headless chrome can't capture screenvideo or animation about devtools-protocol HOT 5 CLOSED

@t-io I was curious so I decided to implement this in my Go library (cdp) and I think I know why this is not working for you, there are two reasons:

1. After receiving a frame, you must acknowledge it (Page.screencastFrameAck) with the received session ID (e.g. do this in your screencastFrame-handler)
2. No events also means there will be no frames, try scrolling, highlighting, writing, etc. that will trigger new frames to be created

Implemented in Go, the relevant part would look like this.

All this makes sense, from a protocol standpoint, on the other hand it's not very intuitive for a user, easy to miss.

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Try to call Page.enable before subscribing to the events. https://chromedevtools.github.io/devtools-protocol/tot/Page/#method-enable

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@auchenberg thanks for the quick response.
I already enabled the page. Here is a more complete code snippet:

await Page.enable();
await Page.navigate({url: 'http://www.goodboydigital.com/pixijs/examples/12-2/'});
await Page.loadEventFired();
await Page.startScreencast({format: 'png', everyNthFrame: 1});
Page.screencastFrame( image =>{
  const {data, metadata} = image;
  console.log(metadata);
});

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@t-io This seems like a problem with the Node client you are using. Please open the issue in the repo for the client, as this isn't a protocol issue.

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@mafredri thanks a lot!
You are totally right. I was not aware of the fact that you have to acknowledge the frames. After I adjusted my code according your example it works.
All the frames are triggered and saved.

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