fix(exporter): default Lightning render backend to webgl before webgpu

src/lib/exporter/modernFrameRenderer.test.ts

@@ -203,6 +203,59 @@ function createRenderer() {
 }
 
 describe("ModernFrameRenderer Pixi lifecycle", () => {
+	it("defaults to webgl before webgpu when no explicit backend is requested", async () => {
+		pixiApplicationInstancesMock.length = 0;
+		pixiInitializationErrorsMock.length = 0;
+		vi.stubGlobal("navigator", { gpu: {} });
+
+		try {
+			const renderer = createRenderer() as unknown as {
+				config: { preferredRenderBackend?: "webgl" | "webgpu" };
+				createPixiApplication: (
+					canvas: HTMLCanvasElement,
+				) => Promise<{ backend: "webgl" | "webgpu" }>;
+			};
+			delete renderer.config.preferredRenderBackend;
+
+			await expect(
+				renderer.createPixiApplication({} as HTMLCanvasElement),
+			).resolves.toMatchObject({
+				backend: "webgl",
+			});
+
+			expect(pixiApplicationInstancesMock).toHaveLength(1);
+		} finally {
+			vi.unstubAllGlobals();
+		}
+	});
+
+	it("falls back to webgpu when webgl initialization fails and no backend was requested", async () => {
+		pixiApplicationInstancesMock.length = 0;
+		pixiInitializationErrorsMock.length = 0;
+		pixiInitializationErrorsMock.push(new Error("WebGL initialization failed"), undefined);
+		vi.stubGlobal("navigator", { gpu: {} });
+
+		try {
+			const renderer = createRenderer() as unknown as {
+				config: { preferredRenderBackend?: "webgl" | "webgpu" };
+				createPixiApplication: (
+					canvas: HTMLCanvasElement,
+				) => Promise<{ backend: "webgl" | "webgpu" }>;
+			};
+			delete renderer.config.preferredRenderBackend;
+
+			await expect(
+				renderer.createPixiApplication({} as HTMLCanvasElement),
+			).resolves.toMatchObject({
+				backend: "webgpu",
+			});
+
+			expect(pixiApplicationInstancesMock).toHaveLength(2);
+		} finally {
+			vi.unstubAllGlobals();
+		}
+	});
+
 	it("continues to the next backend when failed-init cleanup would throw", async () => {
 		pixiApplicationInstancesMock.length = 0;
 		pixiInitializationErrorsMock.length = 0;

src/lib/exporter/modernFrameRenderer.ts

@@ -100,6 +100,7 @@ import { buildTemporalSamplePlanUs, getTemporalMotionBlurConfig } from "./tempor
 
 const TEMPORAL_ZOOM_MOTION_BLUR_ENABLED = false;
 
+import { getDefaultLightningRenderBackend } from "./backendPolicy";
 import type { ExportRenderBackend } from "./types";
 
 interface FrameRenderConfig {
@@ -639,15 +640,10 @@ export class FrameRenderer {
 			powerPreference: "high-performance" as const,
 		};
 
-		const preferredRenderBackend = this.config.preferredRenderBackend;
+		const preferredRenderBackend =
+			this.config.preferredRenderBackend ?? getDefaultLightningRenderBackend();
 		const backendOrder: ExportRenderBackend[] =
-			preferredRenderBackend === "webgl"
-				? ["webgl", "webgpu"]
-				: preferredRenderBackend === "webgpu"
-					? ["webgpu", "webgl"]
-					: typeof navigator !== "undefined" && "gpu" in navigator
-						? ["webgpu", "webgl"]
-						: ["webgl"];
+			preferredRenderBackend === "webgpu" ? ["webgpu", "webgl"] : ["webgl", "webgpu"];
 		const failures: PixiRendererAttempt[] = [];
 
 		for (const backend of backendOrder) {

src/lib/exporter/modernVideoExporter.ts

@@ -53,6 +53,7 @@ import {
 } from "@/lib/wallpapers";
 import { AudioProcessor, isAacAudioEncodingSupported } from "./audioEncoder";
 import {
+	getDefaultLightningRenderBackend,
 	normalizeLightningRuntimePlatform,
 	shouldPreferNativeAutoBackend,
 	shouldPreferNativeStaticLayoutBeforeBreeze,
@@ -588,7 +589,8 @@ export class ModernVideoExporter {
 				this.renderer = new ModernFrameRenderer({
 					width: this.config.width,
 					height: this.config.height,
-					preferredRenderBackend: undefined,
+					preferredRenderBackend:
+						this.config.preferredRenderBackend ?? getDefaultLightningRenderBackend(),
 					wallpaper: this.config.wallpaper,
 					zoomRegions: this.config.zoomRegions,
 					showShadow: this.config.showShadow,