src/mesa/main/extensions.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  7.6
   4  *
   5  * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
   6  * Copyright (C) 2009  VMware, Inc.  All Rights Reserved.
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a
   9  * copy of this software and associated documentation files (the "Software"),
  10  * to deal in the Software without restriction, including without limitation
  11  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12  * and/or sell copies of the Software, and to permit persons to whom the
  13  * Software is furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be included
  16  * in all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  21  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  22  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  23  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  24  */
  25
  26
  27 /**
  28  * \file
  29  * \brief Extension handling
  30  */
  31
  32
  33 #include "glheader.h"
  34 #include "imports.h"
  35 #include "context.h"
  36 #include "extensions.h"
  37 #include "macros.h"
  38 #include "mtypes.h"
  39
  40 enum {
  41    DISABLE = 0,
  42    GLL = 1 << API_OPENGL_COMPAT,       /* GL Legacy / Compatibility */
  43    GLC = 1 << API_OPENGL_CORE,  /* GL Core */
  44    GL  = (1 << API_OPENGL_COMPAT) | (1 << API_OPENGL_CORE),
  45    ES1 = 1 << API_OPENGLES,
  46    ES2 = 1 << API_OPENGLES2,
  47    ES3 = 1 << (API_OPENGL_LAST + 1),
  48 };
  49
  50 /**
  51  * \brief An element of the \c extension_table.
  52  */
  53 struct extension {
  54    /** Name of extension, such as "GL_ARB_depth_clamp". */
  55    const char *name;
  56
  57    /** Offset (in bytes) of the corresponding member in struct gl_extensions. */
  58    size_t offset;
  59
  60    /** Set of API's in which the extension exists, as a bitset. */
  61    uint8_t api_set;
  62
  63    /** Year the extension was proposed or approved.  Used to sort the
  64     * extension string chronologically. */
  65    uint16_t year;
  66 };
  67
  68
  69 /**
  70  * Given a member \c x of struct gl_extensions, return offset of
  71  * \c x in bytes.
  72  */
  73 #define o(x) offsetof(struct gl_extensions, x)
  74
  75
  76 /**
  77  * \brief Table of supported OpenGL extensions for all API's.
  78  */
  79 static const struct extension extension_table[] = {
  80    /* ARB Extensions */
  81    { "GL_ARB_ES2_compatibility",                   o(ARB_ES2_compatibility),                   GL,             2009 },
  82    { "GL_ARB_ES3_compatibility",                   o(ARB_ES3_compatibility),                   GL,             2012 },
  83    { "GL_ARB_base_instance",                       o(ARB_base_instance),                       GL,             2011 },
  84    { "GL_ARB_blend_func_extended",                 o(ARB_blend_func_extended),                 GL,             2009 },
  85    { "GL_ARB_color_buffer_float",                  o(ARB_color_buffer_float),                  GL,             2004 },
  86    { "GL_ARB_copy_buffer",                         o(dummy_true),                              GL,             2008 },
  87    { "GL_ARB_conservative_depth",                  o(ARB_conservative_depth),                  GL,             2011 },
  88    { "GL_ARB_debug_output",                        o(dummy_true),                              GL,             2009 },
  89    { "GL_ARB_depth_buffer_float",                  o(ARB_depth_buffer_float),                  GL,             2008 },
  90    { "GL_ARB_depth_clamp",                         o(ARB_depth_clamp),                         GL,             2003 },
  91    { "GL_ARB_depth_texture",                       o(ARB_depth_texture),                       GLL,            2001 },
  92    { "GL_ARB_draw_buffers",                        o(dummy_true),                              GL,             2002 },
  93    { "GL_ARB_draw_buffers_blend",                  o(ARB_draw_buffers_blend),                  GL,             2009 },
  94    { "GL_ARB_draw_elements_base_vertex",           o(ARB_draw_elements_base_vertex),           GL,             2009 },
  95    { "GL_ARB_draw_instanced",                      o(ARB_draw_instanced),                      GL,             2008 },
  96    { "GL_ARB_explicit_attrib_location",            o(ARB_explicit_attrib_location),            GL,             2009 },
  97    { "GL_ARB_fragment_coord_conventions",          o(ARB_fragment_coord_conventions),          GL,             2009 },
  98    { "GL_ARB_fragment_program",                    o(ARB_fragment_program),                    GLL,            2002 },
  99    { "GL_ARB_fragment_program_shadow",             o(ARB_fragment_program_shadow),             GLL,            2003 },
 100    { "GL_ARB_fragment_shader",                     o(ARB_fragment_shader),                     GL,             2002 },
 101    { "GL_ARB_framebuffer_object",                  o(ARB_framebuffer_object),                  GL,             2005 },
 102    { "GL_ARB_framebuffer_sRGB",                    o(EXT_framebuffer_sRGB),                    GL,             1998 },
 103    { "GL_ARB_get_program_binary",                  o(ARB_shader_objects),                      GL,             2010 },
 104    { "GL_ARB_half_float_pixel",                    o(ARB_half_float_pixel),                    GL,             2003 },
 105    { "GL_ARB_half_float_vertex",                   o(ARB_half_float_vertex),                   GL,             2008 },
 106    { "GL_ARB_instanced_arrays",                    o(ARB_instanced_arrays),                    GL,             2008 },
 107    { "GL_ARB_internalformat_query",                o(ARB_internalformat_query),                GL,             2011 },
 108    { "GL_ARB_invalidate_subdata",                  o(dummy_true),                              GL,             2012 },
 109    { "GL_ARB_map_buffer_alignment",                o(ARB_map_buffer_alignment),                GL,             2011 },
 110    { "GL_ARB_map_buffer_range",                    o(ARB_map_buffer_range),                    GL,             2008 },
 111    { "GL_ARB_multisample",                         o(dummy_true),                              GLL,            1994 },
 112    { "GL_ARB_multitexture",                        o(dummy_true),                              GLL,            1998 },
 113    { "GL_ARB_occlusion_query2",                    o(ARB_occlusion_query2),                    GL,             2003 },
 114    { "GL_ARB_occlusion_query",                     o(ARB_occlusion_query),                     GLL,            2001 },
 115    { "GL_ARB_pixel_buffer_object",                 o(EXT_pixel_buffer_object),                 GL,             2004 },
 116    { "GL_ARB_point_parameters",                    o(EXT_point_parameters),                    GLL,            1997 },
 117    { "GL_ARB_point_sprite",                        o(ARB_point_sprite),                        GL,             2003 },
 118    { "GL_ARB_provoking_vertex",                    o(EXT_provoking_vertex),                    GL,             2009 },
 119    { "GL_ARB_robustness",                          o(dummy_true),                              GL,             2010 },
 120    { "GL_ARB_sampler_objects",                     o(dummy_true),                              GL,             2009 },
 121    { "GL_ARB_seamless_cube_map",                   o(ARB_seamless_cube_map),                   GL,             2009 },
 122    { "GL_ARB_shader_bit_encoding",                 o(ARB_shader_bit_encoding),                 GL,             2010 },
 123    { "GL_ARB_shader_objects",                      o(ARB_shader_objects),                      GL,             2002 },
 124    { "GL_ARB_shader_stencil_export",               o(ARB_shader_stencil_export),               GL,             2009 },
 125    { "GL_ARB_shader_texture_lod",                  o(ARB_shader_texture_lod),                  GL,             2009 },
 126    { "GL_ARB_shading_language_100",                o(ARB_shading_language_100),                GLL,            2003 },
 127    { "GL_ARB_shading_language_packing",            o(ARB_shading_language_packing),            GL,             2011 },
 128    { "GL_ARB_shadow",                              o(ARB_shadow),                              GLL,            2001 },
 129    { "GL_ARB_sync",                                o(ARB_sync),                                GL,             2003 },
 130    { "GL_ARB_texture_border_clamp",                o(ARB_texture_border_clamp),                GLL,            2000 },
 131    { "GL_ARB_texture_buffer_object",               o(ARB_texture_buffer_object),               GLC,            2008 },
 132    { "GL_ARB_texture_buffer_object_rgb32",         o(ARB_texture_buffer_object_rgb32),         GLC,            2009 },
 133    { "GL_ARB_texture_buffer_range",                o(ARB_texture_buffer_range),                GLC,            2012 },
 134    { "GL_ARB_texture_compression",                 o(dummy_true),                              GLL,            2000 },
 135    { "GL_ARB_texture_compression_rgtc",            o(ARB_texture_compression_rgtc),            GL,             2004 },
 136    { "GL_ARB_texture_cube_map",                    o(ARB_texture_cube_map),                    GLL,            1999 },
 137    { "GL_ARB_texture_cube_map_array",              o(ARB_texture_cube_map_array),              GL,             2009 },
 138    { "GL_ARB_texture_env_add",                     o(dummy_true),                              GLL,            1999 },
 139    { "GL_ARB_texture_env_combine",                 o(ARB_texture_env_combine),                 GLL,            2001 },
 140    { "GL_ARB_texture_env_crossbar",                o(ARB_texture_env_crossbar),                GLL,            2001 },
 141    { "GL_ARB_texture_env_dot3",                    o(ARB_texture_env_dot3),                    GLL,            2001 },
 142    { "GL_ARB_texture_float",                       o(ARB_texture_float),                       GL,             2004 },
 143    { "GL_ARB_texture_mirrored_repeat",             o(dummy_true),                              GLL,            2001 },
 144    { "GL_ARB_texture_multisample",                 o(ARB_texture_multisample),                 GL,             2009 },
 145    { "GL_ARB_texture_non_power_of_two",            o(ARB_texture_non_power_of_two),            GL,             2003 },
 146    { "GL_ARB_texture_query_lod",                   o(ARB_texture_query_lod),                   GL,             2009 },
 147    { "GL_ARB_texture_rectangle",                   o(NV_texture_rectangle),                    GL,             2004 },
 148    { "GL_ARB_texture_rgb10_a2ui",                  o(ARB_texture_rgb10_a2ui),                  GL,             2009 },
 149    { "GL_ARB_texture_rg",                          o(ARB_texture_rg),                          GL,             2008 },
 150    { "GL_ARB_texture_storage",                     o(ARB_texture_storage),                     GL,             2011 },
 151    { "GL_ARB_texture_storage_multisample",         o(ARB_texture_storage_multisample),         GL,             2012 },
 152    { "GL_ARB_texture_swizzle",                     o(EXT_texture_swizzle),                     GL,             2008 },
 153    { "GL_ARB_timer_query",                         o(ARB_timer_query),                         GL,             2010 },
 154    { "GL_ARB_transform_feedback2",                 o(ARB_transform_feedback2),                 GL,             2010 },
 155    { "GL_ARB_transform_feedback3",                 o(ARB_transform_feedback3),                 GL,             2010 },
 156    { "GL_ARB_transform_feedback_instanced",        o(ARB_transform_feedback_instanced),        GL,             2011 },
 157    { "GL_ARB_transpose_matrix",                    o(dummy_true),                              GLL,            1999 },
 158    { "GL_ARB_uniform_buffer_object",               o(ARB_uniform_buffer_object),               GL,             2009 },
 159    { "GL_ARB_vertex_array_bgra",                   o(EXT_vertex_array_bgra),                   GL,             2008 },
 160    { "GL_ARB_vertex_array_object",                 o(dummy_true),                              GL,             2006 },
 161    { "GL_ARB_vertex_buffer_object",                o(dummy_true),                              GLL,            2003 },
 162    { "GL_ARB_vertex_program",                      o(ARB_vertex_program),                      GLL,            2002 },
 163    { "GL_ARB_vertex_shader",                       o(ARB_vertex_shader),                       GL,             2002 },
 164    { "GL_ARB_vertex_type_2_10_10_10_rev",          o(ARB_vertex_type_2_10_10_10_rev),          GL,             2009 },
 165    { "GL_ARB_window_pos",                          o(dummy_true),                              GLL,            2001 },
 166    /* EXT extensions */
 167    { "GL_EXT_abgr",                                o(dummy_true),                              GL,             1995 },
 168    { "GL_EXT_bgra",                                o(dummy_true),                              GLL,            1995 },
 169    { "GL_EXT_blend_color",                         o(EXT_blend_color),                         GLL,            1995 },
 170    { "GL_EXT_blend_equation_separate",             o(EXT_blend_equation_separate),             GL,             2003 },
 171    { "GL_EXT_blend_func_separate",                 o(EXT_blend_func_separate),                 GLL,            1999 },
 172    { "GL_EXT_discard_framebuffer",                 o(EXT_framebuffer_object),                        ES1 | ES2, 2009 },
 173    { "GL_EXT_blend_minmax",                        o(EXT_blend_minmax),                        GLL | ES1 | ES2, 1995 },
 174    { "GL_EXT_blend_subtract",                      o(dummy_true),                              GLL,            1995 },
 175    { "GL_EXT_clip_volume_hint",                    o(EXT_clip_volume_hint),                    GL,             1996 },
 176    { "GL_EXT_compiled_vertex_array",               o(dummy_true),                              GLL,            1996 },
 177    { "GL_EXT_copy_texture",                        o(dummy_true),                              GLL,            1995 },
 178    { "GL_EXT_depth_bounds_test",                   o(EXT_depth_bounds_test),                   GL,             2002 },
 179    { "GL_EXT_draw_buffers2",                       o(EXT_draw_buffers2),                       GL,             2006 },
 180    { "GL_EXT_draw_instanced",                      o(ARB_draw_instanced),                      GL,             2006 },
 181    { "GL_EXT_draw_range_elements",                 o(dummy_true),                              GLL,            1997 },
 182    { "GL_EXT_fog_coord",                           o(EXT_fog_coord),                           GLL,            1999 },
 183    { "GL_EXT_framebuffer_blit",                    o(EXT_framebuffer_blit),                    GL,             2005 },
 184    { "GL_EXT_framebuffer_multisample",             o(EXT_framebuffer_multisample),             GL,             2005 },
 185    { "GL_EXT_framebuffer_object",                  o(EXT_framebuffer_object),                  GL,             2000 },
 186    { "GL_EXT_framebuffer_sRGB",                    o(EXT_framebuffer_sRGB),                    GL,             1998 },
 187    { "GL_EXT_gpu_program_parameters",              o(EXT_gpu_program_parameters),              GLL,            2006 },
 188    { "GL_EXT_gpu_shader4",                         o(EXT_gpu_shader4),                         GL,             2006 },
 189    { "GL_EXT_map_buffer_range",                    o(ARB_map_buffer_range),                          ES1 | ES2, 2012 },
 190    { "GL_EXT_multi_draw_arrays",                   o(dummy_true),                              GLL | ES1 | ES2, 1999 },
 191    { "GL_EXT_packed_depth_stencil",                o(EXT_packed_depth_stencil),                GL,             2005 },
 192    { "GL_EXT_packed_float",                        o(EXT_packed_float),                        GL,             2004 },
 193    { "GL_EXT_packed_pixels",                       o(dummy_true),                              GLL,            1997 },
 194    { "GL_EXT_pixel_buffer_object",                 o(EXT_pixel_buffer_object),                 GL,             2004 },
 195    { "GL_EXT_point_parameters",                    o(EXT_point_parameters),                    GLL,            1997 },
 196    { "GL_EXT_polygon_offset",                      o(dummy_true),                              GLL,            1995 },
 197    { "GL_EXT_provoking_vertex",                    o(EXT_provoking_vertex),                    GL,             2009 },
 198    { "GL_EXT_rescale_normal",                      o(dummy_true),                              GLL,            1997 },
 199    { "GL_EXT_secondary_color",                     o(EXT_secondary_color),                     GLL,            1999 },
 200    { "GL_EXT_separate_shader_objects",             o(EXT_separate_shader_objects),             GLL,            2008 },
 201    { "GL_EXT_separate_specular_color",             o(dummy_true),                              GLL,            1997 },
 202    { "GL_EXT_shadow_funcs",                        o(EXT_shadow_funcs),                        GLL,            2002 },
 203    { "GL_EXT_stencil_two_side",                    o(EXT_stencil_two_side),                    GLL,            2001 },
 204    { "GL_EXT_stencil_wrap",                        o(dummy_true),                              GLL,            2002 },
 205    { "GL_EXT_subtexture",                          o(dummy_true),                              GLL,            1995 },
 206    { "GL_EXT_texture3D",                           o(EXT_texture3D),                           GLL,            1996 },
 207    { "GL_EXT_texture_array",                       o(EXT_texture_array),                       GL,             2006 },
 208    { "GL_EXT_texture_compression_dxt1",            o(ANGLE_texture_compression_dxt),           GL | ES1 | ES2, 2004 },
 209    { "GL_ANGLE_texture_compression_dxt3",          o(ANGLE_texture_compression_dxt),           GL | ES1 | ES2, 2011 },
 210    { "GL_ANGLE_texture_compression_dxt5",          o(ANGLE_texture_compression_dxt),           GL | ES1 | ES2, 2011 },
 211    { "GL_EXT_texture_compression_latc",            o(EXT_texture_compression_latc),            GL,             2006 },
 212    { "GL_EXT_texture_compression_rgtc",            o(ARB_texture_compression_rgtc),            GL,             2004 },
 213    { "GL_EXT_texture_compression_s3tc",            o(EXT_texture_compression_s3tc),            GL,             2000 },
 214    { "GL_EXT_texture_cube_map",                    o(ARB_texture_cube_map),                    GLL,            2001 },
 215    { "GL_EXT_texture_edge_clamp",                  o(dummy_true),                              GLL,            1997 },
 216    { "GL_EXT_texture_env_add",                     o(dummy_true),                              GLL,            1999 },
 217    { "GL_EXT_texture_env_combine",                 o(dummy_true),                              GLL,            2000 },
 218    { "GL_EXT_texture_env_dot3",                    o(EXT_texture_env_dot3),                    GLL,            2000 },
 219    { "GL_EXT_texture_filter_anisotropic",          o(EXT_texture_filter_anisotropic),          GL | ES1 | ES2, 1999 },
 220    { "GL_EXT_texture_format_BGRA8888",             o(dummy_true),                                   ES1 | ES2, 2005 },
 221    { "GL_EXT_texture_rg",                          o(ARB_texture_rg),                                     ES2, 2011 },
 222    { "GL_EXT_read_format_bgra",                    o(dummy_true),                                   ES1 | ES2, 2009 },
 223    { "GL_EXT_texture_integer",                     o(EXT_texture_integer),                     GL,             2006 },
 224    { "GL_EXT_texture_lod_bias",                    o(dummy_true),                              GLL | ES1,      1999 },
 225    { "GL_EXT_texture_mirror_clamp",                o(EXT_texture_mirror_clamp),                GL,             2004 },
 226    { "GL_EXT_texture_object",                      o(dummy_true),                              GLL,            1995 },
 227    { "GL_EXT_texture",                             o(dummy_true),                              GLL,            1996 },
 228    { "GL_EXT_texture_rectangle",                   o(NV_texture_rectangle),                    GLL,            2004 },
 229    { "GL_EXT_texture_shared_exponent",             o(EXT_texture_shared_exponent),             GL,             2004 },
 230    { "GL_EXT_texture_snorm",                       o(EXT_texture_snorm),                       GL,             2009 },
 231    { "GL_EXT_texture_sRGB",                        o(EXT_texture_sRGB),                        GL,             2004 },
 232    { "GL_EXT_texture_sRGB_decode",                 o(EXT_texture_sRGB_decode),                        GL,      2006 },
 233    { "GL_EXT_texture_swizzle",                     o(EXT_texture_swizzle),                     GL,             2008 },
 234    { "GL_EXT_texture_type_2_10_10_10_REV",         o(dummy_true),                                         ES2, 2008 },
 235    { "GL_EXT_timer_query",                         o(EXT_timer_query),                         GL,             2006 },
 236    { "GL_EXT_transform_feedback",                  o(EXT_transform_feedback),                  GL,             2011 },
 237    { "GL_EXT_unpack_subimage",                     o(dummy_true),                                         ES2, 2011 },
 238    { "GL_EXT_vertex_array_bgra",                   o(EXT_vertex_array_bgra),                   GL,             2008 },
 239    { "GL_EXT_vertex_array",                        o(dummy_true),                              GLL,            1995 },
 240    { "GL_EXT_color_buffer_float",                  o(dummy_true),                                         ES3, 2013 },
 241
 242    /* OES extensions */
 243    { "GL_OES_blend_equation_separate",             o(EXT_blend_equation_separate),                  ES1,       2009 },
 244    { "GL_OES_blend_func_separate",                 o(EXT_blend_func_separate),                      ES1,       2009 },
 245    { "GL_OES_blend_subtract",                      o(dummy_true),                                   ES1,       2009 },
 246    { "GL_OES_byte_coordinates",                    o(dummy_true),                                   ES1,       2002 },
 247    { "GL_OES_compressed_ETC1_RGB8_texture",        o(OES_compressed_ETC1_RGB8_texture),             ES1 | ES2, 2005 },
 248    { "GL_OES_compressed_paletted_texture",         o(dummy_true),                                   ES1,       2003 },
 249    { "GL_OES_depth24",                             o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
 250    { "GL_OES_depth32",                             o(dummy_false),                     DISABLE,                2005 },
 251    { "GL_OES_depth_texture",                       o(ARB_depth_texture),                                  ES2, 2006 },
 252    { "GL_OES_depth_texture_cube_map",              o(OES_depth_texture_cube_map),                         ES2, 2012 },
 253    { "GL_OES_draw_texture",                        o(OES_draw_texture),                             ES1,       2004 },
 254    /*  FIXME: Mesa expects GL_OES_EGL_image to be available in OpenGL contexts. */
 255    { "GL_OES_EGL_image",                           o(OES_EGL_image),                           GL | ES1 | ES2, 2006 },
 256    { "GL_OES_EGL_image_external",                  o(OES_EGL_image_external),                       ES1 | ES2, 2010 },
 257    { "GL_OES_element_index_uint",                  o(dummy_true),                                   ES1 | ES2, 2005 },
 258    { "GL_OES_fbo_render_mipmap",                   o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
 259    { "GL_OES_fixed_point",                         o(dummy_true),                                   ES1,       2002 },
 260    { "GL_OES_framebuffer_object",                  o(EXT_framebuffer_object),                       ES1,       2005 },
 261    { "GL_OES_get_program_binary",                  o(ARB_shader_objects),                                 ES2, 2008 },
 262    { "GL_OES_mapbuffer",                           o(dummy_true),                                   ES1 | ES2, 2005 },
 263    { "GL_OES_matrix_get",                          o(dummy_true),                                   ES1,       2004 },
 264    { "GL_OES_packed_depth_stencil",                o(EXT_packed_depth_stencil),                     ES1 | ES2, 2007 },
 265    { "GL_OES_point_size_array",                    o(dummy_true),                                   ES1,       2004 },
 266    { "GL_OES_point_sprite",                        o(ARB_point_sprite),                             ES1,       2004 },
 267    { "GL_OES_query_matrix",                        o(dummy_true),                                   ES1,       2003 },
 268    { "GL_OES_read_format",                         o(dummy_true),                              GL | ES1,       2003 },
 269    { "GL_OES_rgb8_rgba8",                          o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
 270    { "GL_OES_single_precision",                    o(dummy_true),                                   ES1,       2003 },
 271    { "GL_OES_standard_derivatives",                o(OES_standard_derivatives),                           ES2, 2005 },
 272    { "GL_OES_stencil1",                            o(dummy_false),                     DISABLE,                2005 },
 273    { "GL_OES_stencil4",                            o(dummy_false),                     DISABLE,                2005 },
 274    { "GL_OES_stencil8",                            o(EXT_framebuffer_object),                       ES1 | ES2, 2005 },
 275    { "GL_OES_stencil_wrap",                        o(dummy_true),                                   ES1,       2002 },
 276    { "GL_OES_texture_3D",                          o(EXT_texture3D),                                      ES2, 2005 },
 277    { "GL_OES_texture_cube_map",                    o(ARB_texture_cube_map),                         ES1,       2007 },
 278    { "GL_OES_texture_env_crossbar",                o(ARB_texture_env_crossbar),                     ES1,       2005 },
 279    { "GL_OES_texture_mirrored_repeat",             o(dummy_true),                                   ES1,       2005 },
 280    { "GL_OES_texture_npot",                        o(ARB_texture_non_power_of_two),                       ES2, 2005 },
 281    { "GL_OES_vertex_array_object",                 o(dummy_true),                                   ES1 | ES2, 2010 },
 282
 283    /* Vendor extensions */
 284    { "GL_3DFX_texture_compression_FXT1",           o(TDFX_texture_compression_FXT1),           GL,             1999 },
 285    { "GL_AMD_conservative_depth",                  o(ARB_conservative_depth),                  GL,             2009 },
 286    { "GL_AMD_draw_buffers_blend",                  o(ARB_draw_buffers_blend),                  GL,             2009 },
 287    { "GL_AMD_seamless_cubemap_per_texture",        o(AMD_seamless_cubemap_per_texture),        GL,             2009 },
 288    { "GL_AMD_shader_stencil_export",               o(ARB_shader_stencil_export),               GL,             2009 },
 289    { "GL_APPLE_object_purgeable",                  o(APPLE_object_purgeable),                  GL,             2006 },
 290    { "GL_APPLE_packed_pixels",                     o(dummy_true),                              GLL,            2002 },
 291    { "GL_APPLE_texture_max_level",                 o(dummy_true),                                   ES1 | ES2, 2009 },
 292    { "GL_APPLE_vertex_array_object",               o(dummy_true),                              GLL,            2002 },
 293    { "GL_ATI_blend_equation_separate",             o(EXT_blend_equation_separate),             GL,             2003 },
 294    { "GL_ATI_draw_buffers",                        o(dummy_true),                              GLL,            2002 },
 295    { "GL_ATI_envmap_bumpmap",                      o(ATI_envmap_bumpmap),                      GLL,            2001 },
 296    { "GL_ATI_fragment_shader",                     o(ATI_fragment_shader),                     GLL,            2001 },
 297    { "GL_ATI_separate_stencil",                    o(ATI_separate_stencil),                    GLL,            2006 },
 298    { "GL_ATI_texture_compression_3dc",             o(ATI_texture_compression_3dc),             GL,             2004 },
 299    { "GL_ATI_texture_env_combine3",                o(ATI_texture_env_combine3),                GLL,            2002 },
 300    { "GL_ATI_texture_float",                       o(ARB_texture_float),                       GL,             2002 },
 301    { "GL_ATI_texture_mirror_once",                 o(ATI_texture_mirror_once),                 GL,             2006 },
 302    { "GL_IBM_multimode_draw_arrays",               o(dummy_true),                              GL,             1998 },
 303    { "GL_IBM_rasterpos_clip",                      o(dummy_true),                              GLL,            1996 },
 304    { "GL_IBM_texture_mirrored_repeat",             o(dummy_true),                              GLL,            1998 },
 305    { "GL_INGR_blend_func_separate",                o(EXT_blend_func_separate),                 GLL,            1999 },
 306    { "GL_MESA_pack_invert",                        o(MESA_pack_invert),                        GL,             2002 },
 307    { "GL_MESA_resize_buffers",                     o(MESA_resize_buffers),                     GL,             1999 },
 308    { "GL_MESA_texture_array",                      o(MESA_texture_array),                      GLL,            2007 },
 309    { "GL_MESA_texture_signed_rgba",                o(EXT_texture_snorm),                       GL,             2009 },
 310    { "GL_MESA_window_pos",                         o(dummy_true),                              GLL,            2000 },
 311    { "GL_MESA_ycbcr_texture",                      o(MESA_ycbcr_texture),                      GL,             2002 },
 312    { "GL_NV_blend_square",                         o(NV_blend_square),                         GLL,            1999 },
 313    { "GL_NV_conditional_render",                   o(NV_conditional_render),                   GL,             2008 },
 314    { "GL_NV_depth_clamp",                          o(ARB_depth_clamp),                         GL,             2001 },
 315    { "GL_NV_draw_buffers",                         o(dummy_true),                                         ES2, 2011 },
 316    { "GL_NV_fbo_color_attachments",                o(EXT_framebuffer_object),                             ES2, 2010 },
 317    { "GL_NV_fog_distance",                         o(NV_fog_distance),                         GLL,            2001 },
 318    { "GL_NV_fragment_program_option",              o(NV_fragment_program_option),              GLL,            2005 },
 319    { "GL_NV_light_max_exponent",                   o(dummy_true),                              GLL,            1999 },
 320    { "GL_NV_packed_depth_stencil",                 o(EXT_packed_depth_stencil),                GL,             2000 },
 321    { "GL_NV_point_sprite",                         o(NV_point_sprite),                         GL,             2001 },
 322    { "GL_NV_primitive_restart",                    o(NV_primitive_restart),                    GLL,            2002 },
 323    { "GL_NV_read_buffer",                          o(dummy_true),                              ES2,            2011 },
 324    { "GL_NV_texgen_reflection",                    o(dummy_true),                              GLL,            1999 },
 325    { "GL_NV_texture_barrier",                      o(NV_texture_barrier),                      GL,             2009 },
 326    { "GL_NV_texture_env_combine4",                 o(NV_texture_env_combine4),                 GLL,            1999 },
 327    { "GL_NV_texture_rectangle",                    o(NV_texture_rectangle),                    GLL,            2000 },
 328    { "GL_S3_s3tc",                                 o(ANGLE_texture_compression_dxt),           GL,             1999 },
 329    { "GL_SGIS_generate_mipmap",                    o(dummy_true),                              GLL,            1997 },
 330    { "GL_SGIS_texture_border_clamp",               o(ARB_texture_border_clamp),                GLL,            1997 },
 331    { "GL_SGIS_texture_edge_clamp",                 o(dummy_true),                              GLL,            1997 },
 332    { "GL_SGIS_texture_lod",                        o(dummy_true),                              GLL,            1997 },
 333    { "GL_SUN_multi_draw_arrays",                   o(dummy_true),                              GLL,            1999 },
 334
 335    { 0, 0, 0, 0 },
 336 };
 337
 338
 339 /**
 340  * Given an extension name, lookup up the corresponding member of struct
 341  * gl_extensions and return that member's offset (in bytes).  If the name is
 342  * not found in the \c extension_table, return 0.
 343  *
 344  * \param name Name of extension.
 345  * \return Offset of member in struct gl_extensions.
 346  */
 347 static size_t
 348 name_to_offset(const char* name)
 349 {
 350    const struct extension *i;
 351
 352    if (name == 0)
 353       return 0;
 354
 355    for (i = extension_table; i->name != 0; ++i) {
 356       if (strcmp(name, i->name) == 0)
 357          return i->offset;
 358    }
 359
 360    return 0;
 361 }
 362
 363
 364 /**
 365  * Enable all extensions suitable for a software-only renderer.
 366  * This is a convenience function used by the XMesa, OSMesa, GGI drivers, etc.
 367  */
 368 void
 369 _mesa_enable_sw_extensions(struct gl_context *ctx)
 370 {
 371    ctx->Extensions.ARB_depth_clamp = GL_TRUE;
 372    ctx->Extensions.ARB_depth_texture = GL_TRUE;
 373    ctx->Extensions.ARB_draw_elements_base_vertex = GL_TRUE;
 374    ctx->Extensions.ARB_draw_instanced = GL_TRUE;
 375    ctx->Extensions.ARB_explicit_attrib_location = GL_TRUE;
 376    ctx->Extensions.ARB_fragment_coord_conventions = GL_TRUE;
 377    ctx->Extensions.ARB_fragment_program = GL_TRUE;
 378    ctx->Extensions.ARB_fragment_program_shadow = GL_TRUE;
 379    ctx->Extensions.ARB_fragment_shader = GL_TRUE;
 380    ctx->Extensions.ARB_framebuffer_object = GL_TRUE;
 381    /* XXX re-enable when GLSL compiler again supports geometry shaders */
 382 #if 0
 383    ctx->Extensions.ARB_geometry_shader4 = GL_TRUE;
 384 #endif
 385    ctx->Extensions.ARB_half_float_pixel = GL_TRUE;
 386    ctx->Extensions.ARB_half_float_vertex = GL_TRUE;
 387    ctx->Extensions.ARB_map_buffer_range = GL_TRUE;
 388    ctx->Extensions.ARB_occlusion_query = GL_TRUE;
 389    ctx->Extensions.ARB_occlusion_query2 = GL_TRUE;
 390    ctx->Extensions.ARB_point_sprite = GL_TRUE;
 391    ctx->Extensions.ARB_shader_objects = GL_TRUE;
 392    ctx->Extensions.EXT_separate_shader_objects = GL_TRUE;
 393    ctx->Extensions.ARB_shading_language_100 = GL_TRUE;
 394    ctx->Extensions.ARB_shadow = GL_TRUE;
 395    ctx->Extensions.ARB_texture_border_clamp = GL_TRUE;
 396    ctx->Extensions.ARB_texture_cube_map = GL_TRUE;
 397    ctx->Extensions.ARB_texture_env_combine = GL_TRUE;
 398    ctx->Extensions.ARB_texture_env_crossbar = GL_TRUE;
 399    ctx->Extensions.ARB_texture_env_dot3 = GL_TRUE;
 400 #ifdef TEXTURE_FLOAT_ENABLED
 401    ctx->Extensions.ARB_texture_float = GL_TRUE;
 402 #endif
 403    ctx->Extensions.ARB_texture_non_power_of_two = GL_TRUE;
 404    ctx->Extensions.ARB_texture_rg = GL_TRUE;
 405    ctx->Extensions.ARB_texture_compression_rgtc = GL_TRUE;
 406    ctx->Extensions.ARB_texture_storage = GL_TRUE;
 407    ctx->Extensions.ARB_vertex_program = GL_TRUE;
 408    ctx->Extensions.ARB_vertex_shader = GL_TRUE;
 409    ctx->Extensions.ARB_sync = GL_TRUE;
 410    ctx->Extensions.APPLE_object_purgeable = GL_TRUE;
 411    ctx->Extensions.ATI_envmap_bumpmap = GL_TRUE;
 412    ctx->Extensions.ATI_fragment_shader = GL_TRUE;
 413    ctx->Extensions.ATI_texture_compression_3dc = GL_TRUE;
 414    ctx->Extensions.ATI_texture_env_combine3 = GL_TRUE;
 415    ctx->Extensions.ATI_texture_mirror_once = GL_TRUE;
 416    ctx->Extensions.ATI_separate_stencil = GL_TRUE;
 417    ctx->Extensions.EXT_blend_color = GL_TRUE;
 418    ctx->Extensions.EXT_blend_equation_separate = GL_TRUE;
 419    ctx->Extensions.EXT_blend_func_separate = GL_TRUE;
 420    ctx->Extensions.EXT_blend_minmax = GL_TRUE;
 421    ctx->Extensions.EXT_depth_bounds_test = GL_TRUE;
 422    ctx->Extensions.EXT_draw_buffers2 = GL_TRUE;
 423    ctx->Extensions.EXT_fog_coord = GL_TRUE;
 424    ctx->Extensions.EXT_framebuffer_object = GL_TRUE;
 425    ctx->Extensions.EXT_framebuffer_blit = GL_TRUE;
 426    ctx->Extensions.EXT_packed_depth_stencil = GL_TRUE;
 427    ctx->Extensions.EXT_pixel_buffer_object = GL_TRUE;
 428    ctx->Extensions.EXT_point_parameters = GL_TRUE;
 429    ctx->Extensions.EXT_provoking_vertex = GL_TRUE;
 430    ctx->Extensions.EXT_shadow_funcs = GL_TRUE;
 431    ctx->Extensions.EXT_secondary_color = GL_TRUE;
 432    ctx->Extensions.EXT_stencil_two_side = GL_TRUE;
 433    ctx->Extensions.EXT_texture_array = GL_TRUE;
 434    ctx->Extensions.EXT_texture_compression_latc = GL_TRUE;
 435    ctx->Extensions.EXT_texture_env_dot3 = GL_TRUE;
 436    ctx->Extensions.EXT_texture_filter_anisotropic = GL_TRUE;
 437    ctx->Extensions.EXT_texture_mirror_clamp = GL_TRUE;
 438    ctx->Extensions.EXT_texture_shared_exponent = GL_TRUE;
 439    ctx->Extensions.EXT_texture_sRGB = GL_TRUE;
 440    ctx->Extensions.EXT_texture_sRGB_decode = GL_TRUE;
 441    ctx->Extensions.EXT_texture_swizzle = GL_TRUE;
 442    /*ctx->Extensions.EXT_transform_feedback = GL_TRUE;*/
 443    ctx->Extensions.EXT_vertex_array_bgra = GL_TRUE;
 444    ctx->Extensions.MESA_pack_invert = GL_TRUE;
 445    ctx->Extensions.MESA_resize_buffers = GL_TRUE;
 446    ctx->Extensions.MESA_texture_array = GL_TRUE;
 447    ctx->Extensions.MESA_ycbcr_texture = GL_TRUE;
 448    ctx->Extensions.NV_blend_square = GL_TRUE;
 449    ctx->Extensions.NV_conditional_render = GL_TRUE;
 450    ctx->Extensions.NV_point_sprite = GL_TRUE;
 451    ctx->Extensions.NV_texture_env_combine4 = GL_TRUE;
 452    ctx->Extensions.NV_texture_rectangle = GL_TRUE;
 453    ctx->Extensions.NV_fragment_program_option = GL_TRUE;
 454    ctx->Extensions.EXT_gpu_program_parameters = GL_TRUE;
 455    ctx->Extensions.OES_standard_derivatives = GL_TRUE;
 456    _mesa_enable_extension(ctx, "GL_3DFX_texture_compression_FXT1");
 457    if (ctx->Mesa_DXTn) {
 458       ctx->Extensions.ANGLE_texture_compression_dxt = GL_TRUE;
 459       _mesa_enable_extension(ctx, "GL_EXT_texture_compression_s3tc");
 460       _mesa_enable_extension(ctx, "GL_S3_s3tc");
 461    }
 462 }
 463
 464
 465 /**
 466  * Enable all OpenGL 1.3 features and extensions.
 467  * A convenience function to be called by drivers.
 468  */
 469 void
 470 _mesa_enable_1_3_extensions(struct gl_context *ctx)
 471 {
 472    ctx->Extensions.ARB_texture_border_clamp = GL_TRUE;
 473    ctx->Extensions.ARB_texture_cube_map = GL_TRUE;
 474    ctx->Extensions.ARB_texture_env_combine = GL_TRUE;
 475    ctx->Extensions.ARB_texture_env_dot3 = GL_TRUE;
 476 }
 477
 478
 479
 480 /**
 481  * Enable all OpenGL 1.4 features and extensions.
 482  * A convenience function to be called by drivers.
 483  */
 484 void
 485 _mesa_enable_1_4_extensions(struct gl_context *ctx)
 486 {
 487    ctx->Extensions.ARB_depth_texture = GL_TRUE;
 488    ctx->Extensions.ARB_shadow = GL_TRUE;
 489    ctx->Extensions.ARB_texture_env_crossbar = GL_TRUE;
 490    ctx->Extensions.EXT_blend_color = GL_TRUE;
 491    ctx->Extensions.EXT_blend_func_separate = GL_TRUE;
 492    ctx->Extensions.EXT_blend_minmax = GL_TRUE;
 493    ctx->Extensions.EXT_fog_coord = GL_TRUE;
 494    ctx->Extensions.EXT_point_parameters = GL_TRUE;
 495    ctx->Extensions.EXT_secondary_color = GL_TRUE;
 496 }
 497
 498
 499 /**
 500  * Enable all OpenGL 1.5 features and extensions.
 501  * A convenience function to be called by drivers.
 502  */
 503 void
 504 _mesa_enable_1_5_extensions(struct gl_context *ctx)
 505 {
 506    ctx->Extensions.ARB_occlusion_query = GL_TRUE;
 507    ctx->Extensions.EXT_shadow_funcs = GL_TRUE;
 508 }
 509
 510
 511 /**
 512  * Enable all OpenGL 2.0 features and extensions.
 513  * A convenience function to be called by drivers.
 514  */
 515 void
 516 _mesa_enable_2_0_extensions(struct gl_context *ctx)
 517 {
 518    ctx->Extensions.ARB_fragment_shader = GL_TRUE;
 519    ctx->Extensions.ARB_point_sprite = GL_TRUE;
 520    ctx->Extensions.EXT_blend_equation_separate = GL_TRUE;
 521    ctx->Extensions.ARB_texture_non_power_of_two = GL_TRUE;
 522    ctx->Extensions.ARB_shader_objects = GL_TRUE;
 523    ctx->Extensions.ARB_shading_language_100 = GL_TRUE;
 524    ctx->Extensions.EXT_stencil_two_side = GL_TRUE;
 525    ctx->Extensions.ARB_vertex_shader = GL_TRUE;
 526 }
 527
 528
 529 /**
 530  * Enable all OpenGL 2.1 features and extensions.
 531  * A convenience function to be called by drivers.
 532  */
 533 void
 534 _mesa_enable_2_1_extensions(struct gl_context *ctx)
 535 {
 536    ctx->Extensions.EXT_pixel_buffer_object = GL_TRUE;
 537    ctx->Extensions.EXT_texture_sRGB = GL_TRUE;
 538 }
 539
 540
 541 /**
 542  * Either enable or disable the named extension.
 543  * \return GL_TRUE for success, GL_FALSE if invalid extension name
 544  */
 545 static GLboolean
 546 set_extension( struct gl_context *ctx, const char *name, GLboolean state )
 547 {
 548    size_t offset;
 549
 550    if (ctx->Extensions.String) {
 551       /* The string was already queried - can't change it now! */
 552       _mesa_problem(ctx, "Trying to enable/disable extension after glGetString(GL_EXTENSIONS): %s", name);
 553       return GL_FALSE;
 554    }
 555
 556    offset = name_to_offset(name);
 557    if (offset == 0) {
 558       _mesa_problem(ctx, "Trying to enable/disable unknown extension %s",
 559                     name);
 560       return GL_FALSE;
 561    } else if (offset == o(dummy_true) && state == GL_FALSE) {
 562       _mesa_problem(ctx, "Trying to disable a permanently enabled extension: "
 563                           "%s", name);
 564       return GL_FALSE;
 565    } else {
 566       GLboolean *base = (GLboolean *) &ctx->Extensions;
 567       base[offset] = state;
 568       return GL_TRUE;
 569    }
 570 }
 571
 572
 573 /**
 574  * Enable the named extension.
 575  * Typically called by drivers.
 576  */
 577 void
 578 _mesa_enable_extension( struct gl_context *ctx, const char *name )
 579 {
 580    if (!set_extension(ctx, name, GL_TRUE))
 581       _mesa_problem(ctx, "Trying to enable unknown extension: %s", name);
 582 }
 583
 584
 585 /**
 586  * Disable the named extension.
 587  * XXX is this really needed???
 588  */
 589 void
 590 _mesa_disable_extension( struct gl_context *ctx, const char *name )
 591 {
 592    if (!set_extension(ctx, name, GL_FALSE))
 593       _mesa_problem(ctx, "Trying to disable unknown extension: %s", name);
 594 }
 595
 596
 597 /**
 598  * Test if the named extension is enabled in this context.
 599  */
 600 GLboolean
 601 _mesa_extension_is_enabled( struct gl_context *ctx, const char *name )
 602 {
 603    size_t offset;
 604    GLboolean *base;
 605
 606    if (name == 0)
 607       return GL_FALSE;
 608
 609    offset = name_to_offset(name);
 610    if (offset == 0)
 611       return GL_FALSE;
 612    base = (GLboolean *) &ctx->Extensions;
 613    return base[offset];
 614 }
 615
 616
 617 /**
 618  * \brief Apply the \c MESA_EXTENSION_OVERRIDE environment variable.
 619  *
 620  * \c MESA_EXTENSION_OVERRIDE is a space-separated list of extensions to
 621  * enable or disable. The list is processed thus:
 622  *    - Enable recognized extension names that are prefixed with '+'.
 623  *    - Disable recognized extension names that are prefixed with '-'.
 624  *    - Enable recognized extension names that are not prefixed.
 625  *    - Collect unrecognized extension names in a new string.
 626  *
 627  * \return Space-separated list of unrecognized extension names (which must
 628  *    be freed). Does not return \c NULL.
 629  */
 630 static char *
 631 get_extension_override( struct gl_context *ctx )
 632 {
 633    const char *env_const = _mesa_getenv("MESA_EXTENSION_OVERRIDE");
 634    char *env;
 635    char *ext;
 636    char *extra_exts;
 637    int len;
 638
 639    if (env_const == NULL) {
 640       /* Return the empty string rather than NULL. This simplifies the logic
 641        * of client functions. */
 642       return calloc(4, sizeof(char));
 643    }
 644
 645    /* extra_exts: List of unrecognized extensions. */
 646    extra_exts = calloc(ALIGN(strlen(env_const) + 2, 4), sizeof(char));
 647
 648    /* Copy env_const because strtok() is destructive. */
 649    env = strdup(env_const);
 650    for (ext = strtok(env, " "); ext != NULL; ext = strtok(NULL, " ")) {
 651       int enable;
 652       int recognized;
 653       switch (ext[0]) {
 654       case '+':
 655          enable = 1;
 656          ++ext;
 657          break;
 658       case '-':
 659          enable = 0;
 660          ++ext;
 661          break;
 662       default:
 663          enable = 1;
 664          break;
 665       }
 666       recognized = set_extension(ctx, ext, enable);
 667       if (!recognized) {
 668          strcat(extra_exts, ext);
 669          strcat(extra_exts, " ");
 670       }
 671    }
 672
 673    free(env);
 674
 675    /* Remove trailing space. */
 676    len = strlen(extra_exts);
 677    if (len > 0 && extra_exts[len - 1] == ' ')
 678       extra_exts[len - 1] = '\0';
 679
 680    return extra_exts;
 681 }
 682
 683
 684 /**
 685  * \brief Initialize extension tables and enable default extensions.
 686  *
 687  * This should be called during context initialization.
 688  * Note: Sets gl_extensions.dummy_true to true.
 689  */
 690 void
 691 _mesa_init_extensions( struct gl_context *ctx )
 692 {
 693    GLboolean *base = (GLboolean *) &ctx->Extensions;
 694    GLboolean *sentinel = base + o(extension_sentinel);
 695    GLboolean *i;
 696
 697    /* First, turn all extensions off. */
 698    for (i = base; i != sentinel; ++i)
 699       *i = GL_FALSE;
 700
 701    /* Then, selectively turn default extensions on. */
 702    ctx->Extensions.dummy_true = GL_TRUE;
 703    ctx->Extensions.EXT_texture3D = GL_TRUE;
 704 }
 705
 706
 707 typedef unsigned short extension_index;
 708
 709
 710 /**
 711  * Compare two entries of the extensions table.  Sorts first by year,
 712  * then by name.
 713  *
 714  * Arguments are indices into extension_table.
 715  */
 716 static int
 717 extension_compare(const void *p1, const void *p2)
 718 {
 719    extension_index i1 = * (const extension_index *) p1;
 720    extension_index i2 = * (const extension_index *) p2;
 721    const struct extension *e1 = &extension_table[i1];
 722    const struct extension *e2 = &extension_table[i2];
 723    int res;
 724
 725    res = (int)e1->year - (int)e2->year;
 726
 727    if (res == 0) {
 728       res = strcmp(e1->name, e2->name);
 729    }
 730
 731    return res;
 732 }
 733
 734
 735 /**
 736  * Construct the GL_EXTENSIONS string.  Called the first time that
 737  * glGetString(GL_EXTENSIONS) is called.
 738  */
 739 GLubyte*
 740 _mesa_make_extension_string(struct gl_context *ctx)
 741 {
 742    /* The extension string. */
 743    char *exts = 0;
 744    /* Length of extension string. */
 745    size_t length = 0;
 746    /* Number of extensions */
 747    unsigned count;
 748    /* Indices of the extensions sorted by year */
 749    extension_index *extension_indices;
 750    /* String of extra extensions. */
 751    char *extra_extensions = get_extension_override(ctx);
 752    GLboolean *base = (GLboolean *) &ctx->Extensions;
 753    const struct extension *i;
 754    unsigned j;
 755    unsigned maxYear = ~0;
 756    unsigned api_set = (1 << ctx->API);
 757    if (_mesa_is_gles3(ctx))
 758       api_set |= ES3;
 759
 760    /* Check if the MESA_EXTENSION_MAX_YEAR env var is set */
 761    {
 762       const char *env = getenv("MESA_EXTENSION_MAX_YEAR");
 763       if (env) {
 764          maxYear = atoi(env);
 765          _mesa_debug(ctx, "Note: limiting GL extensions to %u or earlier\n",
 766                      maxYear);
 767       }
 768    }
 769
 770    /* Compute length of the extension string. */
 771    count = 0;
 772    for (i = extension_table; i->name != 0; ++i) {
 773       if (base[i->offset] &&
 774           i->year <= maxYear &&
 775           (i->api_set & api_set)) {
 776          length += strlen(i->name) + 1; /* +1 for space */
 777          ++count;
 778       }
 779    }
 780    if (extra_extensions != NULL)
 781       length += 1 + strlen(extra_extensions); /* +1 for space */
 782
 783    exts = calloc(ALIGN(length + 1, 4), sizeof(char));
 784    if (exts == NULL) {
 785       free(extra_extensions);
 786       return NULL;
 787    }
 788
 789    extension_indices = malloc(count * sizeof(extension_index));
 790    if (extension_indices == NULL) {
 791       free(exts);
 792       free(extra_extensions);
 793       return NULL;
 794    }
 795
 796    /* Sort extensions in chronological order because certain old applications (e.g.,
 797     * Quake3 demo) store the extension list in a static size buffer so chronologically
 798     * order ensure that the extensions that such applications expect will fit into
 799     * that buffer.
 800     */
 801    j = 0;
 802    for (i = extension_table; i->name != 0; ++i) {
 803       if (base[i->offset] &&
 804           i->year <= maxYear &&
 805           (i->api_set & api_set)) {
 806          extension_indices[j++] = i - extension_table;
 807       }
 808    }
 809    assert(j == count);
 810    qsort(extension_indices, count, sizeof *extension_indices, extension_compare);
 811
 812    /* Build the extension string.*/
 813    for (j = 0; j < count; ++j) {
 814       i = &extension_table[extension_indices[j]];
 815       assert(base[i->offset] && (i->api_set & api_set));
 816       strcat(exts, i->name);
 817       strcat(exts, " ");
 818    }
 819    free(extension_indices);
 820    if (extra_extensions != 0) {
 821       strcat(exts, extra_extensions);
 822       free(extra_extensions);
 823    }
 824
 825    return (GLubyte *) exts;
 826 }
 827
 828 /**
 829  * Return number of enabled extensions.
 830  */
 831 GLuint
 832 _mesa_get_extension_count(struct gl_context *ctx)
 833 {
 834    GLboolean *base;
 835    const struct extension *i;
 836    unsigned api_set = (1 << ctx->API);
 837    if (_mesa_is_gles3(ctx))
 838       api_set |= ES3;
 839
 840    /* only count once */
 841    if (ctx->Extensions.Count != 0)
 842       return ctx->Extensions.Count;
 843
 844    base = (GLboolean *) &ctx->Extensions;
 845    for (i = extension_table; i->name != 0; ++i) {
 846       if (base[i->offset] && (i->api_set & api_set)) {
 847          ctx->Extensions.Count++;
 848       }
 849    }
 850    return ctx->Extensions.Count;
 851 }
 852
 853 /**
 854  * Return name of i-th enabled extension
 855  */
 856 const GLubyte *
 857 _mesa_get_enabled_extension(struct gl_context *ctx, GLuint index)
 858 {
 859    const GLboolean *base;
 860    size_t n;
 861    const struct extension *i;
 862    unsigned api_set = (1 << ctx->API);
 863    if (_mesa_is_gles3(ctx))
 864       api_set |= ES3;
 865
 866    base = (GLboolean*) &ctx->Extensions;
 867    n = 0;
 868    for (i = extension_table; i->name != 0; ++i) {
 869       if (base[i->offset] && (i->api_set & api_set)) {
 870          if (n == index)
 871             return (const GLubyte*) i->name;
 872          else
 873             ++n;
 874       }
 875    }
 876
 877    return NULL;
 878 }