New drag and drop API

Cargo.toml

@@ -32,6 +32,7 @@ cursor-icon = "1.1.0"
 dpi = { version = "0.1.2", path = "dpi" }
 keyboard-types = "0.8.0"
 mint = "0.5.6"
+rustversion = "1.0"
 rwh_06 = { package = "raw-window-handle", version = "0.6", features = ["std"] }
 serde = { version = "1", features = ["serde_derive"] }
 smol_str = "0.3"

typos.toml

@@ -5,6 +5,7 @@ TME_LEAVE = "TME_LEAVE"             # From windows_sys::Win32::UI::Input::Keyboa
 XF86_Calculater = "XF86_Calculater" # From xkbcommon_dl::keysyms::XF86_Calculater
 ptd = "ptd"                         # From windows_sys::Win32::System::Com::FORMATETC { ptd, ..}
 requestor = "requestor"             # From x11_dl::xlib::XSelectionEvent { requestor ..}
+unknwn = "unknwn"                   # Windows SDK header filename `unknwn.h`
 
 [files]
 extend-exclude = ["*.drawio"]

winit-appkit/Cargo.toml

@@ -36,6 +36,8 @@ objc2-app-kit = { workspace = true, features = [
     "NSControl",
     "NSCursor",
     "NSDragging",
+    "NSDraggingItem",
+    "NSDraggingSession",
     "NSEvent",
     "NSGraphics",
     "NSGraphicsContext",
@@ -46,6 +48,7 @@ objc2-app-kit = { workspace = true, features = [
     "NSOpenGLView",
     "NSPanel",
     "NSPasteboard",
+    "NSPasteboardItem",
     "NSResponder",
     "NSRunningApplication",
     "NSScreen",

winit-appkit/src/app_state.rs

@@ -1,27 +1,34 @@
 use std::cell::{Cell, OnceCell, RefCell};
+use std::collections::HashMap;
 use std::mem;
 use std::rc::Rc;
 use std::sync::Arc;
 use std::time::Instant;
 
 use dispatch2::MainThreadBound;
 use objc2::MainThreadMarker;
+use objc2::rc::{Retained, Weak};
 use objc2_app_kit::{NSApplication, NSApplicationActivationPolicy, NSRunningApplication};
 use objc2_foundation::NSNotification;
 use winit_common::core_foundation::{EventLoopProxy, MainRunLoop};
 use winit_common::event_handler::EventHandler;
 use winit_core::application::ApplicationHandler;
+use winit_core::data_transfer::DataTransferId;
 use winit_core::event::{StartCause, WindowEvent};
 use winit_core::event_loop::ControlFlow;
 use winit_core::window::WindowId;
 
 use super::event_loop::{ActiveEventLoop, notify_windows_of_exit, stop_app_immediately};
 use super::menu;
 use super::observer::EventLoopWaker;
+use crate::dnd::{DragOperation, Pasteboards};
+use crate::window_delegate::WindowDelegate;
 
 #[derive(Debug)]
 pub(super) struct AppState {
     mtm: MainThreadMarker,
+    drag_state: Cell<Option<DragState>>,
+    pasteboards: Pasteboards,
     activation_policy: Option<NSApplicationActivationPolicy>,
     default_menu: bool,
     activate_ignoring_other_apps: bool,
@@ -43,10 +50,17 @@ pub(super) struct AppState {
     start_time: Cell<Option<Instant>>,
     wait_timeout: Cell<Option<Instant>>,
     pending_redraw: RefCell<Vec<WindowId>>,
+    windows: RefCell<HashMap<WindowId, MainThreadBound<Weak<WindowDelegate>>>>,
     // NOTE: This is strongly referenced by our `NSWindowDelegate` and our `NSView` subclass, and
     // as such should be careful to not add fields that, in turn, strongly reference those.
 }
 
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct DragState {
+    pub id: DataTransferId,
+    pub valid_operations: DragOperation,
+}
+
 // SAFETY: Creating `MainThreadBound` in a `const` context, where there is no concept of the
 // main thread.
 static GLOBAL: MainThreadBound<OnceCell<Rc<AppState>>> =
@@ -65,6 +79,8 @@ impl AppState {
 
         let this = Rc::new(Self {
             mtm,
+            pasteboards: Default::default(),
+            drag_state: Default::default(),
             activation_policy,
             default_menu,
             activate_ignoring_other_apps,
@@ -82,6 +98,7 @@ impl AppState {
             waker: RefCell::new(EventLoopWaker::new()),
             start_time: Cell::new(None),
             wait_timeout: Cell::new(None),
+            windows: Default::default(),
             pending_redraw: RefCell::new(vec![]),
         });
 
@@ -96,6 +113,20 @@ impl AppState {
             .clone()
     }
 
+    pub fn with_window_delegate_on_main<F, R>(&self, id: WindowId, func: F) -> Option<R>
+    where
+        F: FnOnce(Retained<WindowDelegate>) -> R + Send,
+        R: Send,
+    {
+        self.windows.borrow_mut().get(&id)?.get_on_main(move |delegate| delegate.load().map(func))
+    }
+
+    pub fn new_window(&self, window: &Retained<WindowDelegate>, mtm: MainThreadMarker) {
+        let id = window.id();
+        let window_downgraded = Weak::from_retained(window);
+        self.windows.borrow_mut().insert(id, MainThreadBound::new(window_downgraded, mtm));
+    }
+
     // NOTE: This notification will, globally, only be emitted once,
     // no matter how many `EventLoop`s the user creates.
     pub fn did_finish_launching(self: &Rc<Self>, _notification: &NSNotification) {
@@ -371,6 +402,14 @@ impl AppState {
         };
         self.waker.borrow_mut().start_at(min_timeout(wait_timeout, app_timeout));
     }
+
+    pub fn pasteboards(&self) -> &Pasteboards {
+        &self.pasteboards
+    }
+
+    pub fn drag_state(&self) -> &Cell<Option<DragState>> {
+        &self.drag_state
+    }
 }
 
 /// Returns the minimum `Option<Instant>`, taking into account that `None`

winit-appkit/src/cursor.rs

@@ -14,6 +14,7 @@ use objc2_foundation::{
 };
 use winit_core::cursor::{CursorIcon, CursorImage, CustomCursorProvider, CustomCursorSource};
 use winit_core::error::{NotSupportedError, RequestError};
+use winit_core::icon::{Icon, RgbaIcon};
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct CustomCursor(pub(crate) Retained<NSCursor>);
@@ -42,6 +43,40 @@ impl CustomCursor {
     }
 }
 
+pub(crate) fn image_from_icon(icon: &Icon) -> Result<Retained<NSImage>, RequestError> {
+    let rgba_icon = icon
+        .cast_ref::<RgbaIcon>()
+        .ok_or(NotSupportedError::new("Only RGBA icons can be converted to `NSImage`"))?;
+
+    let width = rgba_icon.width();
+    let height = rgba_icon.height();
+
+    let bitmap = unsafe {
+        NSBitmapImageRep::initWithBitmapDataPlanes_pixelsWide_pixelsHigh_bitsPerSample_samplesPerPixel_hasAlpha_isPlanar_colorSpaceName_bytesPerRow_bitsPerPixel(
+            NSBitmapImageRep::alloc(),
+            std::ptr::null_mut::<*mut c_uchar>(),
+            width as isize,
+            height as isize,
+            8,
+            4,
+            true,
+            false,
+            NSDeviceRGBColorSpace,
+            width as isize * 4,
+            32,
+        )
+    }.ok_or_else(|| os_error!("parent view should be installed in a window"))?;
+
+    let bitmap_data =
+        unsafe { slice::from_raw_parts_mut(bitmap.bitmapData(), rgba_icon.buffer().len()) };
+    bitmap_data.copy_from_slice(rgba_icon.buffer());
+
+    let image = NSImage::initWithSize(NSImage::alloc(), NSSize::new(width.into(), height.into()));
+    image.addRepresentation(&bitmap);
+
+    Ok(image)
+}
+
 pub(crate) fn cursor_from_image(cursor: &CursorImage) -> Result<Retained<NSCursor>, RequestError> {
     let width = cursor.width();
     let height = cursor.height();