Address Copilot: cache shared gradient render, doc scratch array, fix test name

- Gradient: skip re-render when same gradient/coords already on shared target
- dashPath: document return value as internal scratch array
- Fix test description for all-zero pattern behavior

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: obiot

packages/melonjs/src/video/gradient.js

@@ -11,6 +11,9 @@ import CanvasRenderTarget from "./rendertarget/canvasrendertarget.js";
  * @ignore
  */
 let sharedRenderTarget = null;
+let sharedLastGradient = null;
+let sharedLastX = NaN;
+let sharedLastY = NaN;
 
 /**
  * A Gradient object representing a linear or radial gradient fill.
@@ -144,6 +147,20 @@ export class Gradient {
 		const tw = nextPowerOfTwo(Math.max(1, Math.ceil(width)));
 		const th = nextPowerOfTwo(Math.max(1, Math.ceil(height)));
 
+		// skip if this gradient already rendered to the shared target at these coords
+		if (
+			sharedRenderTarget &&
+			sharedLastGradient === this &&
+			!this._dirty &&
+			sharedLastX === x &&
+			sharedLastY === y &&
+			sharedRenderTarget.width === tw &&
+			sharedRenderTarget.height === th
+		) {
+			this._renderTarget = sharedRenderTarget;
+			return this._renderTarget.canvas;
+		}
+
 		// reuse the shared render target to avoid GPU memory leaks
 		if (!sharedRenderTarget) {
 			sharedRenderTarget = new CanvasRenderTarget(tw, th);
@@ -189,6 +206,9 @@ export class Gradient {
 		ctx.fillRect(0, 0, tw, th);
 
 		this._dirty = false;
+		sharedLastGradient = this;
+		sharedLastX = x;
+		sharedLastY = y;
 		this._renderTarget.invalidate(renderer);
 		return this._renderTarget.canvas;
 	}

packages/melonjs/src/video/utils/dash.js

@@ -3,7 +3,7 @@
  * Carries the dash state across segment boundaries for continuous dashing.
  * @param {Array<{x: number, y: number}>} pts - pairs of start/end points
  * @param {number[]} pattern - dash pattern [on, off, on, off, ...]
- * @returns {Array<{x: number, y: number}>} dashed segment pairs
+ * @returns {Array<{x: number, y: number}>} dashed segment pairs (internal scratch array — consume immediately, do not store)
  */
 // pre-allocated scratch array to avoid per-frame allocations
 const _dashPathResult = [];

packages/melonjs/tests/dash.spec.js

@@ -81,7 +81,7 @@ describe("dash utilities", () => {
 			expect(multiSeg.length).toEqual(singleSeg.length);
 		});
 
-		it("should return copy for all-zero pattern", () => {
+		it("should return original points for all-zero pattern", () => {
 			const pts = [
 				{ x: 0, y: 0 },
 				{ x: 100, y: 0 },