{

  Translation of the Mesa GLX headers for FreePascal
  Copyright (C) 1999 Sebastian Guenther


  Mesa 3-D graphics library
  Version:  3.0
  Copyright (C) 1995-1998  Brian Paul

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Library General Public
  License as published by the Free Software Foundation; either
  version 2 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Library General Public License for more details.

  You should have received a copy of the GNU Library General Public
  License along with this library; if not, write to the Free
  Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  MA 02110-1301, USA.
}

{$MODE delphi}  // objfpc would not work because of direct proc var assignments

{You have to enable Macros (compiler switch "-Sm") for compiling this unit!
 This is necessary for supporting different platforms with different calling
 conventions via a single unit.}

{$IFNDEF FPC_DOTTEDUNITS}
unit GLX;
{$ENDIF FPC_DOTTEDUNITS}

interface

{$MACRO ON}

{$IFDEF Unix}
{$IFDEF FPC_DOTTEDUNITS}
  uses
    System.CTypes, Api.X11.X, Api.X11.Xlib, Api.X11.Xutil;
{$ELSE FPC_DOTTEDUNITS}
  uses
    ctypes, X, XLib, XUtil;
{$ENDIF FPC_DOTTEDUNITS}
  {$DEFINE HasGLX}  // Activate GLX stuff
{$ELSE}
  {$MESSAGE Unsupported platform.}
{$ENDIF}

{$IFNDEF HasGLX}
  {$MESSAGE GLX not present on this platform.}
{$ENDIF}


// =======================================================
//   Unit specific extensions
// =======================================================

// Note: Requires that the GL library has already been initialized
function InitGLX: Boolean;

var
  GLXDumpUnresolvedFunctions,
  GLXInitialized: Boolean;


// =======================================================
//   GLX consts, types and functions
// =======================================================

// Tokens for glXChooseVisual and glXGetConfig:
const
  GLX_USE_GL                            = 1;
  GLX_BUFFER_SIZE                       = 2;
  GLX_LEVEL                             = 3;
  GLX_RGBA                              = 4;
  GLX_DOUBLEBUFFER                      = 5;
  GLX_STEREO                            = 6;
  GLX_AUX_BUFFERS                       = 7;
  GLX_RED_SIZE                          = 8;
  GLX_GREEN_SIZE                        = 9;
  GLX_BLUE_SIZE                         = 10;
  GLX_ALPHA_SIZE                        = 11;
  GLX_DEPTH_SIZE                        = 12;
  GLX_STENCIL_SIZE                      = 13;
  GLX_ACCUM_RED_SIZE                    = 14;
  GLX_ACCUM_GREEN_SIZE                  = 15;
  GLX_ACCUM_BLUE_SIZE                   = 16;
  GLX_ACCUM_ALPHA_SIZE                  = 17;

  // Error codes returned by glXGetConfig:
  GLX_BAD_SCREEN                        = 1;
  GLX_BAD_ATTRIBUTE                     = 2;
  GLX_NO_EXTENSION                      = 3;
  GLX_BAD_VISUAL                        = 4;
  GLX_BAD_CONTEXT                       = 5;
  GLX_BAD_VALUE                         = 6;
  GLX_BAD_ENUM                          = 7;

  // GLX 1.1 and later:
  GLX_VENDOR                            = 1;
  GLX_VERSION                           = 2;
  GLX_EXTENSIONS                        = 3;

  // GLX 1.3 and later:
  GLX_CONFIG_CAVEAT               = $20;
  GLX_DONT_CARE                   = $FFFFFFFF;
  GLX_X_VISUAL_TYPE               = $22;
  GLX_TRANSPARENT_TYPE            = $23;
  GLX_TRANSPARENT_INDEX_VALUE     = $24;
  GLX_TRANSPARENT_RED_VALUE       = $25;
  GLX_TRANSPARENT_GREEN_VALUE     = $26;
  GLX_TRANSPARENT_BLUE_VALUE      = $27;
  GLX_TRANSPARENT_ALPHA_VALUE     = $28;
  GLX_WINDOW_BIT                  = $00000001;
  GLX_PIXMAP_BIT                  = $00000002;
  GLX_PBUFFER_BIT                 = $00000004;
  GLX_AUX_BUFFERS_BIT             = $00000010;
  GLX_FRONT_LEFT_BUFFER_BIT       = $00000001;
  GLX_FRONT_RIGHT_BUFFER_BIT      = $00000002;
  GLX_BACK_LEFT_BUFFER_BIT        = $00000004;
  GLX_BACK_RIGHT_BUFFER_BIT       = $00000008;
  GLX_DEPTH_BUFFER_BIT            = $00000020;
  GLX_STENCIL_BUFFER_BIT          = $00000040;
  GLX_ACCUM_BUFFER_BIT            = $00000080;
  GLX_NONE                        = $8000;
  GLX_SLOW_CONFIG                 = $8001;
  GLX_TRUE_COLOR                  = $8002;
  GLX_DIRECT_COLOR                = $8003;
  GLX_PSEUDO_COLOR                = $8004;
  GLX_STATIC_COLOR                = $8005;
  GLX_GRAY_SCALE                  = $8006;
  GLX_STATIC_GRAY                 = $8007;
  GLX_TRANSPARENT_RGB             = $8008;
  GLX_TRANSPARENT_INDEX           = $8009;
  GLX_VISUAL_ID                   = $800B;
  GLX_SCREEN                      = $800C;
  GLX_NON_CONFORMANT_CONFIG       = $800D;
  GLX_DRAWABLE_TYPE               = $8010;
  GLX_RENDER_TYPE                 = $8011;
  GLX_X_RENDERABLE                = $8012;
  GLX_FBCONFIG_ID                 = $8013;
  GLX_RGBA_TYPE                   = $8014;
  GLX_COLOR_INDEX_TYPE            = $8015;
  GLX_MAX_PBUFFER_WIDTH           = $8016;
  GLX_MAX_PBUFFER_HEIGHT          = $8017;
  GLX_MAX_PBUFFER_PIXELS          = $8018;
  GLX_PRESERVED_CONTENTS          = $801B;
  GLX_LARGEST_PBUFFER             = $801C;
  GLX_WIDTH                       = $801D;
  GLX_HEIGHT                      = $801E;
  GLX_EVENT_MASK                  = $801F;
  GLX_DAMAGED                     = $8020;
  GLX_SAVED                       = $8021;
  GLX_WINDOW                      = $8022;
  GLX_PBUFFER                     = $8023;
  GLX_PBUFFER_HEIGHT              = $8040;
  GLX_PBUFFER_WIDTH               = $8041;
  GLX_RGBA_BIT                    = $00000001;
  GLX_COLOR_INDEX_BIT             = $00000002;
  GLX_PBUFFER_CLOBBER_MASK        = $08000000;

  // GLX 1.4 and later:
  GLX_SAMPLE_BUFFERS              = $186a0; // 100000
  GLX_SAMPLES                     = $186a1; // 100001

  // Extensions:

  // GLX_ARB_multisample
  GLX_SAMPLE_BUFFERS_ARB             = 100000;
  GLX_SAMPLES_ARB                    = 100001;

  // GLX_ARB_create_context (http://www.opengl.org/registry/specs/ARB/glx_create_context.txt)
  GLX_CONTEXT_DEBUG_BIT_ARB          = $00000001;
  GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB = $00000002;
  GLX_CONTEXT_MAJOR_VERSION_ARB      = $2091;
  GLX_CONTEXT_MINOR_VERSION_ARB      = $2092;
  GLX_CONTEXT_FLAGS_ARB              = $2094;

  // GLX_ARB_create_context_profile
  GLX_CONTEXT_CORE_PROFILE_BIT_ARB   = $00000001;
  GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB = $00000002;
  GLX_CONTEXT_PROFILE_MASK_ARB       = $9126;

  // GLX_ARB_create_context_robustness
  GLX_CONTEXT_ROBUST_ACCESS_BIT_ARB  = $00000004;
  GLX_LOSE_CONTEXT_ON_RESET_ARB      = $8252;
  GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB = $8256;
  GLX_NO_RESET_NOTIFICATION_ARB      = $8261;

  // GLX_SGIS_multisample
  GLX_SAMPLE_BUFFERS_SGIS            = 100000;
  GLX_SAMPLES_SGIS                   = 100001;

  // GLX_EXT_visual_info
  GLX_X_VISUAL_TYPE_EXT                 = $22;
  GLX_TRANSPARENT_TYPE_EXT              = $23;
  GLX_TRANSPARENT_INDEX_VALUE_EXT       = $24;
  GLX_TRANSPARENT_RED_VALUE_EXT         = $25;
  GLX_TRANSPARENT_GREEN_VALUE_EXT       = $26;
  GLX_TRANSPARENT_BLUE_VALUE_EXT        = $27;
  GLX_TRANSPARENT_ALPHA_VALUE_EXT       = $28;

  GLX_TRUE_COLOR_EXT                    = $8002;
  GLX_DIRECT_COLOR_EXT                  = $8003;
  GLX_PSEUDO_COLOR_EXT                  = $8004;
  GLX_STATIC_COLOR_EXT                  = $8005;
  GLX_GRAY_SCALE_EXT                    = $8006;
  GLX_STATIC_GRAY_EXT                   = $8007;
  GLX_NONE_EXT                          = $8000;
  GLX_TRANSPARENT_RGB_EXT               = $8008;
  GLX_TRANSPARENT_INDEX_EXT             = $8009;

type
  // From XLib:
  XPixmap = TXID;
  XFont = TXID;
  XColormap = TXID;

  GLXContext = Pointer;
  GLXPixmap = TXID;
  GLXDrawable = TXID;
  GLXContextID = TXID;

  TXPixmap = XPixmap;
  TXFont = XFont;
  TXColormap = XColormap;

  TGLXContext = GLXContext;
  TGLXPixmap = GLXPixmap;
  TGLXDrawable = GLXDrawable;
  // GLX 1.3 and later
  TGLXFBConfigRec = record { internal, use only a pointer to this } end;
  TGLXFBConfig = ^TGLXFBConfigRec;
  { PGLXFBConfig is a pointer to TGLXFBConfig (which is also a pointer).
    glX uses this to represent an array of FB configs. }
  PGLXFBConfig = ^TGLXFBConfig;
  TGLXFBConfigID = TXID;
  TGLXContextID = GLXContextID;
  TGLXWindow = TXID;
  TGLXPbuffer = TXID;

var
  glXChooseVisual: function(dpy: PDisplay; screen: cint; attribList: Pcint): PXVisualInfo; cdecl;
  //glXCreateContext -> internal_glXCreateContext in implementation
  glXDestroyContext: procedure(dpy: PDisplay; ctx: GLXContext); cdecl;
  glXMakeCurrent: function(dpy: PDisplay; drawable: GLXDrawable; ctx: GLXContext): TBoolResult; cdecl;
  glXCopyContext: procedure(dpy: PDisplay; src, dst: GLXContext; mask: culong); cdecl;
  glXSwapBuffers: procedure(dpy: PDisplay; drawable: GLXDrawable); cdecl;
  glXCreateGLXPixmap: function(dpy: PDisplay; visual: PXVisualInfo; pixmap: XPixmap): GLXPixmap; cdecl;
  glXDestroyGLXPixmap: procedure(dpy: PDisplay; pixmap: GLXPixmap); cdecl;
  glXQueryExtension: function(dpy: PDisplay; var errorb, event: cint): TBoolResult; cdecl;
  glXQueryVersion: function(dpy: PDisplay; var maj, min: cint): TBoolResult; cdecl;
  glXIsDirect: function(dpy: PDisplay; ctx: GLXContext): TBoolResult; cdecl;
  glXGetConfig: function(dpy: PDisplay; visual: PXVisualInfo; attrib: cint; var value: cint): cint; cdecl;
  glXGetCurrentContext: function: GLXContext; cdecl;
  glXGetCurrentDrawable: function: GLXDrawable; cdecl;
  glXWaitGL: procedure; cdecl;
  glXWaitX: procedure; cdecl;
  glXUseXFont: procedure(font: XFont; first, count, list: cint); cdecl;

  // GLX 1.1 and later
  glXQueryExtensionsString: function(dpy: PDisplay; screen: cint): PAnsiChar; cdecl;
  glXQueryServerString: function(dpy: PDisplay; screen, name: cint): PAnsiChar; cdecl;
  glXGetClientString: function(dpy: PDisplay; name: cint): PAnsiChar; cdecl;

  // GLX 1.2 and later
  glXGetCurrentDisplay: function: PDisplay; cdecl;

  // GLX 1.3 and later
  glXChooseFBConfig: function(dpy: PDisplay; screen: cint; attribList: Pcint; var nitems: cint): PGLXFBConfig; cdecl;
  glXGetFBConfigAttrib: function(dpy: PDisplay; config: TGLXFBConfig; attribute: cint; var value: cint): cint; cdecl;
  glXGetFBConfigs: function(dpy: PDisplay; screen: cint; var nelements: cint): PGLXFBConfig; cdecl;
  glXGetVisualFromFBConfig: function(dpy: PDisplay; config: TGLXFBConfig): PXVisualInfo; cdecl;
  glXCreateWindow: function(dpy: PDisplay; config: TGLXFBConfig; win: {$IFDEF FPC_DOTTEDUNITS}Api.X11.{$ENDIF}X.TWindow; attribList: Pcint): TGLXWindow; cdecl;
  glXDestroyWindow: procedure (dpy: PDisplay; window: TGLXWindow); cdecl;
  glXCreatePixmap: function(dpy: PDisplay; config: TGLXFBConfig; pixmap: TXPixmap; attribList: Pcint): TGLXPixmap; cdecl;
  glXDestroyPixmap: procedure (dpy: PDisplay; pixmap: TGLXPixmap); cdecl;
  glXCreatePbuffer: function(dpy: PDisplay; config: TGLXFBConfig; attribList: Pcint): TGLXPbuffer; cdecl;
  glXDestroyPbuffer: procedure (dpy: PDisplay; pbuf: TGLXPbuffer); cdecl;
  glXQueryDrawable: procedure (dpy: PDisplay; draw: TGLXDrawable; attribute: cint; value: Pcuint); cdecl;
  //glXCreateNewContext -> internal_glXCreateNewContext in implementation
  glXMakeContextCurrent: function(dpy: PDisplay; draw: TGLXDrawable; read: GLXDrawable; ctx: TGLXContext): TBoolResult; cdecl;
  glXGetCurrentReadDrawable: function: TGLXDrawable; cdecl;
  glXQueryContext: function(dpy: PDisplay; ctx: TGLXContext; attribute: cint; var value: cint): cint; cdecl;
  glXSelectEvent: procedure (dpy: PDisplay; drawable: TGLXDrawable; mask: culong); cdecl;
  glXGetSelectedEvent: procedure (dpy: PDisplay; drawable: TGLXDrawable; mask: Pculong); cdecl;

  // GLX 1.4 and later
  glXGetProcAddress: function(procname: PAnsiChar): Pointer; cdecl;

  // Extensions:

  // GLX_ARB_get_proc_address
  glXGetProcAddressARB: function(procname: PAnsiChar): Pointer; cdecl;

  // GLX_ARB_create_context
  //glXCreateContextAttribsARB -> internal_glXCreateContextAttribsARB in implementation

  // GLX_EXT_swap_control
  glXSwapIntervalEXT: function(dpy: PDisplay; drawable: TGLXDrawable; interval: cint): cint; cdecl;

  // GLX_MESA_pixmap_colormap
  glXCreateGLXPixmapMESA: function(dpy: PDisplay; visual: PXVisualInfo; pixmap: XPixmap; cmap: XColormap): GLXPixmap; cdecl;

  // GLX_MESA_swap_control
  glXSwapIntervalMESA: function(interval: cuint): cint; cdecl;
  glXGetSwapIntervalMESA: function: cint; cdecl;

  // Unknown Mesa GLX extension (undocumented in current GLX C headers?)
  glXReleaseBuffersMESA: function(dpy: PDisplay; d: GLXDrawable): TBoolResult; cdecl;
  glXCopySubBufferMESA: procedure(dpy: PDisplay; drawable: GLXDrawable; x, y, width, height: cint); cdecl;

  // GLX_SGI_swap_control
  glXSwapIntervalSGI: function(interval: cint): cint; cdecl;

  // GLX_SGI_video_sync
  glXGetVideoSyncSGI: function(var count: cuint): cint; cdecl;
  glXWaitVideoSyncSGI: function(divisor, remainder: cint; var count: cuint): cint; cdecl;

// =======================================================
//
// =======================================================

// Overloaded functions to handle TBool parameters as actual booleans.
function glXCreateContext(dpy: PDisplay; vis: PXVisualInfo; shareList: GLXContext; direct: Boolean): GLXContext;
function glXCreateNewContext(dpy: PDisplay; config: TGLXFBConfig; renderType: cint; shareList: TGLXContext; direct: Boolean): TGLXContext;
function glXCreateContextAttribsARB(dpy: PDisplay; config: TGLXFBConfig; share_context: TGLXContext; direct: Boolean; attrib_list: Pcint): TGLXContext;

{
  Safe checking of glX version and extension presence.

  For each glX version, these functions check that
  - glXQueryExtension indicates that glX extension is present at all on this display.
  - glXQueryVersion indicates that (at least) this version is supported.
  - all the entry points defined for this glX version were
    successfully loaded from the library.
    For now, all glX versions are fully backward-compatible,
    so e.g. if GLX_version_1_3 is true, you know that also GLX_version_1_2
    and GLX_version_1_1 etc. are true,
    and all entry points up to glX 1.3 are assigned.

  For each extension, these functions check that
  - it is declared within glXQueryExtensionsString (which in turn means
    that glXQueryExtensionsString must be available, which requires glX 1.1)
  - all it's entry points were successfully loaded from library

  As such, these functions are the safest way to check if given
  extension/glX version is available.

  Note that the availability of glX version and extension may depend
  on the X display and (in case of extension) even screen number.
}

function GLX_version_1_0(Display: PDisplay): boolean;
function GLX_version_1_1(Display: PDisplay): boolean;
function GLX_version_1_2(Display: PDisplay): boolean;
function GLX_version_1_3(Display: PDisplay): boolean;
function GLX_version_1_4(Display: PDisplay): boolean;

function GLX_ARB_get_proc_address(Display: PDisplay; Screen: Integer): boolean;
function GLX_ARB_create_context(Display: PDisplay; Screen: Integer): boolean;
function GLX_ARB_create_context_profile(Display: PDisplay; Screen: Integer): boolean;
function GLX_ARB_create_context_robustness(Display: PDisplay; Screen: Integer): boolean;
function GLX_ARB_multisample(Display: PDisplay; Screen: Integer): boolean;
function GLX_EXT_swap_control(Display: PDisplay; Screen: Integer): boolean;
function GLX_EXT_visual_info(Display: PDisplay; Screen: Integer): boolean;
function GLX_MESA_pixmap_colormap(Display: PDisplay; Screen: Integer): boolean;
function GLX_MESA_swap_control(Display: PDisplay; Screen: Integer): boolean;
function GLX_SGI_swap_control(Display: PDisplay; Screen: Integer): boolean;
function GLX_SGI_video_sync(Display: PDisplay; Screen: Integer): boolean;
function GLX_SGIS_multisample(Display: PDisplay; Screen: Integer): boolean;

implementation

{$IFDEF FPC_DOTTEDUNITS}
uses Api.OpenGL.Gl, System.DynLibs, Api.OpenGL.Glext { for glext_ExtensionSupported Amiga.Core.Utility };
{$ELSE FPC_DOTTEDUNITS}
uses GL, dynlibs, GLExt { for glext_ExtensionSupported utility };
{$ENDIF FPC_DOTTEDUNITS}

{$LINKLIB m}

var
  internal_glXCreateContext: function(dpy: PDisplay; vis: PXVisualInfo; shareList: GLXContext; direct: TBool): GLXContext; cdecl;
  internal_glXCreateNewContext: function(dpy: PDisplay; config: TGLXFBConfig; renderType: cint; shareList: TGLXContext; direct: TBool): TGLXContext; cdecl;
  internal_glXCreateContextAttribsARB: function (dpy: PDisplay; config: TGLXFBConfig; share_context: TGLXContext; direct: TBool; attrib_list: Pcint): TGLXContext; cdecl;

function glXCreateContext(dpy: PDisplay; vis: PXVisualInfo; shareList: GLXContext; direct: Boolean): GLXContext;
begin
  Result := internal_glXCreateContext(dpy, vis, shareList, Ord(direct));
end;

function glXCreateNewContext(dpy: PDisplay; config: TGLXFBConfig; renderType: cint; shareList: TGLXContext; direct: Boolean): TGLXContext;
begin
  Result := internal_glXCreateNewContext(dpy, config, renderType, shareList, Ord(direct));
end;

function glXCreateContextAttribsARB(dpy: PDisplay; config: TGLXFBConfig; share_context: TGLXContext; direct: Boolean; attrib_list: Pcint): TGLXContext;
begin
  Result := internal_glXCreateContextAttribsARB(dpy, config, share_context, Ord(direct), attrib_list);
end;

function GLX_version_1_0(Display: PDisplay): boolean;
var
  IgnoredErrorb, IgnoredEvent, Major, Minor: Integer;
begin
  Result :=
    { check is glX present at all for this display }
    Assigned(glXQueryExtension) and
    glXQueryExtension(Display, IgnoredErrorb, IgnoredEvent) and
    { check glXQueryVersion, although there is no glX with version < 1 }
    Assigned(glXQueryVersion) and
    glXQueryVersion(Display, Major, Minor) and
    (Major >= 1) and
    { check entry points assigned }
    Assigned(glXChooseVisual) and
    Assigned(internal_glXCreateContext) and
    Assigned(glXDestroyContext) and
    Assigned(glXMakeCurrent) and
    Assigned(glXCopyContext) and
    Assigned(glXSwapBuffers) and
    Assigned(glXCreateGLXPixmap) and
    Assigned(glXDestroyGLXPixmap) and
    { Assigned(glXQueryExtension) and } { (already checked) }
    { Assigned(glXQueryVersion) and } { (already checked) }
    Assigned(glXIsDirect) and
    Assigned(glXGetConfig) and
    Assigned(glXGetCurrentContext) and
    Assigned(glXGetCurrentDrawable) and
    Assigned(glXWaitGL) and
    Assigned(glXWaitX) and
    Assigned(glXUseXFont)
end;

function GLX_version_1_1(Display: PDisplay): boolean;
var
  Major, Minor: Integer;
begin
  Result :=
    { check previous version Ok }
    GLX_version_1_0(Display) and
    { check glXQueryVersion }
    glXQueryVersion(Display, Major, Minor) and
    ( (Major > 1) or ((Major = 1) and (Minor >= 1)) ) and
    { check entry points assigned }
    Assigned(glXQueryExtensionsString) and
    Assigned(glXQueryServerString) and
    Assigned(glXGetClientString);
end;

function GLX_version_1_2(Display: PDisplay): boolean;
var
  Major, Minor: Integer;
begin
  Result :=
    { check previous version Ok }
    GLX_version_1_1(Display) and
    { check glXQueryVersion }
    glXQueryVersion(Display, Major, Minor) and
    ( (Major > 1) or ((Major = 1) and (Minor >= 2)) ) and
    { check entry points assigned }
    Assigned(glXGetCurrentDisplay);
end;

function GLX_version_1_3(Display: PDisplay): boolean;
var
  Major, Minor: Integer;
begin
  Result :=
    { check previous version Ok }
    GLX_version_1_2(Display) and
    { check glXQueryVersion }
    glXQueryVersion(Display, Major, Minor) and
    ( (Major > 1) or ((Major = 1) and (Minor >= 3)) ) and
    { check entry points assigned }
    Assigned(glXChooseFBConfig) and
    Assigned(glXGetFBConfigAttrib) and
    Assigned(glXGetFBConfigs) and
    Assigned(glXGetVisualFromFBConfig) and
    Assigned(glXCreateWindow) and
    Assigned(glXDestroyWindow) and
    Assigned(glXCreatePixmap) and
    Assigned(glXDestroyPixmap) and
    Assigned(glXCreatePbuffer) and
    Assigned(glXDestroyPbuffer) and
    Assigned(glXQueryDrawable) and
    Assigned(internal_glXCreateNewContext) and
    Assigned(glXMakeContextCurrent) and
    Assigned(glXGetCurrentReadDrawable) and
    Assigned(glXQueryContext) and
    Assigned(glXSelectEvent) and
    Assigned(glXGetSelectedEvent);
end;

function GLX_version_1_4(Display: PDisplay): boolean;
var
  Major, Minor: Integer;
begin
  Result :=
    { check previous version Ok }
    GLX_version_1_3(Display) and
    { check glXQueryVersion }
    glXQueryVersion(Display, Major, Minor) and
    ( (Major > 1) or ((Major = 1) and (Minor >= 4)) ) and
    { check entry points assigned }
    Assigned(glXGetProcAddress);
end;

function GLX_ARB_get_proc_address(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_ARB_get_proc_address', GlxExtensions) and
      Assigned(glXGetProcAddressARB);
  end;
end;

function GLX_ARB_create_context(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_ARB_create_context', GlxExtensions) and
      Assigned(internal_glXCreateContextAttribsARB);
  end;
end;

function GLX_ARB_create_context_profile(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_ARB_create_context_profile', GlxExtensions);
  end;
end;

function GLX_ARB_create_context_robustness(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_ARB_create_context_robustness', GlxExtensions);
  end;
end;

function GLX_ARB_multisample(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_ARB_multisample', GlxExtensions);
  end;
end;

function GLX_EXT_swap_control(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_EXT_swap_control', GlxExtensions) and
      Assigned(glXSwapIntervalEXT);
  end;
end;

function GLX_EXT_visual_info(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_EXT_visual_info', GlxExtensions);
  end;
end;

function GLX_MESA_pixmap_colormap(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_MESA_pixmap_colormap', GlxExtensions) and
      Assigned(glXCreateGLXPixmapMESA);
  end;
end;

function GLX_MESA_swap_control(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_MESA_swap_control', GlxExtensions) and
      Assigned(glXSwapIntervalMESA) and
      Assigned(glXGetSwapIntervalMESA);
  end;
end;

function GLX_SGI_swap_control(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_SGI_swap_control', GlxExtensions) and
      Assigned(glXSwapIntervalSGI);
  end;
end;

function GLX_SGI_video_sync(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_SGI_video_sync', GlxExtensions) and
      Assigned(glXGetVideoSyncSGI) and
      Assigned(glXWaitVideoSyncSGI);
  end;
end;

function GLX_SGIS_multisample(Display: PDisplay; Screen: Integer): boolean;
var
  GlxExtensions: PAnsiChar;
begin
  Result := GLX_version_1_1(Display);
  if Result then
  begin
    GlxExtensions := glXQueryExtensionsString(Display, Screen);
    Result := glext_ExtensionSupported('GLX_SGIS_multisample', GlxExtensions);
  end;
end;

function GetProc(handle: PtrInt; name: PAnsiChar): Pointer;
begin
  if Assigned(glXGetProcAddress) then
    Result := glXGetProcAddress(name)
  else
    if Assigned(glXGetProcAddressARB) then
      Result := glXGetProcAddressARB(name)
    else
      Result := GetProcAddress(handle, name);
  if (Result = nil) and GLXDumpUnresolvedFunctions then
    WriteLn('Unresolved: ', name);
end;

function InitGLX: Boolean;
var
  OurLibGL: TLibHandle;
begin
  Result := False;

{$ifndef darwin}
  OurLibGL := libGl;
{$else darwin}
  OurLibGL := LoadLibrary('/usr/X11R6/lib/libGL.dylib');
{$endif darwin}

  if OurLibGL = 0 then
    exit;

  // glXGetProcAddress and glXGetProcAddressARB are imported first,
  // so we can use them (when they are available) to resolve all the
  // other imports

  // GLX 1.4 and later
  glXGetProcAddress := GetProc(OurLibGL, 'glXGetProcAddress');
  // GLX_ARB_get_proc_address
  glXGetProcAddressARB := GetProc(OurLibGL, 'glXGetProcAddressARB');

  // GLX 1.0
  glXChooseVisual := GetProc(OurLibGL, 'glXChooseVisual');
  internal_glXCreateContext := GetProc(OurLibGL, 'glXCreateContext');
  glXDestroyContext := GetProc(OurLibGL, 'glXDestroyContext');
  glXMakeCurrent := GetProc(OurLibGL, 'glXMakeCurrent');
  glXCopyContext := GetProc(OurLibGL, 'glXCopyContext');
  glXSwapBuffers := GetProc(OurLibGL, 'glXSwapBuffers');
  glXCreateGLXPixmap := GetProc(OurLibGL, 'glXCreateGLXPixmap');
  glXDestroyGLXPixmap := GetProc(OurLibGL, 'glXDestroyGLXPixmap');
  glXQueryExtension := GetProc(OurLibGL, 'glXQueryExtension');
  glXQueryVersion := GetProc(OurLibGL, 'glXQueryVersion');
  glXIsDirect := GetProc(OurLibGL, 'glXIsDirect');
  glXGetConfig := GetProc(OurLibGL, 'glXGetConfig');
  glXGetCurrentContext := GetProc(OurLibGL, 'glXGetCurrentContext');
  glXGetCurrentDrawable := GetProc(OurLibGL, 'glXGetCurrentDrawable');
  glXWaitGL := GetProc(OurLibGL, 'glXWaitGL');
  glXWaitX := GetProc(OurLibGL, 'glXWaitX');
  glXUseXFont := GetProc(OurLibGL, 'glXUseXFont');
  // GLX 1.1 and later
  glXQueryExtensionsString := GetProc(OurLibGL, 'glXQueryExtensionsString');
  glXQueryServerString := GetProc(OurLibGL, 'glXQueryServerString');
  glXGetClientString := GetProc(OurLibGL, 'glXGetClientString');
  // GLX 1.2 and later
  glXGetCurrentDisplay := GetProc(OurLibGL, 'glXGetCurrentDisplay');
  // GLX 1.3 and later
  glXChooseFBConfig := GetProc(OurLibGL, 'glXChooseFBConfig');
  glXGetFBConfigAttrib := GetProc(OurLibGL, 'glXGetFBConfigAttrib');
  glXGetFBConfigs := GetProc(OurLibGL, 'glXGetFBConfigs');
  glXGetVisualFromFBConfig := GetProc(OurLibGL, 'glXGetVisualFromFBConfig');
  glXCreateWindow := GetProc(OurLibGL, 'glXCreateWindow');
  glXDestroyWindow := GetProc(OurLibGL, 'glXDestroyWindow');
  glXCreatePixmap := GetProc(OurLibGL, 'glXCreatePixmap');
  glXDestroyPixmap := GetProc(OurLibGL, 'glXDestroyPixmap');
  glXCreatePbuffer := GetProc(OurLibGL, 'glXCreatePbuffer');
  glXDestroyPbuffer := GetProc(OurLibGL, 'glXDestroyPbuffer');
  glXQueryDrawable := GetProc(OurLibGL, 'glXQueryDrawable');
  internal_glXCreateNewContext := GetProc(OurLibGL, 'glXCreateNewContext');
  glXMakeContextCurrent := GetProc(OurLibGL, 'glXMakeContextCurrent');
  glXGetCurrentReadDrawable := GetProc(OurLibGL, 'glXGetCurrentReadDrawable');
  glXQueryContext := GetProc(OurLibGL, 'glXQueryContext');
  glXSelectEvent := GetProc(OurLibGL, 'glXSelectEvent');
  glXGetSelectedEvent := GetProc(OurLibGL, 'glXGetSelectedEvent');
  // Extensions
  // GLX_ARB_create_context
  internal_glXCreateContextAttribsARB := GetProc(OurLibGL, 'glXCreateContextAttribsARB');
  // GLX_EXT_swap_control
  glXSwapIntervalEXT := GetProc(OurLibGL, 'glXSwapIntervalEXT');
  // GLX_MESA_pixmap_colormap
  glXCreateGLXPixmapMESA := GetProc(OurLibGL, 'glXCreateGLXPixmapMESA');
  // GLX_MESA_swap_control
  glXSwapIntervalMESA := GetProc(OurLibGL, 'glXSwapIntervalMESA');
  glXGetSwapIntervalMESA := GetProc(OurLibGL, 'glXGetSwapIntervalMESA');
  // Unknown Mesa GLX extension
  glXReleaseBuffersMESA := GetProc(OurLibGL, 'glXReleaseBuffersMESA');
  glXCopySubBufferMESA := GetProc(OurLibGL, 'glXCopySubBufferMESA');
  // GLX_SGI_swap_control
  glXSwapIntervalSGI := GetProc(OurLibGL, 'glXSwapIntervalSGI');
  // GLX_SGI_video_sync
  glXGetVideoSyncSGI := GetProc(OurLibGL, 'glXGetVideoSyncSGI');
  glXWaitVideoSyncSGI := GetProc(OurLibGL, 'glXWaitVideoSyncSGI');

  GLXInitialized := True;
  Result := True;
end;

initialization
  InitGLX;
end.