Revert "internal/ui: bug fix: panic at ReadPixels before running"

This reverts commit 2f6df3d4d6.

Reason: regression by calling (*ebiten.Image).At from a different goroutine

Updates #2820

internal/processtest/testdata/issue2820.go

@@ -1,47 +0,0 @@
-// Copyright 2023 The Ebitengine Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//go:build ignore
-
-package main
-
-import (
-	"time"
-
-	"github.com/hajimehoshi/ebiten/v2"
-)
-
-func init() {
-	defer func() {
-		if e := recover(); e == nil {
-			panic("(*ebiten.Image).At before the main loop must panic but not (1)")
-		}
-	}()
-
-	done := make(chan struct{})
-	go func() {
-		select {
-		case <-done:
-			panic("(*ebiten.Image).At before the main loop must panic but not (2)")
-		case <-time.After(time.Second):
-			panic("(*ebiten.Image).At times out unexpectedly")
-		}
-	}()
-	img := ebiten.NewImage(1, 1)
-	img.At(0, 0)
-	close(done)
-}
-
-func main() {
-}

internal/ui/image.go

@@ -154,10 +154,6 @@ func (i *Image) WritePixels(pix []byte, region image.Rectangle) {
 }
 
 func (i *Image) ReadPixels(pixels []byte, region image.Rectangle) {
-	if !i.ui.isRunning() {
-		panic("ui: ReadPixels cannot be called before the game starts")
-	}
-
 	// Check the error existence and avoid unnecessary calls.
 	if i.ui.error() != nil {
 		return

internal/ui/input_js.go

@@ -200,7 +200,7 @@ func init() {
 }
 
 func (u *UserInterface) KeyName(key Key) string {
-	if !u.isRunning() {
+	if !u.running {
 		return ""
 	}
 

internal/ui/run_glfw_notsinglethread.go

@@ -26,6 +26,8 @@ import (
 )
 
 func (u *UserInterface) Run(game Game, options *RunOptions) error {
+	u.context = newContext(game)
+
 	u.mainThread = thread.NewOSThread()
 	u.renderThread = thread.NewOSThread()
 	graphicscommand.SetRenderThread(u.renderThread)
@@ -36,8 +38,6 @@ func (u *UserInterface) Run(game Game, options *RunOptions) error {
 	u.setRunning(true)
 	defer u.setRunning(false)
 
-	u.context = newContext(game)
-
 	if err := u.initOnMainThread(options); err != nil {
 		return err
 	}

internal/ui/run_glfw_singlethread.go

@@ -22,6 +22,8 @@ import (
 )
 
 func (u *UserInterface) Run(game Game, options *RunOptions) error {
+	u.context = newContext(game)
+
 	// Initialize the main thread first so the thread is available at u.run (#809).
 	u.mainThread = thread.NewNoopThread()
 	u.renderThread = thread.NewNoopThread()
@@ -30,8 +32,6 @@ func (u *UserInterface) Run(game Game, options *RunOptions) error {
 	u.setRunning(true)
 	defer u.setRunning(false)
 
-	u.context = newContext(game)
-
 	if err := u.initOnMainThread(options); err != nil {
 		return err
 	}

internal/ui/ui.go

@@ -74,8 +74,6 @@ type UserInterface struct {
 
 	isScreenClearedEveryFrame int32
 	graphicsLibrary           int32
-	running                   int32
-	terminated                int32
 
 	whiteImage *Image
 
@@ -178,23 +176,3 @@ func (u *UserInterface) setGraphicsLibrary(library GraphicsLibrary) {
 func (u *UserInterface) GraphicsLibrary() GraphicsLibrary {
 	return GraphicsLibrary(atomic.LoadInt32(&u.graphicsLibrary))
 }
-
-func (u *UserInterface) isRunning() bool {
-	return atomic.LoadInt32(&u.running) != 0 && !u.isTerminated()
-}
-
-func (u *UserInterface) setRunning(running bool) {
-	if running {
-		atomic.StoreInt32(&u.running, 1)
-	} else {
-		atomic.StoreInt32(&u.running, 0)
-	}
-}
-
-func (u *UserInterface) isTerminated() bool {
-	return atomic.LoadInt32(&u.terminated) != 0
-}
-
-func (u *UserInterface) setTerminated() {
-	atomic.StoreInt32(&u.terminated, 1)
-}

internal/ui/ui_glfw.go

@@ -24,6 +24,7 @@ import (
 	"os"
 	"runtime"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/file"
@@ -60,6 +61,8 @@ type userInterfaceImpl struct {
 	maxWindowWidthInDIP  int
 	maxWindowHeightInDIP int
 
+	running              uint32
+	terminated           uint32
 	runnableOnUnfocused  bool
 	fpsMode              FPSModeType
 	iconImages           []image.Image
@@ -283,6 +286,26 @@ func (u *UserInterface) Monitor() *Monitor {
 	return monitor
 }
 
+func (u *UserInterface) isRunning() bool {
+	return atomic.LoadUint32(&u.running) != 0 && !u.isTerminated()
+}
+
+func (u *UserInterface) isTerminated() bool {
+	return atomic.LoadUint32(&u.terminated) != 0
+}
+
+func (u *UserInterface) setRunning(running bool) {
+	if running {
+		atomic.StoreUint32(&u.running, 1)
+	} else {
+		atomic.StoreUint32(&u.running, 0)
+	}
+}
+
+func (u *UserInterface) setTerminated() {
+	atomic.StoreUint32(&u.terminated, 1)
+}
+
 // setWindowMonitor must be called on the main thread.
 func (u *UserInterface) setWindowMonitor(monitor *Monitor) error {
 	if microsoftgdk.IsXbox() {

internal/ui/ui_js.go

@@ -91,6 +91,7 @@ type userInterfaceImpl struct {
 	runnableOnUnfocused bool
 	fpsMode             FPSModeType
 	renderingScheduled  bool
+	running             bool
 	cursorMode          CursorMode
 	cursorPrevMode      CursorMode
 	captureCursorLater  bool
@@ -743,9 +744,6 @@ func (u *UserInterface) forceUpdateOnMinimumFPSMode() {
 }
 
 func (u *UserInterface) Run(game Game, options *RunOptions) error {
-	u.setRunning(true)
-	defer u.setRunning(false)
-
 	if !options.InitUnfocused && window.Truthy() {
 		// Do not focus the canvas when the current document is in an iframe.
 		// Otherwise, the parent page tries to focus the iframe on every loading, which is annoying (#1373).
@@ -754,7 +752,7 @@ func (u *UserInterface) Run(game Game, options *RunOptions) error {
 			canvas.Call("focus")
 		}
 	}
-
+	u.running = true
 	g, lib, err := newGraphicsDriver(&graphicsDriverCreatorImpl{
 		canvas: canvas,
 	}, options.GraphicsLibrary)

internal/ui/ui_mobile.go

@@ -269,6 +269,8 @@ func (u *UserInterface) run(game Game, mainloop bool, options *RunOptions) (err
 		}
 	}()
 
+	u.context = newContext(game)
+
 	var mgl gl.Context
 	if mainloop {
 		// When gomobile-build is used, GL functions must be called via
@@ -279,11 +281,6 @@ func (u *UserInterface) run(game Game, mainloop bool, options *RunOptions) (err
 		graphicscommand.SetRenderThread(u.renderThread)
 	}
 
-	u.setRunning(true)
-	defer u.setRunning(false)
-
-	u.context = newContext(game)
-
 	g, lib, err := newGraphicsDriver(&graphicsDriverCreatorImpl{
 		gomobileContext: mgl,
 	}, options.GraphicsLibrary)

internal/ui/ui_nintendosdk.go

@@ -84,15 +84,7 @@ func (u *UserInterface) init() error {
 }
 
 func (u *UserInterface) Run(game Game, options *RunOptions) error {
-	u.mainThread = thread.NewOSThread()
-	u.renderThread = thread.NewOSThread()
-	graphicscommand.SetRenderThread(u.renderThread)
-
-	u.setRunning(true)
-	defer u.setRunning(false)
-
 	u.context = newContext(game)
-
 	g, lib, err := newGraphicsDriver(&graphicsDriverCreatorImpl{}, options.GraphicsLibrary)
 	if err != nil {
 		return err
@@ -107,6 +99,10 @@ func (u *UserInterface) Run(game Game, options *RunOptions) error {
 
 	initializeProfiler()
 
+	u.mainThread = thread.NewOSThread()
+	u.renderThread = thread.NewOSThread()
+	graphicscommand.SetRenderThread(u.renderThread)
+
 	ctx, cancel := stdcontext.WithCancel(stdcontext.Background())
 	defer cancel()
 

internal/ui/ui_playstation5.go

@@ -64,9 +64,6 @@ func (u *UserInterface) init() error {
 }
 
 func (u *UserInterface) Run(game Game, options *RunOptions) error {
-	u.setRunning(true)
-	defer u.setRunning(false)
-
 	// TODO: Implement this.
 	return nil
 }