feat: load cursor from data

I want to add a function to load cursor from data

wayland-cursor/src/lib.rs

@@ -45,7 +45,9 @@
 //! # }
 //! ```
 
+use std::borrow::Cow;
 use std::env;
+use std::fmt::Debug;
 use std::fs::File;
 use std::io::{Error as IoError, Read, Result as IoResult, Seek, SeekFrom, Write};
 use std::ops::{Deref, Index};
@@ -81,6 +83,24 @@ pub struct CursorTheme {
  pool_size: i32,
  file: File,
  backend: WeakBackend,
+ fallback: Option<FallBack>,
+}
+
+struct FallBack(Box<dyn Fn(&str) -> Cow<'static, [u8]>>);
+
+impl FallBack {
+ fn new<F>(fallback: F) -> Self
+ where
+ F: Fn(&str) -> Cow<'static, [u8]> + 'static,
+ {
+ Self(Box::new(fallback))
+ }
+}
+
+impl Debug for FallBack {
+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+ f.write_str("fallback function")
+ }
 }
 
 impl CursorTheme {
@@ -160,23 +180,46 @@ impl CursorTheme {
  pool_size: INITIAL_POOL_SIZE,
  cursors: Vec::new(),
  backend: conn.backend().downgrade(),
+ fallback: None,
  })
  }
 
  /// Retrieve a cursor from the theme.
  ///
  /// This method returns [`None`] if this cursor is not provided either by the theme, or by one of its parents.
+ ///
+ /// If a fallback is set, it will use the data from fallback
  pub fn get_cursor(&mut self, name: &str) -> Option<&Cursor> {
  match self.cursors.iter().position(|cursor| cursor.name == name) {
  Some(i) => Some(&self.cursors[i]),
  None => {
- let cursor = self.load_cursor(name, self.size)?;
+ let cursor = match self.load_cursor(name, self.size) {
+ None => {
+ let Some(ref fallback) = self.fallback else {
+ return None;
+ };
+ let data = fallback.0(name);
+ let images = xparser::parse_xcursor(&data)?;
+ let conn = Connection::from_backend(self.backend.upgrade()?);
+ Cursor::new(&conn, name, self, &images, self.size)
+ }
+ Some(cursor) => cursor,
+ };
  self.cursors.push(cursor);
  self.cursors.iter().last()
  }
  }
  }
 
+ /// Set the set_callback, the return value of the fallback function should be the source of
+ /// xcursor
+ pub fn set_callback<F>(&mut self, fallback: F)
+ where
+ F: Fn(&str) -> Cow<'static, [u8]> + 'static,
+ {
+ self.fallback = Some(FallBack::new(fallback))
+ }
+
  /// This function loads a cursor, parses it and pushes the images onto the shm pool.
  ///
  /// Keep in mind that if the cursor is already loaded, the function will make a duplicate.