Text highlight mismatch in view-source when layout.css.devPixelsPerPx is >= 1.2

Bug #1798103 reported by Jani Uusitalo
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Mozilla Firefox
firefox (Ubuntu)

Bug Description

== The issue ==
Search and text selection highlighting visuals get mismatched with the actual selection in view-source when the value of `layout.css.devPixelsPerPx` is 1.2 or larger.

== Steps to reproduce ==
* Open `about:config`, find `layout.css.devPixelsPerPx` and change the value from default (-1.0) to 1.2.
* Open a view-source view with long lines: `view-source:https://www.youtube.com/user/10asti10`
* hit Ctrl+f, search for rss
* using the LMB, try selecting some text, then copy and paste it somewhere

== What happens ==
Screenshot 1: the highlighted text on the page is not ”rss”. The highlight doesn’t even adhere to letter widths.

Screenshot 2: the pasted text is not even close to what you’ve selected to copy.

== What I expect to happen ==
For the search to hightlight an occurence of ”rss”, and for the pasted text to correspond to what I’ve selected from the view-source view.

== Other info ==
* In my testing, a devPixelsPerPx value of 1.1 seems to not trigger this, whereas 1.2 and anything above does.
* In addition to 18.04 (whence the attached info is from) I’ve reproduced this in a VM running up-to-date 18.10.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: firefox 62.0.3+build1-0ubuntu0.18.04.1
ProcVersionSignature: Ubuntu 4.15.0-36.39-generic 4.15.18
Uname: Linux 4.15.0-36-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.9-0ubuntu7.4
Architecture: amd64
BuildID: 20181002130007
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 16 16:59:28 2018
InstallationDate: Installed on 2016-10-13 (733 days ago)
InstallationMedia: Ubuntu-Server 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
 PATH=(custom, no user)
SourcePackage: firefox
UpgradeStatus: No upgrade log present (probably fresh install)

Revision history for this message
Jani Uusitalo (uusijani) wrote :
Revision history for this message
Jani Uusitalo (uusijani) wrote :
Adolfo Jayme (fitojb)
Changed in firefox (Ubuntu):
importance: Undecided → Low
Revision history for this message
Olivier Tilloy (osomon) wrote :

I can reliably reproduce the bug with the steps provided.

@Jani: would you mind reporting the bug upstream at https://bugzilla.mozilla.org/enter_bug.cgi#h=dupes%7CFirefox and sharing the link to it here?

When I search for upstream bug reports containing "layout.css.devPixelsPerPx", I find several issues that are probably related to what you're seeing, but none mention the view-source: view, so I think a new bug would be useful.


Changed in firefox (Ubuntu):
status: New → Confirmed
Revision history for this message
Jani Uusitalo (uusijani) wrote :

Thanks Olivier, I've now added the link to my upstream report.

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