Merge pull request #24: NVIDIA + Wayland keeps the GPU renderer

src-tauri/src/gpu_workarounds.rs

@@ -1,17 +1,22 @@
 //! WebKitGTK workarounds for NVIDIA's proprietary driver on Linux.
 //!
-//! On NVIDIA + Wayland (reported on CachyOS/KDE, driver 615, webkit2gtk 2.52)
-//! the app never shows a window: GDK dies with "Error 71 (Protocol error)
-//! dispatching to Wayland display", and under XWayland WebKit's DMA-BUF
-//! renderer then fails with "Failed to create GBM buffer … Invalid argument".
-//! `WEBKIT_DISABLE_DMABUF_RENDERER=1 GDK_BACKEND=x11` makes it run normally.
+//! Diagnosed on CachyOS/KDE Wayland, RTX 3070, driver 615.71.09, webkit2gtk
+//! 2.52.6 (reported 2026-09-27, WAYLAND_DEBUG trace in the PR):
+//! - Native Wayland: the compositor kills the connection with
+//!   `wp_linux_drm_syncobj_surface_v1 … "explicit sync is used, but no acquire
+//!   point is set"` (GDK: "Error 71 (Protocol error)"), i.e. an explicit-sync
+//!   bug between WebKit and the driver, not a buffer-format problem.
+//!   `__NV_DISABLE_EXPLICIT_SYNC=1` fixes it and keeps WebKit's GPU (DMA-BUF)
+//!   renderer, so that is the default on native Wayland.
+//! - X11 / XWayland: the DMA-BUF renderer can't allocate or import buffers
+//!   ("Failed to create GBM buffer … Invalid argument", "Failed to import
+//!   DMABuf"), so there it is disabled (`WEBKIT_DISABLE_DMABUF_RENDERER=1`,
+//!   shared-memory frames). We never force X11 any more.
 //!
-//! So, before GTK/WebKit initialise, and only when the NVIDIA driver is loaded:
-//! - `WEBKIT_DISABLE_DMABUF_RENDERER=1`;
-//! - on a Wayland session with XWayland available, `GDK_BACKEND=x11`.
-//!
-//! Anything the user already set wins, and `LOTUS_NO_GPU_WORKAROUNDS=1`
-//! disables all of it (e.g. once a newer driver/WebKit fixes this).
+//! Opt-ins / opt-outs (anything the user already set always wins):
+//! - `LOTUS_GPU_SAFE_MODE=1`: last resort, shared-memory rendering on Wayland
+//!   too (slower, especially at high resolutions).
+//! - `LOTUS_NO_GPU_WORKAROUNDS=1`: change nothing.
 
 /// Environment variables to set: pure, for tests.
 pub(crate) fn decide(
@@ -22,15 +27,30 @@ pub(crate) fn decide(
     if !nvidia || set("LOTUS_NO_GPU_WORKAROUNDS") {
         return Vec::new();
     }
-    let mut out = Vec::new();
-    if !set("WEBKIT_DISABLE_DMABUF_RENDERER") {
-        out.push(("WEBKIT_DISABLE_DMABUF_RENDERER", "1"));
-    }
-    let wayland = set("WAYLAND_DISPLAY")
+    let wayland_session = set("WAYLAND_DISPLAY")
         || get("XDG_SESSION_TYPE").is_some_and(|v| v.eq_ignore_ascii_case("wayland"));
-    // Only fall back to X11 when there is an X server (XWayland) to talk to.
-    if wayland && set("DISPLAY") && !set("GDK_BACKEND") {
-        out.push(("GDK_BACKEND", "x11"));
+    // GTK uses Wayland unless GDK_BACKEND says otherwise (it may list
+    // several, e.g. "wayland,x11": the first one wins).
+    let native_wayland = wayland_session
+        && get("GDK_BACKEND").map_or(true, |v| {
+            v.is_empty()
+                || v.trim_start().to_ascii_lowercase().starts_with("wayland")
+                || v.trim() == "*"
+        });
+
+    let mut out = Vec::new();
+    let mut want = |k: &'static str, v: &'static str| {
+        if !set(k) {
+            out.push((k, v));
+        }
+    };
+    if native_wayland {
+        want("__NV_DISABLE_EXPLICIT_SYNC", "1");
+        if set("LOTUS_GPU_SAFE_MODE") {
+            want("WEBKIT_DISABLE_DMABUF_RENDERER", "1");
+        }
+    } else {
+        want("WEBKIT_DISABLE_DMABUF_RENDERER", "1");
     }
     out
 }
@@ -44,9 +64,20 @@ fn nvidia_driver_loaded() -> bool {
 /// Call first thing in `main`, before anything starts GTK or spawns threads.
 pub fn apply() {
     #[cfg(target_os = "linux")]
-    for (key, value) in decide(nvidia_driver_loaded(), |k| std::env::var(k).ok()) {
-        eprintln!("gpu-workarounds: NVIDIA driver detected, setting {key}={value} (LOTUS_NO_GPU_WORKAROUNDS=1 to disable)");
-        std::env::set_var(key, value);
+    {
+        let changes = decide(nvidia_driver_loaded(), |k| std::env::var(k).ok());
+        if changes.is_empty() {
+            return;
+        }
+        let list: Vec<String> = changes.iter().map(|(k, v)| format!("{k}={v}")).collect();
+        eprintln!(
+            "gpu-workarounds: NVIDIA driver detected, setting {} \
+             (LOTUS_GPU_SAFE_MODE=1 for shared-memory rendering, LOTUS_NO_GPU_WORKAROUNDS=1 to disable)",
+            list.join(" ")
+        );
+        for (key, value) in changes {
+            std::env::set_var(key, value);
+        }
     }
 }
 
@@ -71,51 +102,70 @@ mod tests {
     }
 
     #[test]
-    fn nvidia_wayland_gets_both() {
+    fn nvidia_wayland_keeps_gpu_renderer_and_disables_explicit_sync() {
         assert_eq!(
             run(true, WAYLAND),
-            vec![
-                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1"),
-                ("GDK_BACKEND", "x11")
-            ]
+            vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]
         );
     }
 
     #[test]
-    fn nvidia_x11_session_only_disables_dmabuf() {
-        assert_eq!(
-            run(true, &[("DISPLAY", ":0")]),
-            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
-        );
-    }
-
-    #[test]
-    fn wayland_without_xwayland_keeps_wayland() {
-        assert_eq!(
-            run(true, &[("WAYLAND_DISPLAY", "wayland-0")]),
-            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
-        );
+    fn never_forces_x11() {
+        for env in [
+            WAYLAND,
+            &[("DISPLAY", ":0")][..],
+            &[("WAYLAND_DISPLAY", "w")][..],
+        ] {
+            assert!(run(true, env).iter().all(|(k, _)| *k != "GDK_BACKEND"));
+        }
     }
 
     #[test]
     fn xdg_session_type_counts_as_wayland() {
         assert_eq!(
-            run(true, &[("XDG_SESSION_TYPE", "wayland"), ("DISPLAY", ":1")]),
+            run(true, &[("XDG_SESSION_TYPE", "wayland")]),
+            vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]
+        );
+    }
+
+    #[test]
+    fn nvidia_x11_session_disables_dmabuf_renderer() {
+        assert_eq!(
+            run(true, &[("DISPLAY", ":0"), ("XDG_SESSION_TYPE", "x11")]),
+            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
+        );
+    }
+
+    #[test]
+    fn user_forced_x11_on_wayland_counts_as_x11() {
+        let mut env = WAYLAND.to_vec();
+        env.push(("GDK_BACKEND", "x11"));
+        assert_eq!(
+            run(true, &env),
+            vec![("WEBKIT_DISABLE_DMABUF_RENDERER", "1")]
+        );
+        let mut env = WAYLAND.to_vec();
+        env.push(("GDK_BACKEND", "wayland,x11"));
+        assert_eq!(run(true, &env), vec![("__NV_DISABLE_EXPLICIT_SYNC", "1")]);
+    }
+
+    #[test]
+    fn safe_mode_adds_shared_memory_rendering_on_wayland() {
+        let mut env = WAYLAND.to_vec();
+        env.push(("LOTUS_GPU_SAFE_MODE", "1"));
+        assert_eq!(
+            run(true, &env),
             vec![
-                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1"),
-                ("GDK_BACKEND", "x11")
+                ("__NV_DISABLE_EXPLICIT_SYNC", "1"),
+                ("WEBKIT_DISABLE_DMABUF_RENDERER", "1")
             ]
         );
     }
 
     #[test]
     fn user_settings_win() {
-        let env = [
-            ("WAYLAND_DISPLAY", "wayland-0"),
-            ("DISPLAY", ":0"),
-            ("WEBKIT_DISABLE_DMABUF_RENDERER", "0"),
-            ("GDK_BACKEND", "wayland"),
-        ];
+        let mut env = WAYLAND.to_vec();
+        env.push(("__NV_DISABLE_EXPLICIT_SYNC", "0"));
         assert!(run(true, &env).is_empty());
     }