Summary
Environment:
- Unreal Engine 5.8.4 (binary build from Epic, Linux zip)
- Rocky Linux 9.8 (RHEL 9), GNOME 40 on X11 (Mutter compositing)
- NVIDIA RTX 3090, driver 580, Vulkan SM6 only
- AMD Ryzen 9 5900X, 128 GB RAM, 2x 3840x2160 @ 60 Hz
Description:
Every dropdown menu, context menu and popup window in the editor opens with a visible blank/garbage frame before the content appears, and menus feel sluggish compared to Windows.
- First frame glitch: each new popup window shows one or more frames of uninitialized content. It looks like the SDL window is mapped (FLinuxWindow::Show) before the Vulkan swapchain has presented content for it; the swapchain is then recreated. Under a compositing X11 window manager, the empty window is visible during that time.
- Background throttling: on Linux, popup menus are separate top-level windows that take focus, so the main editor window is treated as “in background”. With Editor Preferences → Use Less CPU when in Background ON (default), the editor throttles while a menu is open, making menus noticeably laggy. Turning it OFF improves this, but the first-frame glitch remains.
Workaround: disabling Use Less CPU when in Background partly helps. No workaround found for the first-frame glitch.
What Type of Bug are you experiencing?
Editor
Steps to Reproduce
- Start UE 5.8.4 on Linux under an X11 session with a compositing WM (GNOME/Mutter).
- Open any project and click any main menu (File, Edit, Window) or right-click in the Content Browser.
- Observe a blank/garbage frame before the menu draws; repeat with Use Less CPU when in Background ON and OFF.
Expected Result
menus open instantly with correct content, as on Windows.
Observed Result
a visible blank or garbage frame on every popup, and slow menus when background throttling is active
Affects Versions
5.8
Platform(s)
Linux
Video
