1530045 - Chrome-less windows have a 1-pixel thick horizontal black line

Status: RESOLVED DUPLICATE of bug 1681847

(Core :: Graphics, defect, P3)

Description

[Synetech]

Attachment: Black line in chromeless windows (at top of page)

User Agent: Mozilla/5.0 (Windows NT 6.1; rv:65.0) Gecko/20100101 Firefox/65.0

Steps to reproduce:

Create a chrome-less popup window.

Actual results:

There is a 1-pixel thick black horizontal line at the top of the page (between the page contents and the window frame).

Expected results:

The window should be nothing but the webpage and a window frame.

This might be related to other "1-pixel horizontal black line" bugs listed, but it seems different (those are about the chrome; this one shouldn't have any chrome at all).

Comment 1

[Synetech]

Attachment: Black line in even empty popup windows

For the record, I have manually adjusted the window size in one-pixel increments in both dimensions and it makes no difference. Even empty windows have the line.

Comment 2

[Stefan [:StefanG_QA]]

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:67.0) Gecko/20100101 Firefox/67.0 20190225215823

I've tested this report on Windows 10 using the latest Nightly and Fx release build. I did not manage to reproduce the mentioned behavior. When creating new popup windows I don't see the horizontal black line. Can you provide a minimized test case in order to test this report properly?

Comment 3

[Synetech]

I don't know about nightlies, but in 65.0.1 this works to demonstrate the line:

window.open("about:blank","","width=640,height=360");

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

Layout might be better component, in case there is some rounding error.
DOM at least doesn't deal with any graphics/painting.

Comment 5

[Emilio Cobos Álvarez (:emilio)]

Sotaro, does this sound familiar? I cannot repro on Linux, so probably graphics or widget rather than Layout :)

Comment 6

[Synetech]

This is still present in 79, so the 65 nightly didn't fix it.

Comment 7

[Synetech]

It turns out that this isn't specific to popup windows, EVERYTHING in Firefox has this line, including normal pages. I reported that as a separate bug 1681847 and included a work-around for it there (until the line can be removed from the browser's built-in CSS).

(I guess this can be closed since it's just a side-effect of the more general issue.)