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fix: prevent crash when GPU is unavailable #772

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3 changes: 2 additions & 1 deletion apps/web/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -93,10 +93,11 @@
"cross-env": "^7.0.3",
"dotenv": "^16.5.0",
"drizzle-kit": "^0.31.4",
"patch-package": "^8.0.1",
"postcss": "^8",
"sharp": "^0.34.5",
"tailwindcss": "^4.2.1",
"typescript": "^5.8.3",
"wrangler": "^4.77.0"
}
}
}
177 changes: 90 additions & 87 deletions apps/web/src/services/renderer/canvas-renderer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -5,105 +5,108 @@ import { wasmCompositor } from "./compositor/wasm-compositor";
import { resolveRenderTree } from "./resolve";

export type CanvasRendererParams = {
width: number;
height: number;
fps: FrameRate;
width: number;
height: number;
fps: FrameRate;
};

export class CanvasRenderer {
canvas: OffscreenCanvas | HTMLCanvasElement;
context: OffscreenCanvasRenderingContext2D | CanvasRenderingContext2D;
width: number;
height: number;
fps: FrameRate;
canvas: OffscreenCanvas | HTMLCanvasElement;
context: OffscreenCanvasRenderingContext2D | CanvasRenderingContext2D;
width: number;
height: number;
fps: FrameRate;

constructor({ width, height, fps }: CanvasRendererParams) {
this.width = width;
this.height = height;
this.fps = fps;
constructor({ width, height, fps }: CanvasRendererParams) {
this.width = width;
this.height = height;
this.fps = fps;

try {
this.canvas = new OffscreenCanvas(width, height);
} catch {
this.canvas = document.createElement("canvas");
this.canvas.width = width;
this.canvas.height = height;
}
try {
this.canvas = new OffscreenCanvas(width, height);
} catch {
this.canvas = document.createElement("canvas");
this.canvas.width = width;
this.canvas.height = height;
}

const context = this.canvas.getContext("2d");
if (!context) {
throw new Error("Failed to get canvas context");
}
const context = this.canvas.getContext("2d");
if (!context) {
throw new Error("Failed to get canvas context");
}

this.context = context as
| OffscreenCanvasRenderingContext2D
| CanvasRenderingContext2D;
}
this.context = context as
| OffscreenCanvasRenderingContext2D
| CanvasRenderingContext2D;
}

getOutputCanvas(): HTMLCanvasElement {
wasmCompositor.ensureInitialized({
width: this.width,
height: this.height,
});
return wasmCompositor.getCanvas();
}
getOutputCanvas(): HTMLCanvasElement | null {
wasmCompositor.ensureInitialized({
width: this.width,
height: this.height,
});
return wasmCompositor.getCanvas();
}
Comment on lines +43 to +49
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@coderabbitai coderabbitai Bot Apr 17, 2026

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⚠️ Potential issue | 🔴 Critical

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
rg -nP '\bgetOutputCanvas\s*\(' -C3

Repository: OpenCut-app/OpenCut

Length of output: 1266

🏁 Script executed:

#!/bin/bash
# Check the full context around scene-exporter.ts line 100
cat -n apps/web/src/services/renderer/scene-exporter.ts | sed -n '85,115p'

Repository: OpenCut-app/OpenCut

Length of output: 1386

🏁 Script executed:

#!/bin/bash
# Find CanvasSource type definition and constructor signature
rg -n "class CanvasSource|interface CanvasSource|type CanvasSource" -A5

Repository: OpenCut-app/OpenCut

Length of output: 45

🏁 Script executed:

#!/bin/bash
# Check the full implementation of getOutputCanvas
cat -n apps/web/src/services/renderer/canvas-renderer.ts | sed -n '38,55p'

Repository: OpenCut-app/OpenCut

Length of output: 837

🏁 Script executed:

#!/bin/bash
# Check wasmCompositor.getCanvas() return type
rg -n "getCanvas\s*\(" -B2 -A3 apps/web/src/services/renderer/

Repository: OpenCut-app/OpenCut

Length of output: 1680

🏁 Script executed:

#!/bin/bash
# Find CanvasSource definition - could be imported from a library or defined locally
rg "CanvasSource" -B2 -A8 apps/web/src/services/renderer/scene-exporter.ts | head -30

Repository: OpenCut-app/OpenCut

Length of output: 663

🏁 Script executed:

#!/bin/bash
# Search for CanvasSource import/definition across the codebase
rg "class CanvasSource|from.*CanvasSource" -B1 -A1

Repository: OpenCut-app/OpenCut

Length of output: 45

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#!/bin/bash
# Check mediabunny version and any type definitions
cat -n package.json | grep -i mediabunny -B2 -A2

Repository: OpenCut-app/OpenCut

Length of output: 45

🏁 Script executed:

#!/bin/bash
# Search for all uses of getOutputCanvas in the codebase
rg "getOutputCanvas" -B3 -A3

Repository: OpenCut-app/OpenCut

Length of output: 1220

🏁 Script executed:

#!/bin/bash
# Check if there's a try-catch around the export that might handle this
cat -n apps/web/src/services/renderer/scene-exporter.ts | sed -n '75,120p'

Repository: OpenCut-app/OpenCut

Length of output: 1746

Handle null return from getOutputCanvas() in export path.

getOutputCanvas() returns HTMLCanvasElement | null and can return null when GPU is unavailable (see wasm-compositor.ts:74-75). However, scene-exporter.ts:100 passes the result directly to new CanvasSource(...) without a null check. When GPU is unavailable, this will fail during export without a user-friendly error message.

Add a null check in the export method before instantiating CanvasSource, and either:

  1. Return null with a user-friendly error (export requires GPU), or
  2. Throw a descriptive error immediately for faster failure with clear messaging
🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@apps/web/src/services/renderer/canvas-renderer.ts` around lines 43 - 49, The
export path currently assumes getOutputCanvas() returns a non-null
HTMLCanvasElement; add a null check before calling new CanvasSource(...) in the
export method where CanvasSource is instantiated (the code that calls
getOutputCanvas()). If getOutputCanvas() returns null (GPU unavailable via
wasmCompositor.getCanvas/getOutputCanvas), either return null with a clear
user-facing message like "Export failed: GPU unavailable — export requires GPU"
or throw a descriptive Error immediately to fail fast; update the code that
calls new CanvasSource(...) to handle the chosen behavior.


setSize({ width, height }: { width: number; height: number }) {
this.width = width;
this.height = height;
setSize({ width, height }: { width: number; height: number }) {
this.width = width;
this.height = height;

if (this.canvas instanceof OffscreenCanvas) {
this.canvas = new OffscreenCanvas(width, height);
} else {
this.canvas.width = width;
this.canvas.height = height;
}
if (this.canvas instanceof OffscreenCanvas) {
this.canvas = new OffscreenCanvas(width, height);
} else {
this.canvas.width = width;
this.canvas.height = height;
}

const context = this.canvas.getContext("2d");
if (!context) {
throw new Error("Failed to get canvas context");
}
this.context = context as
| OffscreenCanvasRenderingContext2D
| CanvasRenderingContext2D;
}
const context = this.canvas.getContext("2d");
if (!context) {
throw new Error("Failed to get canvas context");
}
this.context = context as
| OffscreenCanvasRenderingContext2D
| CanvasRenderingContext2D;
}

async render({ node, time }: { node: AnyBaseNode; time: number }) {
await resolveRenderTree({ node, renderer: this, time });
const { frame, textures } = await buildFrameDescriptor({
node,
renderer: this,
});
wasmCompositor.ensureInitialized({
width: this.width,
height: this.height,
});
wasmCompositor.syncTextures(textures);
wasmCompositor.render(frame);
}
async render({ node, time }: { node: AnyBaseNode; time: number }) {
await resolveRenderTree({ node, renderer: this, time });
const { frame, textures } = await buildFrameDescriptor({
node,
renderer: this,
});
wasmCompositor.ensureInitialized({
width: this.width,
height: this.height,
});
wasmCompositor.syncTextures(textures);
wasmCompositor.render(frame);
}

async renderToCanvas({
node,
time,
targetCanvas,
}: {
node: AnyBaseNode;
time: number;
targetCanvas: HTMLCanvasElement;
}) {
await this.render({ node, time });
async renderToCanvas({
node,
time,
targetCanvas,
}: {
node: AnyBaseNode;
time: number;
targetCanvas: HTMLCanvasElement;
}) {
await this.render({ node, time });

const ctx = targetCanvas.getContext("2d");
if (!ctx) {
throw new Error("Failed to get target canvas context");
}
const ctx = targetCanvas.getContext("2d");
if (!ctx) {
throw new Error("Failed to get target canvas context");
}

ctx.drawImage(
wasmCompositor.getCanvas(),
0,
0,
targetCanvas.width,
targetCanvas.height,
);
}
}
const compositorCanvas = wasmCompositor.getCanvas();
if (!compositorCanvas) return;

ctx.drawImage(
compositorCanvas,
0,
0,
targetCanvas.width,
targetCanvas.height,
);
}
}
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