auto: 2026-07-26 20:41 (ESD_LAPTOP)

B07_wf4_DesignDetail/openwebcad/src/drawControllers/screenCanvas.drawController.ts

@@ -238,6 +238,29 @@ export class ScreenCanvasDrawController implements DrawController {
 		this.context.fillStyle = fillColor;
 	}
 
+	/**
+	 * Temporarily redirect all draw calls to another 2d context (eg an
+	 * offscreen canvas used as static scene cache), reusing the current
+	 * offset/scale/canvasSize without touching state or react triggers.
+	 */
+	public withContext(temporaryContext: CanvasRenderingContext2D, renderFunction: () => void) {
+		const originalContext = this.context;
+		this.context = temporaryContext;
+		try {
+			renderFunction();
+		} finally {
+			this.context = originalContext;
+		}
+	}
+
+	/**
+	 * Blit a pre-rendered bitmap (static scene cache) onto the canvas at a
+	 * pixel offset. Used while panning to avoid re-stroking every entity.
+	 */
+	public blitImage(source: CanvasImageSource, dx: number, dy: number) {
+		this.context.drawImage(source, dx, dy);
+	}
+
 	public clear() {
 		if (this.canvasSize === null) return;