From 151dfffad6f57561fa2ffa9b84d93468a43f1581 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Wed, 23 Mar 2022 02:45:57 +0900
Subject: [PATCH] internal/restorable: simplify canDetectContextLostExplicitly

This constant was set with some wrong assumptions:

 1. On Android, recovering was needed.
 2. On iOS, OpenGL ES was used when
    a. The architecture was 386 or amd64 == an emulator is used
    b. The build tag ebitengl was not specified
    c. gomobile-build was used
 3. On browsers, recovering was needed.

1., 2b, and 2c are correct.

2a. is not correct: Now emulators are available on all the
architectures with both Metal and OpenGL.

3. is not correct: Ebiten no longer recovers the contest lost.

Now, Ebiten can detect a context lost explicitly when

 1. On Android
 2. On iOS and on gomobile-build
    (When gomobile-build is used, OpenGL should always be used)

Based on this fact, this change changes the constant to a variable,
and fixes the logic to set the variable.
---
 internal/restorable/const_gles.go   | 20 --------------------
 internal/restorable/const_js.go     | 18 ------------------
 internal/restorable/const_others.go | 22 ----------------------
 internal/restorable/images.go       | 10 +++++++---
 4 files changed, 7 insertions(+), 63 deletions(-)
 delete mode 100644 internal/restorable/const_gles.go
 delete mode 100644 internal/restorable/const_js.go
 delete mode 100644 internal/restorable/const_others.go

diff --git a/internal/restorable/const_gles.go b/internal/restorable/const_gles.go
deleted file mode 100644
index 9b8dcd35a..000000000
--- a/internal/restorable/const_gles.go
+++ /dev/null
@@ -1,20 +0,0 @@
-// Copyright 2020 The Ebiten 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 android || (ios && ebitengl)
-// +build android ios,ebitengl
-
-package restorable
-
-const canDetectContextLostExplicitly = true
diff --git a/internal/restorable/const_js.go b/internal/restorable/const_js.go
deleted file mode 100644
index 71de15d31..000000000
--- a/internal/restorable/const_js.go
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright 2020 The Ebiten 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.
-
-package restorable
-
-// canDetectContextLostExplicitly reports whether the context lost can be detected by handlers in an explicit way.
-const canDetectContextLostExplicitly = true
diff --git a/internal/restorable/const_others.go b/internal/restorable/const_others.go
deleted file mode 100644
index 90c07cb79..000000000
--- a/internal/restorable/const_others.go
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright 2020 The Ebiten 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 !android && !js && (!ios || !ebitengl)
-// +build !android
-// +build !js
-// +build !ios !ebitengl
-
-package restorable
-
-const canDetectContextLostExplicitly = false
diff --git a/internal/restorable/images.go b/internal/restorable/images.go
index 218dc060a..0601df01c 100644
--- a/internal/restorable/images.go
+++ b/internal/restorable/images.go
@@ -17,6 +17,7 @@ package restorable
 import (
 	"image"
 	"path/filepath"
+	"runtime"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/debug"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicscommand"
@@ -292,8 +293,11 @@ func MaxImageSize(graphicsDriver graphicsdriver.Graphics) int {
 
 // OnContextLost is called when the context lost is detected in an explicit way.
 func OnContextLost() {
-	if !canDetectContextLostExplicitly {
-		panic("restorable: OnContextLost cannot be called in this environment")
-	}
+	canDetectContextLostExplicitly = true
 	theImages.contextLost = true
 }
+
+// canDetectContextLostExplicitly reports whether Ebiten can detect a context lost in an explicit way.
+// On Android, a context lost can be detected via GLSurfaceView.Renderer.onSurfaceCreated.
+// On iOS w/ OpenGL ES, this can be detected only when gomobile-build is used.
+var canDetectContextLostExplicitly = runtime.GOOS == "android"