From 39b8a66359e01b87477050c04bc7eb62e36fc09f Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sun, 13 Nov 2022 06:29:55 -0800
Subject: [PATCH] internal/graphicsdriver/opengl/gl: dynamic function load for
 OpenGL ES

Updates #292
Updates #2450
---
 .../{default_gles.go => default_android.go}   |  5 +-
 .../opengl/gl/default_notpurego.go            |  2 +-
 .../gl/{procaddr_others.go => procaddr_gl.go} |  0
 .../graphicsdriver/opengl/gl/procaddr_gles.go | 46 +++++++++++++++++++
 4 files changed, 48 insertions(+), 5 deletions(-)
 rename internal/graphicsdriver/opengl/gl/{default_gles.go => default_android.go} (99%)
 rename internal/graphicsdriver/opengl/gl/{procaddr_others.go => procaddr_gl.go} (100%)
 create mode 100644 internal/graphicsdriver/opengl/gl/procaddr_gles.go

diff --git a/internal/graphicsdriver/opengl/gl/default_gles.go b/internal/graphicsdriver/opengl/gl/default_android.go
similarity index 99%
rename from internal/graphicsdriver/opengl/gl/default_gles.go
rename to internal/graphicsdriver/opengl/gl/default_android.go
index 506b32794..5e6232615 100644
--- a/internal/graphicsdriver/opengl/gl/default_gles.go
+++ b/internal/graphicsdriver/opengl/gl/default_android.go
@@ -12,12 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build android || opengles
-
 package gl
 
-// #cgo !android pkg-config: glesv2
-// #cgo android  LDFLAGS:    -lGLESv2
+// #cgo LDFLAGS: -lGLESv2
 //
 // #include <GLES2/gl2.h>
 // #include <stdlib.h>
diff --git a/internal/graphicsdriver/opengl/gl/default_notpurego.go b/internal/graphicsdriver/opengl/gl/default_notpurego.go
index 9c6741a1d..67305030d 100644
--- a/internal/graphicsdriver/opengl/gl/default_notpurego.go
+++ b/internal/graphicsdriver/opengl/gl/default_notpurego.go
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 // SPDX-FileCopyrightText: 2014 Eric Woroshow
 
-//go:build !android && !darwin && !js && !windows && !opengles
+//go:build !android && !darwin && !js && !windows
 
 package gl
 
diff --git a/internal/graphicsdriver/opengl/gl/procaddr_others.go b/internal/graphicsdriver/opengl/gl/procaddr_gl.go
similarity index 100%
rename from internal/graphicsdriver/opengl/gl/procaddr_others.go
rename to internal/graphicsdriver/opengl/gl/procaddr_gl.go
diff --git a/internal/graphicsdriver/opengl/gl/procaddr_gles.go b/internal/graphicsdriver/opengl/gl/procaddr_gles.go
new file mode 100644
index 000000000..8a0dec9e6
--- /dev/null
+++ b/internal/graphicsdriver/opengl/gl/procaddr_gles.go
@@ -0,0 +1,46 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !android && !darwin && !js && !nintendosdk && !windows && opengles
+
+package gl
+
+// #cgo LDFLAGS: -ldl
+//
+// #include <dlfcn.h>
+// #include <stdlib.h>
+//
+// static void* getProcAddress(const char* name) {
+//   static void* libGLES;
+//   if (!libGLES) {
+//     libGLES = dlopen("libGLESv2.so", RTLD_NOW | RTLD_GLOBAL);
+//   }
+//   return dlsym(libGLES, name);
+// }
+import "C"
+
+import (
+	"strings"
+	"unsafe"
+)
+
+func getProcAddress(namea string) unsafe.Pointer {
+	const ext = "EXT"
+	if strings.HasSuffix(namea, ext) {
+		namea = namea[:len(namea)-len(ext)]
+	}
+	cname := C.CString(namea)
+	defer C.free(unsafe.Pointer(cname))
+	return C.getProcAddress(cname)
+}