Expand description
SHM handling helpers
This module provides helpers to handle SHM-based buffers from wayland clients.
SHM (Shared Memory) is the most basic way wayland clients can send content to
the compositor: by sending a file descriptor to some (likely RAM-backed) storage
containing the actual data. This helper handles for you most of the logic for
handling these file descriptor and accessing their contents as simple &[u8] slices.
This module is heavily inspired from the similar helpers of the wayland C libraries.
To use it, first add a ShmGlobal to your display, specifying the formats
you want to support (ARGB8888 and XRGB8888 are always considered as supported,
as specified by the wayland protocol) and obtain its ShmToken.
extern crate wayland_server;
extern crate smithay;
use smithay::wayland::shm::init_shm_global;
use wayland_server::protocol::wl_shm::Format;
// Insert the ShmGlobal into your event loop
// Here, we specify that Yuyv and C8 format are supported
// additionally to the standard Argb8888 and Xrgb8888.
let shm_global = init_shm_global(
&mut display,
vec![Format::Yuyv, Format::C8],
None // we don't provide a logger here
);Then, when you have a WlBuffer
and need to retrieve its contents, use the
with_buffer_contents function to do it:
use smithay::wayland::shm::{with_buffer_contents, BufferData, BufferAccessError};
let content = with_buffer_contents(&buffer,
|slice: &[u8], buffer_metadata: BufferData| {
// do something to extract the contents of the buffer
}
);
match content {
Ok(something) => {
/* `something` is the content you returned from the closure */
},
Err(BufferAccessError::NotManaged) => {
/* This buffer is not managed by the SHM global, but by something else */
},
Err(BufferAccessError::BadMap) => {
/* The client supplied invalid content specification for this buffer,
and was killed.
*/
}
}Note
This handler makes itself safe regarding the client providing a wrong size for the memory pool by using a SIGBUS handler.
If you are already using an handler for this signal, you probably don’t want to use this handler.
Structs
ShmGlobal