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Simplify creation of OpenGL contexts under X11 platform (#1005)

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The previous approach FLTK used to create OpenGL contexts under the X11 platform
followed a different code path to create contexts for OpenGL version 3 and above
than to create contexts for OpenGL versions 1 or 2.
The FLTK code followed exactly "Tutorial: OpenGL 3.0 Context Creation (GLX)"
of the official OpenGL wiki, see:
https://www.khronos.org/opengl/wiki/Tutorial:_OpenGL_3.0_Context_Creation_(GLX)
That code worked OK with Debian 11 and with any tested Linux configurations
in a VM running on Apple hardware. However, it failed with Debian 12 and later
on native Linux boxes to create GL3 contexts with the FL_DOUBLE flag.
That's what issue #1005 reports.

A first attempt to fix #1005 followed instructions given at:
https://registry.khronos.org/OpenGL-Refpages/gl2.1/xhtml/glXIntro.xml
which supposedly describe how to create OpenGL contexts with GLX.
That had no effect on issue #1005.

This commit erases all attempts to use OpenGL3-specific calls or even
the more modern glXCreateNewContext() function that appears with
GLX version 1.3. The committed code uses only OpenGL 1-age
functions to create OpenGL contexts for X11 windows.
Created contexts follow the "Compatibility Profile" which means they
are compatible with both modern OpenGL3-style and legacy OpenGL1/2-style.

This appears to fix issue #1005.
This commit is contained in:
ManoloFLTK 2024-07-17 17:12:23 +02:00
parent fd257a7bf3
commit 325004fb33
1 changed files with 8 additions and 114 deletions
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122
src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx
View File

@ -1,7 +1,7 @@
//
// Class Fl_X11_Gl_Window_Driver for the Fast Light Tool Kit (FLTK).
//
// Copyright 2021-2022 by Bill Spitzak and others.
// Copyright 2021-2024 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this
@ -20,10 +20,7 @@
#include "../../Fl_Gl_Choice.H"
#include "../../Fl_Screen_Driver.H"
#include "Fl_X11_Gl_Window_Driver.H"
# include <GL/glx.h>
# if ! defined(GLX_VERSION_1_3)
# typedef void *GLXFBConfig;
# endif
#include <GL/glx.h>
#if ! USE_XFT
# include "../Xlib/Fl_Font.H"
#endif
@ -35,12 +32,10 @@ class Fl_X11_Gl_Choice : public Fl_Gl_Choice {
private:
XVisualInfo *vis; /* the visual to use */
Colormap colormap; /* a colormap for that visual */
GLXFBConfig best_fb;
public:
Fl_X11_Gl_Choice(int m, const int *alistp, Fl_Gl_Choice *n) : Fl_Gl_Choice(m, alistp, n) {
vis = NULL;
colormap = 0;
best_fb = NULL;
}
};
@ -120,53 +115,6 @@ Fl_Font_Descriptor** Fl_X11_Gl_Window_Driver::fontnum_to_fontdescriptor(int fnum
#endif
static XVisualInfo *gl3_getvisual(const int *blist, GLXFBConfig *pbestFB)
{
int glx_major, glx_minor;
// FBConfigs were added in GLX version 1.3.
if ( !glXQueryVersion(fl_display, &glx_major, &glx_minor) ||
( ( glx_major == 1 ) && ( glx_minor < 3 ) ) || ( glx_major < 1 ) ) {
return NULL;
}
//printf( "Getting matching framebuffer configs\n" );
int fbcount;
GLXFBConfig* fbc = glXChooseFBConfig(fl_display, DefaultScreen(fl_display), blist, &fbcount);
if (!fbc) {
//printf( "Failed to retrieve a framebuffer config\n" );
return NULL;
}
//printf( "Found %d matching FB configs.\n", fbcount );
// Pick the FB config/visual with the most samples per pixel
int best_fbc = -1, worst_fbc = -1, best_num_samp = -1, worst_num_samp = 999;
for (int i = 0; i < fbcount; ++i)
{
XVisualInfo *vi = glXGetVisualFromFBConfig( fl_display, fbc[i] );
if (vi) {
int samp_buf, samples;
glXGetFBConfigAttrib(fl_display, fbc[i], GLX_SAMPLE_BUFFERS, &samp_buf);
glXGetFBConfigAttrib(fl_display, fbc[i], GLX_SAMPLES , &samples );
/*printf( " Matching fbconfig %d, visual ID 0x%2lx: SAMPLE_BUFFERS = %d, SAMPLES = %d\n",
i, vi -> visualid, samp_buf, samples );*/
if ( best_fbc < 0 || (samp_buf && samples > best_num_samp) )
best_fbc = i, best_num_samp = samples;
if ( worst_fbc < 0 || !samp_buf || samples < worst_num_samp )
worst_fbc = i, worst_num_samp = samples;
}
XFree(vi);
}
GLXFBConfig bestFbc = fbc[ best_fbc ];
// Be sure to free the FBConfig list allocated by glXChooseFBConfig()
XFree(fbc);
// Get a visual
XVisualInfo *vi = glXGetVisualFromFBConfig(fl_display, bestFbc);
*pbestFB = bestFbc;
return vi;
}
Fl_Gl_Choice *Fl_X11_Gl_Window_Driver::find(int m, const int *alistp)
{
Fl_X11_Gl_Choice *g = (Fl_X11_Gl_Choice*)Fl_Gl_Window_Driver::find_begin(m, alistp);
@ -222,26 +170,18 @@ Fl_Gl_Choice *Fl_X11_Gl_Window_Driver::find(int m, const int *alistp)
}
fl_open_display();
XVisualInfo *visp = NULL;
GLXFBConfig best_fb = NULL;
if (m & FL_OPENGL3) {
visp = gl3_getvisual((const int *)blist, &best_fb);
}
XVisualInfo *visp = glXChooseVisual(fl_display, fl_screen, (int *)blist);
if (!visp) {
visp = glXChooseVisual(fl_display, fl_screen, (int *)blist);
if (!visp) {
# if defined(GLX_VERSION_1_1) && defined(GLX_SGIS_multisample)
if (m&FL_MULTISAMPLE) return find(m&~FL_MULTISAMPLE, 0);
# endif
# if defined(GLX_VERSION_1_1) && defined(GLX_SGIS_multisample)
if (m&FL_MULTISAMPLE) return find(m&~FL_MULTISAMPLE, 0);
# endif
return 0;
}
}
g = new Fl_X11_Gl_Choice(m, alistp, first);
first = g;
g->vis = visp;
g->best_fb = best_fb;
if (/*MaxCmapsOfScreen(ScreenOfDisplay(fl_display,fl_screen))==1 && */
visp->visualid == fl_visual->visualid &&
@ -265,60 +205,14 @@ GLContext Fl_X11_Gl_Window_Driver::create_gl_context(Fl_Window* window,
(void)window;
GLContext shared_ctx = 0;
if (context_list && nContext) shared_ctx = context_list[0];
typedef GLContext (*glXCreateContextAttribsARBProc)(Display*, GLXFBConfig, GLContext, Bool, const int*);
// It is not necessary to create or make current to a context before calling glXGetProcAddressARB
static glXCreateContextAttribsARBProc glXCreateContextAttribsARB =
#if defined(HAVE_GLXGETPROCADDRESSARB)
(glXCreateContextAttribsARBProc)glXGetProcAddressARB((const GLubyte *)"glXCreateContextAttribsARB");
#else
NULL;
#endif
GLContext ctx = 0;
// Check for the GLX_ARB_create_context extension string and the function.
// If either is not present, use GLX 1.3 context creation method.
const char *glxExts = glXQueryExtensionsString(fl_display, fl_screen);
if (((Fl_X11_Gl_Choice*)g)->best_fb && strstr(glxExts, "GLX_ARB_create_context") && glXCreateContextAttribsARB ) {
int context_attribs[] =
{
GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
GLX_CONTEXT_MINOR_VERSION_ARB, 2,
//GLX_CONTEXT_FLAGS_ARB , GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
GLX_CONTEXT_PROFILE_MASK_ARB, GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB,
None
};
ctxErrorOccurred = false;
XErrorHandler oldHandler = XSetErrorHandler(&ctxErrorHandler);
ctx = glXCreateContextAttribsARB(fl_display, ((Fl_X11_Gl_Choice*)g)->best_fb, shared_ctx, true, context_attribs);
XSync(fl_display, false); // Sync to ensure any errors generated are processed.
if (ctxErrorOccurred) ctx = 0;
if (!ctx) { // if did not work, try again asking for core profile
ctxErrorOccurred = false;
context_attribs[5] = GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
ctx = glXCreateContextAttribsARB(fl_display, ((Fl_X11_Gl_Choice*)g)->best_fb, shared_ctx, true, context_attribs);
if (ctxErrorOccurred) ctx = 0;
}
XSetErrorHandler(oldHandler);
}
if (!ctx) { // use OpenGL 1-style context creation
ctx = glXCreateContext(fl_display, ((Fl_X11_Gl_Choice*)g)->vis, (GLXContext)shared_ctx, true);
}
// use OpenGL 1-style context creation
GLContext ctx = glXCreateContext(fl_display, ((Fl_X11_Gl_Choice*)g)->vis, (GLXContext)shared_ctx, true);
if (ctx)
add_context(ctx);
//glXMakeCurrent(fl_display, fl_xid(window), ctx);printf("%s\n", glGetString(GL_VERSION));
return ctx;
}
/* This is no longer used
GLContext Fl_X11_Gl_Window_Driver::create_gl_context(XVisualInfo *vis) {
GLContext shared_ctx = 0;
if (context_list && nContext) shared_ctx = context_list[0];
GLContext context = glXCreateContext(fl_display, vis, (GLXContext)shared_ctx, 1);
if (context)
add_context(context);
return context;
}*/
void Fl_X11_Gl_Window_Driver::set_gl_context(Fl_Window* w, GLContext context) {
GLContext current_context = glXGetCurrentContext();