From 2a8e8d0eb66ec909486b75c4717ff00d33c1b2d8 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Thu, 24 Jun 2021 12:49:36 +0900
Subject: [PATCH] internal/graphicsdriver/opengl: Stop using PBO

PBO was introduced to improve the performance at ReplacePixels,
but we found that PBO can degrades the performance. Also, now
multiple glTexImage2Ds are called successively like a batch, so
the situation is now different from that time when PBO was
introduced.

Let's remove PBO usages and wait and see.

Closes #1678
---
 internal/graphicsdriver/opengl/context_desktop.go | 2 +-
 internal/graphicsdriver/opengl/context_js.go      | 2 +-
 internal/graphicsdriver/opengl/image.go           | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/internal/graphicsdriver/opengl/context_desktop.go b/internal/graphicsdriver/opengl/context_desktop.go
index eaf4bec3e..b412eb39c 100644
--- a/internal/graphicsdriver/opengl/context_desktop.go
+++ b/internal/graphicsdriver/opengl/context_desktop.go
@@ -449,7 +449,7 @@ func (c *context) needsRestoring() bool {
 }
 
 func (c *context) canUsePBO() bool {
-	return isPBOAvailable()
+	return false
 }
 
 func (c *context) texSubImage2D(t textureNative, args []*driver.ReplacePixelsArgs) {
diff --git a/internal/graphicsdriver/opengl/context_js.go b/internal/graphicsdriver/opengl/context_js.go
index 33bf47c6a..cf863bc31 100644
--- a/internal/graphicsdriver/opengl/context_js.go
+++ b/internal/graphicsdriver/opengl/context_js.go
@@ -530,7 +530,7 @@ func (c *context) needsRestoring() bool {
 }
 
 func (c *context) canUsePBO() bool {
-	return isWebGL2Available
+	return false
 }
 
 func (c *context) texSubImage2D(t textureNative, args []*driver.ReplacePixelsArgs) {
diff --git a/internal/graphicsdriver/opengl/image.go b/internal/graphicsdriver/opengl/image.go
index 48f151539..3a9a6295c 100644
--- a/internal/graphicsdriver/opengl/image.go
+++ b/internal/graphicsdriver/opengl/image.go
@@ -120,6 +120,7 @@ func (i *Image) ReplacePixels(args []*driver.ReplacePixelsArgs) {
 	}
 	i.graphics.drawCalled = false
 
+	// TODO: Now canUsePBO always returns false (#1678). Remove the code for PBO.
 	if !i.graphics.context.canUsePBO() {
 		i.graphics.context.texSubImage2D(i.textureNative, args)
 		return