From 99902e0ab497ae56575d562b877b26437416ea91 Mon Sep 17 00:00:00 2001
From: Zsolt Tasnadi <rastasi@gmail.com>
Date: Thu, 30 Jul 2026 07:23:20 +0200
Subject: [PATCH] add AssetFS hook so assets can load from an embed.FS
 (js/wasm)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 asset.audio.go   |  3 +--
 asset.fs.go      | 31 +++++++++++++++++++++++++++++++
 asset.manager.go |  3 +--
 3 files changed, 33 insertions(+), 4 deletions(-)
 create mode 100644 asset.fs.go

diff --git a/asset.audio.go b/asset.audio.go
index eedfbed..d152ad5 100644
--- a/asset.audio.go
+++ b/asset.audio.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"os"
 	"path/filepath"
 	"strings"
 
@@ -174,7 +173,7 @@ type audioStream interface {
 }
 
 func decodeAudioStream(path string, sampleRate int) (audioStream, int64, error) {
-	f, err := os.Open(path)
+	f, err := openAsset(path)
 	if err != nil {
 		return nil, 0, err
 	}
diff --git a/asset.fs.go b/asset.fs.go
new file mode 100644
index 0000000..ae57eee
--- /dev/null
+++ b/asset.fs.go
@@ -0,0 +1,31 @@
+package pncdsl
+
+import (
+	"io/fs"
+	"os"
+)
+
+// AssetFS, when non-nil, is the filesystem asset files (images, audio)
+// are read from instead of the OS filesystem. Set it to an embed.FS
+// before Run to ship assets inside the binary — required for js/wasm
+// builds, where there is no OS filesystem and every asset would fall
+// back to a placeholder:
+//
+//	//go:embed assets
+//	var assetsFS embed.FS
+//
+//	func init() { pncdsl.AssetFS = assetsFS }
+//
+// Asset.Path values are used as-is, so they must be slash-separated
+// and relative (e.g. "assets/bg/bedroom.png") — the same form that
+// works with os.Open from the project root.
+var AssetFS fs.FS
+
+// openAsset opens an asset file honoring AssetFS. Every asset read in
+// the package goes through here.
+func openAsset(path string) (fs.File, error) {
+	if AssetFS != nil {
+		return AssetFS.Open(path)
+	}
+	return os.Open(path)
+}
diff --git a/asset.manager.go b/asset.manager.go
index 5ae9c1c..4fd81e2 100644
--- a/asset.manager.go
+++ b/asset.manager.go
@@ -6,7 +6,6 @@ import (
 	"image/color"
 	_ "image/jpeg"
 	_ "image/png"
-	"os"
 
 	"github.com/hajimehoshi/ebiten/v2"
 )
@@ -57,7 +56,7 @@ func (la *loadedAssets) isPlaceholder(name string) bool {
 }
 
 func loadImageFile(path string) *ebiten.Image {
-	f, err := os.Open(path)
+	f, err := openAsset(path)
 	if err != nil {
 		return nil
 	}