Implement dragging layers into the group/new/delete buttons in the Layers panel

editor/src/messages/layout/layout_message.rs

@@ -26,4 +26,8 @@ pub enum LayoutMessage {
 		widget_id: WidgetId,
 		value: serde_json::Value,
 	},
+	WidgetValueDragDrop {
+		layout_target: LayoutTarget,
+		widget_id: WidgetId,
+	},
 }

editor/src/messages/layout/layout_message_handler.rs

@@ -62,6 +62,19 @@ impl MessageHandler<LayoutMessage, LayoutMessageContext<'_>> for LayoutMessageHa
 			LayoutMessage::WidgetValueUpdate { layout_target, widget_id, value } => {
 				self.handle_widget_callback(layout_target, widget_id, value, WidgetValueAction::Update, responses);
 			}
+			LayoutMessage::WidgetValueDragDrop { layout_target, widget_id } => {
+				let Some(layout) = self.layouts.get_mut(layout_target as usize) else {
+					warn!("WidgetValueDragDrop referenced an invalid layout. `widget_id: {widget_id}`, `layout_target: {layout_target:?}`");
+					return;
+				};
+				let Some(widget_instance) = layout.iter_mut().find(|widget| widget.widget_id == widget_id) else {
+					warn!("WidgetValueDragDrop referenced an invalid widget ID. `widget_id: {widget_id}`, `layout_target: {layout_target:?}`");
+					return;
+				};
+				if let Widget::IconButton(icon_button) = &mut *widget_instance.widget {
+					responses.add((icon_button.on_drag_drop.callback)(icon_button));
+				}
+			}
 		}
 	}
 

editor/src/messages/layout/utility_types/widgets/button_widgets.rs

@@ -39,6 +39,9 @@ pub struct IconButton {
 	#[serde(skip)]
 	#[derivative(Debug = "ignore", PartialEq = "ignore")]
 	pub on_commit: WidgetCallback<()>,
+	#[serde(skip)]
+	#[derivative(Debug = "ignore", PartialEq = "ignore")]
+	pub on_drag_drop: WidgetCallback<IconButton>,
 }
 
 #[cfg_attr(feature = "wasm", derive(tsify::Tsify))]

editor/src/messages/portfolio/document/document_message_handler.rs

@@ -3288,17 +3288,23 @@ impl DocumentMessageHandler {
 					let group_folder_type = GroupFolderType::Layer;
 					DocumentMessage::GroupSelectedLayers { group_folder_type }.into()
 				})
+				.on_drag_drop(|_| {
+					let group_folder_type = GroupFolderType::Layer;
+					DocumentMessage::GroupSelectedLayers { group_folder_type }.into()
+				})
 				.disabled(!has_selection)
 				.widget_instance(),
 			IconButton::new("NewLayer", 24)
 				.tooltip_label("New Layer")
 				.tooltip_shortcut(action_shortcut!(DocumentMessageDiscriminant::CreateEmptyFolder))
 				.on_update(|_| DocumentMessage::CreateEmptyFolder.into())
+				.on_drag_drop(|_| DocumentMessage::DuplicateSelectedLayers.into())
 				.widget_instance(),
 			IconButton::new("Trash", 24)
 				.tooltip_label("Delete Selected")
 				.tooltip_shortcut(action_shortcut!(DocumentMessageDiscriminant::DeleteSelectedLayers))
 				.on_update(|_| DocumentMessage::DeleteSelectedLayers.into())
+				.on_drag_drop(|_| DocumentMessage::DeleteSelectedLayers.into())
 				.disabled(!has_selection)
 				.widget_instance(),
 		];

frontend/src/components/panels/Layers.svelte

@@ -64,6 +64,7 @@
 	let fakeHighlightOfNotYetSelectedLayerBeingDragged: undefined | bigint = undefined;
 	let justFinishedDrag = false; // Used to prevent click events after a drag
 	let dragInPanel = false;
+	let dragDropTarget: HTMLElement | undefined = undefined;
 
 	// Interactive clipping
 	let layerToClipUponClick: LayerListingInfo | undefined = undefined;
@@ -258,7 +259,7 @@
 
 		let markerHeight = 0;
 		const layerPanel = document.querySelector("[data-layer-panel]"); // Selects the element with the data-layer-panel attribute
-		if (layerPanel !== null && treeChildren !== undefined && treeOffset !== undefined) {
+		if (layerPanel && treeChildren && treeOffset !== undefined) {
 			let layerPanelTop = layerPanel.getBoundingClientRect().top;
 			Array.from(treeChildren).forEach((treeChild) => {
 				const indexAttribute = treeChild.getAttribute("data-index");
@@ -358,6 +359,18 @@
 
 		// Perform drag calculations if a drag is occurring
 		if (internalDragState.active) {
+			// Check if the cursor is over any element flagged as a drag drop target
+			// (e.g. a bottom-bar action button whose backend widget has an `on_drag_drop` callback set)
+			const droppable = (e.target instanceof Element && e.target.closest("[data-drag-droppable]")) || undefined;
+			dragDropTarget = droppable instanceof HTMLElement ? droppable : undefined;
+
+			// Hide the move-in-tree insert indicator whenever the cursor enters the bottom bar
+			const overBottomBar = ((e.target instanceof Element && e.target.closest("[data-layer-bottom-bar]")) || undefined) !== undefined;
+			if (dragDropTarget || overBottomBar) {
+				draggingData = undefined;
+				return;
+			}
+
 			const select = () => {
 				if (internalDragState && !$nodeGraph.selected.includes(internalDragState.layerId)) {
 					selectLayer(internalDragState.listing, false, false);
@@ -369,7 +382,15 @@
 	}
 
 	function draggingPointerUp() {
-		if (internalDragState?.active && draggingData) {
+		if (internalDragState?.active && dragDropTarget) {
+			// Ensure the dragged layer is part of the selection, matching the move-in-tree behavior
+			if (!$nodeGraph.selected.includes(internalDragState.layerId)) selectLayer(internalDragState.listing, false, false);
+
+			// Hand off to the button's backend `on_drag_drop` callback via the custom event
+			dragDropTarget.dispatchEvent(new CustomEvent("dragdrop"));
+
+			justFinishedDrag = true;
+		} else if (internalDragState?.active && draggingData) {
 			const { select, insertParentId, insertIndex } = draggingData;
 
 			// Commit the move
@@ -394,6 +415,7 @@
 		draggingData = undefined;
 		fakeHighlightOfNotYetSelectedLayerBeingDragged = undefined;
 		dragInPanel = false;
+		dragDropTarget = undefined;
 	}
 
 	function draggingMouseDown(e: MouseEvent) {
@@ -658,7 +680,7 @@
 			<div class="insert-mark" style:left={`${4 + draggingData.insertDepth * 16}px`} style:top={`${draggingData.markerHeight}px`}></div>
 		{/if}
 	</LayoutRow>
-	<LayoutRow class="bottom-bar" scrollableX={true}>
+	<LayoutRow class="bottom-bar" classes={{ "layer-drag-active": Boolean(internalDragState?.active) }} scrollableX={true} data-layer-bottom-bar>
 		<WidgetLayout layout={$layersPanelBottomBarLayout} layoutTarget="LayersPanelBottomBar" />
 	</LayoutRow>
 </LayoutCol>
@@ -698,6 +720,26 @@
 			&:not(:has(*)) {
 				display: none;
 			}
+
+			&.layer-drag-active .icon-button,
+			&.layer-drag-active .popover-button {
+				&.drag-droppable:hover {
+					background: var(--color-e-nearwhite);
+
+					svg {
+						fill: var(--color-2-mildblack);
+					}
+				}
+
+				&:not(.drag-droppable) {
+					pointer-events: none;
+					background: none;
+
+					svg {
+						fill: var(--color-8-uppergray);
+					}
+				}
+			}
 		}
 
 		// Layer hierarchy

frontend/src/components/widgets/WidgetSpan.svelte

@@ -65,6 +65,10 @@
 		editor.widgetValueCommitAndUpdate(layoutTarget, widgets[widgetIndex].widgetId, value, resendWidget);
 	}
 
+	function widgetValueDragDrop(widgetIndex: number) {
+		editor.widgetValueDragDrop(layoutTarget, widgets[widgetIndex].widgetId);
+	}
+
 	// Extracts the kind and props from a Widget tagged enum, validated against the widget registry.
 	// The overload declares the precise correlated return type while the implementation uses broader types.
 	function unwrapWidget(widgetInstance: WidgetInstance): UnwrappedWidget | undefined;
@@ -175,6 +179,7 @@
 			getProps: (props, index) => ({
 				...props,
 				action: () => widgetValueCommitAndUpdate(index, undefined, true),
+				actionDragDrop: () => widgetValueDragDrop(index),
 			}),
 		},
 		IconLabel: {

frontend/src/components/widgets/buttons/IconButton.svelte

@@ -1,4 +1,5 @@
 <script lang="ts">
+	import { onMount, onDestroy } from "svelte";
 	import IconLabel from "/src/components/widgets/labels/IconLabel.svelte";
 	import type { IconName, IconSize } from "/src/icons";
 	import type { ActionShortcut } from "/wrapper/pkg/graphite_wasm_wrapper";
@@ -16,6 +17,9 @@
 	export let tooltipShortcut: ActionShortcut | undefined = undefined;
 	// Callbacks
 	export let action: (e?: MouseEvent) => void;
+	// Fired when a draggable item is dropped onto this button. Setting this also flags the button as a valid drop target
+	// (the consumer of the drag interaction looks for `[data-drag-droppable]` and dispatches a `dragdrop` event on it).
+	export let actionDragDrop: (() => void) | undefined = undefined;
 
 	let className = "";
 	export { className as class };
@@ -24,18 +28,29 @@
 	$: extraClasses = Object.entries(classes)
 		.flatMap(([className, stateName]) => (stateName ? [className] : []))
 		.join(" ");
+
+	// Element-level listener for the `dragdrop` custom event that consumers dispatch when something is dropped on this button
+	let buttonElement: HTMLButtonElement | undefined;
+	function handleDragDrop() {
+		actionDragDrop?.();
+	}
+	onMount(() => buttonElement?.addEventListener("dragdrop", handleDragDrop));
+	onDestroy(() => buttonElement?.removeEventListener("dragdrop", handleDragDrop));
 </script>
 
 <button
 	class={`icon-button size-${size} ${className} ${extraClasses}`.trim()}
 	class:hover-icon={hoverIcon && !disabled}
 	class:disabled
 	class:emphasized
+	class:drag-droppable={Boolean(actionDragDrop)}
+	bind:this={buttonElement}
 	on:click={action}
 	{disabled}
 	data-tooltip-label={tooltipLabel}
 	data-tooltip-description={tooltipDescription}
 	data-tooltip-shortcut={tooltipShortcut?.shortcut ? JSON.stringify(tooltipShortcut.shortcut) : undefined}
+	data-drag-droppable={actionDragDrop ? "" : undefined}
 	tabindex={emphasized ? -1 : 0}
 	{...$$restProps}
 >

frontend/wrapper/src/editor_wrapper.rs

@@ -343,6 +343,13 @@ impl EditorWrapper {
 		Ok(())
 	}
 
+	/// Fire a widget's drag-drop action (e.g. when a draggable item is dropped on a button)
+	#[wasm_bindgen(js_name = widgetValueDragDrop)]
+	pub fn widget_value_drag_drop(&self, layout_target: LayoutTarget, widget_id: u64) {
+		let widget_id = WidgetId(widget_id);
+		self.dispatch(LayoutMessage::WidgetValueDragDrop { layout_target, widget_id });
+	}
+
 	/// Closes out the current transaction (drag-end / text-commit end), so emits during a slider drag collapse into one history step instead of N
 	#[wasm_bindgen(js_name = endTransaction)]
 	pub fn end_transaction(&self) {