Merge pull request #148 from ilmai/drag-and-drop

Drag and drop

Cargo.toml

@@ -29,7 +29,7 @@ xcb-util = { version = "0.3", features = ["icccm"] }
 nix = "0.22.0"
 
 [target.'cfg(target_os="windows")'.dependencies]
-winapi = { version = "0.3.8", features = ["libloaderapi", "winuser", "windef", "minwindef", "guiddef", "combaseapi", "wingdi", "errhandlingapi"] }
+winapi = { version = "0.3.8", features = ["libloaderapi", "winuser", "windef", "minwindef", "guiddef", "combaseapi", "wingdi", "errhandlingapi", "ole2", "oleidl", "shellapi", "winerror"] }
 uuid = { version = "0.8", features = ["v4"], optional = true }
 
 [target.'cfg(target_os="macos")'.dependencies]

src/event.rs

@@ -1,3 +1,5 @@
+use std::path::PathBuf;
+
 use keyboard_types::{KeyboardEvent, Modifiers};
 
 use crate::{Point, WindowInfo};
@@ -32,7 +34,7 @@ pub enum ScrollDelta {
     },
 }
 
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Debug, Clone, PartialEq)]
 pub enum MouseEvent {
     /// The mouse cursor was moved
     CursorMoved {
@@ -75,6 +77,35 @@ pub enum MouseEvent {
     ///
     /// May not be available on all platforms.
     CursorLeft,
+
+    DragEntered {
+        /// The logical coordinates of the mouse position
+        position: Point,
+        /// The modifiers that were held down just before the event.
+        modifiers: Modifiers,
+        /// Data being dragged
+        data: DropData,
+    },
+
+    DragMoved {
+        /// The logical coordinates of the mouse position
+        position: Point,
+        /// The modifiers that were held down just before the event.
+        modifiers: Modifiers,
+        /// Data being dragged
+        data: DropData,
+    },
+
+    DragLeft,
+
+    DragDropped {
+        /// The logical coordinates of the mouse position
+        position: Point,
+        /// The modifiers that were held down just before the event.
+        modifiers: Modifiers,
+        /// Data being dragged
+        data: DropData,
+    },
 }
 
 #[derive(Debug, Clone)]
@@ -92,6 +123,20 @@ pub enum Event {
     Window(WindowEvent),
 }
 
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum DropEffect {
+    Copy,
+    Move,
+    Link,
+    Scroll,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum DropData {
+    None,
+    Files(Vec<PathBuf>),
+}
+
 /// Return value for [WindowHandler::on_event](`crate::WindowHandler::on_event()`),
 /// indicating whether the event was handled by your window or should be passed
 /// back to the platform.
@@ -111,4 +156,7 @@ pub enum EventStatus {
     /// DAW functionality for playing piano keys with the keyboard while a
     /// plugin window is in focus.
     Ignored,
+    /// We are prepared to handle the data in the drag and dropping will
+    /// result in [DropEffect] 
+    AcceptDrop(DropEffect),
 }

src/win/drop_target.rs

@@ -0,0 +1,268 @@
+use std::ffi::OsString;
+use std::mem::transmute;
+use std::os::windows::prelude::OsStringExt;
+use std::ptr::null_mut;
+use std::rc::{Weak, Rc};
+
+use winapi::Interface;
+use winapi::shared::guiddef::{REFIID, IsEqualIID};
+use winapi::shared::minwindef::{DWORD, WPARAM};
+use winapi::shared::ntdef::{HRESULT, ULONG};
+use winapi::shared::windef::POINTL;
+use winapi::shared::winerror::{S_OK, E_NOINTERFACE, E_UNEXPECTED};
+use winapi::shared::wtypes::DVASPECT_CONTENT;
+use winapi::um::objidl::{IDataObject, FORMATETC, TYMED_HGLOBAL, STGMEDIUM};
+use winapi::um::oleidl::{IDropTarget, IDropTargetVtbl, DROPEFFECT_COPY, DROPEFFECT_MOVE, DROPEFFECT_LINK, DROPEFFECT_SCROLL, DROPEFFECT_NONE};
+use winapi::um::shellapi::DragQueryFileW;
+use winapi::um::unknwnbase::{IUnknownVtbl, IUnknown};
+use winapi::um::winuser::CF_HDROP;
+
+use crate::{Point, DropData, MouseEvent, Event, EventStatus, DropEffect, PhyPoint};
+
+use super::WindowState;
+
+// These function pointers have to be stored in a (const) variable before they can be transmuted
+// Transmuting is needed because winapi has a bug where the pt parameter has an incorrect
+// type `*const POINTL`
+const DRAG_ENTER_PTR: unsafe extern "system" fn(this: *mut IDropTarget, pDataObj: *const IDataObject, grfKeyState: DWORD, pt: POINTL, pdwEffect: *mut DWORD) -> HRESULT = DropTarget::drag_enter;
+const DRAG_OVER_PTR: unsafe extern "system" fn(this: *mut IDropTarget, grfKeyState: DWORD, pt: POINTL, pdwEffect: *mut DWORD) -> HRESULT = DropTarget::drag_over;
+const DROP_PTR: unsafe extern "system" fn(this: *mut IDropTarget, pDataObj: *const IDataObject, grfKeyState: DWORD, pt: POINTL, pdwEffect: *mut DWORD) -> HRESULT = DropTarget::drop;
+const DROP_TARGET_VTBL: IDropTargetVtbl = IDropTargetVtbl {
+    parent: IUnknownVtbl {
+        QueryInterface: DropTarget::query_interface,
+        AddRef: DropTarget::add_ref,
+        Release: DropTarget::release,
+    },
+    DragEnter: unsafe { transmute(DRAG_ENTER_PTR) },
+    DragOver: unsafe { transmute(DRAG_OVER_PTR) },
+    DragLeave: DropTarget::drag_leave,
+    Drop: unsafe { transmute(DROP_PTR) },
+};
+
+#[repr(C)]
+pub(super) struct DropTarget {
+    base: IDropTarget,
+
+    window_state: Weak<WindowState>,
+
+    // These are cached since DragOver and DragLeave callbacks don't provide them,
+    // and handling drag move events gets awkward on the client end otherwise
+    drag_position: Point,
+    drop_data: DropData,
+}
+
+impl DropTarget {
+    pub(super) fn new(window_state: Weak<WindowState>) -> Self {
+        Self {
+            base: IDropTarget { lpVtbl: &DROP_TARGET_VTBL },
+
+            window_state,
+
+            drag_position: Point::new(0.0, 0.0),
+            drop_data: DropData::None,
+        }
+    }
+
+    fn on_event(&self, pdwEffect: Option<*mut DWORD>, event: MouseEvent) {
+        let Some(window_state) = self.window_state.upgrade() else {
+            return;
+        };
+
+        unsafe {
+            let mut window = window_state.create_window();
+            let mut window = crate::Window::new(&mut window);
+    
+            let event = Event::Mouse(event);
+            let event_status = window_state.handler_mut().as_mut().unwrap().on_event(&mut window, event);
+
+            if let Some(pdwEffect) = pdwEffect {
+                match event_status {
+                    EventStatus::AcceptDrop(DropEffect::Copy) => *pdwEffect = DROPEFFECT_COPY,
+                    EventStatus::AcceptDrop(DropEffect::Move) => *pdwEffect = DROPEFFECT_MOVE,
+                    EventStatus::AcceptDrop(DropEffect::Link) => *pdwEffect = DROPEFFECT_LINK,
+                    EventStatus::AcceptDrop(DropEffect::Scroll) => *pdwEffect = DROPEFFECT_SCROLL,
+                    _ => *pdwEffect = DROPEFFECT_NONE,
+                }        
+            } 
+        }
+    }
+
+    fn parse_coordinates(&mut self, pt: POINTL) {
+        let Some(window_state) = self.window_state.upgrade() else {
+            return;
+        };
+
+        let phy_point = PhyPoint::new(pt.x, pt.y);
+        self.drag_position = phy_point.to_logical(&window_state.window_info());
+    }
+
+    fn parse_drop_data(&mut self, data_object: &IDataObject) {
+        let format = FORMATETC {
+            cfFormat: CF_HDROP as u16,
+            ptd: null_mut(),
+            dwAspect: DVASPECT_CONTENT,
+            lindex: -1,
+            tymed: TYMED_HGLOBAL,
+        };
+
+        let mut medium = STGMEDIUM {
+            tymed: 0,
+            u: null_mut(),
+            pUnkForRelease: null_mut(),
+        };
+
+        unsafe {
+            let hresult = data_object.GetData(&format, &mut medium);
+            if hresult != S_OK {
+                self.drop_data = DropData::None;
+                return;
+            }
+
+            let hdrop = transmute((*medium.u).hGlobal());
+       
+            let item_count = DragQueryFileW(hdrop, 0xFFFFFFFF, null_mut(), 0);
+            if item_count == 0 {
+                self.drop_data = DropData::None;
+                return;
+            }
+            
+            let mut paths = Vec::with_capacity(item_count as usize);
+
+            for i in 0..item_count {
+                let characters = DragQueryFileW(hdrop, i, null_mut(), 0);
+                let buffer_size = characters as usize + 1;
+                let mut buffer = Vec::<u16>::with_capacity(buffer_size);
+
+                DragQueryFileW(hdrop, i, transmute(buffer.spare_capacity_mut().as_mut_ptr()), buffer_size as u32);
+                buffer.set_len(buffer_size);
+
+                paths.push(OsString::from_wide(&buffer[..characters as usize]).into())
+            }
+
+            self.drop_data = DropData::Files(paths);
+        }
+    }
+
+    unsafe extern "system" fn query_interface(
+        this: *mut IUnknown,
+        riid: REFIID,
+        ppvObject: *mut *mut winapi::ctypes::c_void,
+    ) -> HRESULT
+    {
+        if IsEqualIID(&*riid, &IUnknown::uuidof()) || IsEqualIID(&*riid, &IDropTarget::uuidof()){
+            Self::add_ref(this);
+            *ppvObject = this as *mut winapi::ctypes::c_void;
+            return S_OK;
+        }
+    
+        return E_NOINTERFACE;
+    }
+    
+    unsafe extern "system" fn add_ref(this: *mut IUnknown) -> ULONG {
+        let arc = Rc::from_raw(this);
+        let result = Rc::strong_count(&arc) + 1;
+        let _ = Rc::into_raw(arc);
+
+        Rc::increment_strong_count(this);
+
+        result as ULONG
+    }
+    
+    unsafe extern "system" fn release(this: *mut IUnknown) -> ULONG {
+        let arc = Rc::from_raw(this);
+        let result = Rc::strong_count(&arc) - 1;
+        let _ = Rc::into_raw(arc);
+
+        Rc::decrement_strong_count(this);
+
+        result as ULONG
+    }
+        
+    unsafe extern "system" fn drag_enter(
+        this: *mut IDropTarget,
+        pDataObj: *const IDataObject,
+        grfKeyState: DWORD,
+        pt: POINTL,
+        pdwEffect: *mut DWORD,
+    ) -> HRESULT
+    {
+        let drop_target = &mut *(this as *mut DropTarget);
+        let Some(window_state) = drop_target.window_state.upgrade() else {
+            return E_UNEXPECTED;
+        };
+
+        let modifiers = window_state.keyboard_state().get_modifiers_from_mouse_wparam(grfKeyState as WPARAM);
+
+        drop_target.parse_coordinates(pt);
+        drop_target.parse_drop_data(&*pDataObj);
+
+        let event = MouseEvent::DragEntered {
+            position: drop_target.drag_position,
+            modifiers,
+            data: drop_target.drop_data.clone(),
+        };
+
+        drop_target.on_event(Some(pdwEffect), event);
+        S_OK
+    }
+    
+    unsafe extern "system" fn drag_over(
+        this: *mut IDropTarget,
+        grfKeyState: DWORD,
+        pt: POINTL,
+        pdwEffect: *mut DWORD,
+    ) -> HRESULT
+    {
+        let drop_target = &mut *(this as *mut DropTarget);
+        let Some(window_state) = drop_target.window_state.upgrade() else {
+            return E_UNEXPECTED;
+        };
+
+        let modifiers = window_state.keyboard_state().get_modifiers_from_mouse_wparam(grfKeyState as WPARAM);
+
+        drop_target.parse_coordinates(pt);
+
+        let event = MouseEvent::DragMoved {
+            position: drop_target.drag_position,
+            modifiers,
+            data: drop_target.drop_data.clone(),
+        };
+
+        drop_target.on_event(Some(pdwEffect), event);
+        S_OK
+    }
+    
+    unsafe extern "system" fn drag_leave(this: *mut IDropTarget) -> HRESULT {
+        let drop_target = &mut *(this as *mut DropTarget);
+        drop_target.on_event(None, MouseEvent::DragLeft);
+        S_OK
+    }
+    
+    unsafe extern "system" fn drop(
+        this: *mut IDropTarget,
+        pDataObj: *const IDataObject,
+        grfKeyState: DWORD,
+        pt: POINTL,
+        pdwEffect: *mut DWORD,
+    ) -> HRESULT
+    {
+        let drop_target = &mut *(this as *mut DropTarget);
+        let Some(window_state) = drop_target.window_state.upgrade() else {
+            return E_UNEXPECTED;
+        };
+
+        let modifiers = window_state.keyboard_state().get_modifiers_from_mouse_wparam(grfKeyState as WPARAM);
+
+        drop_target.parse_coordinates(pt);
+        drop_target.parse_drop_data(&*pDataObj);
+
+        let event = MouseEvent::DragDropped {
+            position: drop_target.drag_position,
+            modifiers,
+            data: drop_target.drop_data.clone(),
+        };
+
+        drop_target.on_event(Some(pdwEffect), event);
+        S_OK
+    }
+}

src/win/mod.rs

@@ -1,3 +1,4 @@
+mod drop_target;
 mod keyboard;
 mod window;
 

src/win/window.rs

@@ -2,6 +2,8 @@ use winapi::shared::guiddef::GUID;
 use winapi::shared::minwindef::{ATOM, FALSE, LPARAM, LRESULT, UINT, WPARAM};
 use winapi::shared::windef::{HWND, RECT};
 use winapi::um::combaseapi::CoCreateGuid;
+use winapi::um::ole2::{RegisterDragDrop, OleInitialize, RevokeDragDrop};
+use winapi::um::oleidl::LPDROPTARGET;
 use winapi::um::winuser::{
     AdjustWindowRectEx, CreateWindowExW, DefWindowProcW, DestroyWindow, DispatchMessageW,
     GetDpiForWindow, GetMessageW, GetWindowLongPtrW, LoadCursorW, PostMessageW, RegisterClassW,
@@ -16,7 +18,7 @@ use winapi::um::winuser::{
     XBUTTON1, XBUTTON2,
 };
 
-use std::cell::{Cell, RefCell};
+use std::cell::{Cell, RefCell, Ref, RefMut};
 use std::collections::VecDeque;
 use std::ffi::{c_void, OsStr};
 use std::marker::PhantomData;
@@ -33,6 +35,7 @@ use crate::{
     WindowHandler, WindowInfo, WindowOpenOptions, WindowScalePolicy,
 };
 
+use super::drop_target::DropTarget;
 use super::keyboard::KeyboardState;
 
 #[cfg(feature = "opengl")]
@@ -147,9 +150,10 @@ unsafe extern "system" fn wnd_proc(
 
         // NOTE: This is not handled in `wnd_proc_inner` because of the deferred task loop above
         if msg == WM_NCDESTROY {
+            RevokeDragDrop(hwnd);
             unregister_wnd_class((*window_state_ptr).window_class);
             SetWindowLongPtrW(hwnd, GWLP_USERDATA, 0);
-            drop(Box::from_raw(window_state_ptr));
+            drop(Rc::from_raw(window_state_ptr));
         }
 
         // The actual custom window proc has been moved to another function so we can always handle
@@ -446,7 +450,7 @@ unsafe fn unregister_wnd_class(wnd_class: ATOM) {
 /// because of the Windows message loops' reentrant nature. Care still needs to be taken to prevent
 /// `handler` from indirectly triggering other events that would also need to be handled using
 /// `handler`.
-struct WindowState {
+pub(super) struct WindowState {
     /// The HWND belonging to this window. The window's actual state is stored in the `WindowState`
     /// struct associated with this HWND through `unsafe { GetWindowLongPtrW(self.hwnd,
     /// GWLP_USERDATA) } as *const WindowState`.
@@ -458,6 +462,7 @@ struct WindowState {
     mouse_button_counter: Cell<usize>,
     // Initialized late so the `Window` can hold a reference to this `WindowState`
     handler: RefCell<Option<Box<dyn WindowHandler>>>,
+    _drop_target: RefCell<Option<Rc<DropTarget>>>,
     scale_policy: WindowScalePolicy,
     dw_style: u32,
 
@@ -473,10 +478,22 @@ struct WindowState {
 }
 
 impl WindowState {
-    fn create_window(&self) -> Window {
+    pub(super) fn create_window(&self) -> Window {
         Window { state: self }
     }
 
+    pub(super) fn window_info(&self) -> Ref<WindowInfo> {
+        self.window_info.borrow()
+    }
+
+    pub(super) fn keyboard_state(&self) -> Ref<KeyboardState> {
+        self.keyboard_state.borrow()
+    }
+
+    pub(super) fn handler_mut(&self) -> RefMut<Option<Box<dyn WindowHandler>>> {
+        self.handler.borrow_mut()
+    }
+
     /// Handle a deferred task as described in [`Self::deferred_tasks
     pub(self) fn handle_deferred_task(&self, task: WindowTask) {
         match task {
@@ -517,7 +534,7 @@ impl WindowState {
 /// Tasks that must be deferred until the end of [`wnd_proc()`] to avoid reentrant `WindowState`
 /// borrows. See the docstring on [`WindowState::deferred_tasks`] for more information.
 #[derive(Debug, Clone)]
-enum WindowTask {
+pub(super) enum WindowTask {
     /// Resize the window to the given size. The size is in logical pixels. DPI scaling is applied
     /// automatically.
     Resize(Size),
@@ -654,7 +671,7 @@ impl Window<'_> {
             let (parent_handle, window_handle) = ParentHandle::new(hwnd);
             let parent_handle = if parented { Some(parent_handle) } else { None };
 
-            let window_state = Box::new(WindowState {
+            let window_state = Rc::new(WindowState {
                 hwnd,
                 window_class,
                 window_info: RefCell::new(window_info),
@@ -664,6 +681,7 @@ impl Window<'_> {
                 // The Window refers to this `WindowState`, so this `handler` needs to be
                 // initialized later
                 handler: RefCell::new(None),
+                _drop_target: RefCell::new(None),
                 scale_policy: options.scale,
                 dw_style: flags,
 
@@ -711,7 +729,13 @@ impl Window<'_> {
                 None
             };
 
-            SetWindowLongPtrW(hwnd, GWLP_USERDATA, Box::into_raw(window_state) as *const _ as _);
+            let drop_target = Rc::new(DropTarget::new(Rc::downgrade(&window_state)));
+            *window_state._drop_target.borrow_mut() = Some(drop_target.clone());
+
+            OleInitialize(null_mut());
+            RegisterDragDrop(hwnd, Rc::as_ptr(&drop_target) as LPDROPTARGET);
+
+            SetWindowLongPtrW(hwnd, GWLP_USERDATA, Rc::into_raw(window_state) as *const _ as _);
             SetTimer(hwnd, WIN_FRAME_TIMER, 15, None);
 
             if let Some(mut new_rect) = new_rect {