Adding upstream version 0.0~git20250520.a1d9079+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

exp/gl/glutil/context_darwin_desktop.go

@@ -0,0 +1,94 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin && !ios
+
+package glutil
+
+// TODO(crawshaw): Only used in glutil tests for now (cgo is not support in _test.go files).
+// TODO(crawshaw): Export some kind of Context. Work out what we can offer, where. Maybe just for tests.
+// TODO(crawshaw): Support android and windows.
+
+/*
+#cgo CFLAGS: -DGL_SILENCE_DEPRECATION
+#cgo LDFLAGS: -framework OpenGL
+#import <OpenGL/OpenGL.h>
+#import <OpenGL/gl3.h>
+
+CGLError CGCreate(CGLContextObj* ctx) {
+	CGLError err;
+	CGLPixelFormatAttribute attributes[] = {
+		kCGLPFAOpenGLProfile, (CGLPixelFormatAttribute)kCGLOGLPVersion_3_2_Core,
+		kCGLPFAColorSize, (CGLPixelFormatAttribute)24,
+		kCGLPFAAlphaSize, (CGLPixelFormatAttribute)8,
+		kCGLPFADepthSize, (CGLPixelFormatAttribute)16,
+		kCGLPFAAccelerated,
+		kCGLPFADoubleBuffer,
+		(CGLPixelFormatAttribute) 0
+	};
+	CGLPixelFormatObj pix;
+	GLint num;
+
+	if ((err = CGLChoosePixelFormat(attributes, &pix, &num)) != kCGLNoError) {
+		return err;
+	}
+	if ((err = CGLCreateContext(pix, 0, ctx)) != kCGLNoError) {
+		return err;
+	}
+	if ((err = CGLDestroyPixelFormat(pix)) != kCGLNoError) {
+		return err;
+	}
+	if ((err = CGLSetCurrentContext(*ctx)) != kCGLNoError) {
+		return err;
+	}
+	if ((err = CGLLockContext(*ctx)) != kCGLNoError) {
+		return err;
+	}
+	return kCGLNoError;
+}
+*/
+import "C"
+
+import (
+	"fmt"
+	"runtime"
+)
+
+// contextGL holds a copy of the OpenGL Context from thread-local storage.
+//
+// Do not move a contextGL between goroutines or OS threads.
+type contextGL struct {
+	ctx C.CGLContextObj
+}
+
+// createContext creates an OpenGL context, binds it as the current context
+// stored in thread-local storage, and locks the current goroutine to an os
+// thread.
+func createContext() (*contextGL, error) {
+	// The OpenGL active context is stored in TLS.
+	runtime.LockOSThread()
+
+	c := new(contextGL)
+	if cglErr := C.CGCreate(&c.ctx); cglErr != C.kCGLNoError {
+		return nil, fmt.Errorf("CGL: %v", C.GoString(C.CGLErrorString(cglErr)))
+	}
+
+	// Using attribute arrays in OpenGL 3.3 requires the use of a VBA.
+	// But VBAs don't exist in ES 2. So we bind a default one.
+	var id C.GLuint
+	C.glGenVertexArrays(1, &id)
+	C.glBindVertexArray(id)
+
+	return c, nil
+}
+
+// destroy destroys an OpenGL context and unlocks the current goroutine from
+// its os thread.
+func (c *contextGL) destroy() {
+	C.CGLUnlockContext(c.ctx)
+	C.CGLSetCurrentContext(nil)
+	C.CGLDestroyContext(c.ctx)
+	c.ctx = nil
+	runtime.UnlockOSThread()
+}