The Canvas Debugger is a new tool we’ll be demoing at the Game Developers Conference in San Francisco. It’s a tool for debugging animation frames rendered on a Canvas element. Whether you’re creating a visualization, animation or debugging a game, this tool will help you understand and optimize your animation loop. It will let you debug either a WebGL or 2D Canvas context.
How it works
Certain types of Canvas context functions are highlighted to make them easier to spot in the snapshot. Quickly scrolling through the list, a developer can easily spot draw calls or redundant operations.
Each draw call has an associated screenshot arranged in a timeline at the bottom of the screen as a “film-strip” view. You can “scrub” through this film-strip using a slider to quickly locate a draw call associated with a particular bit of rendering. You can also click a thumbnail to be taken directly to the associated draw call in the animation frame snapshot.
The thumbnail film-strip gives you get a quick overview of the drawing process. You can easily see how the scene is composed to get the final rendering.
- “Resume” – Jump to the next draw call.
- “Step Over” – Goes over the current context call.
- “Step Out” – Jumps out of the animation frame (typically to the next requestAnimationFrame call).
We’re not done. We have some enhancements to make this tool even better.
- Add the ability to inspect the context’s state at each method call. Highlight the differences in state between calls.
- Measure Time spent in each draw call. This will readily show expensive canvas operations.
- Make it easier to know which programs and shaders are currently in use at each draw call, allowing you to jump to the Shader Editor and tinkering with shaders in real time. Better linkage to the Shader Editor in general.
- Inspecting Hit Regions by either drawing individual regions separately, colored differently by id, or showing the hit region id of a pixel when hovering over the preview panel using the mouse.
And we’re just getting started. The Canvas Debugger should be landing in Firefox Nightly any day now. Watch this space for news of its landing and more updates.
About Victor Porof
Mozillian, hacker, working on Firefox DevTools.