off-screen render event

[Jonas]

Is there a way to synchronize the process of updating the DOM and capturing a screenshot? I want to capture the screenshot immediately after the updated webpage is rendered in memory.

[Czarek]

Not clear what you're asking for. You want some callback in the Renderer process?

[Jonas]

I think so -- I think I need a callback to the rendering process.

I am updating the DOM and then saving the rendered off-screen buffer data to disk (as a test). My issue is that when I save the buffer it does not always reflect the latest DOM update. I'm guessing this is because Chromium renders in a separate thread. Probably what this requires is an event that gets called by the rendering thread when it completes so that my main thread knows the buffer is has been rendered with the updated DOM and is ready to be used.

My eventual goal is to write the rendered data to a video I/O card. So, I would need to update the DOM and get a signal that it has been rendered to the off-screen buffer all within 16.6 milliseconds.

[magreenblatt]

The short answer is that it's not possible without significant code changes in Chromium/Blink. You would basically need to remove the existing compositing scheduler and implement your own mechanism for scheduling paint events and merging invalidated regions (potentially generated from different renderer processes). See https://www.chromium.org/developers/des ... -in-chrome for background.