int pixel_attributes[] = { WGL_SUPPORT_OPENGL_ARB, TRUE, WGL_DOUBLE_BUFFER_ARB, TRUE, WGL_SWAP_METHOD_ARB, WGL_SWAP_UNDEFINED_ARB, 0 }; This is causing ANGLE to fail to get a valid pixel format when using Mesa as its OpenGL backend: https://chromium.googlesource.com/angle/angle.git/+/master/src/libANGLE/renderer/gl/wgl/wgl_utils.cpp#35