From 3df198f68eea502c524e79aaa78a87c0574752ce Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Fri, 22 Nov 2019 00:27:18 +0900
Subject: [PATCH] graphicsdriver/opengl: Use GL_READ_WRITE at glMapBuffer

Updates #993
---
 internal/graphicsdriver/opengl/context_desktop.go | 2 +-
 internal/graphicsdriver/opengl/gl/package.go      | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/internal/graphicsdriver/opengl/context_desktop.go b/internal/graphicsdriver/opengl/context_desktop.go
index 5928db8a9..7a57d7ecd 100644
--- a/internal/graphicsdriver/opengl/context_desktop.go
+++ b/internal/graphicsdriver/opengl/context_desktop.go
@@ -529,7 +529,7 @@ func (c *context) mapPixelBuffer(buffer buffer) unsafe.Pointer {
 	var ptr unsafe.Pointer
 	_ = c.t.Call(func() error {
 		gl.BindBuffer(gl.PIXEL_UNPACK_BUFFER, uint32(buffer))
-		ptr = gl.MapBuffer(gl.PIXEL_UNPACK_BUFFER, gl.WRITE_ONLY)
+		ptr = gl.MapBuffer(gl.PIXEL_UNPACK_BUFFER, gl.READ_WRITE)
 		return nil
 	})
 	return ptr
diff --git a/internal/graphicsdriver/opengl/gl/package.go b/internal/graphicsdriver/opengl/gl/package.go
index a4ce01dc5..5fd5480ef 100644
--- a/internal/graphicsdriver/opengl/gl/package.go
+++ b/internal/graphicsdriver/opengl/gl/package.go
@@ -47,6 +47,7 @@ const (
 	MAX_TEXTURE_SIZE     = 0x0D33
 	NEAREST              = 0x2600
 	NO_ERROR             = 0
+	READ_WRITE           = 0x88BA
 	RGBA                 = 0x1908
 	TEXTURE_2D           = 0x0DE1
 	TEXTURE_MAG_FILTER   = 0x2800