update one more frame after canvas source paused

[ansis]

Calling canvasSource.pause() lets us know we can stop pulling in updates from it. Since it is possible that changes were made to the canvas source since the last render we should pull in one more update
before stopping. This also lets you call play and pause immediately to render just one frame:

ctx.fillRect(10, 10, 50, 50);
canvasSource.play();
canvasSource.pause();

Launch Checklist

• briefly describe the changes in this PR
• write tests for all new functionality
• [N/A] document any changes to public APIs
• [N/A] post benchmark scores
• manually test the debug page

[mourner]

The change looks great, but I'm confused about the test: there's a new updateFakeCanvas operation but no corresponding style.json that would invoke it, did you accidentally forget to commit it?

[asheemmamoowala]

As a developer I would expect that calling CanvasSource#pause allows me to make updates to the underlying canvas without updating the rendered map. With this change, is it possible for unwanted updates to be rendered in the case when:

1. call pause()
2. update the canvas element
3. map renders next frame

[ansis]

did you accidentally forget to commit it?

Yep, 6f8feba adds that.

As a developer I would expect that calling CanvasSource#pause allows me to make updates to the underlying canvas without updating the rendered map.

95dc749 fixes that

[asheemmamoowala]

This is putting the logic to be tested in the suite implementation instead of in a specific test. It is not a good precedent, but there is probably not a better way to do this with the current render test framework. Maybe an additional note here tying it back to a specific ticket or render-test would make it easier to remember why it is done this way.

[ansis]

Yeah, I agree that expanding the suite implementation further is not great but I'm not seeing a better way. I'm hesitant to add a note pointing to a specific test because notes tend to get outdated. I think searching for "updateFakeCanvas" within tests should be good enough.

[mourner]

I would try making the render test / image smaller if possible, but otherwise 👍