feat(all): Custom cursor images for all desktop platforms

There seems to be many PRs relating to this issue, but they don't include all
platforms and for some reason lost steam. This PR again tries to make this
feature happen, and does it for all desktop platforms (x11, wayland, macos,
windows, web).

I think the best user of this feature and the reason I'm doing this is Bevy and
game engines in general. There non laggy hardware cursors with custom images are
very important. Game devs also like their PNGs so supporting platform native
cursor files is not that important, but I guess could be added too.

Co-authored-by: daxpedda <daxpedda@gmail.com>
Co-authored-by: Mads Marquart <mads@marquart.dk>
Co-authored-by: Kirill Chibisov <contact@kchibisov.com>

src/platform_impl/linux/mod.rs

@@ -14,6 +14,7 @@ use std::{ffi::CStr, mem::MaybeUninit, os::raw::*, sync::Mutex};
 use once_cell::sync::Lazy;
 use smol_str::SmolStr;
 
+use crate::cursor::CustomCursor;
 #[cfg(x11_platform)]
 use crate::platform::x11::XlibErrorHook;
 use crate::{
@@ -40,6 +41,7 @@ pub use x11::XNotSupported;
 #[cfg(x11_platform)]
 use x11::{util::WindowType as XWindowType, X11Error, XConnection, XError};
 
+pub(crate) use crate::cursor::CursorImage as PlatformCustomCursor;
 pub(crate) use crate::icon::RgbaIcon as PlatformIcon;
 pub(crate) use crate::platform_impl::Fullscreen;
 
@@ -424,6 +426,11 @@ impl Window {
         x11_or_wayland!(match self; Window(w) => w.set_cursor_icon(cursor))
     }
 
+    #[inline]
+    pub fn set_custom_cursor(&self, cursor: CustomCursor) {
+        x11_or_wayland!(match self; Window(w) => w.set_custom_cursor(cursor))
+    }
+
     #[inline]
     pub fn set_cursor_grab(&self, mode: CursorGrabMode) -> Result<(), ExternalError> {
         x11_or_wayland!(match self; Window(window) => window.set_cursor_grab(mode))

src/platform_impl/linux/wayland/state.rs

@@ -19,6 +19,7 @@ use sctk::seat::SeatState;
 use sctk::shell::xdg::window::{Window, WindowConfigure, WindowHandler};
 use sctk::shell::xdg::XdgShell;
 use sctk::shell::WaylandSurface;
+use sctk::shm::slot::SlotPool;
 use sctk::shm::{Shm, ShmHandler};
 use sctk::subcompositor::SubcompositorState;
 
@@ -58,6 +59,9 @@ pub struct WinitState {
     /// The shm for software buffers, such as cursors.
     pub shm: Shm,
 
+    /// The pool where custom cursors are allocated.
+    pub custom_cursor_pool: Arc<Mutex<SlotPool>>,
+
     /// The XDG shell that is used for widnows.
     pub xdg_shell: XdgShell,
 
@@ -153,13 +157,17 @@ impl WinitState {
                 (None, None)
             };
 
+        let shm = Shm::bind(globals, queue_handle).map_err(WaylandError::Bind)?;
+        let custom_cursor_pool = Arc::new(Mutex::new(SlotPool::new(2, &shm).unwrap()));
+
         Ok(Self {
             registry_state,
             compositor_state: Arc::new(compositor_state),
             subcompositor_state: subcompositor_state.map(Arc::new),
             output_state,
             seat_state,
-            shm: Shm::bind(globals, queue_handle).map_err(WaylandError::Bind)?,
+            shm,
+            custom_cursor_pool,
 
             xdg_shell: XdgShell::bind(globals, queue_handle).map_err(WaylandError::Bind)?,
             xdg_activation: XdgActivationState::bind(globals, queue_handle).ok(),

src/platform_impl/linux/wayland/types/cursor.rs

@@ -0,0 +1,56 @@
+use cursor_icon::CursorIcon;
+
+use sctk::reexports::client::protocol::wl_shm::Format;
+use sctk::shm::slot::{Buffer, SlotPool};
+
+use crate::cursor::CursorImage;
+
+#[derive(Debug)]
+pub enum SelectedCursor {
+    Named(CursorIcon),
+    Custom(CustomCursor),
+}
+
+impl Default for SelectedCursor {
+    fn default() -> Self {
+        Self::Named(Default::default())
+    }
+}
+
+#[derive(Debug)]
+pub struct CustomCursor {
+    pub buffer: Buffer,
+    pub w: i32,
+    pub h: i32,
+    pub hotspot_x: i32,
+    pub hotspot_y: i32,
+}
+
+impl CustomCursor {
+    pub fn new(pool: &mut SlotPool, image: &CursorImage) -> Self {
+        let (buffer, canvas) = pool
+            .create_buffer(
+                image.width as i32,
+                image.height as i32,
+                4 * (image.width as i32),
+                Format::Argb8888,
+            )
+            .unwrap();
+
+        for (canvas_chunk, rgba_chunk) in canvas.chunks_exact_mut(4).zip(image.rgba.chunks_exact(4))
+        {
+            canvas_chunk[0] = rgba_chunk[2];
+            canvas_chunk[1] = rgba_chunk[1];
+            canvas_chunk[2] = rgba_chunk[0];
+            canvas_chunk[3] = rgba_chunk[3];
+        }
+
+        CustomCursor {
+            buffer,
+            w: image.width as i32,
+            h: image.height as i32,
+            hotspot_x: image.hotspot_x as i32,
+            hotspot_y: image.hotspot_y as i32,
+        }
+    }
+}

src/platform_impl/linux/wayland/types/mod.rs

@@ -1,5 +1,6 @@
 //! Wayland protocol implementation boilerplate.
 
+pub mod cursor;
 pub mod kwin_blur;
 pub mod wp_fractional_scaling;
 pub mod wp_viewporter;

src/platform_impl/linux/wayland/window/mod.rs

@@ -15,6 +15,7 @@ use sctk::shell::xdg::window::Window as SctkWindow;
 use sctk::shell::xdg::window::WindowDecorations;
 use sctk::shell::WaylandSurface;
 
+use crate::cursor::CustomCursor;
 use crate::dpi::{LogicalSize, PhysicalPosition, PhysicalSize, Position, Size};
 use crate::error::{ExternalError, NotSupportedError, OsError as RootOsError};
 use crate::event::{Ime, WindowEvent};
@@ -506,6 +507,11 @@ impl Window {
         self.window_state.lock().unwrap().set_cursor(cursor);
     }
 
+    #[inline]
+    pub fn set_custom_cursor(&self, cursor: CustomCursor) {
+        self.window_state.lock().unwrap().set_custom_cursor(cursor);
+    }
+
     #[inline]
     pub fn set_cursor_visible(&self, visible: bool) {
         self.window_state

src/platform_impl/linux/wayland/window/state.rs

@@ -1,7 +1,7 @@
 //! The state of the window, which is shared with the event-loop.
 
 use std::num::NonZeroU32;
-use std::sync::{Arc, Weak};
+use std::sync::{Arc, Mutex, Weak};
 use std::time::Duration;
 
 use log::{info, warn};
@@ -18,20 +18,23 @@ use sctk::reexports::protocols::wp::text_input::zv3::client::zwp_text_input_v3::
 use sctk::reexports::protocols::wp::viewporter::client::wp_viewport::WpViewport;
 use sctk::reexports::protocols::xdg::shell::client::xdg_toplevel::ResizeEdge as XdgResizeEdge;
 
-use sctk::compositor::{CompositorState, Region};
-use sctk::seat::pointer::ThemedPointer;
+use sctk::compositor::{CompositorState, Region, SurfaceData, SurfaceDataExt};
+use sctk::seat::pointer::{PointerDataExt, ThemedPointer};
 use sctk::shell::xdg::window::{DecorationMode, Window, WindowConfigure};
 use sctk::shell::xdg::XdgSurface;
 use sctk::shell::WaylandSurface;
+use sctk::shm::slot::SlotPool;
 use sctk::shm::Shm;
 use sctk::subcompositor::SubcompositorState;
 use wayland_protocols_plasma::blur::client::org_kde_kwin_blur::OrgKdeKwinBlur;
 
+use crate::cursor::CustomCursor as RootCustomCursor;
 use crate::dpi::{LogicalPosition, LogicalSize, PhysicalSize, Size};
 use crate::error::{ExternalError, NotSupportedError};
 use crate::event::WindowEvent;
 use crate::platform_impl::wayland::event_loop::sink::EventSink;
 use crate::platform_impl::wayland::make_wid;
+use crate::platform_impl::wayland::types::cursor::{CustomCursor, SelectedCursor};
 use crate::platform_impl::wayland::types::kwin_blur::KWinBlurManager;
 use crate::platform_impl::WindowId;
 use crate::window::{CursorGrabMode, CursorIcon, ImePurpose, ResizeDirection, Theme};
@@ -60,14 +63,16 @@ pub struct WindowState {
     /// The `Shm` to set cursor.
     pub shm: WlShm,
 
+    // A shared pool where to allocate custom cursors.
+    custom_cursor_pool: Arc<Mutex<SlotPool>>,
+
     /// The last received configure.
     pub last_configure: Option<WindowConfigure>,
 
     /// The pointers observed on the window.
     pub pointers: Vec<Weak<ThemedPointer<WinitPointerData>>>,
 
-    /// Cursor icon.
-    pub cursor_icon: CursorIcon,
+    selected_cursor: SelectedCursor,
 
     /// Wether the cursor is visible.
     pub cursor_visible: bool,
@@ -178,7 +183,7 @@ impl WindowState {
             connection,
             csd_fails: false,
             cursor_grab_mode: GrabState::new(),
-            cursor_icon: CursorIcon::Default,
+            selected_cursor: Default::default(),
             cursor_visible: true,
             decorate: true,
             fractional_scale,
@@ -197,6 +202,7 @@ impl WindowState {
             resizable: true,
             scale_factor: 1.,
             shm: winit_state.shm.wl_shm().clone(),
+            custom_cursor_pool: winit_state.custom_cursor_pool.clone(),
             size: initial_size.to_logical(1.),
             stateless_size: initial_size.to_logical(1.),
             initial_size: Some(initial_size),
@@ -603,7 +609,10 @@ impl WindowState {
     /// Reload the cursor style on the given window.
     pub fn reload_cursor_style(&mut self) {
         if self.cursor_visible {
-            self.set_cursor(self.cursor_icon);
+            match &self.selected_cursor {
+                SelectedCursor::Named(icon) => self.set_cursor(*icon),
+                SelectedCursor::Custom(cursor) => self.apply_custom_cursor(cursor),
+            }
         } else {
             self.set_cursor_visible(self.cursor_visible);
         }
@@ -689,10 +698,8 @@ impl WindowState {
     }
 
     /// Set the cursor icon.
-    ///
-    /// Providing `None` will hide the cursor.
     pub fn set_cursor(&mut self, cursor_icon: CursorIcon) {
-        self.cursor_icon = cursor_icon;
+        self.selected_cursor = SelectedCursor::Named(cursor_icon);
 
         if !self.cursor_visible {
             return;
@@ -705,6 +712,54 @@ impl WindowState {
         })
     }
 
+    /// Set the custom cursor icon.
+    pub fn set_custom_cursor(&mut self, cursor: RootCustomCursor) {
+        let cursor = {
+            let mut pool = self.custom_cursor_pool.lock().unwrap();
+            CustomCursor::new(&mut pool, &cursor.inner)
+        };
+
+        if self.cursor_visible {
+            self.apply_custom_cursor(&cursor);
+        }
+
+        self.selected_cursor = SelectedCursor::Custom(cursor);
+    }
+
+    fn apply_custom_cursor(&self, cursor: &CustomCursor) {
+        self.apply_on_poiner(|pointer, _| {
+            let surface = pointer.surface();
+
+            let scale = surface
+                .data::<SurfaceData>()
+                .unwrap()
+                .surface_data()
+                .scale_factor();
+
+            surface.set_buffer_scale(scale);
+            surface.attach(Some(cursor.buffer.wl_buffer()), 0, 0);
+            if surface.version() >= 4 {
+                surface.damage_buffer(0, 0, cursor.w, cursor.h);
+            } else {
+                surface.damage(0, 0, cursor.w / scale, cursor.h / scale);
+            }
+            surface.commit();
+
+            let serial = pointer
+                .pointer()
+                .data::<WinitPointerData>()
+                .and_then(|data| data.pointer_data().latest_enter_serial())
+                .unwrap();
+
+            pointer.pointer().set_cursor(
+                serial,
+                Some(surface),
+                cursor.hotspot_x / scale,
+                cursor.hotspot_y / scale,
+            );
+        });
+    }
+
     /// Set maximum inner window size.
     pub fn set_min_inner_size(&mut self, size: Option<LogicalSize<u32>>) {
         // Ensure that the window has the right minimum size.
@@ -839,7 +894,10 @@ impl WindowState {
         self.cursor_visible = cursor_visible;
 
         if self.cursor_visible {
-            self.set_cursor(self.cursor_icon);
+            match &self.selected_cursor {
+                SelectedCursor::Named(icon) => self.set_cursor(*icon),
+                SelectedCursor::Custom(cursor) => self.apply_custom_cursor(cursor),
+            }
         } else {
             for pointer in self.pointers.iter().filter_map(|pointer| pointer.upgrade()) {
                 let latest_enter_serial = pointer.pointer().winit_data().latest_enter_serial();

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

@@ -1,9 +1,8 @@
-use std::ffi::CString;
-use std::iter;
+use std::{ffi::CString, iter, slice, sync::Arc};
 
 use x11rb::connection::Connection;
 
-use crate::window::CursorIcon;
+use crate::{cursor::CursorImage, window::CursorIcon};
 
 use super::*;
 
@@ -20,6 +19,11 @@ impl XConnection {
             .expect("Failed to set cursor");
     }
 
+    pub fn set_custom_cursor(&self, window: xproto::Window, cursor: &CustomCursor) {
+        self.update_cursor(window, cursor.inner.cursor)
+            .expect("Failed to set cursor");
+    }
+
     fn create_empty_cursor(&self) -> ffi::Cursor {
         let data = 0;
         let pixmap = unsafe {
@@ -87,3 +91,74 @@ impl XConnection {
         Ok(())
     }
 }
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum SelectedCursor {
+    Custom(CustomCursor),
+    Named(CursorIcon),
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CustomCursor {
+    inner: Arc<CustomCursorInner>,
+}
+
+impl CustomCursor {
+    pub(crate) unsafe fn new(xconn: &Arc<XConnection>, image: &CursorImage) -> Self {
+        unsafe {
+            let ximage =
+                (xconn.xcursor.XcursorImageCreate)(image.width as i32, image.height as i32);
+            if ximage.is_null() {
+                panic!("failed to allocate cursor image");
+            }
+            (*ximage).xhot = image.hotspot_x as u32;
+            (*ximage).yhot = image.hotspot_y as u32;
+            (*ximage).delay = 0;
+
+            let dst = slice::from_raw_parts_mut((*ximage).pixels, image.rgba.len() / 4);
+            for (dst, chunk) in dst.iter_mut().zip(image.rgba.chunks_exact(4)) {
+                *dst = (chunk[0] as u32) << 16
+                    | (chunk[1] as u32) << 8
+                    | (chunk[2] as u32)
+                    | (chunk[3] as u32) << 24;
+            }
+
+            let cursor = (xconn.xcursor.XcursorImageLoadCursor)(xconn.display, ximage);
+            (xconn.xcursor.XcursorImageDestroy)(ximage);
+            Self {
+                inner: Arc::new(CustomCursorInner {
+                    xconn: xconn.clone(),
+                    cursor,
+                }),
+            }
+        }
+    }
+}
+
+#[derive(Debug)]
+struct CustomCursorInner {
+    xconn: Arc<XConnection>,
+    cursor: ffi::Cursor,
+}
+
+impl Drop for CustomCursorInner {
+    fn drop(&mut self) {
+        unsafe {
+            (self.xconn.xlib.XFreeCursor)(self.xconn.display, self.cursor);
+        }
+    }
+}
+
+impl PartialEq for CustomCursorInner {
+    fn eq(&self, other: &Self) -> bool {
+        self.cursor == other.cursor
+    }
+}
+
+impl Eq for CustomCursorInner {}
+
+impl Default for SelectedCursor {
+    fn default() -> Self {
+        SelectedCursor::Named(Default::default())
+    }
+}

src/platform_impl/linux/x11/util/mod.rs

@@ -13,7 +13,7 @@ mod randr;
 mod window_property;
 mod wm;
 
-pub use self::{geometry::*, hint::*, input::*, window_property::*, wm::*};
+pub use self::{cursor::*, geometry::*, hint::*, input::*, window_property::*, wm::*};
 
 use std::{
     mem::{self, MaybeUninit},

src/platform_impl/linux/x11/window.rs

@@ -7,6 +7,9 @@ use std::{
     sync::{Arc, Mutex, MutexGuard},
 };
 
+use crate::cursor::CustomCursor as RootCustomCursor;
+
+use cursor_icon::CursorIcon;
 use x11rb::{
     connection::Connection,
     properties::{WmHints, WmHintsState, WmSizeHints, WmSizeHintsSpecification},
@@ -33,13 +36,15 @@ use crate::{
         PlatformSpecificWindowBuilderAttributes, VideoMode as PlatformVideoMode,
     },
     window::{
-        CursorGrabMode, CursorIcon, ImePurpose, ResizeDirection, Theme, UserAttentionType,
-        WindowAttributes, WindowButtons, WindowLevel,
+        CursorGrabMode, ImePurpose, ResizeDirection, Theme, UserAttentionType, WindowAttributes,
+        WindowButtons, WindowLevel,
     },
 };
 
 use super::{
-    ffi, util, CookieResultExt, EventLoopWindowTarget, ImeRequest, ImeSender, VoidCookie, WindowId,
+    ffi,
+    util::{self, CustomCursor, SelectedCursor},
+    CookieResultExt, EventLoopWindowTarget, ImeRequest, ImeSender, VoidCookie, WindowId,
     XConnection,
 };
 
@@ -126,7 +131,7 @@ pub(crate) struct UnownedWindow {
     root: xproto::Window,               // never changes
     #[allow(dead_code)]
     screen_id: i32, // never changes
-    cursor: Mutex<CursorIcon>,
+    selected_cursor: Mutex<SelectedCursor>,
     cursor_grabbed_mode: Mutex<CursorGrabMode>,
     #[allow(clippy::mutex_atomic)]
     cursor_visible: Mutex<bool>,
@@ -355,7 +360,7 @@ impl UnownedWindow {
             visual,
             root,
             screen_id,
-            cursor: Default::default(),
+            selected_cursor: Default::default(),
             cursor_grabbed_mode: Mutex::new(CursorGrabMode::None),
             cursor_visible: Mutex::new(true),
             ime_sender: Mutex::new(event_loop.ime_sender.clone()),
@@ -1535,13 +1540,29 @@ impl UnownedWindow {
 
     #[inline]
     pub fn set_cursor_icon(&self, cursor: CursorIcon) {
-        let old_cursor = replace(&mut *self.cursor.lock().unwrap(), cursor);
+        let old_cursor = replace(
+            &mut *self.selected_cursor.lock().unwrap(),
+            SelectedCursor::Named(cursor),
+        );
+
         #[allow(clippy::mutex_atomic)]
-        if cursor != old_cursor && *self.cursor_visible.lock().unwrap() {
+        if SelectedCursor::Named(cursor) != old_cursor && *self.cursor_visible.lock().unwrap() {
             self.xconn.set_cursor_icon(self.xwindow, Some(cursor));
         }
     }
 
+    #[inline]
+    pub fn set_custom_cursor(&self, cursor: RootCustomCursor) {
+        let new_cursor = unsafe { CustomCursor::new(&self.xconn, &cursor.inner) };
+
+        #[allow(clippy::mutex_atomic)]
+        if *self.cursor_visible.lock().unwrap() {
+            self.xconn.set_custom_cursor(self.xwindow, &new_cursor);
+        }
+
+        *self.selected_cursor.lock().unwrap() = SelectedCursor::Custom(new_cursor);
+    }
+
     #[inline]
     pub fn set_cursor_grab(&self, mode: CursorGrabMode) -> Result<(), ExternalError> {
         let mut grabbed_lock = self.cursor_grabbed_mode.lock().unwrap();
@@ -1628,13 +1649,23 @@ impl UnownedWindow {
             return;
         }
         let cursor = if visible {
-            Some(*self.cursor.lock().unwrap())
+            Some((*self.selected_cursor.lock().unwrap()).clone())
         } else {
             None
         };
         *visible_lock = visible;
         drop(visible_lock);
-        self.xconn.set_cursor_icon(self.xwindow, cursor);
+        match cursor {
+            Some(SelectedCursor::Custom(cursor)) => {
+                self.xconn.set_custom_cursor(self.xwindow, &cursor);
+            }
+            Some(SelectedCursor::Named(cursor)) => {
+                self.xconn.set_cursor_icon(self.xwindow, Some(cursor));
+            }
+            None => {
+                self.xconn.set_cursor_icon(self.xwindow, None);
+            }
+        }
     }
 
     #[inline]