fe3aa8b8b3
The GL3 context is created using the glXCreateContextAttribs function which is part of the GLX_ARB_create_context extension. However previously the function pointers from GLX extensions were only retrieved once the GL context is created. That meant that the GL3 context creation function would always assume that the extension is not supported so it would always fail. This patch changes it to query the functions when the renderer is set up instead. The base winsys feature flags that are determined while querying the functions are stored in a member of CoglGLXRenderer. These are then copied to the CoglContext when it is initialised. The spec for glXGetProcAddress says that the functions returned are context-independent. That implies that it is safe to call it without binding a context although that is not explicitly stated as far as I can tell. A big of googling finds this DRI documentation which says it can be used without a context: http://dri.freedesktop.org/wiki/glXGetProcAddressNeverReturnsNULL And also this code sample: http://www.opengl.org/wiki/Tutorial:_OpenGL_3.0_Context_Creation_%28GLX%29 One point that makes me concerned that this might not always work in practice is that the code in SDL2 to create a GL3 context first creates a dummy GL2 context in order to have something bound before it calls glXGetProcAddress. I think this may just be a misunderstanding based on how wglGetProcAddress works however. Reviewed-by: Robert Bragg <robert@linux.intel.com> (cherry picked from commit 04a7aca9a98e84e43ac5559305a1358112902e30)
87 lines
2.7 KiB
C
87 lines
2.7 KiB
C
/*
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* Cogl
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*
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* An object oriented GL/GLES Abstraction/Utility Layer
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*
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* Copyright (C) 2011 Intel Corporation.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see
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* <http://www.gnu.org/licenses/>.
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*
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*
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*/
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#ifndef __COGL_RENDERER_GLX_PRIVATE_H
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#define __COGL_RENDERER_GLX_PRIVATE_H
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#include <gmodule.h>
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#include "cogl-object-private.h"
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#include "cogl-xlib-renderer-private.h"
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typedef struct _CoglGLXRenderer
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{
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int glx_major;
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int glx_minor;
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int glx_error_base;
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int glx_event_base;
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CoglBool is_direct;
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/* Vblank stuff */
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int dri_fd;
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/* GModule pointing to libGL which we use to get glX functions out of */
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GModule *libgl_module;
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/* Copy of the winsys features that are based purely on the
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* information we can get without using a GL context. We want to
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* determine this before we have a context so that we can use the
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* function pointers from the extensions earlier. This is necessary
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* to use the glXCreateContextAttribs function. */
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unsigned long base_winsys_features
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[COGL_FLAGS_N_LONGS_FOR_SIZE (COGL_WINSYS_FEATURE_N_FEATURES)];
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CoglFeatureFlags legacy_feature_flags;
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/* Function pointers for core GLX functionality. We can't just link
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against these directly because we need to conditionally load
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libGL when we are using GLX so that it won't conflict with a GLES
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library if we are using EGL + GLES. These are just the functions
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that we want to use before calling glXGetProcAddress */
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Bool
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(* glXQueryExtension) (Display *dpy, int *errorb, int *event);
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const char *
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(* glXQueryExtensionsString) (Display *dpy, int screen);
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Bool
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(* glXQueryVersion) (Display *dpy, int *maj, int *min);
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void *
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(* glXGetProcAddress) (const GLubyte *procName);
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/* Function pointers for GLX specific extensions */
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#define COGL_WINSYS_FEATURE_BEGIN(a, b, c, d, e, f, g)
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#define COGL_WINSYS_FEATURE_FUNCTION(ret, name, args) \
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ret (APIENTRY * name) args;
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#define COGL_WINSYS_FEATURE_END()
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#include "cogl-winsys-glx-feature-functions.h"
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#undef COGL_WINSYS_FEATURE_BEGIN
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#undef COGL_WINSYS_FEATURE_FUNCTION
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#undef COGL_WINSYS_FEATURE_END
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} CoglGLXRenderer;
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#endif /* __COGL_RENDERER_GLX_PRIVATE_H */
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