From cc1accc32a347b4131e01bfefeffd3e96a150390 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Fri, 6 Aug 2021 03:08:01 +0900
Subject: [PATCH] internal/uidriver/glfw: Bug fix: Disable vsync when resizing
 the window

Closes #1740
---
 internal/graphicsdriver/metal/view.go | 9 ++++++++-
 internal/uidriver/glfw/ui.go          | 8 +++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/internal/graphicsdriver/metal/view.go b/internal/graphicsdriver/metal/view.go
index 381fc2323..10a12a3c2 100644
--- a/internal/graphicsdriver/metal/view.go
+++ b/internal/graphicsdriver/metal/view.go
@@ -30,6 +30,7 @@ type view struct {
 
 	windowChanged bool
 	vsync         bool
+	vsyncInited   bool
 
 	device mtl.Device
 	ml     ca.MetalLayer
@@ -46,8 +47,12 @@ func (v *view) getMTLDevice() mtl.Device {
 }
 
 func (v *view) setDisplaySyncEnabled(enabled bool) {
+	if v.vsync == enabled && !v.vsyncInited {
+		return
+	}
 	v.ml.SetDisplaySyncEnabled(enabled)
 	v.vsync = enabled
+	v.vsyncInited = true
 }
 
 func (v *view) colorPixelFormat() mtl.PixelFormat {
@@ -75,7 +80,9 @@ func (v *view) reset() error {
 	v.ml.SetMaximumDrawableCount(2)
 
 	// The vsync state might be reset. Set the state again (#1364).
-	v.ml.SetDisplaySyncEnabled(v.vsync)
+	if v.vsyncInited {
+		v.ml.SetDisplaySyncEnabled(v.vsync)
+	}
 	v.ml.SetFramebufferOnly(true)
 
 	return nil
diff --git a/internal/uidriver/glfw/ui.go b/internal/uidriver/glfw/ui.go
index f4cfe249b..edfef9cc2 100644
--- a/internal/uidriver/glfw/ui.go
+++ b/internal/uidriver/glfw/ui.go
@@ -781,6 +781,9 @@ func (u *UserInterface) registerWindowSetSizeCallback() {
 			}
 
 			if err := u.runOnAnotherThreadFromMainThread(func() error {
+				// Disable Vsync temporarily. On macOS, getting a next frame can get stuck (#1740).
+				u.Graphics().SetVsyncEnabled(false)
+
 				var outsideWidth, outsideHeight float64
 				var outsideSizeChanged bool
 
@@ -967,10 +970,13 @@ func (u *UserInterface) update() (float64, float64, bool, error) {
 	// Calling this inside setWindowSize didn't work (#1363).
 	if !u.fpsModeInited {
 		u.fpsMode = u.getInitFPSMode()
-		u.updateVsync()
 		u.fpsModeInited = true
 	}
 
+	// Call updateVsync even though fpsMode is not updated.
+	// The vsync state might be changed in other places (e.g., the SetSizeCallback).
+	u.updateVsync()
+
 	outsideWidth, outsideHeight, outsideSizeChanged := u.updateSize()
 
 	if u.fpsMode != driver.FPSModeVsyncOffMinimum {