From 965fd4cac8e58f8e05ab1a98349ac8b9a3440a90 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 25 Feb 2023 23:11:39 +0900
Subject: [PATCH] internal/restoring: bug fix: stop keeping pixel data on 32bit
 architecture

Updates #4259
---
 internal/restorable/image.go  | 7 +++++++
 internal/restorable/images.go | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/internal/restorable/image.go b/internal/restorable/image.go
index 5e009e7e9..ef7c8703a 100644
--- a/internal/restorable/image.go
+++ b/internal/restorable/image.go
@@ -446,6 +446,13 @@ func (i *Image) readPixelsFromGPUIfNeeded(graphicsDriver graphicsdriver.Graphics
 }
 
 func (i *Image) ReadPixels(graphicsDriver graphicsdriver.Graphics, pixels []byte, x, y, width, height int) error {
+	if alwaysReadPixelsFromGPU() {
+		if err := i.image.ReadPixels(graphicsDriver, pixels, x, y, width, height); err != nil {
+			return err
+		}
+		return nil
+	}
+
 	if err := i.readPixelsFromGPUIfNeeded(graphicsDriver); err != nil {
 		return err
 	}
diff --git a/internal/restorable/images.go b/internal/restorable/images.go
index 6730bac7d..c49a9111f 100644
--- a/internal/restorable/images.go
+++ b/internal/restorable/images.go
@@ -16,6 +16,7 @@ package restorable
 
 import (
 	"runtime"
+	"unsafe"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/debug"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
@@ -32,6 +33,12 @@ func needsRestoring() bool {
 	return forceRestoring || needsRestoringByGraphicsDriver
 }
 
+// alwaysReadPixelsFromGPU reports whether ReadPixels alwasy reads pixels from GPU or not.
+// This is true for low-end machines like 32bit architecture without much memory.
+func alwaysReadPixelsFromGPU() bool {
+	return !needsRestoring() && unsafe.Sizeof(uintptr(0)) < 8
+}
+
 // EnableRestoringForTesting forces to enable restoring for testing.
 func EnableRestoringForTesting() {
 	forceRestoring = true