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

editor/src/dispatcher.rs

@@ -2,6 +2,7 @@ use crate::messages::debug::utility_types::MessageLoggingVerbosity;
 use crate::messages::defer::DeferMessageContext;
 use crate::messages::dialog::DialogMessageContext;
 use crate::messages::layout::layout_message_handler::LayoutMessageContext;
+use crate::messages::portfolio::utility_types::PanelType;
 use crate::messages::preferences::preferences_message_handler::PreferencesMessageContext;
 use crate::messages::prelude::*;
 use crate::messages::tool::common_functionality::utility_functions::make_path_editable_is_allowed;
@@ -234,9 +235,10 @@ impl Dispatcher {
 					let menu_bar_message_handler = &mut self.message_handlers.menu_bar_message_handler;
 
 					menu_bar_message_handler.focus_document = self.message_handlers.portfolio_message_handler.focus_document;
-					menu_bar_message_handler.data_panel_open = self.message_handlers.portfolio_message_handler.data_panel_open;
-					menu_bar_message_handler.layers_panel_open = self.message_handlers.portfolio_message_handler.layers_panel_open;
-					menu_bar_message_handler.properties_panel_open = self.message_handlers.portfolio_message_handler.properties_panel_open;
+					let layout = &self.message_handlers.portfolio_message_handler.workspace_panel_layout;
+					menu_bar_message_handler.data_panel_open = layout.is_panel_present(PanelType::Data);
+					menu_bar_message_handler.layers_panel_open = layout.is_panel_present(PanelType::Layers);
+					menu_bar_message_handler.properties_panel_open = layout.is_panel_present(PanelType::Properties);
 					menu_bar_message_handler.message_logging_verbosity = self.message_handlers.debug_message_handler.message_logging_verbosity;
 					menu_bar_message_handler.reset_node_definitions_on_open = self.message_handlers.portfolio_message_handler.reset_node_definitions_on_open;
 

editor/src/messages/frontend/frontend_message.rs

@@ -9,6 +9,7 @@ use crate::messages::portfolio::document::node_graph::utility_types::{
 };
 use crate::messages::portfolio::document::utility_types::nodes::{LayerPanelEntry, LayerStructureEntry};
 use crate::messages::portfolio::document::utility_types::wires::{WirePath, WirePathUpdate};
+use crate::messages::portfolio::utility_types::WorkspacePanelLayout;
 use crate::messages::prelude::*;
 use crate::messages::tool::tool_messages::eyedropper_tool::PrimarySecondary;
 use graph_craft::document::NodeId;
@@ -194,14 +195,9 @@ pub enum FrontendMessage {
 	UpdateGraphViewOverlay {
 		open: bool,
 	},
-	UpdateDataPanelState {
-		open: bool,
-	},
-	UpdatePropertiesPanelState {
-		open: bool,
-	},
-	UpdateLayersPanelState {
-		open: bool,
+	UpdateWorkspacePanelLayout {
+		#[serde(rename = "panelLayout")]
+		panel_layout: WorkspacePanelLayout,
 	},
 	UpdateLayout {
 		#[serde(rename = "layoutTarget")]

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

@@ -1021,8 +1021,8 @@ impl MessageHandler<DocumentMessage, DocumentMessageContext<'_>> for DocumentMes
 					}
 				}
 			}
-			DocumentMessage::SetActivePanel { active_panel: panel } => {
-				match panel {
+			DocumentMessage::SetActivePanel { active_panel } => {
+				match active_panel {
 					PanelType::Document => {
 						if self.graph_view_overlay_open {
 							self.selection_network_path.clone_from(&self.breadcrumb_network_path);

editor/src/messages/portfolio/portfolio_message.rs

@@ -1,5 +1,5 @@
 use super::document::utility_types::document_metadata::LayerNodeIdentifier;
-use super::utility_types::PanelType;
+use super::utility_types::PanelGroupId;
 use crate::messages::frontend::utility_types::{ExportBounds, FileType};
 use crate::messages::portfolio::document::utility_types::clipboards::Clipboard;
 use crate::messages::portfolio::utility_types::FontCatalog;
@@ -61,6 +61,11 @@ pub enum PortfolioMessage {
 	LoadDocumentResources {
 		document_id: DocumentId,
 	},
+	MovePanelTab {
+		source_group: PanelGroupId,
+		target_group: PanelGroupId,
+		insert_index: usize,
+	},
 	NewDocumentWithName {
 		name: String,
 	},
@@ -130,10 +135,16 @@ pub enum PortfolioMessage {
 		document_id: DocumentId,
 		new_index: usize,
 	},
+	ReorderPanelGroupTab {
+		group: PanelGroupId,
+		old_index: usize,
+		new_index: usize,
+	},
 	RequestWelcomeScreenButtonsLayout,
 	RequestStatusBarInfoLayout,
-	SetActivePanel {
-		panel: PanelType,
+	SetPanelGroupActiveTab {
+		group: PanelGroupId,
+		tab_index: usize,
 	},
 	SelectDocument {
 		document_id: DocumentId,
@@ -161,4 +172,5 @@ pub enum PortfolioMessage {
 	ToggleRulers,
 	UpdateDocumentWidgets,
 	UpdateOpenDocumentsList,
+	UpdateWorkspacePanelLayout,
 }

editor/src/messages/portfolio/portfolio_message_handler.rs

@@ -1,6 +1,6 @@
 use super::document::utility_types::document_metadata::LayerNodeIdentifier;
 use super::document::utility_types::network_interface;
-use super::utility_types::{PanelType, PersistentData};
+use super::utility_types::{PanelGroupId, PanelType, PersistentData, WorkspacePanelLayout};
 use crate::application::{Editor, generate_uuid};
 use crate::consts::{DEFAULT_DOCUMENT_NAME, DEFAULT_STROKE_WIDTH, FILE_EXTENSION};
 use crate::messages::animation::TimingInformation;
@@ -24,7 +24,6 @@ use crate::messages::tool::common_functionality::graph_modification_utils;
 use crate::messages::tool::utility_types::{HintData, ToolType};
 use crate::messages::viewport::ToPhysical;
 use crate::node_graph_executor::{ExportConfig, NodeGraphExecutor};
-use derivative::*;
 use glam::{DAffine2, DVec2};
 use graph_craft::document::NodeId;
 use graphene_std::Color;
@@ -48,12 +47,10 @@ pub struct PortfolioMessageContext<'a> {
 	pub viewport: &'a ViewportMessageHandler,
 }
 
-#[derive(Debug, Derivative, ExtractField)]
-#[derivative(Default)]
+#[derive(Debug, Default, ExtractField)]
 pub struct PortfolioMessageHandler {
 	pub documents: HashMap<DocumentId, DocumentMessageHandler>,
 	document_ids: VecDeque<DocumentId>,
-	active_panel: PanelType,
 	pub(crate) active_document_id: Option<DocumentId>,
 	copy_buffer: [Vec<CopyBufferEntry>; INTERNAL_CLIPBOARD_COUNT as usize],
 	pub persistent_data: PersistentData,
@@ -61,11 +58,7 @@ pub struct PortfolioMessageHandler {
 	pub selection_mode: SelectionMode,
 	pub reset_node_definitions_on_open: bool,
 	pub focus_document: bool,
-	#[derivative(Default(value = "true"))]
-	pub properties_panel_open: bool,
-	#[derivative(Default(value = "true"))]
-	pub layers_panel_open: bool,
-	pub data_panel_open: bool,
+	pub workspace_panel_layout: WorkspacePanelLayout,
 }
 
 #[message_handler_data]
@@ -95,9 +88,9 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 						current_tool,
 						preferences,
 						viewport,
-						data_panel_open: self.data_panel_open && !self.focus_document,
-						layers_panel_open: self.layers_panel_open && !self.focus_document,
-						properties_panel_open: self.properties_panel_open && !self.focus_document,
+						data_panel_open: self.workspace_panel_layout.is_panel_visible(PanelType::Data) && !self.focus_document,
+						layers_panel_open: self.workspace_panel_layout.is_panel_visible(PanelType::Layers) && !self.focus_document,
+						properties_panel_open: self.workspace_panel_layout.is_panel_visible(PanelType::Properties) && !self.focus_document,
 					};
 					document.process_message(message, responses, document_inputs)
 				}
@@ -122,6 +115,9 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 				// Display the menu bar at the top of the window
 				responses.add(MenuBarMessage::SendLayout);
 
+				// Send the initial workspace panel layout to the frontend
+				responses.add(PortfolioMessage::UpdateWorkspacePanelLayout);
+
 				// Send the information for tooltips and categories for each node/input.
 				responses.add(FrontendMessage::SendUIMetadata {
 					node_descriptions: document_node_definitions::collect_node_descriptions(),
@@ -159,9 +155,9 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 						current_tool,
 						preferences,
 						viewport,
-						data_panel_open: self.data_panel_open && !self.focus_document,
-						layers_panel_open: self.layers_panel_open && !self.focus_document,
-						properties_panel_open: self.properties_panel_open && !self.focus_document,
+						data_panel_open: self.workspace_panel_layout.is_panel_visible(PanelType::Data) && !self.focus_document,
+						layers_panel_open: self.workspace_panel_layout.is_panel_visible(PanelType::Layers) && !self.focus_document,
+						properties_panel_open: self.workspace_panel_layout.is_panel_visible(PanelType::Properties) && !self.focus_document,
 					};
 					document.process_message(message, responses, document_inputs)
 				}
@@ -464,6 +460,48 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 				self.load_document(new_document, document_id, responses, false);
 				responses.add(PortfolioMessage::SelectDocument { document_id });
 			}
+			PortfolioMessage::MovePanelTab {
+				source_group,
+				target_group,
+				insert_index,
+			} => {
+				if source_group == target_group {
+					return;
+				}
+
+				let source_state = self.workspace_panel_layout.panel_group(source_group);
+				let Some(panel_type) = source_state.active_panel_type() else { return };
+
+				// Destroy layouts for the moved panel (so backend and frontend start in sync when it remounts)
+				// and for the panel that was previously active in the target panel group (it will be displaced by the incoming tab)
+				Self::destroy_panel_layouts(panel_type, responses);
+				if let Some(old_target_panel) = self.workspace_panel_layout.panel_group(target_group).active_panel_type() {
+					Self::destroy_panel_layouts(old_target_panel, responses);
+				}
+
+				// Remove from source panel group
+				let source = self.workspace_panel_layout.panel_group_mut(source_group);
+				source.tabs.retain(|&t| t != panel_type);
+				source.active_tab_index = source.active_tab_index.min(source.tabs.len().saturating_sub(1));
+
+				// Insert into target panel group
+				let target = self.workspace_panel_layout.panel_group_mut(target_group);
+				let index = insert_index.min(target.tabs.len());
+				target.tabs.insert(index, panel_type);
+				target.active_tab_index = index;
+
+				responses.add(MenuBarMessage::SendLayout);
+				responses.add(PortfolioMessage::UpdateWorkspacePanelLayout);
+
+				// Refresh the moved panel's content in its new location
+				self.refresh_panel_content(panel_type, responses);
+
+				// Refresh the source panel group's newly active tab (if any remain) so it's not left stale
+				if let Some(new_source_active) = self.workspace_panel_layout.panel_group(source_group).active_panel_type() {
+					Self::destroy_panel_layouts(new_source_active, responses);
+					self.refresh_panel_content(new_source_active, responses);
+				}
+			}
 			PortfolioMessage::NextDocument => {
 				if let Some(active_document_id) = self.active_document_id {
 					let current_index = self.document_index(active_document_id);
@@ -1071,6 +1109,25 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 					}
 				}
 			}
+			PortfolioMessage::ReorderPanelGroupTab { group, old_index, new_index } => {
+				let group_state = self.workspace_panel_layout.panel_group_mut(group);
+
+				if old_index < group_state.tabs.len() && new_index < group_state.tabs.len() && old_index != new_index {
+					let tab = group_state.tabs.remove(old_index);
+					group_state.tabs.insert(new_index, tab);
+
+					// Keep the active tab following the reorder
+					if group_state.active_tab_index == old_index {
+						group_state.active_tab_index = new_index;
+					} else if old_index < group_state.active_tab_index && new_index >= group_state.active_tab_index {
+						group_state.active_tab_index = group_state.active_tab_index.saturating_sub(1);
+					} else if old_index > group_state.active_tab_index && new_index <= group_state.active_tab_index {
+						group_state.active_tab_index += 1;
+					}
+
+					responses.add(PortfolioMessage::UpdateWorkspacePanelLayout);
+				}
+			}
 			PortfolioMessage::RequestWelcomeScreenButtonsLayout => {
 				let donate = "https://graphite.art/donate/";
 
@@ -1131,9 +1188,26 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 					layout_target: LayoutTarget::StatusBarInfo,
 				});
 			}
-			PortfolioMessage::SetActivePanel { panel } => {
-				self.active_panel = panel;
-				responses.add(DocumentMessage::SetActivePanel { active_panel: self.active_panel });
+			PortfolioMessage::SetPanelGroupActiveTab { group, tab_index } => {
+				let group_state = self.workspace_panel_layout.panel_group(group);
+				if tab_index < group_state.tabs.len() && tab_index != group_state.active_tab_index {
+					// Destroy layouts for the old and new panels so the backend's diffing state is in sync with the frontend's fresh mount
+					if let Some(old_panel_type) = group_state.active_panel_type() {
+						Self::destroy_panel_layouts(old_panel_type, responses);
+					}
+					let new_panel_type = group_state.tabs[tab_index];
+					Self::destroy_panel_layouts(new_panel_type, responses);
+
+					// Update the active tab index for the panel
+					self.workspace_panel_layout.panel_group_mut(group).active_tab_index = tab_index;
+
+					// Send the layout update first so the frontend mounts the new panel component before it receives content
+					responses.add(PortfolioMessage::UpdateWorkspacePanelLayout);
+
+					if let Some(panel_type) = self.workspace_panel_layout.panel_group(group).active_panel_type() {
+						self.refresh_panel_content(panel_type, responses);
+					}
+				}
 			}
 			PortfolioMessage::SelectDocument { document_id } => {
 				// Auto-save the document we are leaving
@@ -1289,113 +1363,61 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 				self.focus_document = !self.focus_document;
 				responses.add(MenuBarMessage::SendLayout);
 
+				let properties_present = self.workspace_panel_layout.is_panel_present(PanelType::Properties);
+				let layers_present = self.workspace_panel_layout.is_panel_present(PanelType::Layers);
+				let data_present = self.workspace_panel_layout.is_panel_present(PanelType::Data);
+
 				if self.focus_document {
-					if self.properties_panel_open {
-						responses.add(PropertiesPanelMessage::Clear);
-						responses.add(FrontendMessage::UpdatePropertiesPanelState { open: false });
+					if properties_present {
+						Self::destroy_panel_layouts(PanelType::Properties, responses);
 					}
-
-					if self.layers_panel_open {
-						responses.add(DocumentMessage::ClearLayersPanel);
-						responses.add(FrontendMessage::UpdateLayersPanelState { open: false });
+					if layers_present {
+						Self::destroy_panel_layouts(PanelType::Layers, responses);
 					}
-
-					if self.data_panel_open {
-						responses.add(DataPanelMessage::ClearLayout);
-						responses.add(FrontendMessage::UpdateDataPanelState { open: false });
+					if data_present {
+						Self::destroy_panel_layouts(PanelType::Data, responses);
 					}
 				} else {
-					if self.properties_panel_open {
-						responses.add(FrontendMessage::UpdatePropertiesPanelState { open: true });
-					}
-					if self.layers_panel_open {
-						responses.add(FrontendMessage::UpdateLayersPanelState { open: true });
-					}
-					if self.data_panel_open {
-						responses.add(FrontendMessage::UpdateDataPanelState { open: true });
-					}
-
 					// Run the graph to grab the data
-					if self.properties_panel_open || self.layers_panel_open || self.data_panel_open {
+					if properties_present || layers_present || data_present {
 						responses.add(NodeGraphMessage::RunDocumentGraph);
 					}
 
-					if self.properties_panel_open {
+					if properties_present {
 						responses.add(PropertiesPanelMessage::Refresh);
 					}
-					if self.layers_panel_open && self.active_document_id.is_some() {
+					if layers_present && self.active_document_id.is_some() {
 						responses.add(DeferMessage::AfterGraphRun {
 							messages: vec![NodeGraphMessage::UpdateLayerPanel.into(), DocumentMessage::DocumentStructureChanged.into()],
 						});
 					}
 				}
+
+				responses.add(PortfolioMessage::UpdateWorkspacePanelLayout);
 			}
 			PortfolioMessage::TogglePropertiesPanelOpen => {
 				if self.focus_document {
 					return;
 				}
 
-				self.properties_panel_open = !self.properties_panel_open;
-				responses.add(MenuBarMessage::SendLayout);
-
-				// Run the graph to grab the data
-				if self.properties_panel_open {
-					responses.add(FrontendMessage::UpdatePropertiesPanelState { open: self.properties_panel_open });
-					responses.add(NodeGraphMessage::RunDocumentGraph);
-					responses.add(PropertiesPanelMessage::Refresh);
-				} else {
-					responses.add(PropertiesPanelMessage::Clear);
-					responses.add(FrontendMessage::UpdatePropertiesPanelState { open: self.properties_panel_open });
-				}
+				let panel_type = PanelType::Properties;
+				self.toggle_dockable_panel(panel_type, responses);
 			}
 			PortfolioMessage::ToggleLayersPanelOpen => {
 				if self.focus_document {
 					return;
 				}
 
-				self.layers_panel_open = !self.layers_panel_open;
-				responses.add(MenuBarMessage::SendLayout);
-
-				// Run the graph to grab the data
-				if self.layers_panel_open {
-					// When opening, we make the frontend show the panel first so it can start receiving its message subscriptions for the data it will display
-					responses.add(FrontendMessage::UpdateLayersPanelState { open: self.layers_panel_open });
-
-					responses.add(NodeGraphMessage::RunDocumentGraph);
-					if self.active_document_id.is_some() {
-						responses.add(DeferMessage::AfterGraphRun {
-							messages: vec![NodeGraphMessage::UpdateLayerPanel.into(), DocumentMessage::DocumentStructureChanged.into()],
-						});
-					}
-				} else {
-					// If we don't clear the panel, the layout diffing system will assume widgets still exist when it attempts to update the layers panel next time it is opened
-					responses.add(DocumentMessage::ClearLayersPanel);
-
-					// When closing, we make the frontend hide the panel last so it can finish receiving its message subscriptions before it is destroyed
-					responses.add(FrontendMessage::UpdateLayersPanelState { open: self.layers_panel_open });
-				}
+				let panel_type = PanelType::Layers;
+				self.toggle_dockable_panel(panel_type, responses);
 			}
 			PortfolioMessage::ToggleDataPanelOpen => {
 				if self.focus_document {
 					return;
 				}
 
-				self.data_panel_open = !self.data_panel_open;
-				responses.add(MenuBarMessage::SendLayout);
-
-				// Run the graph to grab the data
-				if self.data_panel_open {
-					// When opening, we make the frontend show the panel first so it can start receiving its message subscriptions for the data it will display
-					responses.add(FrontendMessage::UpdateDataPanelState { open: self.data_panel_open });
-
-					responses.add(NodeGraphMessage::RunDocumentGraph);
-				} else {
-					// If we don't clear the panel, the layout diffing system will assume widgets still exist when it attempts to update the data panel next time it is opened
-					responses.add(DataPanelMessage::ClearLayout);
-
-					// When closing, we make the frontend hide the panel last so it can finish receiving its message subscriptions before it is destroyed
-					responses.add(FrontendMessage::UpdateDataPanelState { open: self.data_panel_open });
-				}
+				let panel_type = PanelType::Data;
+				self.toggle_dockable_panel(panel_type, responses);
 			}
 			PortfolioMessage::ToggleRulers => {
 				if let Some(document) = self.active_document_mut() {
@@ -1410,6 +1432,11 @@ impl MessageHandler<PortfolioMessage, PortfolioMessageContext<'_>> for Portfolio
 					document.update_document_widgets(responses, animation.is_playing(), timing_information.animation_time);
 				}
 			}
+			PortfolioMessage::UpdateWorkspacePanelLayout => {
+				responses.add(FrontendMessage::UpdateWorkspacePanelLayout {
+					panel_layout: self.workspace_panel_layout.clone(),
+				});
+			}
 			PortfolioMessage::UpdateOpenDocumentsList => {
 				// Send the list of document tab names
 				let open_documents = self
@@ -1562,8 +1589,8 @@ impl PortfolioMessageHandler {
 		} else {
 			self.document_ids.push_back(document_id);
 		}
-		new_document.update_layers_panel_control_bar_widgets(self.layers_panel_open && !self.focus_document, responses);
-		new_document.update_layers_panel_bottom_bar_widgets(self.layers_panel_open && !self.focus_document, responses);
+		new_document.update_layers_panel_control_bar_widgets(self.workspace_panel_layout.is_panel_visible(PanelType::Layers) && !self.focus_document, responses);
+		new_document.update_layers_panel_bottom_bar_widgets(self.workspace_panel_layout.is_panel_visible(PanelType::Layers) && !self.focus_document, responses);
 
 		self.documents.insert(document_id, new_document);
 
@@ -1610,7 +1637,7 @@ impl PortfolioMessageHandler {
 	/// Get the ID of the selected node that should be used as the current source for the Data panel.
 	pub fn node_to_inspect(&self) -> Option<NodeId> {
 		// Skip if the Data panel is not open
-		if !self.data_panel_open || self.focus_document {
+		if !self.workspace_panel_layout.is_panel_visible(PanelType::Data) || self.focus_document {
 			return None;
 		}
 
@@ -1624,4 +1651,85 @@ impl PortfolioMessageHandler {
 
 		selected_nodes.first().copied()
 	}
+
+	/// Remove a dockable panel type from whichever panel group currently contains it.
+	fn remove_panel_from_layout(&mut self, panel_type: PanelType) {
+		for group_id in [PanelGroupId::PropertiesGroup, PanelGroupId::LayersGroup, PanelGroupId::DataGroup] {
+			let group = self.workspace_panel_layout.panel_group_mut(group_id);
+			if let Some(index) = group.tabs.iter().position(|&t| t == panel_type) {
+				group.tabs.remove(index);
+				group.active_tab_index = group.active_tab_index.min(group.tabs.len().saturating_sub(1));
+				break;
+			}
+		}
+	}
+
+	/// Toggle a dockable panel on or off. When toggling off, refresh the newly active tab in its panel group (if any).
+	fn toggle_dockable_panel(&mut self, panel_type: PanelType, responses: &mut VecDeque<Message>) {
+		if let Some(group_id) = self.workspace_panel_layout.find_panel(panel_type) {
+			// Panel is present, remove it
+			let was_visible = self.workspace_panel_layout.panel_group(group_id).is_visible(panel_type);
+			Self::destroy_panel_layouts(panel_type, responses);
+			self.remove_panel_from_layout(panel_type);
+
+			// If the removed panel was the active tab, refresh whichever panel is now active in that panel group
+			if was_visible && let Some(new_active) = self.workspace_panel_layout.panel_group(group_id).active_panel_type() {
+				Self::destroy_panel_layouts(new_active, responses);
+				self.refresh_panel_content(new_active, responses);
+			}
+		} else {
+			// Panel is not present, add it to its default panel group
+			self.add_panel_to_its_default_group(panel_type);
+			self.refresh_panel_content(panel_type, responses);
+		}
+
+		responses.add(MenuBarMessage::SendLayout);
+		responses.add(PortfolioMessage::UpdateWorkspacePanelLayout);
+	}
+
+	/// Add a dockable panel type to its default panel group.
+	fn add_panel_to_its_default_group(&mut self, panel_type: PanelType) {
+		let group = self.workspace_panel_layout.panel_group_mut(panel_type.default_panel_group());
+		if !group.tabs.contains(&panel_type) {
+			group.tabs.push(panel_type);
+			group.active_tab_index = group.tabs.len() - 1;
+		}
+	}
+
+	/// Destroy the stored layout for a panel that is no longer the active tab.
+	/// This resets the backend's diffing state so it won't try to send updates to a frontend component that has been unmounted.
+	fn destroy_panel_layouts(panel_type: PanelType, responses: &mut VecDeque<Message>) {
+		let targets: &[LayoutTarget] = match panel_type {
+			PanelType::Properties => &[LayoutTarget::PropertiesPanel],
+			PanelType::Layers => &[LayoutTarget::LayersPanelControlLeftBar, LayoutTarget::LayersPanelControlRightBar, LayoutTarget::LayersPanelBottomBar],
+			PanelType::Data => &[LayoutTarget::DataPanel],
+			PanelType::Document | PanelType::Welcome => return,
+		};
+
+		for &layout_target in targets {
+			responses.add(LayoutMessage::DestroyLayout { layout_target });
+		}
+	}
+
+	/// Trigger a content refresh for a panel that just became the active tab.
+	fn refresh_panel_content(&self, panel_type: PanelType, responses: &mut VecDeque<Message>) {
+		responses.add(NodeGraphMessage::RunDocumentGraph);
+
+		match panel_type {
+			PanelType::Properties => {
+				responses.add(PropertiesPanelMessage::Refresh);
+			}
+			PanelType::Layers => {
+				if self.active_document_id.is_some() {
+					responses.add(DeferMessage::AfterGraphRun {
+						messages: vec![NodeGraphMessage::UpdateLayerPanel.into(), DocumentMessage::DocumentStructureChanged.into()],
+					});
+				}
+			}
+			PanelType::Data => {
+				// The Data panel's content is populated automatically as a side effect of the graph run completing, so there's nothing to do here
+			}
+			PanelType::Document | PanelType::Welcome => {}
+		}
+	}
 }

editor/src/messages/portfolio/utility_types.rs

@@ -83,29 +83,150 @@ impl FontCatalogStyle {
 	}
 }
 
-#[derive(PartialEq, Eq, Clone, Copy, Debug, Default, serde::Serialize, serde::Deserialize)]
+#[cfg_attr(feature = "wasm", derive(tsify::Tsify))]
+#[derive(PartialEq, Eq, Clone, Copy, Debug, serde::Serialize, serde::Deserialize)]
 pub enum PanelType {
-	#[default]
-	Document,
 	Welcome,
+	Document,
 	Layers,
 	Properties,
-	DataPanel,
+	Data,
+}
+
+impl PanelType {
+	/// Returns the default panel group for this panel type.
+	pub fn default_panel_group(self) -> PanelGroupId {
+		match self {
+			PanelType::Document => PanelGroupId::DocumentGroup,
+			PanelType::Properties => PanelGroupId::PropertiesGroup,
+			PanelType::Layers => PanelGroupId::LayersGroup,
+			PanelType::Data => PanelGroupId::DataGroup,
+			PanelType::Welcome => panic!("PanelType::{self:?} has no default panel group (not a dockable panel)"),
+		}
+	}
 }
 
 impl From<String> for PanelType {
 	fn from(value: String) -> Self {
 		match value.as_str() {
-			"Document" => PanelType::Document,
 			"Welcome" => PanelType::Welcome,
+			"Document" => PanelType::Document,
 			"Layers" => PanelType::Layers,
 			"Properties" => PanelType::Properties,
-			"Data" => PanelType::DataPanel,
+			"Data" => PanelType::Data,
 			_ => panic!("Unknown panel type: {value}"),
 		}
 	}
 }
 
+/// Identifies a panel group in the workspace that can hold tabbed panels.
+#[cfg_attr(feature = "wasm", derive(tsify::Tsify))]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, serde::Serialize, serde::Deserialize)]
+pub enum PanelGroupId {
+	DocumentGroup,
+	PropertiesGroup,
+	LayersGroup,
+	DataGroup,
+}
+
+impl From<String> for PanelGroupId {
+	fn from(value: String) -> Self {
+		match value.as_str() {
+			"DocumentGroup" => PanelGroupId::DocumentGroup,
+			"PropertiesGroup" => PanelGroupId::PropertiesGroup,
+			"LayersGroup" => PanelGroupId::LayersGroup,
+			"DataGroup" => PanelGroupId::DataGroup,
+			_ => panic!("Unknown panel group: {value}"),
+		}
+	}
+}
+
+/// State of a single panel group in the workspace.
+#[derive(Clone, Debug, Default, PartialEq, serde::Serialize, serde::Deserialize)]
+pub struct PanelGroupState {
+	pub tabs: Vec<PanelType>,
+	#[serde(rename = "activeTabIndex")]
+	pub active_tab_index: usize,
+}
+
+impl PanelGroupState {
+	pub fn active_panel_type(&self) -> Option<PanelType> {
+		self.tabs.get(self.active_tab_index).copied()
+	}
+
+	pub fn contains(&self, panel_type: PanelType) -> bool {
+		self.tabs.contains(&panel_type)
+	}
+
+	pub fn is_visible(&self, panel_type: PanelType) -> bool {
+		self.active_panel_type() == Some(panel_type)
+	}
+}
+
+/// The complete workspace panel layout describing which dockable panels are in which panel groups.
+#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
+pub struct WorkspacePanelLayout {
+	#[serde(rename = "propertiesGroup")]
+	pub properties_group: PanelGroupState,
+	#[serde(rename = "layersGroup")]
+	pub layers_group: PanelGroupState,
+	#[serde(rename = "dataGroup")]
+	pub data_group: PanelGroupState,
+}
+
+impl Default for WorkspacePanelLayout {
+	fn default() -> Self {
+		Self {
+			properties_group: PanelGroupState {
+				tabs: vec![PanelType::Properties],
+				active_tab_index: 0,
+			},
+			layers_group: PanelGroupState {
+				tabs: vec![PanelType::Layers],
+				active_tab_index: 0,
+			},
+			data_group: PanelGroupState { tabs: vec![], active_tab_index: 0 },
+		}
+	}
+}
+
+impl WorkspacePanelLayout {
+	pub fn panel_group(&self, panel_group_id: PanelGroupId) -> &PanelGroupState {
+		match panel_group_id {
+			PanelGroupId::DocumentGroup => panic!("PanelGroupId::{panel_group_id:?} is not a dockable panel group"),
+			PanelGroupId::PropertiesGroup => &self.properties_group,
+			PanelGroupId::LayersGroup => &self.layers_group,
+			PanelGroupId::DataGroup => &self.data_group,
+		}
+	}
+
+	pub fn panel_group_mut(&mut self, panel_group_id: PanelGroupId) -> &mut PanelGroupState {
+		match panel_group_id {
+			PanelGroupId::DocumentGroup => panic!("PanelGroupId::{panel_group_id:?} is not a dockable panel group"),
+			PanelGroupId::PropertiesGroup => &mut self.properties_group,
+			PanelGroupId::LayersGroup => &mut self.layers_group,
+			PanelGroupId::DataGroup => &mut self.data_group,
+		}
+	}
+
+	/// Find which panel group contains a given panel type.
+	pub fn find_panel(&self, panel_type: PanelType) -> Option<PanelGroupId> {
+		[PanelGroupId::PropertiesGroup, PanelGroupId::LayersGroup, PanelGroupId::DataGroup]
+			.into_iter()
+			.find(|&group_id| self.panel_group(group_id).contains(panel_type))
+	}
+
+	/// Check if a panel type is the active (visible) tab in any panel group.
+	pub fn is_panel_visible(&self, panel_type: PanelType) -> bool {
+		self.find_panel(panel_type).is_some_and(|group_id| self.panel_group(group_id).is_visible(panel_type))
+	}
+
+	/// Check if a panel type is present (as any tab) in any panel group, whether or not it's the active tab.
+	pub fn is_panel_present(&self, panel_type: PanelType) -> bool {
+		self.find_panel(panel_type).is_some()
+	}
+}
+
 pub enum FileContent {
 	/// A Graphite document.
 	Document(String),

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>

frontend/src/stores/panel-drag.ts

@@ -0,0 +1,61 @@
+import { writable } from "svelte/store";
+import type { Writable } from "svelte/store";
+
+export type PanelDragState = {
+	active: boolean;
+	sourcePanelId: string | undefined;
+	draggedTabLabel: string | undefined;
+	sourceTabIndex: number;
+	// Which panel's tab bar the pointer is currently hovering over (undefined if none)
+	hoverTargetPanelId: string | undefined;
+	hoverInsertionIndex: number | undefined;
+	hoverInsertionMarkerLeft: number | undefined;
+};
+
+const initialState: PanelDragState = {
+	active: false,
+	sourcePanelId: undefined,
+	draggedTabLabel: undefined,
+	sourceTabIndex: 0,
+	hoverTargetPanelId: undefined,
+	hoverInsertionIndex: undefined,
+	hoverInsertionMarkerLeft: undefined,
+};
+
+// Store state persisted across HMR to maintain reactive subscriptions in the component tree
+const store: Writable<PanelDragState> = import.meta.hot?.data?.store || writable<PanelDragState>(initialState);
+if (import.meta.hot) import.meta.hot.data.store = store;
+
+export const panelDrag = store;
+
+export function startCrossPanelDrag(sourcePanelId: string, draggedTabLabel: string, sourceTabIndex: number) {
+	store.update((state) => {
+		state.active = true;
+		state.sourcePanelId = sourcePanelId;
+		state.draggedTabLabel = draggedTabLabel;
+		state.sourceTabIndex = sourceTabIndex;
+		return state;
+	});
+}
+
+export function endCrossPanelDrag() {
+	store.update((state) => {
+		state.active = false;
+		state.sourcePanelId = undefined;
+		state.draggedTabLabel = undefined;
+		state.sourceTabIndex = 0;
+		state.hoverTargetPanelId = undefined;
+		state.hoverInsertionIndex = undefined;
+		state.hoverInsertionMarkerLeft = undefined;
+		return state;
+	});
+}
+
+export function updateCrossPanelHover(hoverTargetPanelId: string | undefined, hoverInsertionIndex: number | undefined, hoverInsertionMarkerLeft: number | undefined) {
+	store.update((state) => {
+		state.hoverTargetPanelId = hoverTargetPanelId;
+		state.hoverInsertionIndex = hoverInsertionIndex;
+		state.hoverInsertionMarkerLeft = hoverInsertionMarkerLeft;
+		return state;
+	});
+}

frontend/src/stores/portfolio.ts

@@ -4,25 +4,36 @@ import type { SubscriptionsRouter } from "/src/subscriptions-router";
 import { downloadFile, downloadFileBlob, upload } from "/src/utility-functions/files";
 import { storeDocumentTabOrder } from "/src/utility-functions/persistence";
 import { rasterizeSVG } from "/src/utility-functions/rasterization";
-import type { EditorWrapper, OpenDocument } from "/wrapper/pkg/graphite_wasm_wrapper";
+import type { EditorWrapper, OpenDocument, PanelType } from "/wrapper/pkg/graphite_wasm_wrapper";
 
 export type PortfolioStore = ReturnType<typeof createPortfolioStore>;
 
+export type PanelGroupState = {
+	tabs: PanelType[];
+	activeTabIndex: number;
+};
+
+export type WorkspacePanelLayout = {
+	propertiesGroup: PanelGroupState;
+	layersGroup: PanelGroupState;
+	dataGroup: PanelGroupState;
+};
+
 type PortfolioStoreState = {
 	unsaved: boolean;
 	documents: OpenDocument[];
 	activeDocumentIndex: number;
-	dataPanelOpen: boolean;
-	propertiesPanelOpen: boolean;
-	layersPanelOpen: boolean;
+	panelLayout: WorkspacePanelLayout;
 };
 const initialState: PortfolioStoreState = {
 	unsaved: false,
 	documents: [],
 	activeDocumentIndex: 0,
-	dataPanelOpen: false,
-	propertiesPanelOpen: true,
-	layersPanelOpen: true,
+	panelLayout: {
+		propertiesGroup: { tabs: ["Properties"], activeTabIndex: 0 },
+		layersGroup: { tabs: ["Layers"], activeTabIndex: 0 },
+		dataGroup: { tabs: [], activeTabIndex: 0 },
+	},
 };
 
 let subscriptionsRouter: SubscriptionsRouter | undefined = undefined;
@@ -103,23 +114,15 @@ export function createPortfolioStore(subscriptions: SubscriptionsRouter, editor:
 		}
 	});
 
-	subscriptions.subscribeFrontendMessage("UpdateDataPanelState", async (data) => {
-		update((state) => {
-			state.dataPanelOpen = data.open;
-			return state;
-		});
-	});
+	subscriptions.subscribeFrontendMessage("UpdateWorkspacePanelLayout", (data) => {
+		// Coerce activeTabIndex from BigInt (produced by serde_wasm_bindgen for usize) to number
+		const layout = data.panelLayout;
+		layout.propertiesGroup.activeTabIndex = Number(layout.propertiesGroup.activeTabIndex);
+		layout.layersGroup.activeTabIndex = Number(layout.layersGroup.activeTabIndex);
+		layout.dataGroup.activeTabIndex = Number(layout.dataGroup.activeTabIndex);
 
-	subscriptions.subscribeFrontendMessage("UpdatePropertiesPanelState", async (data) => {
 		update((state) => {
-			state.propertiesPanelOpen = data.open;
-			return state;
-		});
-	});
-
-	subscriptions.subscribeFrontendMessage("UpdateLayersPanelState", async (data) => {
-		update((state) => {
-			state.layersPanelOpen = data.open;
+			state.panelLayout = layout;
 			return state;
 		});
 	});
@@ -139,7 +142,5 @@ export function destroyPortfolioStore() {
 	subscriptions.unsubscribeFrontendMessage("TriggerSaveDocument");
 	subscriptions.unsubscribeFrontendMessage("TriggerSaveFile");
 	subscriptions.unsubscribeFrontendMessage("TriggerExportImage");
-	subscriptions.unsubscribeFrontendMessage("UpdateDataPanelState");
-	subscriptions.unsubscribeFrontendMessage("UpdatePropertiesPanelState");
-	subscriptions.unsubscribeFrontendMessage("UpdateLayersPanelState");
+	subscriptions.unsubscribeFrontendMessage("UpdateWorkspacePanelLayout");
 }

frontend/wrapper/src/editor_wrapper.rs

@@ -434,6 +434,29 @@ impl EditorWrapper {
 		self.dispatch(message);
 	}
 
+	#[wasm_bindgen(js_name = reorderPanelGroupTab)]
+	pub fn reorder_panel_group_tab(&self, group: String, old_index: usize, new_index: usize) {
+		let group = group.into();
+		let message = PortfolioMessage::ReorderPanelGroupTab { group, old_index, new_index };
+		self.dispatch(message);
+	}
+
+	#[wasm_bindgen(js_name = movePanelTab)]
+	pub fn move_panel_tab(&self, source_group: String, target_group: String, insert_index: usize) {
+		let message = PortfolioMessage::MovePanelTab {
+			source_group: source_group.into(),
+			target_group: target_group.into(),
+			insert_index,
+		};
+		self.dispatch(message);
+	}
+
+	#[wasm_bindgen(js_name = setPanelGroupActiveTab)]
+	pub fn set_panel_group_active_tab(&self, group: String, tab_index: usize) {
+		let message = PortfolioMessage::SetPanelGroupActiveTab { group: group.into(), tab_index };
+		self.dispatch(message);
+	}
+
 	#[wasm_bindgen(js_name = closeDocumentWithConfirmation)]
 	pub fn close_document_with_confirmation(&self, document_id: u64) {
 		let document_id = DocumentId(document_id);
@@ -874,7 +897,7 @@ impl EditorWrapper {
 	/// Set the active panel to the most recently clicked panel
 	#[wasm_bindgen(js_name = setActivePanel)]
 	pub fn set_active_panel(&self, panel: String) {
-		let message = PortfolioMessage::SetActivePanel { panel: panel.into() };
+		let message = DocumentMessage::SetActivePanel { active_panel: panel.into() };
 		self.dispatch(message);
 	}
 

website/content/features.md

@@ -142,6 +142,10 @@ Marrying vector and raster under one roof enables both art forms to complement e
 			<img class="atlas" style="--atlas-index: 73" src="https://static.graphite.art/icons/icon-atlas-roadmap__5.png" alt="" />
 			<span>Blend tool to morph between shapes</span>
 		</div>
+		<div class="feature-icon ongoing" title="Development Ongoing">
+			<img class="atlas" style="--atlas-index: 24" src="https://static.graphite.art/icons/icon-atlas-roadmap__5.png" alt="" />
+			<span>Dockable and multi-window panels</span>
+		</div>
 		<div class="feature-icon ongoing" title="Development Ongoing">
 			<img class="atlas" style="--atlas-index: 17" src="https://static.graphite.art/icons/icon-atlas-roadmap__5.png" alt="" />
 			<span>Stable document format</span>
@@ -250,10 +254,6 @@ Marrying vector and raster under one roof enables both art forms to complement e
 		<div class="feature-icon heading" data-year="2027">
 			<h3>— Beta 2 —</h3>
 		</div>
-		<div class="feature-icon">
-			<img class="atlas" style="--atlas-index: 24" src="https://static.graphite.art/icons/icon-atlas-roadmap__5.png" alt="" />
-			<span>Dockable and multi-window panels</span>
-		</div>
 		<div class="feature-icon">
 			<img class="atlas" style="--atlas-index: 52" src="https://static.graphite.art/icons/icon-atlas-roadmap__5.png" alt="" />
 			<span>Command palette</span>