dioxus-dnd 3.1.0

Modular, accessible drag-and-drop for Dioxus: sortable lists, kanban boards, trees, grids, file drops, multi-select, touch support and more
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382

//! The Windows/WebView2 leg: raw input, because nothing else works there.
//!
//! Probed on Win 11 (see the repo's UPSTREAM-multiwindow notes for the
//! recordings): the origin webview keeps receiving the full mouse stream
//! while the button is held - including moves and the release outside
//! its own viewport - but those events target `<html>` (nothing
//! retargets without pointer capture), so no component handler ever
//! hears them; and tao never fires `CursorMoved`/`MouseInput` at all,
//! because the WebView2 child HWND consumes the messages before the tao
//! window sees them. Both portable legs are therefore dead on Windows.
//!
//! This leg goes one layer lower: tao registers Windows raw input
//! (`WM_INPUT`) on the event loop's thread target, which no HWND can
//! swallow, and dioxus-desktop forwards `Event::DeviceEvent` to EVERY
//! wry event handler (only `WindowEvent`s are per-window filtered). The
//! origin's bridge hears the raw button-up wherever it happens and
//! completes the drop at `cursor_position()` - the same
//! global-physical-px source the poller uses; raw motion retracks
//! mid-drag at event rate, out-pacing the 30ms poller.
//!
//! Requires `DeviceEventFilter::Never`: the default `Unfocused`
//! registers without `RIDEV_INPUTSINK`, and the foreground input owner
//! is the WebView2 process's HWND, so raw input never arrives otherwise.
//! **The leg sets that filter process-globally on first use**, and only
//! on Windows - the handler returns before claiming it anywhere else -
//! but apps with their own raw-input needs should know the bridge flips
//! it there.

use dioxus::prelude::{use_hook, Modifiers};
use dioxus_desktop::tao::event::{DeviceEvent, ElementState, Event};
use dioxus_desktop::tao::event_loop::DeviceEventFilter;
use dioxus_desktop::tao::keyboard::KeyCode;
use dioxus_desktop::{use_wry_event_handler, window};
use std::cell::Cell;
use std::rc::Rc;
use std::sync::atomic::{AtomicBool, Ordering};

use crate::core::{DndContext, JoinedWindow, Point};

use super::super::bridge::{bridged, current_bridged_generation, BridgeGeneration};

static DEVICE_FILTER_CLAIMED: AtomicBool = AtomicBool::new(false);

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum FilterSetupAction {
    Install,
    AlreadyInstalled,
}

fn filter_setup_action(was_claimed: bool) -> FilterSetupAction {
    if was_claimed {
        FilterSetupAction::AlreadyInstalled
    } else {
        FilterSetupAction::Install
    }
}

// Live modifiers need the same raw layer as the pointer (probed on Win 11,
// same recordings): tao never fires `ModifiersChanged` because the WebView2
// child HWND owns keyboard focus, and the origin's streamed `<html>`-target
// events carry the state but reach no component handler. The
// `DeviceEventFilter::Never` registration below already includes keyboards,
// so `DeviceEvent::Key` arrives here regardless of focus; each physical
// modifier side is tracked so releasing one Ctrl while the other is held
// cannot clear the state.
const CONTROL_SIDES: u8 = 0b0000_0011;
const ALT_SIDES: u8 = 0b0000_1100;
const SHIFT_SIDES: u8 = 0b0011_0000;
const SUPER_SIDES: u8 = 0b1100_0000;

fn raw_modifier_bit(key: KeyCode) -> Option<u8> {
    Some(match key {
        KeyCode::ControlLeft => 1 << 0,
        KeyCode::ControlRight => 1 << 1,
        KeyCode::AltLeft => 1 << 2,
        KeyCode::AltRight => 1 << 3,
        KeyCode::ShiftLeft => 1 << 4,
        KeyCode::ShiftRight => 1 << 5,
        KeyCode::SuperLeft => 1 << 6,
        KeyCode::SuperRight => 1 << 7,
        _ => return None,
    })
}

fn apply_raw_key(mask: u8, key: KeyCode, pressed: bool) -> u8 {
    match raw_modifier_bit(key) {
        Some(bit) if pressed => mask | bit,
        Some(bit) => mask & !bit,
        None => mask,
    }
}

fn mask_modifiers(mask: u8) -> Modifiers {
    let mut mods = Modifiers::empty();
    if mask & CONTROL_SIDES != 0 {
        mods.insert(Modifiers::CONTROL);
    }
    if mask & ALT_SIDES != 0 {
        mods.insert(Modifiers::ALT);
    }
    if mask & SHIFT_SIDES != 0 {
        mods.insert(Modifiers::SHIFT);
    }
    if mask & SUPER_SIDES != 0 {
        mods.insert(Modifiers::META);
    }
    mods
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum RawInputKind {
    Motion,
    PrimaryRelease,
    Other,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum RawInputAction {
    Track,
    Drop,
}

fn raw_input_action(
    kind: RawInputKind,
    captured: BridgeGeneration,
    live: Option<BridgeGeneration>,
    needs_bridge: bool,
    owns_origin: bool,
    outside_origin: bool,
) -> Option<RawInputAction> {
    if live != Some(captured) || !needs_bridge || !owns_origin || !outside_origin {
        return None;
    }
    match kind {
        RawInputKind::Motion => Some(RawInputAction::Track),
        RawInputKind::PrimaryRelease => Some(RawInputAction::Drop),
        RawInputKind::Other => None,
    }
}

/// Raw-input release detection + event-rate tracking. DeviceEvents reach
/// every window's handler; the origin gate keeps exactly one bridge
/// acting.
pub(crate) fn use_raw_input_leg<T: Clone + PartialEq + 'static>(
    joined: JoinedWindow<T>,
    ctx: DndContext<T>,
) {
    let key_mask = use_hook(|| Rc::new(Cell::new(0u8)));
    let engaged = use_hook(|| Rc::new(Cell::new(None::<BridgeGeneration>)));
    use_wry_event_handler(move |event, target| {
        if !cfg!(target_os = "windows") {
            return;
        }
        if filter_setup_action(DEVICE_FILTER_CLAIMED.swap(true, Ordering::AcqRel))
            == FilterSetupAction::Install
        {
            // The process-global first claim owns raw-input installation;
            // mounting or retiring any individual window cannot re-arm it.
            target.set_device_event_filter(DeviceEventFilter::Never);
        }
        if let Event::DeviceEvent {
            event: DeviceEvent::Key(key),
            ..
        } = event
        {
            // Track modifier keys even while idle so a drag that starts with
            // one already held sees it; every window's mask converges on the
            // same stream, and only the origin's live drag feeds the world.
            let mask = apply_raw_key(
                key_mask.get(),
                key.physical_key,
                key.state == ElementState::Pressed,
            );
            key_mask.set(mask);
            if bridged(joined, &ctx)
                && joined.world.origin_window() == Some(joined.key)
                && current_bridged_generation(joined, &ctx).is_some()
            {
                joined.world.update_modifiers(mask_modifiers(mask));
            }
            return;
        }
        if !bridged(joined, &ctx) || joined.world.origin_window() != Some(joined.key) {
            return;
        }
        let Event::DeviceEvent { event, .. } = event else {
            return;
        };
        let kind = match event {
            DeviceEvent::Button {
                button: 1,
                state: ElementState::Released,
                ..
            } => RawInputKind::PrimaryRelease,
            DeviceEvent::MouseMotion { .. } => RawInputKind::Motion,
            _ => RawInputKind::Other,
        };
        if kind == RawInputKind::Other {
            return;
        }
        // Capture the composite generation before cursor lookup. An untracked
        // `session: None` is authoritative only with its mandatory world id;
        // replacement `begin_from` mints a different id and makes this inert.
        let Some(generation) = current_bridged_generation(joined, &ctx) else {
            return;
        };
        let Ok(pos) = window().cursor_position() else {
            return;
        };
        let global = Point::new(pos.x, pos.y);
        // Inside the origin viewport the webview owns the gesture (the
        // capture substitute feeds moves, the Draggable's pointerup
        // finishes drops). Outside it, this leg is the drag's ears.
        let live = current_bridged_generation(joined, &ctx);
        let action = raw_input_action(
            kind,
            generation,
            live,
            bridged(joined, &ctx),
            joined.world.origin_window() == Some(joined.key),
            !joined.geometry.contains_global(global),
        );
        // Leg diagnostics, once per drag (motion arrives at event rate):
        // after an upstream update, a bug report's engaged-leg trace tells
        // us which platform assumption moved.
        if action.is_some() && engaged.get() != Some(generation) {
            engaged.set(Some(generation));
            tracing::debug!(leg = "raw-input", ?generation, "bridge leg engaged");
        }
        // The captured generation owns this raw observation. Completion or
        // replacement invalidates it immediately before any world mutation.
        match action {
            Some(RawInputAction::Drop) => joined.world.drop_at_global(global),
            Some(RawInputAction::Track) => {
                joined.world.track_global(global);
                None
            }
            None => None,
        };
    });
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::core::DragSessionId;

    #[test]
    fn device_filter_setup_is_process_once() {
        let first = filter_setup_action(false);
        let claimed = first == FilterSetupAction::Install;

        assert_eq!(first, FilterSetupAction::Install);
        assert_eq!(
            filter_setup_action(claimed),
            FilterSetupAction::AlreadyInstalled
        );
    }

    #[test]
    fn raw_key_mask_tracks_paired_modifier_sides() {
        let mut mask = 0;
        mask = apply_raw_key(mask, KeyCode::ControlLeft, true);
        assert_eq!(mask_modifiers(mask), Modifiers::CONTROL);
        mask = apply_raw_key(mask, KeyCode::ControlRight, true);
        mask = apply_raw_key(mask, KeyCode::ControlLeft, false);
        assert_eq!(mask_modifiers(mask), Modifiers::CONTROL);
        mask = apply_raw_key(mask, KeyCode::ControlRight, false);
        assert_eq!(mask_modifiers(mask), Modifiers::empty());
    }

    #[test]
    fn raw_key_mask_maps_each_modifier_and_ignores_other_keys() {
        assert_eq!(
            mask_modifiers(apply_raw_key(0, KeyCode::AltRight, true)),
            Modifiers::ALT
        );
        assert_eq!(
            mask_modifiers(apply_raw_key(0, KeyCode::ShiftLeft, true)),
            Modifiers::SHIFT
        );
        assert_eq!(
            mask_modifiers(apply_raw_key(0, KeyCode::SuperLeft, true)),
            Modifiers::META
        );
        assert_eq!(apply_raw_key(0, KeyCode::KeyA, true), 0);
        assert_eq!(apply_raw_key(0, KeyCode::ControlLeft, false), 0);
    }

    #[test]
    fn raw_input_action_requires_the_captured_live_generation() {
        let drag_n = BridgeGeneration {
            world: 10,
            session: Some(DragSessionId(20)),
        };
        let drag_n_plus_one = BridgeGeneration {
            world: 11,
            session: Some(DragSessionId(21)),
        };

        assert_eq!(
            raw_input_action(RawInputKind::Motion, drag_n, Some(drag_n), true, true, true),
            Some(RawInputAction::Track)
        );
        assert_eq!(
            raw_input_action(
                RawInputKind::PrimaryRelease,
                drag_n,
                Some(drag_n),
                true,
                true,
                true
            ),
            Some(RawInputAction::Drop)
        );
        assert_eq!(
            raw_input_action(
                RawInputKind::PrimaryRelease,
                drag_n,
                Some(drag_n_plus_one),
                true,
                true,
                true
            ),
            None
        );

        let untracked_n = BridgeGeneration {
            world: 30,
            session: None,
        };
        let untracked_n_plus_one = BridgeGeneration {
            world: 31,
            session: None,
        };
        assert_eq!(
            raw_input_action(
                RawInputKind::Motion,
                untracked_n,
                Some(untracked_n),
                true,
                true,
                true
            ),
            Some(RawInputAction::Track)
        );
        assert_eq!(
            raw_input_action(
                RawInputKind::Motion,
                untracked_n,
                Some(untracked_n_plus_one),
                true,
                true,
                true
            ),
            None
        );
        assert_eq!(
            raw_input_action(RawInputKind::PrimaryRelease, drag_n, None, true, true, true),
            None
        );
    }

    #[test]
    fn raw_input_action_requires_every_ownership_gate() {
        let drag = BridgeGeneration {
            world: 5,
            session: None,
        };
        for (kind, bridge, origin, outside) in [
            (RawInputKind::PrimaryRelease, false, true, true),
            (RawInputKind::PrimaryRelease, true, false, true),
            (RawInputKind::PrimaryRelease, true, true, false),
            (RawInputKind::Other, true, true, true),
        ] {
            assert_eq!(
                raw_input_action(kind, drag, Some(drag), bridge, origin, outside),
                None
            );
        }
    }
}