LP#1964493 "gdm has a black background now"

[github-actions]

Reported first on Launchpad at https://bugs.launchpad.net/ubuntu/+source/yaru-theme/+bug/1964493

Using the GNOME 42 updates in proposed the login screen background is black, that feels buggy, we should revert to the old style

[vitalkanev]

The background was changed as part of #2910

[lyubomir-popov]

The chosen colour (#222?) seems ok to me. It is dark enough to allow white or light text to be readable on it, and it will work well with any theme colours that are about to be introduced.

Once theme colours are introduced, it would make sense to derive a background colour from the accent colour as an alternative.

Accessibility considerations

(There are some WCAG requirements regarding contrast between text colours and backgrounds:. These come from the web, so not 100% sure if they would be mandatory in an OS context, please let me know if you use different OS colour guidelines.

In case the web guidance applies, before selecting a colour, it would be good to establish whether text colours other than white need to be displayed on this background. If so, then the background colour must be dark enough to allow for any other text colour to provide:
a) 4.5:1 contrast against the background
b) 3:1 contrast against white text

A safe bet is any dark grey under #2d2d2d (the chosen #222 already satisfies this requirement), which allows white and an additional colour to satisfy the above requirements. For example:

Consistency considerations

From a consistency perspective, should this match any of the existing os colours?
From the theming there are a number of colours, e.g.

$jet: #181818;
----
$base_color: lighten($jet, 6%);
$text_color: white;
$bg_color: lighten($jet, 8%);

which are close to #222, would be good if it resolves to one of those existing colour variables (it may already come from these, I'm new to the repo so maybe one of those lighten() functions is already used to derive it).

[Muqtxdir]

hi @lyubomir-popov 👋

thank you for sharing a detailed analysis regarding the background-color for gdm. Really great points presented regarding the accessibility and consistency aspects. However I'd like to just add few points and elaborate from yaru's scope of themeing:

Some context related to the change:

Since, the accent-colors will be introduced in 22.04, it made sense to use a darker background (lighten($jet, 4%) to make it look similiar to GNOME upstream rather than purple because it would give the user a false sense that this a bug and it is expected behaviour to change to a shade based on their accent-color. Another reason for dropping the purple is also because there were several discussions on discourse.ubuntu.com and some here on github by dekstop-users pointing out that they felt the presence of purple on login-screen felt weird.

Once theme colours are introduced, it would make sense to derive a background colour from the accent colour as an alternative

Having the background color for gdm inherit the choosen desired-color is a nice suggestion but this would require a patch made to gdm to swap the style-sheet depending upon the color choosen. I think it's possible to add it in gnome-shell-theme-gresource as gdm.css(default), gdm-aqua.css, gdm-blue.css and so on... but @3v1n0 is better person to answer if it's really possible and ok to make patch for such a change to gdm.

Even if the gdm makes use of accented background. It would be problem for sytems having multiple-users, as that would conflict.

which are close to #222, would be good if it resolves to one of those existing colour variables (it may already come from these, I'm new to the repo so maybe one of those lighten() functions is already used to derive it).

the palette makes use of the above colors and if you'd like to see where it's being done, see: screen-sheild.scss #lockDialogGroup

EDIT: also see @Feichtmeier comment on launchpad as well: https://bugs.launchpad.net/ubuntu/+source/yaru-theme/+bug/1964493/comments/3

[Jupi007]

The GDM background have to be as neutral as possible.
Users can pick an accent color for their own session.
But the login screen is shared across users and so should be unaccented.

[3v1n0]

Technically we could do what unity did changing bg-color based on user accent, but definitely not for 22.04.

[lyubomir-popov]

But the login screen is shared across users and so should be unaccented.

Is this colour only ever used on the login screen? And does any small text (under 14px) appear on top of it?
Asking these questions to understand how light the gray can be before it breaches accessibility guidelines.

Someone mentioned elsewhere that this current dark grey (perceived as black by them) confuses them into thinking something went wrong, if this is a shared feeling then moving to lighter grey could potentially solve that problem.

Alternatively, if we can change the text colour as well, we could use a silver-like grey and black text on top.

[Jupi007]

Is this colour only ever used on the login screen?

This colour is the same used for the overview background.
It is a very specific color which aim to be lighten than dash but darken than $bg-color.

Here is screenshots of the two states of this screen:

Someone mentioned elsewhere that this current dark grey (perceived as black by them) confuses them into thinking something went wrong, if this is a shared feeling then moving to lighter grey could potentially solve that problem.
Alternatively, if we can change the text colour as well, we could use a silver-like grey and black text on top.

We could try, but I wouldn't visually fit with Yaru look.
Compared to upstream we are a bit darker, it is part of our identity.

And we can't use dark text because the ubuntu logo is white, and this cannot be changed.
This logo is the same displayed in startup and shutdown screen, which is pure black (to have a flicker free booting).
Using a dark logo doesn't work.

[lyubomir-popov]

@Jupi007 thank you for the screenshots and additional context. To be honest, given the presence of the logo and user choices, I don't think this can be confused with a "something went wrong" situation, so I see no need to change this in any way from a design or accessibility perspective.

[Jupi007]

It's also my opinion :)

[vanvugt]

Whatever the final colour of the login screen is, remember we need to patch gnome-shell to inherit the same colour for its system background used briefly during the login animation.

[Jupi007]

The bg shouldn't change now.
So the final color is the one from screenshots: #222222.

[vanvugt]

Seems people agreed in #2910 that it should not be changed to grey, and the PR was closed in September. Then it was reopened and merged in January without any explanation. Did I miss something?

[Jupi007]

I'm sorry to not have given a correct explanation of why I reopened and merged this PR.
After a discussion in a private chat, we all decided to merge this PR for testing in real conditions the grey bg.

[vanvugt]

I do like grey, and I will change the gnome-shell login animation to match if need be. I just don't want the strong supporters of purple to be upset.

[Jupi007]

I understand, and I'm really sorry 😕

Honestly, I really prefer this color over purple.
I looks more professional, and the dark entry blends much better.

[Jupi007]

@3v1n0 I think we can close this issue?

[vanvugt]

@3v1n0 I think we can close this issue?

Maybe check with @seb128 first since he opened the bug.

[seb128]

You can close it yes, it still feels buggy to me like if the login manager was failing to load but that's just my packager eye, I will trust the designers in their choice