From 5c755f2f310bbce0f3faff88e2ad42f7dac50616 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Fri, 2 Jan 2015 23:52:40 +0900
Subject: [PATCH] Fix BindFramebuffer to pass JS null object explicitly

---
 internal/opengl/context_js.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/internal/opengl/context_js.go b/internal/opengl/context_js.go
index 0082801fa..9a71e33a5 100644
--- a/internal/opengl/context_js.go
+++ b/internal/opengl/context_js.go
@@ -32,6 +32,9 @@ type context struct {
 	gl *webgl.Context
 }
 
+// TODO: Is there any better way to get null value?
+var nullVal = js.Global.Call("eval", "null")
+
 func NewContext(gl *webgl.Context) *Context {
 	c := &Context{
 		Nearest:            FilterType(gl.NEAREST),
@@ -123,7 +126,11 @@ func (c *Context) NewFramebuffer(texture Texture) (Framebuffer, error) {
 func (c *Context) SetViewport(f Framebuffer, width, height int) error {
 	gl := c.gl
 	gl.Flush()
-	gl.BindFramebuffer(gl.FRAMEBUFFER, f)
+	if f != nil {
+		gl.BindFramebuffer(gl.FRAMEBUFFER, f)
+	} else {
+		gl.BindFramebuffer(gl.FRAMEBUFFER, nullVal)
+	}
 	err := gl.CheckFramebufferStatus(gl.FRAMEBUFFER)
 	if err != gl.FRAMEBUFFER_COMPLETE {
 		if gl.GetError() != 0 {