UE 5.7 Window, Tooltip, and Popup bugs on Linux w/ Wayland

Summary

UE 5.7 has numerous bugs on Linux (particularly Wayland) and I’ve started chasing them down in the engine source.

  1. Tooltips do not properly render/resize, resulting in broken, messy, layered, cropped, unreadable tooltips.
  2. Menu dropdowns do not render in the correct location on the screen or relative to the window. Instead, they render vertically and horizontally centered relative to the parent window.
  3. Mouse targeting of UI elements (buttons, menu items, etc) is mismatched / shifted downward.
  4. Notification popups are not interactable and will stay in the middle of the screen permanently as a result.
  5. Single-click interactions do not register, requiring multiple clicks.

I cluster these things together because they all seem to be related and may have the same fix (or small set of fixes, at least).

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

UI/Tools

Steps to Reproduce

Run UE 5.7 (download or compile from source) on a Linux distro that using Wayland as it’s compositor (which is most modern desktop environments). Attempt to interact with menus or anything at all.

Expected Result

Menus, sub-windows, notifications, tooltips, etc should render in the correct locations, be interactable with the mouse at the cursor location, and should render neatly at the correct size.

Observed Result

Menus display in the wrong place (centered on window), single-clicks require multiple clicks before they register, tooltips are badly broken in multiple ways, popups are centered on screen and cannot be dismissed or interacted with.

Platform(s)

Linux - any desktop environment that is using Wayland

Additional Notes

I’ve started working on some patches. For the time being, there are some workarounds…

Workarounds

  1. Problems with window locations can be fixed by forcing X11. This is done by adding an environment variable when launching UE: SDL_VIDEODRIVER=x11

The following contains fixes for Tooltip rendering, though the focus problem that causes single clicks to require multiple clicks is still present (I am chasing that down).

https://github.com/Veraxus/UnrealEngine/blob/feature/linux-wayland-tooltip-fix/Engine/Source/Runtime/Slate/Private/Framework/Application/SlateUser.cpp