wayland_backend/sys/

mod.rs

//! Implementations of the Wayland backends using the system `libwayland`

use smallvec::SmallVec;
use std::ffi::CString;
use std::num::NonZeroU32;
use std::os::unix::io::{AsRawFd, FromRawFd, OwnedFd};
use std::ptr::{self, NonNull};
use std::sync::Arc;

use wayland_sys::client::wl_proxy;
use wayland_sys::common::{wl_argument, wl_array};

use crate::protocol::{Argument, ArgumentType, Interface, OwnedArgument};

#[cfg(any(test, feature = "client_system", feature = "server_system"))]
use std::ffi::c_void;

#[cfg(any(test, feature = "client_system"))]
mod client_impl;
#[cfg(any(test, feature = "server_system"))]
mod server_impl;

/// Magic static for wayland objects managed by wayland-client or wayland-server
///
/// This static serves no purpose other than existing at a stable address.
static RUST_MANAGED: u8 = 42;

/// Client-side implementation of a Wayland protocol backend using `libwayland`
///
/// Entrypoints are:
/// - [`Backend::connect()`][client::Backend::connect()] method if you're creating the Wayland connection
/// - [`Backend::from_foreign_display()`][client::Backend::from_foreign_display()] if you're interacting with an
///   already existing Wayland connection through FFI.
#[cfg(any(test, feature = "client_system"))]
#[path = "../client_api.rs"]
pub mod client;
#[cfg(any(test, feature = "client_system"))]
use client::{ObjectData, ObjectId};

// API complements for FFI

#[cfg(any(test, feature = "client_system"))]
impl client::ObjectId {
    /// Creates an object id from a libwayland-client pointer.
    ///
    /// # Errors
    ///
    /// This function returns an [`InvalidId`][client::InvalidId] error if the interface of the proxy does
    /// not match the provided interface.
    ///
    /// # Safety
    ///
    /// The provided pointer must be a valid pointer to a `wl_resource` and remain valid for as
    /// long as the retrieved `ObjectId` is used.
    pub unsafe fn from_ptr(
        interface: &'static crate::protocol::Interface,
        ptr: NonNull<c_void>,
    ) -> Result<Self, client::InvalidId> {
        Ok(Self {
            id: unsafe { client_impl::InnerObjectId::from_ptr(interface, ptr.cast::<wl_proxy>()) }?,
        })
    }

    /// Get the underlying libwayland pointer for this object
    ///
    /// # Errors
    ///
    /// This function returns an [`InvalidId`][client::InvalidId] error if proxy has already
    /// been destroyed.
    pub fn as_ptr(&self) -> Result<NonNull<c_void>, client::InvalidId> {
        Ok(self.id.as_ptr()?.cast())
    }

    /// Get the underlying display pointer for this object.
    ///
    /// This pointer is associated with the original display this object
    /// belongs to.
    #[cfg(feature = "libwayland_client_1_23")]
    pub fn display_ptr(&self) -> Result<NonNull<c_void>, crate::types::client::InvalidId> {
        Ok(self.id.display_ptr()?.cast())
    }
}

#[cfg(any(test, feature = "client_system"))]
impl client::Backend {
    /// Creates a Backend from a foreign `*mut wl_display`.
    ///
    /// This is useful if you are writing a library that is expected to plug itself into an existing
    /// Wayland connection.
    ///
    /// This will initialize the [`Backend`][Self] in "guest" mode, meaning it will not close the
    /// connection on drop. After the [`Backend`][Self] is dropped, if the server sends an event
    /// to an object that was created from it, that event will be silently discarded. This may lead to
    /// protocol errors if the server expects an answer to that event, as such you should make sure to
    /// cleanup your Wayland state before dropping the [`Backend`][Self].
    ///
    /// # Safety
    ///
    /// You need to ensure the `*mut wl_display` remains live as long as the  [`Backend`][Self]
    /// (or its clones) exist.
    pub unsafe fn from_foreign_display(display: NonNull<c_void>) -> Self {
        Self {
            backend: unsafe {
                client_impl::InnerBackend::from_foreign_display(
                    display.cast::<wayland_sys::client::wl_display>(),
                )
            },
        }
    }

    /// Returns the underlying `wl_display` pointer to this backend.
    ///
    /// This pointer is needed to interface with EGL, Vulkan and other C libraries.
    ///
    /// This pointer is only valid for the lifetime of the backend.
    pub fn display_ptr(&self) -> *mut c_void {
        self.backend.display_ptr().cast()
    }

    /// Take over handling for a proxy created by a third party.
    ///
    /// # Safety
    ///
    /// There must never be more than one party managing an object. This is only
    /// safe to call when a third party gave you ownership of an unmanaged proxy.
    ///
    /// The caller is also responsible for making sure the passed interface matches
    /// the proxy.
    #[inline]
    pub unsafe fn manage_object(
        &self,
        interface: &'static Interface,
        proxy: *mut c_void,
        data: Arc<dyn ObjectData>,
    ) -> ObjectId {
        unsafe { self.backend.manage_object(interface, proxy.cast::<wl_proxy>(), data) }
    }
}

#[cfg(any(test, feature = "client_system"))]
impl client::ReadEventsGuard {
    /// The same as [`read`], but doesn't dispatch events.
    ///
    /// To dispatch them, use [`dispatch_inner_queue`].
    ///
    /// [`read`]: client::ReadEventsGuard::read
    /// [`dispatch_inner_queue`]: client::Backend::dispatch_inner_queue
    pub fn read_without_dispatch(mut self) -> Result<(), client::WaylandError> {
        self.guard.read_non_dispatch()
    }
}

#[cfg(all(feature = "rwh_06", feature = "client_system"))]
impl rwh_06::HasDisplayHandle for client::Backend {
    fn display_handle(&self) -> Result<rwh_06::DisplayHandle<'_>, rwh_06::HandleError> {
        use std::ptr::NonNull;

        // SAFETY:
        // - The display_ptr will be valid, either because we have created the pointer or the caller which created the
        //   backend has ensured the pointer is valid when `Backend::from_foreign_display` was called.
        let ptr = unsafe { NonNull::new_unchecked(self.display_ptr().cast()) };
        let handle = rwh_06::WaylandDisplayHandle::new(ptr);
        let raw = rwh_06::RawDisplayHandle::Wayland(handle);

        // SAFETY:
        // - The display_ptr will be valid, either because we have created the pointer or the caller which created the
        //   backend has ensured the pointer is valid when `Backend::from_foreign_display` was called.
        // - The lifetime assigned to the DisplayHandle borrows the Backend, ensuring the display pointer
        //   is valid..
        // - The display_ptr will not change for the lifetime of the backend.
        Ok(unsafe { rwh_06::DisplayHandle::borrow_raw(raw) })
    }
}

/// Server-side implementation of a Wayland protocol backend using `libwayland`
///
/// The main entrypoint is the [`Backend::new()`][server::Backend::new()] method.
#[cfg(any(test, feature = "server_system"))]
#[path = "../server_api.rs"]
pub mod server;

#[cfg(any(test, feature = "server_system"))]
impl server::ObjectId {
    /// Creates an object from a C pointer.
    ///
    /// # Errors
    ///
    /// This function returns an [`InvalidId`][server::InvalidId] error if the interface of the
    /// resource does not match the provided interface.
    ///
    /// # Safety
    ///
    /// The provided pointer must be a valid pointer to a `wl_resource` and remain valid for as
    /// long as the retrieved `ObjectId` is used.
    pub unsafe fn from_ptr(
        interface: &'static crate::protocol::Interface,
        ptr: NonNull<c_void>,
    ) -> Result<Self, server::InvalidId> {
        Ok(Self {
            id: unsafe {
                server_impl::InnerObjectId::from_ptr(
                    Some(interface),
                    ptr.cast::<wayland_sys::server::wl_resource>(),
                )
            }?,
        })
    }

    /// Returns the pointer that represents this object.
    ///
    /// The pointer may be used to interoperate with libwayland.
    ///
    /// # Errors
    ///
    /// This function returns an [`InvalidId`][server::InvalidId] error if resource has already
    /// been destroyed.
    pub fn as_ptr(&self) -> Result<NonNull<c_void>, server::InvalidId> {
        Ok(self.id.as_ptr()?.cast())
    }
}

#[cfg(any(test, feature = "server_system"))]
impl server::Handle {
    /// Access the underlying `*mut wl_display` pointer
    pub fn display_ptr(&self) -> *mut c_void {
        self.handle.display_ptr().cast()
    }
}

unsafe fn parse_arg<O>(
    typ: &ArgumentType,
    arg: &wl_argument,
) -> OwnedArgument<Option<NonNull<O>>, Option<NonZeroU32>> {
    match typ {
        ArgumentType::Uint => OwnedArgument::Uint(unsafe { arg.u }),
        ArgumentType::Int => OwnedArgument::Int(unsafe { arg.i }),
        ArgumentType::Fixed => OwnedArgument::Fixed(unsafe { arg.f }),
        ArgumentType::Fd => OwnedArgument::Fd(unsafe { OwnedFd::from_raw_fd(arg.h) }),
        ArgumentType::Array => {
            let array = unsafe { &*arg.a };
            // Safety: the array provided by libwayland must be valid
            let content = unsafe { std::slice::from_raw_parts(array.data as *mut u8, array.size) };
            OwnedArgument::Array(Box::new(content.into()))
        }
        ArgumentType::Str(_) => {
            let ptr = unsafe { arg.s };
            // Safety: the c-string provided by libwayland must be valid
            OwnedArgument::Str(if !ptr.is_null() {
                // TODO: Should we error on invalid UTF-8?
                let s = unsafe { std::ffi::CStr::from_ptr(ptr) }.to_string_lossy();
                Some(Box::new(s.into_owned()))
            } else {
                None
            })
        }
        ArgumentType::Object(_) => OwnedArgument::Object(NonNull::new(unsafe { arg.o as *mut O })),
        ArgumentType::NewId => OwnedArgument::NewId(NonZeroU32::new(unsafe { arg.n })),
    }
}

struct SerializedArgs {
    signature: &'static [ArgumentType],
    args: SmallVec<[wl_argument; 4]>,
}

impl SerializedArgs {
    fn new(signature: &'static [ArgumentType]) -> Self {
        Self { signature, args: SmallVec::<[wl_argument; 4]>::with_capacity(signature.len()) }
    }

    fn add<O>(&mut self, arg: Argument<Option<NonNull<O>>, Option<NonZeroU32>>) {
        self.args.push(match arg {
            Argument::Uint(u) => wl_argument { u },
            Argument::Int(i) => wl_argument { i },
            Argument::Fixed(f) => wl_argument { f },
            Argument::Fd(h) => wl_argument { h: h.as_raw_fd() },
            Argument::Array(ref a) => {
                let a = Box::new(wl_array {
                    size: a.len(),
                    alloc: a.len(),
                    data: a.as_ptr() as *mut _,
                });
                wl_argument { a: Box::into_raw(a) }
            }
            Argument::Str(Some(ref s)) => {
                // Panic if string contains internal \0 byte
                let s = CString::new((**s).to_owned()).unwrap();
                wl_argument { s: s.into_raw() }
            }
            Argument::Str(None) => wl_argument { s: std::ptr::null() },
            Argument::Object(o) => {
                wl_argument { o: o.map_or_else(ptr::null, |o| o.as_ptr()) as *const _ }
            }
            Argument::NewId(n) => wl_argument { n: n.map_or(0, |n| n.get()) },
        });
    }
}

impl Drop for SerializedArgs {
    fn drop(&mut self) {
        for (typ, arg) in self.signature.iter().zip(self.args.iter()) {
            // Safety: the arglist provided arglist must be valid for associated signature
            // and contains pointers to boxed arrays/cstrings as appropriate
            if let ArgumentType::Array = typ {
                let _ = unsafe { Box::from_raw(arg.a as *mut wl_array) };
            } else if let ArgumentType::Str(_) = typ {
                let ptr = unsafe { arg.s };
                if !ptr.is_null() {
                    let _ = unsafe { CString::from_raw(ptr as *mut _) };
                }
            }
        }
    }
}

fn cast_non_null_ref<T>(ptr: &NonNull<T>) -> &Option<NonNull<T>> {
    // SAFETY: `Option<NonNull<T>>` is guaranteed to have same repr as `NonNull<T>`
    unsafe { &*(ptr as *const _ as *const _) }
}