From 79f037f983a76cb8ee67722681e03a049305ef8b Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Tue, 17 May 2022 09:30:35 +0200
Subject: [PATCH] app: lock GPU context during present

The OpenGL backend needs it, but I keep forgetting to test it when
rearranging the window rendering code. The gogio X11 end-to-end test
tests this issue, but unfortunately it is disabled because of flakiness.

Fixes: https://todo.sr.ht/~eliasnaur/gio/412
Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 app/window.go | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/app/window.go b/app/window.go
index 292fa6e8..6169fde6 100644
--- a/app/window.go
+++ b/app/window.go
@@ -204,14 +204,16 @@ func (w *Window) validateAndProcess(d driver, size image.Point, sync bool, frame
 				return err
 			}
 		}
-		if w.gpu == nil && !w.nocontext {
+		if w.ctx != nil {
 			if err := w.ctx.Lock(); err != nil {
 				w.destroyGPU()
 				return err
 			}
+		}
+		if w.gpu == nil && !w.nocontext {
 			gpu, err := gpu.New(w.ctx.API())
-			w.ctx.Unlock()
 			if err != nil {
+				w.ctx.Unlock()
 				w.destroyGPU()
 				return err
 			}
@@ -219,6 +221,7 @@ func (w *Window) validateAndProcess(d driver, size image.Point, sync bool, frame
 		}
 		if w.gpu != nil {
 			if err := w.frame(frame, size); err != nil {
+				w.ctx.Unlock()
 				if errors.Is(err, errOutOfDate) {
 					// GPU surface needs refreshing.
 					sync = true
@@ -236,18 +239,16 @@ func (w *Window) validateAndProcess(d driver, size image.Point, sync bool, frame
 		if signal != nil {
 			signal <- struct{}{}
 		}
+		var err error
 		if w.gpu != nil {
-			return w.ctx.Present()
+			err = w.ctx.Present()
+			w.ctx.Unlock()
 		}
-		return nil
+		return err
 	}
 }
 
 func (w *Window) frame(frame *op.Ops, viewport image.Point) error {
-	if err := w.ctx.Lock(); err != nil {
-		return err
-	}
-	defer w.ctx.Unlock()
 	if runtime.GOOS == "js" {
 		// Use transparent black when Gio is embedded, to allow mixing of Gio and
 		// foreign content below.