From 0fdc88d2d7b55c0d90a138117b90c798901366a7 Mon Sep 17 00:00:00 2001
From: ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
Date: Fri, 23 Sep 2022 18:09:40 +0200
Subject: GL3 support under X11: ask for compatibility profile if possible.

---
 src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'src/drivers/X11')

diff --git a/src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx b/src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx
index 597801a0f..476d654f3 100644
--- a/src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx
+++ b/src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx
@@ -278,7 +278,7 @@ GLContext Fl_X11_Gl_Window_Driver::create_gl_context(Fl_Window* window, const Fl
       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_CORE_PROFILE_BIT_ARB,
+      GLX_CONTEXT_PROFILE_MASK_ARB, GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB,
       None
     };
     ctxErrorOccurred = false;
@@ -286,6 +286,12 @@ GLContext Fl_X11_Gl_Window_Driver::create_gl_context(Fl_Window* window, const Fl
     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
-- 
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