Rust-XCB is a safe Rust interface to XCB. Rust-XCB uses under the hood the core XCB functions to connect and communicate with the X server.
Documentation: https://rust-x-bindings.github.io/rust-xcb/xcb/
Rust-XCB is constituted of the following components: - the core library - the X protocol and its extensions
See CONTRIBUTING.md for contributions.
The main component is the Connection class which is used to connect and
communicate to the X server. The Connection class wraps calls to the C XCB
functions in a safe to use interface.
In the new API (v1.0+), Rust-XCB takes care of all the heavy lifting of event
and error resolution, including the handling of the different kinds of event
(regular events, "GeGeneric" events, the specifics about Xkb ...) and present
them under a unified and safe to use enum instead of requesting the user to
perform unsafe cast as in the C library.
The core library also provides many traits that are used in the protocol
implementation. e.g. the BaseEvent and BaseError traits, the Reply trait...
The Raw trait is also provided to convert into and from C event or error types.
The core X protocol and all the extensions present in XCB are generated by the
build scripts, entirely written in Rust.
The build script do not generate bindings to the C protocol extensions, it
generates a safe Rust implementation of the protocol:
- Simple structures that have the same memory layout than C are translated in
Rust directly (e.g. points etc.)
- More complex structures wrap a slice of raw data and provide accessor methods
(Debug will still print all the members)
- The masks use the bitflags crate macro
- The enums are enums!
- The unions are also enums, but they carry data
- The Xids (handles to windows, pixmaps etc.) are type-safe implementations of
the Xid trait, not just integers.
- The requests are structures that serialize themselves when passed to the
Connection.
- Each request has two type of cookie, for checked and unchecked requests.
This allows type safe reply fetching and error checking
- The protocol and each extension provide an Event and an Error enum,
which are unified by the core library.
All types in Rust XCB implement Debug in a way that allows recursive debug print.
E.g. iterators will not print a useless pointer value, but will recurse down to each element.
There is in addition the optional "debug_atom_names" cargo feature under which each atom
will print its name for easier debugging in some situations.
For example, Xinput provide some information about input devices with atom identifiers.
This allows you to quickly look-up which atoms you need to intern and seek for.
E.g. the feature would turn:
Atom {
res_id: 303,
}
into
Atom("Abs Pressure" ; 303)
The feature sets global variable to have access to the connection in the Debug::fmt call,
so it should be activated only when needed.
Here are some highlights of the v1.0 API compared to the v0.x API.
Previously, the core X protocol was directly accessible under the xcb crate
namespace. This is no longer the case, the protocol is under the x module,
and each extension gets its own module too like before.
Only the core library is directly accessible under xcb.
This helps for a clean separation of concerns and save a lot of confusion in
regards to the new event and error types.
```rust // v0.x let window = conn.generate_id(); // this is a u32
let values = [ (xcb::CWBACKPIXEL, screen.whitepixel()), ( xcb::CWEVENTMASK, xcb::EVENTMASKEXPOSURE | xcb::EVENTMASKKEYPRESS, ), ];
xcb::createwindow( &conn, xcb::COPYFROMPARENT as u8, window, screen.root(), 0, 0, 150, 150, 10, xcb::WINDOWCLASSINPUTOUTPUT as u16, screen.root_visual(), &values, );
// v1.0
let window: x::Window = conn.generate_id();
conn.sendrequest(&x::CreateWindow { depth: x::COPYFROMPARENT as u8, wid: window, parent: screen.root(), x: 0, y: 0, width: 150, height: 150, borderwidth: 10, class: x::WindowClass::InputOutput, visual: screen.rootvisual(), valuelist: &[ x::Cw::BackPixel(screen.whitepixel()), x::Cw::EventMask(x::EventMask::EXPOSURE | x::EventMask::KEYPRESS), ], }); ```
```rust // v0.x // same cookie than for xcb::mapwindow let cookie = xcb::mapwindowchecked(&conn, window); // this error is a simple wrapper over xcbgenericerrort cookie.request_check()?;
// v1.0
// specific cookie type for the checked request
// code would not compile with conn.send_request(..)
let cookie = conn.sendrequestchecked(&x::MapWindow {window});
// reports a resolved error enum (e.g. x::Error::Drawable(..))
conn.check_request(cookie)?;
```
``rust
// 0.x
loop {
let event = conn.wait_for_event();
// Errors are only wrappers around generic C errors and must be casted
// from the event ifresponsetype` is 0. That seem very safe Rust...
// I am the core author and I don't exactly know how to do proper error
// handling with the 0.x API...
match event {
None => {
break;
}
Some(event) => {
let r = event.responsetype();
if r == 0 {
// This is an error.
panic!("received error from the X server");
} else if r == xcb::KEYPRESS as u8 {
let keypress: &xcb::KeyPressEvent = unsafe {
// so much for the safe interface
xcb::cast_event(&event)
};
// do stuff
} else if r == xkb_first_event {
// resolving extension events like we would in C
// very poor support is provided (not better than C)
}
}
}
}
// 1.0 fn main() -> xcb::Result<()> { // ... loop { match conn.waitforevent()? { xcb::Event::X(x::Event::KeyPress(key_press)) => { // do stuff } xcb::Event::Xkb(xkb::Event::MapNotify(ev)) => { // do other stuff (pass data to xkbcommon for example) } _ => {} } } } ```