1723576 - Thread indentation lines sometimes invisible when printing in a specific MacBook

Status: RESOLVED DUPLICATE of bug 1723716

(Core :: Layout, defect)

Description

[Daniel Bodea [:danibodea]]

+++ This bug was initially created as a clone of Bug #1717873 +++

Steps to reproduce:

Go to an email that contains a multi-level thread and open the email.
OR
Load TC: https://bugzilla.mozilla.org/attachment.cgi?id=9228714
Bring up in Print Preview (cmd+p)

Actual results:
Indentation is NOT visible in print preview.

Expected results:
Indentation is visible in print preview.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Screenshot 2021-08-02 at 21.32.02.png

I couldn't reproduce this, this is what I see, which shows the black line in the print preview. What am I missing?

Comment 2

[Daniel Bodea [:danibodea]]

That is good news because I've just discovered that this issue also occurs without having the Increase Contrast feature activated. Seems I've missed that. Do you have any idea what could cause this? (a similar situation was reported here. This being said, the bug no longer mentions the Increase Contrast activation.

Comment 3

[Daniel Bodea [:danibodea]]

Attachment: about:support

about:support info taken from the affected system

Comment 4

[Emilio Cobos Álvarez (:emilio)]

Is it invisible when printing to an actual printer? Or just in print preview? I wonder if we're snapping the border away somehow given the preview is scaled down or what not. If you zoom using the touchpad into the affected area, does the border start showing up?

Comment 5

[Daniel Bodea [:danibodea]]

You are totally right. So apparently it is caused by the low resolution of the display? Anyway, good catch and my noob mistake in finding the cause.
Furthermore, it appears to have a similar effect on Win7 (bug 1723716). When attempting to zoom in using the trackpad, the little indentation line appears and disappears even though no actual zoom is observed in the print preview.

This means it will not be missing from the actual print, and it is only an issue of the print preview. Not sure whether we should consider lowering the severity or actually rendering the issue invalid. I'll leave that to you.

Comment 6

[Emilio Cobos Álvarez (:emilio)]

Let's unify these two issues into one for the snapping issue. Thanks for confirming.