fix(CAD-13): mirror existing DB elements into pixi renderer - cachedElements was 0 for old projects (only new V2 elements reached pixi), skipElementRendering fallback restored on pixi failure

frontend/src/components/CanvasArea.tsx

@@ -39,6 +39,8 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
   const pixiCanvasRef = useRef<HTMLCanvasElement>(null);
   /** Task C2: Aktiver PixiJS-Renderer (für Cleanup). */
   const pixiRendererRef = useRef<PixiRenderer | null>(null);
+  /** CAD-13-fix: Bereits in Pixi gespiegelte Bestands-Elemente (id -> Referenz). */
+  const pixiMirrorRef = useRef<Map<string, CADElement>>(new Map());
   /** Bereits an onElementCreated gemeldete V2-Element-IDs (verhindert Doppelmeldung bei jedem onChanged-Frame). */
   const announcedV2Ids = useRef<Set<string>>(new Set());
   const spatialIndexRef = useRef<SpatialIndex | null>(null);
@@ -95,11 +97,17 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
             logger.warn('Pixi init failed — V2-Overlay deaktiviert:', err);
             pixi = null;
             pixiRendererRef.current = null;
+            // CAD-13-fix Fallback: Ohne Pixi muss Legacy wieder Elemente zeichnen
+            renderEngine.skipElementRendering = false;
+            renderEngine.render();
           });
         } catch (err) {
           logger.warn('Pixi init exception — V2-Overlay deaktiviert:', err);
           pixi = null;
           pixiRendererRef.current = null;
+          // CAD-13-fix Fallback: Ohne Pixi muss Legacy wieder Elemente zeichnen
+          renderEngine.skipElementRendering = false;
+          renderEngine.render();
         }
       }
       /** Letztes bekanntes Elementobjekt je ID (Referenzdiff statt JSON). */
@@ -297,8 +305,40 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
     spatialIndex.clear();
     spatialIndex.bulkInsert(elements);
     renderEngine.render();
+
+    // CAD-13-fix: Bestands-Elemente (aus DB geladen) müssen in Pixi gespiegelt
+    // werden — nur NEUE V2-Elemente laufen über v2Doc.onChanged in syncPixi.
+    // Ohne diesen Mirror blieben Alt-Projekte leer (Legacy skippt ja jetzt).
+    const pixi = pixiRendererRef.current;
+    if (pixi && renderEngine.skipElementRendering) {
+      void pixi.waitForReady().then(() => {
+        const mirror = pixiMirrorRef.current;
+        const currentIds = new Set<string>();
+        const layerFallback = {
+          id: 'layer-0', name: 'Standard', visible: true, locked: false,
+          color: '#ffffff', lineType: 'solid', transparency: 0,
+          sortOrder: 0, parentId: null,
+        } as never;
+        for (const el of elements) {
+          currentIds.add(el.id);
+          if (mirror.get(el.id) !== el) {
+            mirror.set(el.id, el);
+            const layer = layers.find((l) => l.id === el.layerId) ?? layerFallback;
+            pixi.drawElement(el, layer, {
+              color: '#ffffff', lineType: 'solid', transparency: 0, visible: true,
+            });
+          }
+        }
+        for (const id of Array.from(mirror.keys())) {
+          if (!currentIds.has(id)) {
+            mirror.delete(id);
+            pixi.removeElement(id);
+          }
+        }
+      });
+    }
   // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [elements]);
+  }, [elements, layers]);
 
   // Sync layers to LayerManager + render
   useEffect(() => {