feat: support multi-item drag payloads

Author: Roy Lin

README.md

@@ -68,10 +68,11 @@ versioned [component matrix](docs/react-aria-component-matrix.json) pins
   authoring components;
 - `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 and
-  wildcard negotiation for draggable/drop-target authoring, but multi-item and
-  per-format payloads, collection delegates, external transfer, pixels,
-  accessibility, and real hosts still keep `DropZone` below conformance;
+- 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
+  conformance;
 - Checkbox, Radio, and Switch Field/Button parts plus ToastList and
   ToastContent are recorded as eight explicit API gaps;
 - a component reaches `conformant` only with behavior, layout/hit, Graphics
@@ -301,10 +302,11 @@ independently.
   acknowledgement, and surface-loss replay without changing semantic identity
 - raw pointer, keyboard, Tab-focus, hover, press, cancellation, wheel,
   scheduled long press, incremental captured move, and self-drawn drag/drop
-  routing over `PlatformElementId`; drag sessions negotiate multiple MIME
-  types and wildcards plus copy/move/link/cancel operations, while event-loop
-  deadlines, stable action bubbling, keyed reconciliation, and reducer rollback
-  share one staged interaction session
+  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
 - 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

docs/architecture.md

@@ -480,6 +480,9 @@ such as `onClick`, `onLongPress`, `onMoveStart`, `onMove`, `onMoveEnd`,
 `onDragStart`, `onDragMove`, `onDragEnd`, `onDropEnter`, `onDropMove`,
 `onDropExit`, `onDrop`, `onChange`, `onInput`, `onFocusChange`, `onAction`,
 `onExpandedChange`, `onKeyDown`, and `onKeyUp`.
+Self-drawn drag callbacks carry a typed item array. Each text item preserves its
+complete format map; source events receive every item, while target events
+receive the subset matching that target without flattening per-format data.
 Focus and blur events always carry canonical `true` and `false` payloads for
 `onFocusChange`. These direct focus callbacks are target-only. The runtime
 separately derives `onFocusWithin`, `onBlurWithin`, and

docs/platform-hosts.md

@@ -223,6 +223,8 @@ src/platform_runtime/
 |- drag_drop_tests.rs   pointer negotiation, rollback, and reconcile gates
 |- drag_drop_keyboard_tests.rs
 |                       keyboard and style-only drag/drop gates
+|- drag_drop_items_tests.rs
+|                       multi-item/per-format transfer and filtering gates
 |- presenter.rs         raw-surface prepare/publish contract and recorder
 |- reference_presenter.rs
 |                       transactional software Graphics evidence
@@ -385,15 +387,16 @@ Landed evidence:
   delta, remains captured outside its hit region, retains incremental delta and
   pointer identity, and ends on release, cancellation, or terminal long press;
   arrow keys route a handled one-unit lifecycle through the same action batch
-- callback-driven and style-only drag/drop negotiates multiple MIME/custom
-  types, wildcard patterns, and copy/move/link/cancel operations; pointer drags
-  report target-local coordinates, keyboard Enter/Tab/Escape provides the same
-  accessible source/compatible-target lifecycle, and keyed frames plus reducer
-  errors preserve or roll back the entire session atomically
+- callback-driven and style-only drag/drop retains multiple text items and all
+  per-item MIME/custom representations, filters target items by exact or
+  wildcard types, and negotiates copy/move/link/cancel operations; pointer
+  drags report target-local coordinates, keyboard Enter/Tab/Escape provides the
+  same accessible source/compatible-target lifecycle, and keyed frames plus
+  reducer errors preserve or roll back the entire session atomically
 - 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
-- 44 focused runtime/software tests and four recursive feature/source
+- 48 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

@@ -144,15 +144,16 @@ The first shared interaction milestone is available in the portable runtime:
 - Self-drawn drag routing starts on the first non-zero primary-pointer delta or
   keyboard Enter. It negotiates multiple MIME/custom source types, `image/*`
   and `all` patterns, allowed copy/move/link/cancel operations, and target-local
-  pointer coordinates. Keyboard Tab cycles compatible targets only; Enter
-  drops and Escape cancels. Source/target state, keyed reconciliation, and
-  reducer rollback remain one transaction.
+  pointer coordinates. Multiple text items retain all per-item formats, and
+  accepted types filter whole target items without removing their fallback
+  representations. Keyboard Tab cycles compatible targets only; Enter drops
+  and Escape cancels. Source/target state, keyed reconciliation, and reducer
+  rollback remain one transaction.
 - `use_drag`, `use_drop`, `UiDraggable`, `UiDroppable`, and `UiDropZone` lower
   their source/target metadata and focusable keyboard affordances into that
-  shared runtime. Multi-item and per-format payloads, 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. 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.
 
 - `NativeInputModality` represents keyboard, mouse, touch, pen, virtual, and
   unknown input.

docs/roadmap.md

@@ -506,10 +506,14 @@ Landed evidence:
   custom exact types, and `all`; `DropEnter`/`DropMove`/`DropExit` ordering,
   `data-[dragging]`/`data-[drop-target]` state, keyed-frame reconciliation, and
   reducer failure rollback share the same transactional interaction session
+- drag sources retain multiple text items and every per-item MIME/custom
+  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
 - 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`
-- 44 focused runtime/software tests plus four recursive H1 firewall tests are
+- 48 focused runtime/software tests plus four recursive H1 firewall tests are
   included in `just verify`
 
 Remaining H1 work:
@@ -518,10 +522,10 @@ 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`
-- multi-item and per-format drag payloads, 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 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
 
 Gates:
 

docs/rsx.md

@@ -582,16 +582,23 @@ Semantic UI projections:
 only direct focus by default. Set `within={true}` when descendant focus should
 also display the ring.
 
-Self-drawn drag sources expose `dragType`, `dragValue`, and
-`allowedDropOperations` (comma- or whitespace-separated
-`copy`/`move`/`link`). Drop targets expose `acceptedDragTypes` and
-`dropOperation`; accepted types may contain multiple exact values, `all`, or a
-MIME wildcard such as `image/*`. `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 are not part of this first shared
-runtime slice.
+Self-drawn drag sources expose `dragItems`, a JSON array equivalent to React
+Aria's `getItems()` result. Each array entry maps MIME/custom types to their
+text representation, for example
+`[{"text/plain":"alpha","text/html":"<b>alpha</b>"}]`. Rust hooks may use
+`UseDragProps::drag_items(Vec<DragItem>)` instead of encoding JSON. The legacy
+`dragType` and `dragValue` pair remains supported and normalizes to one text
+item. `allowedDropOperations` accepts comma- or whitespace-separated
+`copy`/`move`/`link` values.
+
+Drop targets expose `acceptedDragTypes` and `dropOperation`; accepted types may
+contain multiple exact values, `all`, or a MIME wildcard such as `image/*`.
+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.
 
 Runtime lifecycle and effects:
 

src/compiler.rs

@@ -2591,6 +2591,10 @@ fn drag_scope_value(props: &CompiledProps) -> GuiResult<JsonValue> {
                 props,
                 &["dragValue", "data-drag-value"],
             ))
+            .drag_items_json(non_empty_attribute(
+                props,
+                &["dragItems", "data-drag-items"],
+            ))
             .allowed_drop_operations(non_empty_attribute(
                 props,
                 &["allowedDropOperations", "data-allowed-drop-operations"],

src/lib.rs

@@ -207,10 +207,11 @@ pub use platform_host::{
 #[cfg(feature = "platform-runtime")]
 pub use platform_runtime::{
     PlatformRenderFrame, PlatformScenePresenter, RecordingPreparedFrame, RecordingScenePresenter,
-    SelfDrawnActionInvocation, SelfDrawnActionPropagation, SelfDrawnElementInteraction,
-    SelfDrawnEventContext, SelfDrawnFrameCommit, SelfDrawnFrameCommitStatus,
-    SelfDrawnFrameSnapshot, SelfDrawnHostEventOutcome, SelfDrawnInputDispatch,
-    SelfDrawnInteractionChange, SelfDrawnRuntimeStats, SelfDrawnWindowRuntime,
+    SelfDrawnActionInvocation, SelfDrawnActionPropagation, SelfDrawnDragContext, SelfDrawnDropItem,
+    SelfDrawnDropOperation, SelfDrawnElementInteraction, SelfDrawnEventContext,
+    SelfDrawnFrameCommit, SelfDrawnFrameCommitStatus, SelfDrawnFrameSnapshot,
+    SelfDrawnHostEventOutcome, SelfDrawnInputDispatch, SelfDrawnInteractionChange,
+    SelfDrawnRuntimeStats, SelfDrawnWindowRuntime,
 };
 #[cfg(all(feature = "platform-runtime", feature = "software-reference"))]
 pub use platform_runtime::{
@@ -437,7 +438,7 @@ pub use semantic_ui::{
     UseLongPressResult, UseMoveProps, UseMoveResult,
 };
 pub use semantic_ui::{
-    use_drag, use_drag_value, use_drop, use_drop_value, DragButtonProps, DragProps,
+    use_drag, use_drag_value, use_drop, use_drop_value, DragButtonProps, DragItem, DragProps,
     DropButtonProps, DropProps, UseDragProps, UseDragResult, UseDropProps, UseDropResult,
 };
 pub use semantic_ui::{