feat: add self-drawn collection drop delegates

Author: Roy Lin

README.md

@@ -69,9 +69,11 @@ versioned [component matrix](docs/react-aria-component-matrix.json) pins
 - `Button` currently has scene/software-pixel smoke evidence through the shared
   calculator, but no component is self-drawn conformant yet;
 - the shared pointer/keyboard drag/drop state machine now covers multi-type,
-  wildcard, multi-item, and per-format payload negotiation for
-  draggable/drop-target authoring, but collection delegates, external
-  transfer, pixels, accessibility, and real hosts still keep `DropZone` below
+  wildcard, multi-item, and per-format payload negotiation plus layout-driven
+  collection `root` and keyed `before`/`on`/`after` targets. Selected
+  collection items drag as one session, and ListBox, GridList, Tree, and Table
+  share the same RSX contract; external transfer, reorder/move policy, pixels,
+  accessibility, and real hosts still keep every affected family below
   conformance;
 - Checkbox, Radio, and Switch Field/Button parts plus ToastList and
   ToastContent are recorded as eight explicit API gaps;
@@ -304,9 +306,12 @@ independently.
   scheduled long press, incremental captured move, and self-drawn drag/drop
   routing over `PlatformElementId`; drag sessions retain multiple text items
   and every MIME/custom representation, filter compatible target items,
-  negotiate wildcards plus copy/move/link/cancel operations, and share
-  event-loop deadlines, stable action bubbling, keyed reconciliation, and
-  reducer rollback in one staged interaction session
+  negotiate wildcards plus copy/move/link/cancel operations, aggregate stable
+  selected collection keys, and resolve root/item/insertion targets from
+  self-drawn layout geometry. A collection is one keyboard Tab stop during a
+  drag, with arrow/Home/End navigation inside it; all paths share event-loop
+  deadlines, stable action bubbling, keyed reconciliation, and reducer
+  rollback in one staged interaction session
 - an identical-frame fast path that performs no layout, scene, host, or
   presentation work, plus semantic-only commits that skip pixel presentation
 - a software Graphics presenter and interactive shared
@@ -322,11 +327,11 @@ independently.
 | M1 · GUI integration | Complete | Pinned Graphics boundary, semantic-only dependency gate, renderer inventory, reference/GPU wrappers, first generic adapter |
 | M2 · GPU backend | Implementation landed | Graphics commit `8748fab`; Metal and Vulkan CI parity evidence remains |
 | M3 · Layout and Scene | Current | Generic calculator rectangle slice landed; full flex, stacking, redraw scheduling, cross-platform fingerprints, and thin-host presentation remain |
-| M4 · Text and interaction cutover | In progress | Stable-id raw input, long press, move, and drag/drop foundations landed; shaping, glyphs, editing/IME, accessibility bridges, overlays, and complete calculator scenarios remain |
+| M4 · Text and interaction cutover | In progress | Stable-id raw input, long press, move, typed and collection drag/drop foundations landed; shaping, glyphs, editing/IME, accessibility bridges, overlays, and complete calculator scenarios remain |
 | M5 · Default cutover | Planned | Make self-drawn content the default, then delete the three legacy widget renderers |
 | H0-H5 · Thin platform hosts | H0 complete; H1 in progress | Atomic frames, lifecycle recovery, stable-id raw input/reducers, long press, captured move, typed drag/drop negotiation, zero-toolkit firewalls, and an interactive calculator landed; the Graphics raw-surface edge remains |
 | T0-T5 · TSX native authoring | Proposed | Automatic JSX runtime, versioned Node-to-host session, state/event runtime, self-drawn native window, packages, and stable SDK |
-| M6-M8 · React Aria components | Catalog pinned; conformance planned | 51/51 families mapped, eight public parts explicitly missing, Button scene smoke only; full software and three-OS self-drawn evidence required |
+| M6-M8 · React Aria components | Catalog pinned; conformance planned | 51/51 families mapped; collection DnD authoring/behavior slice landed; eight public parts, full software, accessibility, and three-OS self-drawn evidence remain |
 
 The dependency-ordered plan and acceptance gates are in the
 [delivery roadmap](docs/roadmap.md).

docs/platform-hosts.md

@@ -396,7 +396,7 @@ Landed evidence:
 - reducer errors restore the staged interaction state and sequence before the
   event is exposed as successful; successful frame reconciliation preserves
   focused stable ids, while rejected frames do not touch them
-- 48 focused runtime/software tests and four recursive feature/source
+- 53 focused runtime/software tests and four recursive feature/source
   firewall tests pass without any legacy renderer or OS toolkit dependency
 - `self_drawn_calculator` reproduces layout fingerprint
   `16529597026056060935`, scene fingerprint `2100550662756266801`, and

docs/react-aria-native.md

@@ -149,11 +149,22 @@ The first shared interaction milestone is available in the portable runtime:
   representations. Keyboard Tab cycles compatible targets only; Enter drops
   and Escape cancels. Source/target state, keyed reconciliation, and reducer
   rollback remain one transaction.
+- Selected draggable collection items now aggregate their stable keys, typed
+  payloads, and `data-[dragging]` state into one session. A layout-backed
+  delegate resolves `{type: root}` and keyed `before`/`on`/`after` targets,
+  filters every target item by accepted type, and exposes `draggingKeys`,
+  `target`, and `isInternal` in the shared context. During keyboard drag, each
+  collection is one Tab stop and Arrow/Home/End keys navigate its internal
+  targets.
 - `use_drag`, `use_drop`, `UiDraggable`, `UiDroppable`, and `UiDropZone` lower
   their source/target metadata and focusable keyboard affordances into that
-  shared runtime. Collection item/between/root delegates, external files and
-  directories, cross-application transfer, and drag previews remain separate
-  M7 work, so the DropZone family is not yet marked conformant.
+  shared runtime. ListBox, GridList, Tree, and Table roots additionally lower
+  `onRootDrop`, `onItemDrop`, `onInsert`, and low-level `onDrop` precedence;
+  their items/rows and explicit DropIndicator parts use the same self-drawn
+  target model. Reorder/move policy, dynamic acceptance, external files and
+  directories, cross-application transfer, drag previews, and conformance
+  evidence remain separate M7 work, so no affected family is marked
+  conformant.
 
 - `NativeInputModality` represents keyboard, mouse, touch, pen, virtual, and
   unknown input.
@@ -587,7 +598,7 @@ props:
 | Priority | Area | Required outcome |
 | --- | --- | --- |
 | P0 | Self-drawn component accounting | Keep all 51 React Aria 1.19.0 families in the executable matrix, implement the eight recorded public-part gaps, and require every upstream catalog delta to update code, matrix, tests, and milestones together. |
-| P0 | Shared self-drawn interaction | Extend the landed stable-id pointer, keyboard, Tab-focus, hover, press, scheduled generic long press, incremental captured move, typed source/target drag negotiation, cancellation, wheel, bubbling, and reducer path with collection item/between/root drag delegates, external file/directory transfer, drag previews, collection long-press selection mode, focus-scope restoration, overlay gestures, text editing/IME, and accessibility activation. |
+| P0 | Shared self-drawn interaction | Extend the landed stable-id pointer, keyboard, Tab-focus, hover, press, scheduled generic long press, incremental captured move, typed source/target drag negotiation, collection item/between/root delegates, cancellation, wheel, bubbling, and reducer path with reorder/move policy, dynamic item acceptance, external file/directory transfer, drag previews, collection long-press selection mode, focus-scope restoration, overlay gestures, text editing/IME, and accessibility activation. |
 | P0 | Native input conformance | WinUI's complete 98-case V1 manifest passes real OS automation. Populate the AppKit and GTK4 manifests with platform-run mouse, pen, touch where applicable, keyboard, assistive activation, disabled, cancellation, and keyed-rerender fixtures for every role currently marked native; then close or retain evidence-backed menu/item exceptions. |
 | P1 | Event propagation | Add platform-run conformance fixtures for conditional `Stop`/`Continue` across nested native controls. |
 | P1 | Focus management | Add platform-run conformance fixtures for post-mount `autoFocus`, nested containment, and restoration. |

docs/roadmap.md

@@ -510,10 +510,17 @@ Landed evidence:
   representation; target callbacks receive only matching items without losing
   the other representations on those items, while legacy `dragType` plus
   `dragValue` normalizes to one compatible text item
+- collection drag sources aggregate the stable keys, payloads, and visual
+  dragging state of selected draggable items. The layout-backed delegate emits
+  React Aria-shaped root and keyed before/on/after targets, routes
+  `onRootDrop`/`onItemDrop`/`onInsert` with low-level `onDrop` precedence, and
+  treats a collection as one Tab target with arrow/Home/End navigation inside
+  it. ListBox, GridList, Tree, Table, and explicit DropIndicator authoring all
+  lower to this shared self-drawn path
 - the shared 410x620 calculator preserves its reviewed layout and scene
   fingerprints, routes eight fake-host events through four reducer actions,
   commits the resulting frames, and reaches display value `10`
-- 48 focused runtime/software tests plus four recursive H1 firewall tests are
+- 53 focused runtime/software tests plus four recursive H1 firewall tests are
   included in `just verify`
 
 Remaining H1 work:
@@ -522,10 +529,10 @@ Remaining H1 work:
   pinned Graphics commit `8748fab` owns only a surface-independent texture and
   readback today, so its safe host-owned surface attachment/recovery contract
   must land before GUI can implement this edge without duplicating `wgpu`
-- collection item/between/root drag delegates, native file/directory and
-  cross-application transfer, drag previews, text editing, IME, overlay
-  gestures, and component-specific interaction conformance remain explicit M4
-  and M6-M8 work
+- collection reorder/move policy and acceptance callbacks, native
+  file/directory and cross-application transfer, drag previews, text editing,
+  IME, overlay gestures, and component-specific pixel/accessibility/real-host
+  conformance remain explicit M4 and M6-M8 work
 
 Gates:
 
@@ -735,6 +742,9 @@ self-drawn conformance.
 - close the executable 1.19.0 behavior deltas: embedded-control keyboard
   navigation for GridList/Tree, Menu action key plus value, arbitrary Popover
   target rectangles, and multi-MIME/wildcard drag type negotiation
+- build on the landed shared collection root/item/insertion delegate with
+  reorder, cross-collection move, dynamic item acceptance, drag previews, and
+  software/accessibility/three-host conformance stories
 
 ### M8 - Date, color, tables, and advanced data
 

docs/rsx.md

@@ -597,8 +597,26 @@ Target callbacks receive only matching items, with every representation on
 those items preserved. `UiDraggable`, `UiDroppable`, and `UiDropZone` include a
 keyboard-focusable affordance: Enter starts or commits a drag, Tab cycles
 compatible targets, and Escape cancels. Pointer and keyboard callbacks receive
-the same typed transfer context. External OS files/directories and collection
-before/after insertion targets remain separate work.
+the same typed transfer context.
+
+`UiListBox`, `UiGridList`, `UiTree`, and `UiTable` also expose the shared
+collection contract. Their roots accept `onRootDrop`, `onItemDrop`, `onInsert`,
+the low-level overriding `onDrop`, lifecycle handlers, `acceptedDragTypes`,
+`dropOperation`, `allowedDropOperations`, and `dropOrientation`. Item/row
+components accept a stable `id` plus `isDraggable`, `dragType`, `dragValue`,
+and `dragItems`; `UiDropIndicator.targetKey` references that `id`.
+Dragging a selected item aggregates all selected draggable item keys and
+payloads; dragging an unselected item keeps a single-item session.
+
+Collection callback context adds `draggingKeys`, `isInternal`, and a `target`
+descriptor shaped as `{type: "root"}` or
+`{type: "item", key, dropPosition: "before" | "on" | "after"}`. Pointer
+delegation derives targets from the committed self-drawn boxes. During a
+keyboard drag, Tab visits the collection once and Arrow/Home/End keys navigate
+inside it. `UiDropIndicator targetKey="..." dropPosition="before|after"`
+provides a stable explicit insertion visual. External OS files/directories,
+cross-application transfer, drag previews, reorder/move policy, and final
+accessibility/host conformance remain separate work.
 
 Runtime lifecycle and effects:
 

src/compiler.rs

@@ -2888,6 +2888,14 @@ fn drop_indicator_scope_value(props: &CompiledProps) -> GuiResult<JsonValue> {
     use_drop_indicator_value(
         UseDropIndicatorProps::new()
             .orientation(orientation_attribute_value(props))
+            .target_key(non_empty_attribute(
+                props,
+                &["targetKey", "data-drop-target-key"],
+            ))
+            .drop_position(non_empty_attribute(
+                props,
+                &["dropPosition", "data-drop-position"],
+            ))
             .target(
                 bool_attribute_value(props, &["isTarget", "target", "data-target"])
                     .unwrap_or(false),

src/lib.rs

@@ -207,11 +207,12 @@ pub use platform_host::{
 #[cfg(feature = "platform-runtime")]
 pub use platform_runtime::{
     PlatformRenderFrame, PlatformScenePresenter, RecordingPreparedFrame, RecordingScenePresenter,
-    SelfDrawnActionInvocation, SelfDrawnActionPropagation, SelfDrawnDragContext, SelfDrawnDropItem,
-    SelfDrawnDropOperation, SelfDrawnElementInteraction, SelfDrawnEventContext,
-    SelfDrawnFrameCommit, SelfDrawnFrameCommitStatus, SelfDrawnFrameSnapshot,
-    SelfDrawnHostEventOutcome, SelfDrawnInputDispatch, SelfDrawnInteractionChange,
-    SelfDrawnRuntimeStats, SelfDrawnWindowRuntime,
+    SelfDrawnActionInvocation, SelfDrawnActionPropagation, SelfDrawnCollectionDropTarget,
+    SelfDrawnDragContext, SelfDrawnDropItem, SelfDrawnDropOperation, SelfDrawnDropPosition,
+    SelfDrawnElementInteraction, SelfDrawnEventContext, SelfDrawnFrameCommit,
+    SelfDrawnFrameCommitStatus, SelfDrawnFrameSnapshot, SelfDrawnHostEventOutcome,
+    SelfDrawnInputDispatch, SelfDrawnInteractionChange, SelfDrawnRuntimeStats,
+    SelfDrawnWindowRuntime,
 };
 #[cfg(all(feature = "platform-runtime", feature = "software-reference"))]
 pub use platform_runtime::{