webkit2gtk-nvidia-quirk 1.3.0

// Copyright 2026 hrzlgnm
// SPDX-License-Identifier: MIT-0

//! # webkit2gtk-nvidia-quirk
//!
//! A crate that provides session-aware workarounds for WebKitGTK rendering issues
//! on Linux systems with the proprietary NVIDIA driver.
//!
//! ## Problem
//!
//! When running WebKitGTK-based applications (such as Tauri apps) on Linux
//! with the proprietary NVIDIA driver, rendering issues occur that vary by session type:
//!
//! - **X11**: The DMABUF renderer causes blank windows
//! - **Wayland**: The application does not start
//!
//! Related upstream issues:
//! - [tauri-apps/tauri#10702](https://github.com/tauri-apps/tauri/issues/10702)
//! - [tauri-apps/tauri#9304](https://github.com/tauri-apps/tauri/issues/9304)
//! - [WebKitGTK Bug #280210](https://bugs.webkit.org/show_bug.cgi?id=280210)
//!
//! ## Solution
//!
//! This crate detects the proprietary NVIDIA driver and the session type (X11/Wayland),
//! then applies the appropriate workaround:
//!
//! | Session Type | Workaround | Environment Variable |
//! |-------------|------------|---------------------|
//! | X11 | Disable DMABUF renderer | `WEBKIT_DISABLE_DMABUF_RENDERER=1` |
//! | Wayland | Disable NVIDIA explicit sync | `__NV_DISABLE_EXPLICIT_SYNC=1` |
//!
//! ## Detection Method
//!
//! The crate detects the NVIDIA driver by:
//! 1. If the primary/boot GPU (via `boot_display` or `boot_vga` attributes) has vendor ID 0x10de
//! 2. If the proprietary `nvidia` kernel module is loaded (`/sys/module/nvidia` exists)
//!
//! GPU detection uses sysfs exclusively (`/sys/class/drm/`). This provides a simpler and
//! more reliable detection mechanism with no external runtime dependencies.
//!
//! This specifically targets the proprietary NVIDIA driver, not the open-source nouveau driver.
//!
//! ## Usage
//!
//! ```rust,no_run
//! use webkit2gtk_nvidia_quirk::{ApplyWorkaroundOptions, apply_workaround_with_options};
//!
//! let disable_dmabuf = std::env::args().any(|arg| arg == "--disable-dmabuf-renderer");
//! let disable_nv_sync = std::env::args().any(|arg| arg == "--disable-nv-explicit-sync");
//!
//! let options = ApplyWorkaroundOptions::default()
//!     .force_disable_dmabuf(disable_dmabuf)
//!     .force_disable_nv_explicit_sync(disable_nv_sync);
//!
//! apply_workaround_with_options(options);
//! ```
//!
//! ## API
//!
//! ### `is_primary_gpu_nvidia() -> bool`
//!
//! Checks whether the primary GPU is an NVIDIA GPU.
//!
//! Returns `true` if the primary GPU (boot_display or boot_vga attribute) has vendor ID 0x10de (NVIDIA),
//! Returns `false` otherwise. This function does not check kernel module loading.
//!
//! ### `needs_workaround() -> WorkaroundKind`
//!
//! Determines which workaround should be applied based on NVIDIA detection and session type.
//!
//! Returns `WorkaroundKind::None` if no workaround is needed, `WorkaroundKind::DisableWebkitDmabufRenderer`
//! for X11 sessions, or `WorkaroundKind::DisableNvExplicitSync` for Wayland sessions.
//!
//! ### `set_webkit_disable_dmabuf_renderer()`
//!
//! Sets the `WEBKIT_DISABLE_DMABUF_RENDERER` environment variable. Use this for X11 sessions.
//!
//! ### `nv_disable_explicit_sync()`
//!
//! Sets the `__NV_DISABLE_EXPLICIT_SYNC` environment variable. Use this for Wayland sessions.
//!
//! ### `apply_workaround_with_options(options: ApplyWorkaroundOptions)`
//!
//! Convenience function that applies workarounds based on the provided options.
//! If any force options are set, it applies those directly. Otherwise, it calls
//! [`needs_workaround`] to detect which workaround is needed.
//!
//! This is the recommended way to apply workarounds from CLI arguments.
//!
//! ### `WorkaroundKind`
//!
//! Enum representing the type of workaround to apply:
//! - `None`: No workaround needed
//! - `DisableWebkitDmabufRenderer`: Disable the DMABUF renderer (for X11)
//! - `DisableNvExplicitSync`: Disable NVIDIA explicit sync (for Wayland)
//!
//! ### `ApplyWorkaroundOptions`
//!
//! Builder struct for configuring which workarounds to force-apply.
//! Use the builder pattern to set options:
//! ```rust,no_run
//! use webkit2gtk_nvidia_quirk::{ApplyWorkaroundOptions, apply_workaround_with_options};
//!
//! let options = ApplyWorkaroundOptions::default()
//!     .force_disable_dmabuf(true);
//!
//! apply_workaround_with_options(options);
//! ```
//!
//! ## Platform Support
//!
//! This crate is Linux-only and provides no functionality on other platforms.

#![cfg(target_os = "linux")]

use std::path::{Path, PathBuf};

#[derive(Debug)]
struct GpuDevice {
    is_primary: bool,
    is_nvidia: bool,
}

fn read_sysfs_file(path: &Path) -> Option<String> {
    std::fs::read_to_string(path)
        .ok()
        .map(|s| s.trim().to_string())
}

fn parse_vendor_id(card_path: &Path) -> u16 {
    let vendor_path = card_path.join("device/vendor");
    if let Some(content) = read_sysfs_file(&vendor_path) {
        return u16::from_str_radix(content.strip_prefix("0x").unwrap_or(&content), 16)
            .unwrap_or(0);
    }
    0
}

fn is_sysfs_attr_one(card_path: &Path, attr: &str) -> bool {
    read_sysfs_file(&card_path.join(attr)).as_deref() == Some("1")
}

fn enumerate_gpus() -> Vec<GpuDevice> {
    let mut devices = Vec::new();
    let drm_path = PathBuf::from("/sys/class/drm");

    let entries = match std::fs::read_dir(&drm_path) {
        Ok(e) => e,
        Err(_) => return devices,
    };

    for entry in entries.flatten() {
        let file_name = entry.file_name();
        let sysname = match file_name.to_str() {
            Some(s) => s,
            None => continue,
        };

        if !sysname.starts_with("card") || sysname.contains('-') {
            continue;
        }

        let card_path = entry.path();
        let vendor_id = parse_vendor_id(&card_path);

        let is_primary = is_sysfs_attr_one(&card_path, "boot_display")
            || is_sysfs_attr_one(&card_path.join("device"), "boot_display")
            || is_sysfs_attr_one(&card_path.join("device"), "boot_vga");

        let is_nvidia = vendor_id == 0x10de;

        devices.push(GpuDevice {
            is_primary,
            is_nvidia,
        });
    }

    devices
}

fn nvidia_driver_loaded() -> bool {
    std::path::Path::new("/sys/module/nvidia").exists()
}

enum SessionType {
    Wayland,
    X11,
    Unknown,
}

/// Detects the used session type based upon the XDG_SESSION_TYPE environment variable
fn get_session_type() -> SessionType {
    match std::env::var("XDG_SESSION_TYPE") {
        Ok(session) => match session.as_str() {
            "x11" => SessionType::X11,
            "wayland" => SessionType::Wayland,
            _ => SessionType::Unknown,
        },
        _ => SessionType::Unknown,
    }
}

/// Represents the type of workaround to apply for NVIDIA WebKitGTK issues.
///
/// Use this enum to determine which workaround is needed based on the session type
/// and whether NVIDIA is detected.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum WorkaroundKind {
    /// No workaround needed.
    None,
    /// Disable the WebKit DMABUF renderer.
    ///
    /// This workaround is needed for X11 sessions with NVIDIA drivers.
    DisableWebkitDmabufRenderer,
    /// Disable NVIDIA explicit sync.
    ///
    /// This workaround is needed for Wayland sessions with NVIDIA drivers.
    DisableNvExplicitSync,
}

/// Checks if a workaround should be applied.
///
/// This function checks if the proprietary NVIDIA driver is loaded and the primary GPU is NVIDIA.
/// If so, it detects the session type (X11 or Wayland) and returns which workaround should be applied.
///
/// # Returns
///
///  `None` if no workaround is needed
///  `DisableWebkitDmabufRenderer` if disabling the dmabuf renderer should be applied
///  `DisableNvExplicitSync` if disabling nvidia explicit sync should be applied
///
/// # Note
///
/// This function only performs detection. Use [`set_webkit_disable_dmabuf_renderer`] or
/// [`nv_disable_explicit_sync`] to apply the respective workaround.
/// Call this first, then call the workaround if needed - ideally before spawning any threads.
pub fn needs_workaround() -> WorkaroundKind {
    let session = get_session_type();

    if !is_primary_gpu_nvidia() || !nvidia_driver_loaded() {
        return WorkaroundKind::None;
    }
    match session {
        SessionType::Wayland => WorkaroundKind::DisableNvExplicitSync,
        SessionType::X11 => WorkaroundKind::DisableWebkitDmabufRenderer,
        SessionType::Unknown => WorkaroundKind::None,
    }
}

/// Checks if the primary GPU is an NVIDIA GPU.
///
/// Returns `true` if the primary GPU (boot_display or boot_vga) is NVIDIA
/// Returns `false` otherwise.
pub fn is_primary_gpu_nvidia() -> bool {
    let devices = enumerate_gpus();

    devices.iter().any(|d| d.is_primary && d.is_nvidia)
}

/// Sets the `WEBKIT_DISABLE_DMABUF_RENDERER` environment variable.
///
/// This function should be called explicitly from single-threaded startup
/// (main) before spawning threads or when launching subprocesses.
///
/// # Note
///
/// This function modifies the process environment. Call it early in your
/// application's startup, before any threading has begun.
pub fn set_webkit_disable_dmabuf_renderer() {
    eprintln!("Note: disabling dmabuf renderer, expect degraded renderer performance.");
    eprintln!("See https://github.com/tauri-apps/tauri/issues/9304 for more details.");
    std::env::set_var("WEBKIT_DISABLE_DMABUF_RENDERER", "1");
}

/// Sets the `__NV_DISABLE_EXPLICIT_SYNC` environment variable.
///
/// This function should be called explicitly from single-threaded startup
/// (main) before spawning threads or when launching subprocesses.
///
/// # Note
///
/// This function modifies the process environment. Call it early in your
/// application's startup, before any threading has begun.
pub fn nv_disable_explicit_sync() {
    eprintln!("Note: disabling nvidia explicit sync.");
    eprintln!("See https://bugs.webkit.org/show_bug.cgi?id=280210 for more details");
    std::env::set_var("__NV_DISABLE_EXPLICIT_SYNC", "1");
}

/// Builder struct for configuring which workarounds to force-apply.
///
/// Use the builder pattern to set options before passing to [`apply_workaround_with_options`].
///
/// # Example
///
/// ```rust,no_run
/// use webkit2gtk_nvidia_quirk::{ApplyWorkaroundOptions, apply_workaround_with_options};
///
/// let options = ApplyWorkaroundOptions::default()
///     .force_disable_dmabuf(true)
///     .force_disable_nv_explicit_sync(true);
///
/// apply_workaround_with_options(options);
/// ```
#[derive(Default)]
pub struct ApplyWorkaroundOptions {
    /// Force disable the DMABUF renderer.
    pub force_disable_dmabuf: bool,
    /// Force disable NVIDIA explicit sync.
    pub force_disable_nv_explicit_sync: bool,
}

impl ApplyWorkaroundOptions {
    /// Sets the `force_disable_dmabuf` option.
    ///
    /// When `true`, the DMABUF renderer will be disabled regardless of
    /// whether NVIDIA is detected.
    pub fn force_disable_dmabuf(mut self, value: bool) -> Self {
        self.force_disable_dmabuf = value;
        self
    }

    /// Sets the `force_disable_nv_explicit_sync` option.
    ///
    /// When `true`, NVIDIA explicit sync will be disabled regardless of
    /// whether NVIDIA is detected.
    pub fn force_disable_nv_explicit_sync(mut self, value: bool) -> Self {
        self.force_disable_nv_explicit_sync = value;
        self
    }
}

/// Applies workarounds based on the provided options.
///
/// If any force options are set in `options`, those workarounds are applied directly.
/// Otherwise, it calls [`needs_workaround`] to detect which workaround is needed.
///
/// # Arguments
///
/// * `options` - The workaround options to apply
///
/// # Note
///
/// This function modifies the process environment. Call it early in your
/// application's startup, before any threading has begun.
pub fn apply_workaround_with_options(options: ApplyWorkaroundOptions) {
    if options.force_disable_dmabuf {
        set_webkit_disable_dmabuf_renderer();
    }
    if options.force_disable_nv_explicit_sync {
        nv_disable_explicit_sync();
    }
    if !options.force_disable_dmabuf && !options.force_disable_nv_explicit_sync {
        match needs_workaround() {
            WorkaroundKind::None => {}
            WorkaroundKind::DisableWebkitDmabufRenderer => set_webkit_disable_dmabuf_renderer(),
            WorkaroundKind::DisableNvExplicitSync => nv_disable_explicit_sync(),
        }
    }
}