#3

frontend/src/App.tsx

@@ -78,6 +78,7 @@ export default () => {
 
   return (
       <BrowserRouter>
+	<ScrollToTop />
 	<div className={cn ('w-screen min-h-screen',
 			    colours[colourIndex],
 			    'transition-colors duration-[3s] ease-linear')}>
@@ -105,7 +106,6 @@ export default () => {
 	    </header>
 	    <main className="mb-8">
 	      <Routes>
-		<ScrollToTop />
 		<Route path="/" element={<Navigate to="/threads" replace />} />
 		<Route path="/threads" element={<ThreadListPage />} />
 		<Route path="/threads/:id" element={<ThreadDetailPage />} />

frontend/src/components/threads/ThreadCanvas.tsx

@@ -29,6 +29,27 @@ const Mode = {
 type Mode = (typeof Mode)[keyof typeof Mode]
 
 
+const isLayer = (obj: unknown): obj is Layer => (
+    typeof obj === 'object'
+    && obj !== null
+    && typeof (obj as Layer).id === 'string'
+    && typeof (obj as Layer).name === 'string'
+    && Array.isArray ((obj as Layer).lines)
+    && (obj as Layer).lines.every (isLine)
+    && Array.isArray ((obj as Layer).history)
+    && Array.isArray ((obj as Layer).future))
+
+
+const isLine = (obj: unknown): obj is Line => (
+    typeof obj === 'object'
+    && obj !== null
+    && Array.isArray ((obj as Line).points)
+    && (obj as Line).points.every (n => typeof n === 'number')
+    && typeof (obj as Line).stroke === 'string'
+    && typeof (obj as Line).strokeWidth === 'number'
+    && Object.values (Mode).includes ((obj as Line).mode))
+
+
 export default () => {
   const drawingRef = useRef (false)
   const fileInputRef = useRef<HTMLInputElement> (null)
@@ -84,19 +105,21 @@ export default () => {
   const handleUndo = () => {
     if (!(activeLayer) || activeLayer.lines.length === 0)
       return
-    const newLines = [...activeLayer.lines]
-    newLines.pop()
+
+    const prev = activeLayer.lines.slice (0, -1)
+    const popped = activeLayer.lines[activeLayer.lines.length - 1]
     updateActiveLayerHistory ([...activeLayer.history, activeLayer.lines])
-    updateActiveLayerFuture ([])
-    updateActiveLayerLines (newLines)
+    updateActiveLayerFuture ([popped, ...activeLayer.future])
+    updateActiveLayerLines (prev)
   }
 
   const handleRedo = () => {
-    if (!(activeLayer) || activeLayer.history.length === 0)
+    if (!(activeLayer) || activeLayer.future.length === 0)
       return
-    const prev = activeLayer.history[activeLayer.history.length - 1]
-    updateActiveLayerLines (prev)
-    updateActiveLayerHistory (activeLayer.history.slice (0, -1))
+
+    const [redoStroke, ...rest] = activeLayer.future
+    updateActiveLayerLines ([...activeLayer.lines, redoStroke])
+    updateActiveLayerFuture (rest)
   }
 
   const handleImportImage: ChangeEventHandler<HTMLInputElement> = ev => {
@@ -152,19 +175,25 @@ export default () => {
     return layer
   }
 
+  const canMoveLayer = (direction: number) => {
+    const idx = layers.findIndex (l => l.id === activeLayerId)
+    if (idx < 0)
+      return false
+
+    const target = idx + direction
+    return 0 <= target && target < layers.length
+  }
+
   const moveLayer = (direction: number) => {
-    setLayers(prev => {
-      const idx = prev.findIndex (l => l.id === activeLayerId)
-      if (idx < 0)
-	return prev
-      const target = idx + direction
-      if (target < 0 || target >= prev.length)
-	return prev
-      const next = [...prev]
-      const [item] = next.splice(idx, 1)
-      next.splice(target, 0, item)
-      return next
-    })
+    if (!(canMoveLayer (direction)))
+      return
+
+    const idx = layers.findIndex (l => l.id === activeLayerId)
+    const target = idx + direction
+    const next = [...layers]
+    const [item] = next.splice (idx, 1)
+    next.splice (target, 0, item)
+    setLayers(next)
   }
 
   const clearCanvas = () => {
@@ -183,16 +212,25 @@ export default () => {
   useEffect (() => {
     try
     {
-      const paintJSON = localStorage.getItem ('paint')
-      if (paintJSON == null)
+      const raw = localStorage.getItem ('paint')
+      if (!(raw))
 	throw new Error
 
-      const paint = JSON.parse (paintJSON)
-      if (!(paint instanceof Array))
+      const parsed: unknown = JSON.parse (raw)
+      if (!(Array.isArray (parsed)))
 	throw new Error
 
-      setLayers (paint)
-      setActiveLayerId (paint[0].id)
+      const restored: Layer[] = parsed.filter (isLayer).map (l => ({
+	  ...l, lines: l.lines.map (s => ({
+	      ...s, mode: (Object.values (Mode).includes (s.mode)
+			   ? s.mode
+			   : Mode.Pen) })) }))
+      if (restored.length === 0)
+	throw new Error
+
+      setLayers (restored)
+      setActiveLayerId (restored[0].id)
+      setLayerCnt (restored.length)
     }
     catch
     {
@@ -207,6 +245,7 @@ export default () => {
       if (layer.image && !(layer.id in images))
 	{
 	  const image = new window.Image
+	  image.crossOrigin = 'anonymous'
 	  image.src = layer.image.src
 	  image.onload = () => {
 	    setImages (prev => ({ ...prev, [layer.id]: image }))
@@ -256,7 +295,7 @@ export default () => {
 
 	    <div>
 	      <label>
-		幅：
+		幅（{stageWidth} px）：
 		<input type="range"
 		       min={32}
 		       max={640}
@@ -264,7 +303,7 @@ export default () => {
 		       onChange={ev => setStageWidth (+ev.target.value)} />
 	      </label>
 	      <label>
-		高さ：
+		高さ（{stageHeight} px）：
 		<input type="range"
 		       min={24}
 		       max={480}
@@ -295,10 +334,12 @@ export default () => {
 	  </div>
 
 	  <div>
-	    <button onClick={handleUndo} disabled={activeLayer?.lines.length === 0}>
+	    <button onClick={handleUndo}
+		    disabled={!(activeLayer) || activeLayer.lines.length === 0}>
 	      <FaUndo />
 	    </button>
-	    <button onClick={handleRedo} disabled={activeLayer?.history.length === 0}>
+	    <button onClick={handleRedo}
+		    disabled={!(activeLayer) || activeLayer.future.length === 0}>
 	      <FaRedo />
 	    </button>
 	  </div>
@@ -331,8 +372,8 @@ export default () => {
 			 onChange={() => setActiveLayerId (layer.id)} />
 		  {layer.name}
 		</label>))}
-	    <button onClick={() => {
-	      if (layers.length === 1)
+	    <button disabled={layers.length <= 1} onClick={() => {
+	      if (layers.length <= 1)
 		{
 		  alert ('何を消そうというのだ．')
 		  return
@@ -350,12 +391,12 @@ export default () => {
 	    }}>
 	      削除
 	    </button>
-	    <button onClick={() => {
+	    <button disabled={!(canMoveLayer (-1))} onClick={() => {
 	      moveLayer (-1)
 	    }}>
 	      下へ
 	    </button>
-	    <button onClick={() => {
+	    <button disabled={!(canMoveLayer (1))} onClick={() => {
 	      moveLayer (1)
 	    }}>
 	      上へ