1648293 - Screenshots of cross-origin iframes are blank, if fission is enabled

Status: RESOLVED DUPLICATE of bug 1636508

(Firefox :: Screenshots, defect, P3)

Description

[Daniel Holbert [:dholbert]]

STR:

1. Set about:config pref fission.autostart to true, and restart Firefox.
2. Visit https://www.milgard.com/brochure/tuscany
3. Take a screenshot (using three-dot-menu, "take a screenshot" option)
   (Doesn't matter whether you copy it or download it, but let's say "download" for the purposes of this STR.)
4. View your screenshot.

ACTUAL RESULTS:
The screenshot is blank.

EXPECTED RESULTS:
The screenshot should show me the content that I screenshotted.

I suspect this has to do with the fact that this page's content is actually being shown via a cross-origin iframe, which fission has trouble with.

• If I perform the STR in a non-fission window (i.e. skipping step 1 or doing File|New Non-Fission Window), then screenshotting works.
  Also:
• If I view the iframe contents directly (e.g. by right-clicking the content and choosing "open frame in new tab"), then screenshotting works (produces non-blank content) even in a fission-enabled window.

Comment 1

[Chris Peterson [:cpeterson]]

I swear there is an existing bug about PDF screenshots not working with Fission, but I can't find it. So we'll track this bug for Fission M6b Nightly.

Comment 2

[Daniel Holbert [:dholbert]]

(In reply to Chris Peterson [:cpeterson] from comment #1)

I swear there is an existing bug about PDF screenshots not working with Fission

Just to be clear - in this case, there's no PDF involved. The "brochure" here is a JS-based dynamic slideshow thing, with <img> elements pointing to content like https://secure.viewer.zmags.com/services/resource/pub/30a53826/pg463x600/344/1 , and with dynamically updating CSS transforms to do the slideshow business.

I think this is just broken, in general, for cross-origin iframes (regardless of their content). I'll post a testcase shortly.

Comment 3

[Daniel Holbert [:dholbert]]

Attachment: testcase 1

Here's a testcase, which has an iframe hosting some cross-origin content (another bug's testcase).

It should render with two large "abc" strings, one of which may be fuzzy (don't worry about that).

If you try to take a screenshot of the "abc" text in this testcase, with fission enabled, you end up just getting a blank result (presumably because it's a cross-origin iframe)

Comment 4

[Daniel Holbert [:dholbert]]

Attachment: testcase 2

Comment 5

[Daniel Holbert [:dholbert]]

Testcase 2 demonstrates that same-origin iframes do screenshot correctly, but their cross-origin descendant iframes do not.

(i.e. when viewing testcase 2, you can successfully screenshot the See if you can take... text in its iframe, as well as the How about this outer page text in the outer document, but you still can't screenshot the abc text in the innermost iframe, presumably because it's cross-origin which interferes with what screenshots is trying to do.)

Comment 6

[Hiroyuki Ikezoe (:hiro)]

This is because the screenshot extension still uses drawWindow, we need to migrate to use drawSnapshot.

Comment 8

[Chris Peterson [:cpeterson]]

Clearing Fission Milestone for bugs resolved as duplicates. We don't need to track duplicates.