From fcd4453e4fab81a18427fc584ed9a4952ee722b1 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Mon, 14 Feb 2022 01:49:39 +0900
Subject: [PATCH] ebiten: remove RunOnMainThread

Unfortunately, there are several issues in RunOnMainThread:

 * RunOnMainThread cannot be portable: It is impossible to implement this
   correctly on mobiles.
 * RunOnMainThread doesn't make sense on mobiles: the rendering works on
   a different thread (goroutine) on mobiles.
 * RunOnMainThread can cause deadlocks very easily.

Until we find a better solution, let's remove this.

Closes #1945
---
 internal/graphicscommand/command.go | 8 ++++----
 internal/graphicscommand/thread.go  | 4 ++--
 run.go                              | 6 ------
 3 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/internal/graphicscommand/command.go b/internal/graphicscommand/command.go
index f1c9f5c73..889893d23 100644
--- a/internal/graphicscommand/command.go
+++ b/internal/graphicscommand/command.go
@@ -225,7 +225,7 @@ func (q *commandQueue) Enqueue(command command) {
 
 // Flush flushes the command queue.
 func (q *commandQueue) Flush() (err error) {
-	RunOnRenderingThread(func() {
+	runOnRenderingThread(func() {
 		err = q.flush()
 	})
 	return
@@ -701,7 +701,7 @@ func (c *newShaderCommand) Exec(indexOffset int) error {
 
 // InitializeGraphicsDriverState initialize the current graphics driver state.
 func InitializeGraphicsDriverState() (err error) {
-	RunOnRenderingThread(func() {
+	runOnRenderingThread(func() {
 		err = theGraphicsDriver.Initialize()
 	})
 	return
@@ -711,7 +711,7 @@ func InitializeGraphicsDriverState() (err error) {
 // If the graphics driver doesn't have an API to reset, ResetGraphicsDriverState does nothing.
 func ResetGraphicsDriverState() (err error) {
 	if r, ok := theGraphicsDriver.(interface{ Reset() error }); ok {
-		RunOnRenderingThread(func() {
+		runOnRenderingThread(func() {
 			err = r.Reset()
 		})
 	}
@@ -721,7 +721,7 @@ func ResetGraphicsDriverState() (err error) {
 // MaxImageSize returns the maximum size of an image.
 func MaxImageSize() int {
 	var size int
-	RunOnRenderingThread(func() {
+	runOnRenderingThread(func() {
 		size = theGraphicsDriver.MaxImageSize()
 	})
 	return size
diff --git a/internal/graphicscommand/thread.go b/internal/graphicscommand/thread.go
index 408e510a9..dcb7d9d61 100644
--- a/internal/graphicscommand/thread.go
+++ b/internal/graphicscommand/thread.go
@@ -25,8 +25,8 @@ func SetRenderingThread(thread Thread) {
 	theThread = thread
 }
 
-// RunOnRenderingThread calls f on the rendering thread, and returns an error if any.
-func RunOnRenderingThread(f func()) {
+// runOnRenderingThread calls f on the rendering thread, and returns an error if any.
+func runOnRenderingThread(f func()) {
 	// The thread is nil when 1) GOOS=js or 2) using golang.org/x/mobile/gl.
 	// When golang.org/x/mobile/gl is used, all the GL functions are called via Context, which already runs on an
 	// appropriate thread.
diff --git a/run.go b/run.go
index f4e024e28..3246cdcb1 100644
--- a/run.go
+++ b/run.go
@@ -18,7 +18,6 @@ import (
 	"sync/atomic"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/clock"
-	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
 	"github.com/hajimehoshi/ebiten/v2/internal/ui"
 )
 
@@ -162,11 +161,6 @@ func RunGame(game Game) error {
 	return nil
 }
 
-// RunOnMainThread calls the given f on the main thread, and blocks until f returns.
-func RunOnMainThread(f func()) {
-	graphicscommand.RunOnRenderingThread(f)
-}
-
 func isRunGameEnded() bool {
 	return atomic.LoadInt32(&isRunGameEnded_) != 0
 }