The 4.12.343 workaround (WEBKIT_DISABLE_DMABUF_RENDERER=1 + GDK_BACKEND=x11)
made the app launch but pushed every frame through shared memory under
XWayland: noticeably laggy at 3840x2058. The reporter's WAYLAND_DEBUG trace
showed the real cause on native Wayland:
wl_display#1.error(wp_linux_drm_syncobj_surface_v1#51, 4,
"explicit sync is used, but no acquire point is set")
Gdk-Message: Error 71 (Protocol error) dispatching to Wayland display.
An explicit-sync bug, not a GBM format/modifier one. Their test matrix
(RTX 3070, driver 615.71.09, webkit2gtk 2.52.6, KDE Wayland):
- __NV_DISABLE_EXPLICIT_SYNC=1 alone: clean, GPU (DMA-BUF) renderer, smooth;
- WEBKIT_DISABLE_DMABUF_RENDERER=1 alone on Wayland: clean (no X11 needed);
- WEBKIT_DMABUF_RENDERER_DISABLE_GBM=1: same explicit-sync error on Wayland,
"Failed to import DMABuf" under XWayland;
- X11/XWayland with the DMA-BUF renderer: "Failed to create GBM buffer".
New defaults when the NVIDIA driver is loaded:
- native Wayland: __NV_DISABLE_EXPLICIT_SYNC=1, GPU renderer kept;
- X11 session or user-forced GDK_BACKEND=x11: WEBKIT_DISABLE_DMABUF_RENDERER=1;
- never force X11 any more;
- LOTUS_GPU_SAFE_MODE=1: opt-in shared-memory rendering on Wayland too;
- LOTUS_NO_GPU_WORKAROUNDS=1 / user-set values: untouched.
One stderr line says what was set. 9 unit tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA
Lotus CIandClaude Opus 5.5
bb5364b53c