Ubuntu logo shifts vertically when the login screen appears (before selecting the user)

[Daniel van Vugt]

Ubuntu logo shifts upward about 1px when the purple login screen appears.

[Daniel van Vugt (vanvugt)]

Changed from a 1920x1200 monitor to 3840x2160 and now it moves downward. Much more than 1px.

[Dimitri John Ledkov (xnox)]

In gnome shell:

Logo is aligned to 1 vertically, and then has margin of 3em

this._logoBin = new St.Widget({
    style_class: 'login-dialog-logo-bin',
    x_align: Clutter.ActorAlign.CENTER,
    y_align: Clutter.ActorAlign.END,
});

.login-dialog-logo-bin {
  margin: 3em 0; }

Where as in plymouth the Watermark has vertical alignment of

themes/bgrt/bgrt.plymouth.desktop:WatermarkVerticalAlignment=.96
view->watermark_area.y = screen_height * plugin->watermark_vertical_alignment - ply_image_get_height (plugin->watermark_image) * plugin->watermark_vertical_alignment;

Which means the margin in plymouth is 4% of screen height.

So one way to fix this is to make plymouth know what "3em" is and calculate that.
Or to teach gnome-shell to use 4% margin of the total screen.
I am going to try to do the latter.

[Dimitri John Ledkov (xnox)]

in jammy gnome-shell it is:

.login-dialog-logo-bin { padding: 24px 0px; }

[Dimitri John Ledkov (xnox)]

hm setting padding to 4% does not do it.

i am starting to suspect the screen total size is off. by a lot.

[Dimitri John Ledkov (xnox)]

aha! patching gnome-shell does nothing, so we need to patch like yaru-themes.

and 4% there doesn't work, as if it doesn't compute.

[Daniel van Vugt (vanvugt)]

Display scale is also a factor but hopefully we can ignore that if computing in prescaled units like "em" or "4%".

If you encounter machines which have a different default scaling factor in plymouth and gnome-shell/gdm then just ignore those for the purposes of this bug.

[Dimitri John Ledkov (xnox)]

This got a lot worse in noble, it's now not just vertical shift, but the scaling of the logo too. It is twice as small as the plymouth one.

Or maybe plymouth shows things twice as large?

I don't know how to figure out which one is getting the maths wrong.

[Daniel van Vugt (vanvugt)]

I run Noble on a bunch of laptops and the scaling issue you mention doesn't affect most of them. So I would like to treat that as a separate bug in which either the default scale threshold in plymouth or gnome-shell needs adjusting to match the other.

[Daniel van Vugt (vanvugt)]

The issue in comments #7 and #8 is being tracked separately in bug 2054769.

[Daniel van Vugt (vanvugt)]

It got a bit worse in Noble recently so we should track that separately in bug 2060893.