[gui] sway: Window contents are not rendered on Wayland backend

Describe the bug When run in Sway, psst only displays the background of the window, but none of the contents. This means when first run, it display7s the log in screen as an empty white square. This is Wayland-specific as it doesn't happen when run in XWayland.

To Reproduce

• Build dev version
• cargo run --bin psst-gui

Expected behavior The contents of the windows should be displayed when using Wayland as the backend.

Screenshots Log in screen, not working:

Log in screen, XWayland:

After setting up a profile via XWayland and launching via Wayland. Notice it seems to skip log-in, and remembers the user's theme setting:

Environment

• OS: nixos unstable
• Version: master / de5c12f8b27385c609e73a9354b1a04a6e0953d2

Additional context

• Working version via XWayland: WAYLAND_DISPLAY= cargo run --bin psst-gui
• Repros on the release build
• I haven't had a chance to try other Wayland-based desktop environments