[snap] artifacts when using HiDPI display

Status changed to 'Confirmed' because the bug affects multiple users.

Can someone with a HiDPI display please try to reproduce this bug with revision 96 or later? This bug is quite old and we have since made great improvements in regard to theme integration which includes cursor themes. It's possible the snap is still not getting the proper scale, but I would like to confirm before digging in to much.

Output of `snap --version`:
snap 2.36.2
snapd 2.36.2
series 16
ubuntu 18.10
kernel 4.18.0-13-generic

The bug is still there (just checked) and it is not only for LibreOffice. Here is from snapcraft forum -> https://forum.snapcraft.io/t/small-cursor-in-snap-apps-on-hidpi-display/5220

@ken-vandine Let me know if I can provide more information here.

I still have the problem in libreoffice, and I have revision 96.

----------
till@till-x1yoga:~/printing/openprinting/cups-filters/x$ snap --version
snap 2.36.2
snapd 2.36.2
series 16
ubuntu 18.10
kernel 4.18.0-11-generic
till@till-x1yoga:~/printing/openprinting/cups-filters/x$ snap list
Name Version Rev Tracking Publisher Notes
core 16-2.36.2 6034 stable canonical✓ core
core18 18 442 stable canonical✓ base
gtk-common-themes 0.1-4-g88bc1b2 818 stable canonical✓ -
libreoffice 6.1.3.2 96 stable canonical✓ -
lxd 3.0.3 9663 3.0/stable/… canonical✓ -
printing-stack-snap 0.1.0 x1 - - -
till@till-x1yoga:~/printing/openprinting/cups-filters/x$
----------

This also effects the Firefox snap.

I don't have a HiDPI-capable monitor, however I am able to observe and confirm the issue by setting the display scale to 200% (on the display control panel, `gnome-control-center display`). All UI elements become big, except for the cursors in some snaps.

Interestingly, not all snaps are affected:

 - libreoffice, chromium and firefox have small cursors
 - telegram-desktop behaves correctly (big cursors)
 - gnome-characters behaves correctly (big cursors)
 - gnome-calculators has mixed results: the arrow cursor is big, but the text caret cursor is small

 - evince snap: the arrow cursor is big, but other cursors (hand for clicking links in PDFs, text caret) are not scaled

I built a simple test snap with the Gtk hello world application (https://developer.gnome.org/gtk3/stable/gtk-getting-started.html#id-1.2.3.5, slightly modified to add a GtkEntry), built against core18 on bionic (Gtk 3.22.30).

With this snap, my observations are consistent with what I'm seeing with the gnome-characters and gnome-calculator snaps: the arrow cursor is scaled correctly, but other cursors (such as text caret) aren't.

This test snap uses the desktop-gtk3 part, plugs into the theme interfaces provided by gtk-common-themes, additionally to desktop, gsettings, unity7 and x11.

We have at least a couple of separate issues here:

 1) Standard GTK+ apps scale only the arrow cursor, other cursors (such as text caret) are not scaled properly

 2) Custom apps (including chromium, libreoffice, firefox) do not scale any cursor

Relevant logs when stracing the test snap execution:

openat(AT_FDCWD, "/snap/gtk-hello-world/x1/usr/share/icons/Yaru/cursors/text", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/snap/gtk-hello-world/x1/usr/share/icons/default/cursors/text", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/snap/gtk-hello-world/x1/usr/share/icons/Yaru/cursors/xterm", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/snap/gtk-hello-world/x1/usr/share/icons/default/cursors/xterm", O_RDONLY) = -1 ENOENT (No such file or directory)

And indeed even at a scale factor of 1.0, cursors are not the ones provided by the theme. They're likely the default X fallback versions.

… and both issues are fixed by this trivial PR: https://github.com/ubuntu/snapcraft-desktop-helpers/pull/170.

Tested and confirmed by rebuilding a simple GTK+ app snap, chromium and libreoffice.
Note that this won't work OOTB for firefox because it doesn't plug into gtk-common-themes.

The fix has been merged, now we need snaps to be rebuilt.

The libreoffice snap has been rebuilt and is now in the candidate channel (revision 99), for everyone interested in testing the fix.

And the chromium snap is currently rebuilding.

Both libreoffice and chromium have been rebuilt and published in the stable channel.
Marking the bug fixed, although other snaps will need to be rebuilt to pick up the fix.

Here we are in March 2020 and I still have a small @$$ cursor in LibreOffice snap version 6.4.1.2.
What the hell? I'm pretty sure the snap has been rebuilt since that fix that you say it's been merged. And it's not only with LibreOffice but with EVERY OTHER SNAP APP!

And here we are in March 2020 and I still get a small @$$ cursor. I mean come on man, I'm pretty sure than since you said that the fix was merged LibreOffice and surely many other snaps have been rebuilt. I am using LibreOffice snap version 6.4.1.2 and still the cursor looks awful, small and black (where instead I have a white cursor on my system).
I have this problem with nearly every other snap, only a small amount do actually respect the HiDPI and the theme of the cursor being consistent with the rest of my OS. The only ones that do work properly are Visual Studio Code, Blender and GIMP

It looks like snaps regressed in this regard. The regression is being tracked and investigated in bug #1900472.