1572995 - regression: Web content does not adapt to window size when layout.css.devPixelsPerPx changes

Status: RESOLVED FIXED

(Core :: Layout, defect, P3)

Description

[Darkspirit]

Attachment: 2019-08-11 01-57-02.mp4

Win10, GTX 1060, 2560x1440

Screencast:

1. Run mozregression --launch 2019-08-10 --pref layout.css.devPixelsPerPx:'0.7' browser.aboutConfig.showWarning:false browser.startup.homepage:'https://bugzilla.mozilla.org/show_bug.cgi?id=wr-70|about:config'
2. Switch to about:config tab and reset layout.css.devPixelsPerPx to default.
3. Switch back to Bugzilla tab and see the bug. Maximizing the window or reloading the page does not help.

---

Linux is affected with Basic, OpenGL and WebRender as well. So it might be a Layout issue?

Debian Testing, KDE (compositor disabled), X11, Macbook Pro A1502
mozregression --good 2017-08-01 --bad 2018-01-15 --pref layout.css.devPixelsPerPx:1.5 browser.aboutConfig.showWarning:false general.warnOnAboutConfig:false browser.startup.homepage:'https://bugzilla.mozilla.org/show_bug.cgi?id=wr-70|about:config?filter=layout.css.devPixelsPerPx'

7:03.63 INFO: Last good revision: 40df5dd35fdb7ce3652fe4448ac8961c075c928e (2017-11-07)
7:03.63 INFO: First bad revision: c10cf7082a9b84839e7c3fdda80bd468e091739a (2017-11-08)
7:03.63 INFO: Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=40df5dd35fdb7ce3652fe4448ac8961c075c928e&tochange=c10cf7082a9b84839e7c3fdda80bd468e091739a

7:41.18 INFO: There are no build artifacts on inbound for these changesets (they are probably too old).

Disabling layout.css.servo.enabled and layout.display-list.retain for first bad build does not help.
Win10 has the same regression range.

Comment 1

[Darkspirit]

The same problem might affect window content as a whole on startup.

Comment 2

[Darkspirit]

Moving to CSS because it's a CSS pref.

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The priority flag is not set for this bug.
:hiro, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 4

[Daniel Holbert [:dholbert]]

Thanks for the report! Triaging as P3 for now, since we've apparently been shipping with this issue without noticing for ~2 years now.

(definitely would be nice to fix / get to the bottom of it, if someone gets a chance!)

Comment 5

[Daniel Holbert [:dholbert]]

(Also, this is more appropriately classified as Layout rather than CSS. Despite .css in the pref-name, the actual implementation of this pixel scaling-factor is closer to layout code than it is to our css parser.)

Comment 6

[janet [:janet]]

Sean, we're making this as wontfix for 70 but affected for 71 in case you feel this should be included on your list.

Comment 7

[Mihaela Velimiroviciu]

I have this issue on Mac, as well.

Environment:
iMac with macOS Mojave
FF version: 75

STR:

1. open a popup in a new window
2. set the layout.css.devPixelsPerPx pref to 2
3. check the popup window.

Expected:
Content covers all window.

Actual:
Content is displayed only on a section of the window.

Note: If I move the window or resize it, the content is displayed as expected.

Comment 8

[Mihaela Velimiroviciu]

Attachment: content trimmed

Comment 9

[BugBot [:suhaib / :marco/ :calixte]]

The severity field for this bug is relatively low, S3. However, the bug has 5 See Also bugs.
:dholbert, could you consider increasing the bug severity?

For more information, please visit auto_nag documentation.

Comment 10

[Hiroyuki Ikezoe (:hiro)]

I did recently change relevant code in bug 1787079, is this still an issue? I haven't tried the Mac's popup case in comment 7, to me the STR in comment 0 doesn't reproduce.

Comment 11

[Hiroyuki Ikezoe (:hiro)]

Confirmed the popup window case works as expected.

Comment 12

[Hiroyuki Ikezoe (:hiro)]

I am pretty sure https://hg.mozilla.org/integration/autoland/rev/03f45da3ba4e changeset fixed the problem. I am unsure which changeset in the regression range in comment 0 regressed this. (I did skim the list twice, but couldn't find any suspicious change)