wayland: ghostty misses mouse cursor DPI rescale when mouse crosses monitor boundaries

[Hylian]

• uname: Linux natura 6.12.9-arch1-1 #1 SMP PREEMPT_DYNAMIC Fri, 10 Jan 2025 00:39:41 +0000 x86_64 GNU/Linux
• Display Server: sway (swayfx version 0.4-3e4b6b75 (Nov 19 2024, branch 'master') (based on sway 1.9.0))
• sway -t get_outputs: sway_get_outputs.txt
• ghostty --version:

Ghostty 1.0.1-arch

Version
  - version: 1.0.1-arch
  - channel: tip
Build Config
  - Zig version: 0.13.0
  - build mode : builtin.OptimizeMode.ReleaseFast
  - app runtime: apprt.Runtime.gtk
  - font engine: font.main.Backend.fontconfig_freetype
  - renderer   : renderer.OpenGL
  - libxev     : main.Backend.io_uring
  - GTK version:
    build      : 4.16.12
    runtime    : 4.16.12
  - libadwaita : enabled
    build      : 1.6.3
    runtime    : 1.6.0
  - libX11     : enabled

• ghostty config: hylian_ghostty_config.txt

Observed Behavior

2025-02-02.16-02-46.mp4

(The two displays are not to scale.)

I have ghostty on a monitor at 1.0 DPI scale, adjacent to a second monitor at 2.0 DPI scale. When I quickly move the mouse between the two monitors, ghostty occasionally draws the mouse cursor at 2x scale. The video first demonstrates the issue with a 3 pixel gap between the screen edge and the ghostty window. It then demos the issue with the ghostty window in fullscreen.

Additionally, this issue always occurs if keybindings are used to move the mouse. With the sway mouse_warping setting, the cursor is automatically moved to the center of the ghostty window when keybindings are used to switch focus. In this scenario, ghostty doesn't seem to be get any sort of "cursor entered window" event, and the cursor is always drawn at 2x scale.

Moving the cursor out of the ghostty window and back in fixes the issue.

Desired Behavior

• On wayland, ghostty should reliably catch cursor DPI scale events, with no races dependent on cursor speed.
• On wayland, ghostty should handle scenarios where the cursor teleports inside the window, and scale the cursor appropriately.

Thanks for building ghostty! The switch to ghostty felt like the first time I tried a high refresh rate monitor. The rendering is fantastic. :)

[Hylian]

Welp, I just saw 1.1.0 is out, and I haven't been able to reproduce it on that so far. So this issue might be out of date.

[mitchellh]

Nice. If you can reproduce it please let me know.