Add support for dragging panel tabs docked into other panel tab bars (#4006)

* Add support for dragging panel tabs docked into other panel tab bars

* Fix terminology

* Add Group suffix to PanelGroupId enums variants

* Code review

frontend/src/components/panels/Data.svelte

@@ -32,6 +32,7 @@
 	.data-panel {
 		flex-grow: 1;
 		padding: 4px;
+		padding-top: 0;
 
 		table {
 			margin: -4px;
@@ -42,7 +43,7 @@
 			}
 
 			&:not(:first-child) {
-				margin-top: 0;
+				margin-top: -4px;
 			}
 
 			tr:first-child:has(td:first-child label:empty) ~ tr td:first-child {

frontend/src/components/widgets/WidgetSection.svelte

@@ -72,7 +72,10 @@
 	.widget-section {
 		flex: 0 0 auto;
 		margin: 0 4px;
-		margin-top: 4px;
+
+		+ .widget-section {
+			margin-top: 4px;
+		}
 
 		.header {
 			text-align: left;

frontend/src/components/window/Panel.svelte

@@ -9,9 +9,8 @@
 	import Welcome from "/src/components/panels/Welcome.svelte";
 	import IconButton from "/src/components/widgets/buttons/IconButton.svelte";
 	import TextLabel from "/src/components/widgets/labels/TextLabel.svelte";
-	import type { EditorWrapper } from "/wrapper/pkg/graphite_wasm_wrapper";
-
-	type PanelType = keyof typeof PANEL_COMPONENTS;
+	import { panelDrag, startCrossPanelDrag, endCrossPanelDrag, updateCrossPanelHover } from "/src/stores/panel-drag";
+	import type { EditorWrapper, PanelType, PanelGroupId } from "/wrapper/pkg/graphite_wasm_wrapper";
 
 	const PANEL_COMPONENTS = {
 		Welcome,
@@ -31,11 +30,13 @@
 	export let tabCloseButtons = false;
 	export let tabLabels: { name: string; unsaved?: boolean; tooltipLabel?: string; tooltipDescription?: string; tooltipShortcut?: string }[];
 	export let tabActiveIndex: number;
-	export let panelType: PanelType | undefined = undefined;
+	export let panelTypes: PanelType[];
+	export let panelId: PanelGroupId;
 	export let clickAction: ((index: number) => void) | undefined = undefined;
 	export let closeAction: ((index: number) => void) | undefined = undefined;
 	export let reorderAction: ((oldIndex: number, newIndex: number) => void) | undefined = undefined;
 	export let emptySpaceAction: (() => void) | undefined = undefined;
+	export let crossPanelDropAction: ((sourcePanelId: string, targetPanelId: string, insertIndex: number) => void) | undefined = undefined;
 
 	let className = "";
 	export { className as class };
@@ -55,7 +56,7 @@
 	let tabGroupElement: LayoutRow | undefined = undefined;
 
 	onDestroy(() => {
-		removeDragListeners();
+		endDrag();
 	});
 
 	function onEmptySpaceAction(e: MouseEvent) {
@@ -77,7 +78,10 @@
 		// Activate the tab upon pointer down
 		clickAction?.(tabIndex);
 
-		if (!reorderAction || tabLabels.length < 2) return;
+		// Allow within-panel reorder if there are multiple tabs, or cross-panel drag if this panel supports docking
+		const canReorder = reorderAction && tabLabels.length > 1;
+		const canCrossPanelDrag = crossPanelDropAction !== undefined;
+		if (!canReorder && !canCrossPanelDrag) return;
 
 		dragStartState = { tabIndex, pointerX: e.clientX, pointerY: e.clientY };
 		dragging = false;
@@ -95,30 +99,72 @@
 			const deltaX = Math.abs(e.clientX - dragStartState.pointerX);
 			const deltaY = Math.abs(e.clientY - dragStartState.pointerY);
 			if (deltaX < DRAG_ACTIVATION_DISTANCE && deltaY < DRAG_ACTIVATION_DISTANCE) return;
+
 			dragging = true;
+
+			if (crossPanelDropAction) {
+				// Notify the shared store that a cross-panel drag has started
+				startCrossPanelDrag(panelId, tabLabels[dragStartState.tabIndex].name, dragStartState.tabIndex);
+			}
 		}
 
 		lastPointerX = e.clientX;
 
-		// Only show insertion line while the cursor is within the tab bar
+		// Exit early in here after we show the insertion marker, if we're within our own tab bar
 		if (pointerIsInsideTabBar(e)) {
 			calculateInsertionIndex(lastPointerX);
-		} else {
-			insertionIndex = undefined;
-			insertionMarkerLeft = undefined;
+			updateCrossPanelHover(undefined, undefined, undefined);
+			return;
+		}
+
+		// Clear local insertion marker since we're outside our own tab bar
+		insertionIndex = undefined;
+		insertionMarkerLeft = undefined;
+
+		// Check if the pointer is over any other dockable panel's tab bar
+		if (crossPanelDropAction) {
+			const target = Array.from(document.querySelectorAll("[data-panel-tab-bar]")).find((element) => {
+				const targetPanelId = element.getAttribute("data-panel-tab-bar");
+				if (!targetPanelId || targetPanelId === panelId) return false;
+
+				const rect = element.getBoundingClientRect();
+				return e.clientX >= rect.left && e.clientX <= rect.right && e.clientY >= rect.top && e.clientY <= rect.bottom;
+			});
+
+			const targetPanelId = target?.getAttribute("data-panel-tab-bar");
+			if (target instanceof HTMLDivElement && targetPanelId) {
+				calculateForeignInsertionIndex(e.clientX, targetPanelId, target);
+			} else {
+				updateCrossPanelHover(undefined, undefined, undefined);
+			}
 		}
 	}
 
 	function dragPointerUp() {
-		if (dragging && dragStartState && insertionIndex !== undefined) {
-			const oldIndex = dragStartState.tabIndex;
+		if (dragging && dragStartState) {
+			const crossPanelState = $panelDrag;
 
-			// Adjust for the fact that removing the dragged tab shifts indices
-			let newIndex = insertionIndex;
-			if (newIndex > oldIndex) newIndex -= 1;
+			// Cross-panel drop: the pointer is over a different panel's tab bar
+			if (
+				crossPanelDropAction &&
+				crossPanelState.active &&
+				crossPanelState.hoverTargetPanelId &&
+				crossPanelState.hoverTargetPanelId !== panelId &&
+				crossPanelState.hoverInsertionIndex !== undefined
+			) {
+				crossPanelDropAction?.(panelId, crossPanelState.hoverTargetPanelId, crossPanelState.hoverInsertionIndex);
+			}
+			// Within-panel reorder
+			else if (insertionIndex !== undefined) {
+				const oldIndex = dragStartState.tabIndex;
 
-			if (oldIndex !== newIndex) {
-				reorderAction?.(oldIndex, newIndex);
+				// Adjust for the fact that removing the dragged tab shifts indices
+				let newIndex = insertionIndex;
+				if (newIndex > oldIndex) newIndex -= 1;
+
+				if (oldIndex !== newIndex) {
+					reorderAction?.(oldIndex, newIndex);
+				}
 			}
 		}
 
@@ -141,6 +187,7 @@
 		dragging = false;
 		insertionIndex = undefined;
 		insertionMarkerLeft = undefined;
+		if (crossPanelDropAction) endCrossPanelDrag();
 		removeDragListeners();
 	}
 
@@ -152,6 +199,30 @@
 		return e.clientX >= rect.left && e.clientX <= rect.right && e.clientY >= rect.top && e.clientY <= rect.bottom;
 	}
 
+	// Calculate the insertion position for a foreign panel's tab bar
+	function calculateForeignInsertionIndex(pointerX: number, targetPanelId: string, tabBarDiv: HTMLDivElement) {
+		const tabBarRect = tabBarDiv.getBoundingClientRect();
+		const tabs = tabBarDiv.querySelectorAll(":scope > [data-tab]");
+		let bestIndex = 0;
+		let bestMarkerLeft = 0;
+
+		for (let i = 0; i < tabs.length; i++) {
+			const tabRect = tabs[i].getBoundingClientRect();
+			const tabCenter = tabRect.left + tabRect.width / 2;
+
+			if (pointerX > tabCenter) {
+				bestIndex = i + 1;
+				bestMarkerLeft = tabRect.right - tabBarRect.left;
+			} else {
+				bestMarkerLeft = tabRect.left - tabBarRect.left;
+				break;
+			}
+		}
+
+		// Must be at least 2px from the left so its left half doesn't get cut off along the left of the tab bar
+		updateCrossPanelHover(targetPanelId, bestIndex, Math.max(2, bestMarkerLeft));
+	}
+
 	function calculateInsertionIndex(pointerX: number) {
 		const groupDiv = tabGroupElement?.div?.();
 		if (!dragStartState || !groupDiv) return;
@@ -199,13 +270,21 @@
 	}
 </script>
 
-<LayoutCol on:pointerdown={() => panelType && editor.setActivePanel(panelType)} class={`panel ${className}`.trim()} {classes} style={styleName} {styles}>
+<LayoutCol on:pointerdown={() => panelTypes[tabActiveIndex] && editor.setActivePanel(panelTypes[tabActiveIndex])} class={`panel ${className}`.trim()} {classes} style={styleName} {styles}>
 	<LayoutRow class="tab-bar" classes={{ "min-widths": tabMinWidths }}>
-		<LayoutRow class="tab-group" scrollableX={true} on:click={onEmptySpaceAction} on:auxclick={onEmptySpaceAction} bind:this={tabGroupElement}>
+		<LayoutRow
+			class="tab-group"
+			scrollableX={true}
+			data-panel-tab-bar={crossPanelDropAction ? panelId : undefined}
+			on:click={onEmptySpaceAction}
+			on:auxclick={onEmptySpaceAction}
+			bind:this={tabGroupElement}
+		>
 			{#each tabLabels as tabLabel, tabIndex}
 				<LayoutRow
 					class="tab"
 					classes={{ active: tabIndex === tabActiveIndex }}
+					data-tab
 					tooltipLabel={tabLabel.tooltipLabel}
 					tooltipDescription={tabLabel.tooltipDescription}
 					on:pointerdown={(e) => tabPointerDown(e, tabIndex)}
@@ -242,10 +321,13 @@
 		{#if dragging && insertionMarkerLeft !== undefined}
 			<div class="tab-insertion-mark" style:left={`${insertionMarkerLeft}px`}></div>
 		{/if}
+		{#if !dragging && crossPanelDropAction && $panelDrag.active && $panelDrag.hoverTargetPanelId === panelId && $panelDrag.hoverInsertionMarkerLeft !== undefined}
+			<div class="tab-insertion-mark" style:left={`${$panelDrag.hoverInsertionMarkerLeft}px`}></div>
+		{/if}
 	</LayoutRow>
 	<LayoutCol class="panel-body">
-		{#if panelType}
-			<svelte:component this={PANEL_COMPONENTS[panelType]} />
+		{#if panelTypes[tabActiveIndex]}
+			<svelte:component this={PANEL_COMPONENTS[panelTypes[tabActiveIndex]]} />
 		{/if}
 	</LayoutCol>
 </LayoutCol>

frontend/src/components/window/Workspace.svelte

@@ -23,9 +23,11 @@
 	let pointerCaptureId: number | undefined = undefined;
 	let activeResizeCleanup: (() => void) | undefined = undefined;
 
-	onDestroy(() => {
-		activeResizeCleanup?.();
-	});
+	// Reactive panel layout derived from backend state
+	$: panelLayout = $portfolio.panelLayout;
+	$: propertiesGroup = panelLayout.propertiesGroup;
+	$: layersGroup = panelLayout.layersGroup;
+	$: dataGroup = panelLayout.dataGroup;
 
 	$: documentPanel?.scrollTabIntoView($portfolio.activeDocumentIndex);
 
@@ -41,6 +43,10 @@
 	const editor = getContext<EditorWrapper>("editor");
 	const portfolio = getContext<PortfolioStore>("portfolio");
 
+	function crossPanelDrop(sourcePanelId: string, targetPanelId: string, insertIndex: number) {
+		editor.movePanelTab(sourcePanelId, targetPanelId, insertIndex);
+	}
+
 	function isPanelName(name: string): name is keyof typeof PANEL_SIZES {
 		return name in PANEL_SIZES;
 	}
@@ -155,6 +161,10 @@
 		addListeners();
 		activeResizeCleanup = removeListeners;
 	}
+
+	onDestroy(() => {
+		activeResizeCleanup?.();
+	});
 </script>
 
 <LayoutRow class="workspace" data-workspace>
@@ -163,7 +173,8 @@
 			<LayoutRow class="workspace-grid-subdivision" styles={{ "flex-grow": panelSizes["document"] }} data-subdivision-name="document">
 				<Panel
 					class="document-panel"
-					panelType={$portfolio.documents.length > 0 ? "Document" : "Welcome"}
+					panelId="DocumentGroup"
+					panelTypes={$portfolio.documents.length > 0 ? $portfolio.documents.map(() => "Document") : ["Welcome"]}
 					tabCloseButtons={true}
 					tabMinWidths={true}
 					tabLabels={documentTabLabels}
@@ -175,27 +186,51 @@
 					bind:this={documentPanel}
 				/>
 			</LayoutRow>
-			{#if $portfolio.dataPanelOpen}
+			{#if dataGroup.tabs.length > 0}
 				<LayoutRow class="workspace-grid-resize-gutter" data-gutter-vertical on:pointerdown={(e) => resizePanel(e)} on:dblclick={(e) => resetPanelSizes(e)} />
 				<LayoutRow class="workspace-grid-subdivision" styles={{ "flex-grow": panelSizes["data"] }} data-subdivision-name="data">
-					<Panel panelType="Data" tabLabels={[{ name: "Data" }]} tabActiveIndex={0} />
+					<Panel
+						panelId="DataGroup"
+						panelTypes={dataGroup.tabs}
+						tabLabels={dataGroup.tabs.map((name) => ({ name }))}
+						tabActiveIndex={dataGroup.activeTabIndex}
+						clickAction={(tabIndex) => editor.setPanelGroupActiveTab("DataGroup", tabIndex)}
+						reorderAction={(oldIndex, newIndex) => editor.reorderPanelGroupTab("DataGroup", oldIndex, newIndex)}
+						crossPanelDropAction={crossPanelDrop}
+					/>
 				</LayoutRow>
 			{/if}
 		</LayoutCol>
-		{#if $portfolio.propertiesPanelOpen || $portfolio.layersPanelOpen}
+		{#if propertiesGroup.tabs.length > 0 || layersGroup.tabs.length > 0}
 			<LayoutCol class="workspace-grid-resize-gutter" data-gutter-horizontal on:pointerdown={(e) => resizePanel(e)} on:dblclick={(e) => resetPanelSizes(e)} />
 			<LayoutCol class="workspace-grid-subdivision" styles={{ "flex-grow": panelSizes["details"] }} data-subdivision-name="details">
-				{#if $portfolio.propertiesPanelOpen}
+				{#if propertiesGroup.tabs.length > 0}
 					<LayoutRow class="workspace-grid-subdivision" styles={{ "flex-grow": panelSizes["properties"] }} data-subdivision-name="properties">
-						<Panel panelType="Properties" tabLabels={[{ name: "Properties" }]} tabActiveIndex={0} />
+						<Panel
+							panelId="PropertiesGroup"
+							panelTypes={propertiesGroup.tabs}
+							tabLabels={propertiesGroup.tabs.map((name) => ({ name }))}
+							tabActiveIndex={propertiesGroup.activeTabIndex}
+							clickAction={(tabIndex) => editor.setPanelGroupActiveTab("PropertiesGroup", tabIndex)}
+							reorderAction={(oldIndex, newIndex) => editor.reorderPanelGroupTab("PropertiesGroup", oldIndex, newIndex)}
+							crossPanelDropAction={crossPanelDrop}
+						/>
 					</LayoutRow>
 				{/if}
-				{#if $portfolio.propertiesPanelOpen && $portfolio.layersPanelOpen}
+				{#if propertiesGroup.tabs.length > 0 && layersGroup.tabs.length > 0}
 					<LayoutRow class="workspace-grid-resize-gutter" data-gutter-vertical on:pointerdown={(e) => resizePanel(e)} on:dblclick={(e) => resetPanelSizes(e)} />
 				{/if}
-				{#if $portfolio.layersPanelOpen}
+				{#if layersGroup.tabs.length > 0}
 					<LayoutRow class="workspace-grid-subdivision" styles={{ "flex-grow": panelSizes["layers"] }} data-subdivision-name="layers">
-						<Panel panelType="Layers" tabLabels={[{ name: "Layers" }]} tabActiveIndex={0} />
+						<Panel
+							panelId="LayersGroup"
+							panelTypes={layersGroup.tabs}
+							tabLabels={layersGroup.tabs.map((name) => ({ name }))}
+							tabActiveIndex={layersGroup.activeTabIndex}
+							clickAction={(tabIndex) => editor.setPanelGroupActiveTab("LayersGroup", tabIndex)}
+							reorderAction={(oldIndex, newIndex) => editor.reorderPanelGroupTab("LayersGroup", oldIndex, newIndex)}
+							crossPanelDropAction={crossPanelDrop}
+						/>
 					</LayoutRow>
 				{/if}
 			</LayoutCol>