Proposing a get endpoint for Take Screenshot that with fullpage option

[k7z45]

Due to the high demand from https://bugs.chromium.org/p/chromedriver/issues/detail?id=294, come up with initial proposal for the spec

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Preview | Diff

[jgraham]

geckodriver supports this, but it's a new endpoint rather than a parameter (…/screenshot/full). Since the existing endpoint is a GET and we don't have other cases that use parameters on the GET, that design would make more sense to me.

[k7z45]

Thanks for the comment, made the change accordingly.

[k7z45]

Note that merging this also requires some web-platform-tests to be submitted/approved for the feature.

Will work on web-platform-tests once I have "verbal" approval for this.

[sideshowbarker]

Hi @k7z45 — in order to accept this PR we need to make our tooling recognize that you’re already a participant in the Browser Testing and Tools Working Group.

You can do that by using https://www.w3.org/users/myprofile to log into your W3C account — and from there, follow the Connected Accounts link in the sidebar to connect your W3C account with your GitHub account.

If you don’t remember your W3C username or password, you can use https://www.w3.org/accounts/recover to recover them.

[k7z45]

Thanks Michael! Just did that.

[sideshowbarker]

Thanks @k7z45 — https://labs.w3.org/repo-manager/pr/id/w3c/webdriver/1536 shows this is now green for the IPR check

[k7z45]

Hi @jgraham , PTAL pending review web-platform-tests: https://github.com/web-platform-tests/wpt/pull/26652 for the feature.

[jugglinmike]

I'm interested in bringing this functionality to WebDriver BiDi. Whether it belongs here in WebDriver "classic" is not a topic I can comment on, but I'm interested in learning if the normative text proposed here is viable for either spec.

Specifically, I haven't found any implementer's perspective on @jgraham's 2021 comment:

One challenge is that the fullPage option may not be trivial to specify; I think we skipped it for WebDriver Classic but in practice implementations have it, although I don't know they all work the same The typical kind of problem is "what if you haven't already rendered the whole page, but just some tiles. Then you might need to simulate scrolling to render the whole page, but what about position:fixed headers, or content that changes duirng scroll". So really you want "render the entire current layout tree as if the viewport length was unbounded", but that might not actually be a thing that's supported in engines.

@chrishtr you and I investigated a Chrome rendering bug a number of years ago; is there any chance you could weigh in here or perhaps refer me to someone more appropriate?

@juliandescottes could you direct me to a subject-matter expert at Mozilla?

[whimboo]

For Chrome there is https://bugs.chromium.org/p/chromium/issues/detail?id=770769&desc=2 which at least for headless seems to still limit the maximum height to 16384px.

For Firefox we currently have the limit set to 32767px for both height and width, and a maximum texture size of 472907776.

As of now we do not have problems in capturing full page screenshots for pages exceeding the visible viewport.

[whimboo]

Note that we will discuss the full screenshot feature for BiDi during the TPAC sessions on Thursday or Friday this week.