From c40b1653532aa08412aa8232fb8a11289512283e Mon Sep 17 00:00:00 2001
From: Matthias Melcher <github@matthiasm.com>
Date: Mon, 29 Jan 2024 13:41:53 +0100
Subject: [PATCH] Fix OpenGL context caching on macOS (#737)

---
 src/Fl_Gl_Window.cxx                           |  1 -
 src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.mm | 10 +++++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/Fl_Gl_Window.cxx b/src/Fl_Gl_Window.cxx
index 4912765c7..3e87a880a 100644
--- a/src/Fl_Gl_Window.cxx
+++ b/src/Fl_Gl_Window.cxx
@@ -536,7 +536,6 @@ float Fl_Gl_Window::pixels_per_unit() {
  */
 
 int Fl_Gl_Window_Driver::copy = COPY;
-GLContext Fl_Gl_Window_Driver::cached_context = NULL;
 Fl_Window* Fl_Gl_Window_Driver::cached_window = NULL;
 float Fl_Gl_Window_Driver::gl_scale = 1; // scaling factor between FLTK and GL drawing units: GL = FLTK * gl_scale
 
diff --git a/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.mm b/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.mm
index 808a6e03a..43a1c1b9e 100644
--- a/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.mm
+++ b/src/drivers/Cocoa/Fl_Cocoa_Gl_Window_Driver.mm
@@ -217,18 +217,18 @@ GLContext Fl_Cocoa_Gl_Window_Driver::create_gl_context(Fl_Window* window, const
 }
 
 void Fl_Cocoa_Gl_Window_Driver::set_gl_context(Fl_Window* w, GLContext context) {
-  if (context != cached_context || w != cached_window) {
-    cached_context = context;
+  NSOpenGLContext *current_context = [NSOpenGLContext currentContext];
+  if (context != current_context || w != cached_window) {
     cached_window = w;
     [(NSOpenGLContext*)context makeCurrentContext];
   }
 }
 
 void Fl_Cocoa_Gl_Window_Driver::delete_gl_context(GLContext context) {
-  if (cached_context == context) {
-    cached_context = 0;
+  NSOpenGLContext *current_context = [NSOpenGLContext currentContext];
+  if (current_context == context) {
     cached_window = 0;
-    [[NSOpenGLContext currentContext] clearDrawable];
+    [current_context clearDrawable];
   }
   [(NSOpenGLContext*)context release];
   del_context(context);