winit/src/platform_impl/linux/x11/util/cursor.rs

use std::ffi::CString;

use crate::window::CursorIcon;

use super::*;

impl XConnection {
    pub fn set_cursor_icon(&self, window: ffi::Window, cursor: Option<CursorIcon>) {
        let cursor = *self
            .cursor_cache
            .lock()
            .unwrap()
            .entry(cursor)
            .or_insert_with(|| self.get_cursor(cursor));

        self.update_cursor(window, cursor);
    }

    fn create_empty_cursor(&self) -> ffi::Cursor {
        let data = 0;
        let pixmap = unsafe {
            let screen = (self.xlib.XDefaultScreen)(self.display);
            let window = (self.xlib.XRootWindow)(self.display, screen);
            (self.xlib.XCreateBitmapFromData)(self.display, window, &data, 1, 1)
        };

        if pixmap == 0 {
            panic!("failed to allocate pixmap for cursor");
        }

        unsafe {
            // We don't care about this color, since it only fills bytes
            // in the pixmap which are not 0 in the mask.
            let mut dummy_color = MaybeUninit::uninit();
            let cursor = (self.xlib.XCreatePixmapCursor)(
                self.display,
                pixmap,
                pixmap,
                dummy_color.as_mut_ptr(),
                dummy_color.as_mut_ptr(),
                0,
                0,
            );
            (self.xlib.XFreePixmap)(self.display, pixmap);

            cursor
        }
    }

    fn get_cursor(&self, cursor: Option<CursorIcon>) -> ffi::Cursor {
        let cursor = match cursor {
            Some(cursor) => cursor,
            None => return self.create_empty_cursor(),
        };

        let name = CString::new(cursor.name()).unwrap();
        unsafe {
            (self.xcursor.XcursorLibraryLoadCursor)(self.display, name.as_ptr() as *const c_char)
        }
    }

    fn update_cursor(&self, window: ffi::Window, cursor: ffi::Cursor) {
        unsafe {
            (self.xlib.XDefineCursor)(self.display, window, cursor);

            self.flush_requests().expect("Failed to set the cursor");
        }
    }
}