feat: load cursor from data (#680)

* feat: load cursor from data

I want to add a function to load cursor from data

* chore: add documents and size parm input

* Update wayland-cursor/src/lib.rs

Co-authored-by: Elinor B. <3009227+elinorbgr@users.noreply.github.com>

* chore: make clippy happy

---------

Co-authored-by: Elinor B. <3009227+elinorbgr@users.noreply.github.com>

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 +83,26 @@ pub struct CursorTheme {
  pool_size: i32,
  file: File,
  backend: WeakBackend,
+ fallback: Option<FallBack>,
+}
+
+type FallBackInner = Box<dyn Fn(&str, u32) -> Option<Cow<'static, [u8]>>>;
+
+struct FallBack(FallBackInner);
+
+impl FallBack {
+ fn new<F>(fallback: F) -> Self
+ where
+ F: Fn(&str, u32) -> Option<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 +182,59 @@ 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 fallback = self.fallback.as_ref()?;
+ let data = fallback.0(name, self.size)?;
+ 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 a callback to load the cursor data, in case the system theme is missing a cursor that you need.
+ ///
+ /// Your callback will be invoked with he name and size of the requested cursor and should return a byte
+ /// array with the contents of an `xcursor` file, or `None` if you don't provide a fallback for this cursor.
+ ///
+ /// For example, this defines a generic fallback cursor image and uses it for all missing cursors:
+ /// ```ignore
+ /// # use wayland_cursor::CursorTheme;
+ /// # use wayland_client::{Connection, backend::InvalidId, protocol::wl_shm};
+ /// # fn example(conn: &Connection, shm: wl_shm::WlShm, size: u32) -> Result<CursorTheme, InvalidId> {
+ /// # let mut theme = CursorTheme::load_or(conn, shm, "default", size)?;
+ /// # theme.set_callback(|name, size| {
+ /// # include_bytes!("./icons/default")
+ /// # });
+ /// # Ok(theme)
+ /// # }
+ /// ```
+ pub fn set_callback<F>(&mut self, fallback: F)
+ where
+ F: Fn(&str, u32) -> Option<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.