Wayland: Window::set_mouse_visible doesn't work when window was clicked.

[tobtobxx]

Description

Calling Window::set_cursor_visible hides or shows the cursor. On Linux Wayland (GNOME 42) though, this doesn't work once you've clicked the window (at least) once.

Demo code

I've composed a demo to reproduce it here: https://git.sr.ht/~tobtobxx/winit-wayland-mouse-demo

Behavior

1. Compile & Run this code.
2. Correct behaviour: C hides and shows the cursor.
3. Click anywhare inside the window.
4. Incorrect behaviour: C doesn't work anymore.
5. Moving the mouse outside the window restores the correct behaviour.

(the hotkey C just toggles the call to set_cursor_visible: source.)

References

I first stumbled across this in veloren. It is reported there too: Veloren, issue #1464

[kchibisov]

Do you have cursor theme installed and configured properly? I can't repro it with alacritty which hides the cursor on typing. Your demo works fine for me, C works regardless of clicking.

Consult https://wiki.archlinux.org/title/Cursor_themes#XDG_specification

[tobtobxx]

Yes, I had tried setting the cursor theme via the env vars XCURSOR_THEME and XCURSOR_SIZE. I have checked, I have the package extra/adwaita-icon-theme (Arch) installed.

As you suggested, I created the file ~/.icons/default/index.theme:

[icon theme]
Inherits=Adwaita

That didn't work. I also edited the ~/.config/gtk-3.0/settings.ini file to include the suggested line:

[Settings]
gtk-application-prefer-dark-theme=1
gtk-font-name=Noto Sans 11
gtk-icon-theme-name=Adwaita
gtk-theme-name=Adwaita
gtk-cursor-theme-name=Adwaita # <--- This is the new line

And I also checked the gnome-specific settings shown in the Arch Wiki:

$ gsettings get org.gnome.desktop.interface cursor-theme
'Adwaita'
$ gsettings get org.gnome.desktop.interface cursor-size
24

Note that showing and hiding the cursor works just fine, arbitrary many times. It breaks down once you clicked within the window and only starts working again once the cursor leaves the window.

[kchibisov]

I can't repro the issue no matter what I do with your example, neither with alacritty. What compositor are you using?

Also, you could try strace it and see what it loads for cursor theme.

[tobtobxx]

neither with alacritty

Weird, I downloaded Alacritty and enabled mouse hiding only to observe the same broken behaviour: Works, until I clicked once within the Window. Which compositor are you using?

What compositor are you using?

Not so sure which Arch package exactly is the gnome compositor, so here all that seem relevant:

gnome-desktop 1:42.1-1
gnome-desktop-4 1:42.1-1
gnome-desktop-common 1:42.1-1
gnome-session 42.0-1
gnome-shell 1:42.0-1
xdg-desktop-portal-gnome 42.1-1

Also, you could try strace it and see what it loads for cursor theme.

Did it, the full log is attached. Grepped for Adwaita and found that it (sucessfully) read at least these files:

• /home/tobtobxx/.icons/default/index.theme file: ASCII text
• /usr/share/icons/default/index.theme file: ASCII text
• /usr/share/icons/Adwaita/index.theme file: ASCII text, with very long lines (1372)
• /usr/share/icons/Adwaita/cursors/left_ptr file: X11 cursor

[...]
statx(AT_FDCWD, "/home/tobtobxx/.icons/default", AT_STATX_SYNC_AS_STAT, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFDIR|0755, stx_size=4096, ...}) = 0
openat(AT_FDCWD, "/home/tobtobxx/.icons/default/index.theme", O_RDONLY|O_CLOEXEC) = 18
statx(18, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=31, ...}) = 0
lseek(18, 0, SEEK_CUR)                  = 0
read(18, "[icon theme]\nInherits=Adwaita\n\n", 31) = 31
read(18, "", 32)                        = 0
close(18)                               = 0
[...]
statx(AT_FDCWD, "/usr/share/icons/default", AT_STATX_SYNC_AS_STAT, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFDIR|0755, stx_size=4096, ...}) = 0
openat(AT_FDCWD, "/usr/share/icons/default/index.theme", O_RDONLY|O_CLOEXEC) = 18
statx(18, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=30, ...}) = 0
lseek(18, 0, SEEK_CUR)                  = 0
read(18, "[Icon Theme]\nInherits=Adwaita\n", 30) = 30
read(18, "", 32)                        = 0
close(18)                               = 0
[...]
statx(AT_FDCWD, "/usr/share/icons/Adwaita", AT_STATX_SYNC_AS_STAT, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFDIR|0755, stx_size=4096, ...}) = 0
openat(AT_FDCWD, "/usr/share/icons/Adwaita/index.theme", O_RDONLY|O_CLOEXEC) = 18
statx(18, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=7425, ...}) = 0
lseek(18, 0, SEEK_CUR)                  = 0
read(18, "[Icon Theme]\nName=Adwaita\nCommen"..., 7425) = 7425
read(18, "", 32)                        = 0
close(18)                               = 0
[...]
statx(AT_FDCWD, "/usr/share/icons/Adwaita/cursors/left_ptr", AT_STATX_SYNC_AS_STAT, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=69120, ...}) = 0
openat(AT_FDCWD, "/usr/share/icons/Adwaita/cursors/left_ptr", O_RDONLY|O_CLOEXEC) = 18
statx(18, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=69120, ...}) = 0
lseek(18, 0, SEEK_CUR)                  = 0
read(18, "Xcur\20\0\0\0\0\0\1\0\5\0\0\0\2\0\375\377\30\0\0\0L\0\0\0\2\0\375\377"..., 69120) = 69120
read(18, "", 32)                        = 0
brk(0x564852bd4000)                     = 0x564852bd4000
lseek(16, 0, SEEK_END)                  = 1024
ftruncate(16, 3328)                     = 0
write(16, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2304) = 2304
close(18)                               = 0

strace.txt

[tobtobxx]

To Debug, I added dbg!(&cursor_icon) line in the platform_impl::wayland::window::shim::WindowHandle::set_cursor_visible() function (here).

I can't say whether this output is what is expected, but it doesn't seem odd:

[/home/tobtobxx/projects/winit/src/platform_impl/linux/wayland/window/shim.rs:342] &cursor_icon = Some(
    Default,
)
[/home/tobtobxx/projects/winit/src/platform_impl/linux/wayland/window/shim.rs:342] &cursor_icon = None
[/home/tobtobxx/projects/winit/src/platform_impl/linux/wayland/window/shim.rs:342] &cursor_icon = Some(
    Default,
)
[/home/tobtobxx/projects/winit/src/platform_impl/linux/wayland/window/shim.rs:342] &cursor_icon = None
[/home/tobtobxx/projects/winit/src/platform_impl/linux/wayland/window/shim.rs:342] &cursor_icon = Some(
    Default,
)
[/home/tobtobxx/projects/winit/src/platform_impl/linux/wayland/window/shim.rs:342] &cursor_icon = None
[/home/tobtobxx/projects/winit/src/platform_impl/linux/wayland/window/shim.rs:342] &cursor_icon = Some(
    Default,
)

(I triggered the bug in between these lines.)

Also btw, another behavior I noticed working correctly is when I set the size using the XCURSOR_SIZE=60 env var. This correctly enlarges the mouse. Issue with hiding still persists though.

[kchibisov]

Weird, I downloaded Alacritty and enabled mouse hiding only to observe the same broken behaviour: Works, until I clicked once within the Window. Which compositor are you using?

I'm using sway. Could you repro the issue on it?

Also btw, another behavior I noticed working correctly is when I set the size using the XCURSOR_SIZE=60 env var. This correctly enlarges the mouse. Issue with hiding still persists though.

Hm, that means that cursor theme is indeed loaded correctly. The output you've linked seems about right...

[kchibisov]

Probably WAYLAND_DEBUG=1 log is something that could help.

[tobtobxx]

Hah, maybe I gottem (maybe not, I'm by no means an expert of Wayland and all that stuff):

Read this last line of the docs:
wayland_client::protocol::wl_pointer::WlPointer::set_cursor():

The serial parameter must match the latest wl_pointer.enter serial number sent to the client. Otherwise the request will be ignored.

I logged the serial number of each call and when (once) clicked, the serial number changes. If I read correctly, due to this line. I removed the line and it works now!

It seems like set_cursor() requires the serial number of the last wl_pointer.enter event, while (probably) other functions need the serial number from any latest event. Thus I think removing this line will probably break stuff, but this is something that you probably know better.

I'm using sway. Could you repro the issue on it?

Nope, couldn't repro it on sway.

This also doesn't definitively explain the discrepancy between sway and gnome. Could be just a laxer implementation of sway, but that'd need to be verified.

[tobtobxx]

I researched further and made a fix. See the PR for more.

[kchibisov]

Read this last line of the docs:

Yeah, that part got added into wayland.xml ~6 month after I wrote that part of wayland backend in winit, so it kind of expected that it broke...