1414311 - New window size is different than expected after changing screen dpi (with privacy.resistFingerprinting pref enabled)

Status: NEW

(Core :: General, defect, P2)

Description

[Hani Yacoub, Desktop QA]

[Affected platforms]:
Platforms: Ubuntu 16.04 x64.

Scenario 1: Open new window on high dpi 2K monitor
[Steps to reproduce]:
1. Go to about:config
2. Turn privacy.resistFingerprinting parameter to true
3. Open new browser window by clicking on "New Window"

[Expected result]: New window size should be 1000x1000.
[Actual result]: New window size is 1000x900

Scenario 2: Change the dpi value of your 2K monitor
[Steps to reproduce]:
1. Go to about:config and turn privacy.resistFingerprinting parameter to true
2. Open new browser window by clicking on "New Window"
3. Change the screen dpi to any value that is lower than the initial value (how to do it will differ by OS)
4. Open new browser window by clicking on "New Window"
5. Change the screen dpi to any value that is higher than the initial value (how to do it will differ by OS)
6. Open new browser window by clicking on "New Window"

[Expected result]: New window size should always be 1000x1000.
[Actual result]: The window size with same resolution is 1000x1000, after changing to a lower resolution the new window is 1000x900 which is not correct according to expected results, and after changing the screen dpi to any value that is higher than the initial value the new window is 1000x1000


Scenario 3: Change the dpi value of your 4K monitor
[Steps to reproduce]:
1. Go to about:config and turn privacy.resistFingerprinting parameter to true
2. Open new browser window by clicking on "New Window"
3. Change the screen dpi to any value that is lower than the initial value (how to do it will differ by OS)
4. Open new browser window by clicking on "New Window"
5. Change the screen dpi to any value that is higher than the initial value (how to do it will differ by OS)
6. Open new browser window by clicking on "New Window"

[Expected result]: New window size should always be 1000x1000.
[Actual result]: The window size with same resolution is 1000x1000, after changing to a lower resolution the new window is 1000x900 which is not correct according to expected results, and after changing the screen dpi to any value that is higher than the initial value the new window is 1000x1000

Comment 1

[Firefox Bug Husbandry Bot]

https://wiki.mozilla.org/Bug_Triage/Projects/Bug_Handling/Bug_Husbandry#Update_affecteds

Comment 2

[Tom Ritter [:tjr] (OOTO until 4/30 at least)]

P2 to investigate more

Comment 3

[Ethan Tseng [:ethan]]

Tim, could you look into this bug?

Comment 4

[Tim Huang[:timhuang]]

Sorry for the late response. Yes, I will look into it.

Comment 5

[Simon Mainey]

how do you add [tor 30625] to the whitelist?

Comment 6

[Simon Mainey]

^^ oophs, I meant whiteboard

Comment 7

[Tim Huang[:timhuang]]

Unassign myself because I am no longer actively working on this.

Comment 8

[Tom Ritter [:tjr] (OOTO until 4/30 at least)]

Removing parent bugs that aren't applicable, this is a bug in fingerprinting. If it's still applicable.