feat: Lifted useCanvasState() from DesignCanvas to App.tsx, threaded al…

- "app/src/App.tsx"
- "app/src/views/DesignCanvas.tsx"

GSD-Task: S01/T02

app/src/App.tsx

@@ -1,5 +1,7 @@
-import { useState } from 'react';
+import { useCallback, useRef, useState } from 'react';
+import type Konva from 'konva';
 import type { TraceMetadata } from './types/engine';
+import { useCanvasState } from './hooks/useCanvasState';
 import ImportConvert from './views/ImportConvert';
 import DesignCanvas from './views/DesignCanvas';
 import './App.css';
@@ -10,6 +12,13 @@ function App() {
   const [view, setView] = useState<ViewState>('import');
   const [svgResult, setSvgResult] = useState<string | null>(null);
   const [traceMetadata, setTraceMetadata] = useState<TraceMetadata | null>(null);
+  const [pngDataUrl, setPngDataUrl] = useState<string | null>(null);
+
+  // Lifted canvas state — shared between View 2 (DesignCanvas) and View 3 (ExportView)
+  const canvasState = useCanvasState(traceMetadata);
+
+  // Stage ref created here so View 3 can capture PNG from View 2's Konva stage
+  const stageRef = useRef<Konva.Stage | null>(null);
 
   const handleUseThis = (svgOutput: string, metadata: TraceMetadata) => {
     setSvgResult(svgOutput);
@@ -17,13 +26,40 @@ function App() {
     setView('canvas');
   };
 
+  const handleExport = useCallback(() => {
+    // Capture PNG data URL from the Konva stage before navigating away
+    if (stageRef.current) {
+      const dataUrl = stageRef.current.toDataURL({ pixelRatio: 2 });
+      setPngDataUrl(dataUrl);
+    }
+    setView('export');
+  }, []);
+
+  const handleBackToCanvas = useCallback(() => {
+    setView('canvas');
+  }, []);
+
   return (
     <div id="app">
       {view === 'import' && <ImportConvert onUseThis={handleUseThis} />}
       {view === 'canvas' && (
-        <DesignCanvas svgData={svgResult} traceMetadata={traceMetadata} />
+        <DesignCanvas
+          svgData={svgResult}
+          stageRef={stageRef}
+          onExport={handleExport}
+          {...canvasState}
+        />
+      )}
+      {view === 'export' && (
+        <div className="placeholder-view" data-testid="export-view">
+          <p>View 3: Export (placeholder)</p>
+          <p>PNG preview captured: {pngDataUrl ? 'Yes' : 'No'}</p>
+          <p>Objects: {canvasState.state.objects.length}</p>
+          <button type="button" onClick={handleBackToCanvas}>
+            ← Back to Design
+          </button>
+        </div>
       )}
-      {view === 'export' && <div className="placeholder-view">View 3: Export</div>}
     </div>
   );
 }

app/src/views/DesignCanvas.tsx

@@ -8,9 +8,8 @@
 
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import type Konva from 'konva';
-import type { TraceMetadata } from '../types/engine';
 import type { ArtboardConfig, CanvasObject, ImageObject } from '../types/canvas';
-import { useCanvasState } from '../hooks/useCanvasState';
+import type { UseCanvasStateReturn } from '../hooks/useCanvasState';
 import ArtboardSetup from '../components/canvas/ArtboardSetup';
 import KonvaStage from '../components/canvas/KonvaStage';
 import type { CanvasTool } from '../components/canvas/KonvaStage';
@@ -21,16 +20,16 @@ import ShapeProperties from '../components/canvas/ShapeProperties';
 import { toPx } from '../utils/artboardShapes';
 import styles from './DesignCanvas.module.css';
 
-interface DesignCanvasProps {
+export interface DesignCanvasProps extends UseCanvasStateReturn {
   svgData: string | null;
-  traceMetadata: TraceMetadata | null;
+  /** Ref to the Konva Stage, created in App.tsx for cross-view access (PNG export). */
+  stageRef: React.RefObject<Konva.Stage | null>;
+  /** Called when user clicks Export — App.tsx navigates to View 3. */
+  onExport: () => void;
 }
 
 export default function DesignCanvas({
   svgData,
-  traceMetadata,
-}: DesignCanvasProps) {
-  const {
   state,
   addObject,
   removeObject,
@@ -45,7 +44,9 @@ export default function DesignCanvas({
   redo,
   canUndo,
   canRedo,
-  } = useCanvasState(traceMetadata);
+  stageRef,
+  onExport,
+}: DesignCanvasProps) {
 
   const [activeTool, setActiveTool] = useState<CanvasTool>('pointer');
   const [showArtboardSetup, setShowArtboardSetup] = useState(true);
@@ -53,7 +54,6 @@ export default function DesignCanvas({
   const [showGrid, setShowGrid] = useState(false);
   const [zoomLevel, setZoomLevel] = useState(1);
 
-  const stageRef = useRef<Konva.Stage | null>(null);
   const canvasContainerRef = useRef<HTMLDivElement | null>(null);
   const [stageSize, setStageSize] = useState({ width: 800, height: 600 });
 
@@ -265,6 +265,15 @@ export default function DesignCanvas({
           onZoomOut={handleZoomOut}
           onZoomFit={handleZoomFit}
         />
+        <button
+          type="button"
+          className="canvas-tool-btn"
+          onClick={onExport}
+          title="Export design"
+          data-testid="export-btn"
+        >
+          ⤓ Export
+        </button>
       </div>
 
       {/* Main area: canvas + right panel */}