1501652 - Rendering artifacts when firefox window spans across multiple screens

Status: RESOLVED INCOMPLETE

(Core :: Graphics, defect, P3)

Description

[spamdefeat-mozilla23]

Attachment: Example of a wide firefox window with misrendered vertical fragments

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0

Steps to reproduce:

I opened firefox on a machine with multiple monitors and extended desktop and sized firefox so that it spans across a screen boundary. Then I load a page (e.g. https://bugzilla.mozilla.org but it happens on other pages as well).
Then I scroll or resize the firefox window.


Actual results:

Some parts of the page are not rendered correctly and are not subject to scrolling/sizing/moving while the rest of the page renders and scrolls correctly.
These parts are narrow (several pixels) vertical lines from top to bottom (at least in the case where the firefox window spans across a screen border horizontally).
The "lines" appear to be on the same "screen global positions" independent of the actual firefox sizing and positioning, but apparently only when firefox crosses a screen boundary. They only appear in firefox.
Did not happen before the update to 63.0.


Expected results:

All visible parts of the page should render and scroll correctly.

Comment 1

[spamdefeat-mozilla23]

Attachment: Unbenannt2.png

Additional info that I didn't realize first: the vertical lines appear on a position left and right to the boundaries of another window below (but not directly below) firefox. For the next screenshot I pulled this window up to directly below firefox

Comment 2

[spamdefeat-mozilla23]

After some experiments it seems I can reproduce this only if I have Outlook open in the background, so it may as well be a problem of Outlook. But Firefox is the only program that I see misbehaving in this funny way when it covers outlook, and I can't remember having seen this before version 63 (and I am an intense multiscreen user so I probably would have noticed). And after all, it's firefox that's not enforcing the correct content in its window (and the area of mispainting is not within the covered area of the outlook window but in the firefox window a few pixels around what would be the outlook window in the background. And what is displayed in the disturbed areas is also most of the times clearly identifyable fragments of the displayed page.

It doesn't even seem to matter whether Outlook is completely hidden by other windows as well (that's why I didn't notice this dependency at first).

Still interesting that it still only happens when the firefox window crosses screen boundaries. When I resize or move the window so it fits on one screen the phenomenon stops.

It is particularly annoying if it happens in a text edit field like just now :-)

Comment 3

[Damira Akh]

Tested with 2 screens and I was not able to reproduce this issue.

If you still can reproduce this issue please feel free to let us know. 
Thank you.

Build ID 	20181029100347
User Agent 	Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:65.0) Gecko/20100101 Firefox/65.0


Build ID 	20181018182531
User Agent 	Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0

Comment 4

[:Gijs (he/him)]

Can you provide the contents of the 'graphics' section of about:support? Thank you!

Comment 5

[spamdefeat-mozilla23]

I'm out of office so it will have to wait until mon 11/5 when I'll have access to that windows machine again. It was 100% reproducible on that machine at the time I reported it.

Comment 6

[spamdefeat-mozilla23]

Attachment: mozsupp1.png

Problem is still occurring.

Graphics section in about:support (sorry: german installation, too large for a single screenshot and I don't know how to preserve the formatting when copying as text)

Comment 7

[spamdefeat-mozilla23]

Attachment: mozsupp2.png

Comment 8

[spamdefeat-mozilla23]

Still occurring with 63.0.1

Comment 9

[spamdefeat-mozilla23]

Attachment: Multiscreen setup. The bug appears when an outlook window is open on screen 3 and firefox in front of it either crosses the 2-3 or the 3-1 border.

Comment 10

[spamdefeat-mozilla23]

Attachment: Screenshot displaying horizontal and vertical misscrolling

The misscrolling can also happen in horizontal regions when scrolling vertically, you can see the partial top of outlook window to the left and the effect on the top+right where the partially hidden window ends in the background

Comment 11

[spamdefeat-mozilla23]

Another potentially helpful information: screens 1+2 are connected to the internal intel hd graphics, while screen 3 (the center one) is connected to a PCIe nvidia graphics card.
So the firefox window crossing any screen boundary is actually split between 2 different graphics drivers. Could this be confusing for the rendering code?

Comment 12

[Wayne Mery (:wsmwk)]

Do you still experience this issue?

Comment 13

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

Redirect a needinfo that is pending on an inactive user to the triage owner.
:bhood, since the bug has recent activity, could you have a look please?

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