From 9298b044e32ec929b28666cecfd72cb98a02dc96 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Tue, 11 Feb 2020 20:28:15 +0900
Subject: [PATCH] graphicsdriver/metal: Bug fix: avoid using
 mtl.LoadActionDontCare

Fixes #1019
---
 internal/graphicsdriver/metal/driver.go | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/internal/graphicsdriver/metal/driver.go b/internal/graphicsdriver/metal/driver.go
index ed0a8ab49..850eab600 100644
--- a/internal/graphicsdriver/metal/driver.go
+++ b/internal/graphicsdriver/metal/driver.go
@@ -587,13 +587,11 @@ func (d *Driver) Draw(indexLen int, indexOffset int, mode driver.CompositeMode,
 		d.view.update()
 
 		rpd := mtl.RenderPassDescriptor{}
-		if d.dst.screen {
-			rpd.ColorAttachments[0].LoadAction = mtl.LoadActionDontCare
-			rpd.ColorAttachments[0].StoreAction = mtl.StoreActionStore
-		} else {
-			rpd.ColorAttachments[0].LoadAction = mtl.LoadActionLoad
-			rpd.ColorAttachments[0].StoreAction = mtl.StoreActionStore
-		}
+		// Even though the destination pixels are not used, mtl.LoadActionDontCare might cause glitches
+		// (#1019). Always using mtl.LoadActionLoad is safe.
+		rpd.ColorAttachments[0].LoadAction = mtl.LoadActionLoad
+		rpd.ColorAttachments[0].StoreAction = mtl.StoreActionStore
+
 		var t mtl.Texture
 		if d.dst.screen {
 			if d.screenDrawable == (ca.MetalDrawable{}) {