Add the History panel

document/format/src/persist.rs

@@ -452,6 +452,23 @@ impl<L: Layout> Gdd<L> {
 		Ok(())
 	}
 
+	/// Move the head back to an ancestor, keeping the later line as a branch. A non-retiring peer asks the retirer.
+	#[cfg(feature = "network")]
+	pub fn move_head(&mut self, rev: Rev) -> Result<(), Error> {
+		if self.retires_locally() {
+			let (moved, touched) = self.session.move_head_to(rev)?;
+			self.remote_changes.touched.extend(touched);
+			self.persist_registry_snapshot()?;
+			self.persist_session_state()?;
+			if let Some(replica) = &mut self.network {
+				replica.broadcast_head_move(moved)?;
+			}
+		} else if let Some(replica) = &mut self.network {
+			replica.request_move(rev)?;
+		}
+		Ok(())
+	}
+
 	/// Redo a dropped step as a copy on top of the line. A non-retiring peer asks the retirer.
 	#[cfg(feature = "network")]
 	pub fn redo_retired_step(&mut self, rev: Rev) -> Result<(), Error> {

editor/src/dispatcher.rs

@@ -307,6 +307,7 @@ impl Dispatcher {
 					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.session_panel_open = layout.is_panel_present(PanelType::Session);
+					menu_bar_message_handler.history_panel_open = layout.is_panel_present(PanelType::History);
 					menu_bar_message_handler.layers_panel_open = layout.is_panel_present(PanelType::Layers);
 					menu_bar_message_handler.inspector_open = layout.is_panel_present(PanelType::Inspector);
 					menu_bar_message_handler.message_logging_verbosity = self.message_handlers.debug_message_handler.message_logging_verbosity;

editor/src/messages/frontend/frontend_message.rs

@@ -196,6 +196,9 @@ pub enum FrontendMessage {
 	UpdateDocumentCursors {
 		cursors: Vec<FrontendRemoteCursor>,
 	},
+	UpdateHistoryPanel {
+		state: crate::messages::portfolio::history::utility_types::HistoryPanelState,
+	},
 	UpdateNodeGraphCursors {
 		cursors: Vec<FrontendRemoteCursor>,
 	},

editor/src/messages/menu_bar/menu_bar_message_handler.rs

@@ -25,6 +25,7 @@ pub struct MenuBarMessageHandler {
 	pub make_path_editable_is_allowed: bool,
 	pub data_panel_open: bool,
 	pub session_panel_open: bool,
+	pub history_panel_open: bool,
 	pub layers_panel_open: bool,
 	pub inspector_open: bool,
 	pub focus_document: bool,
@@ -693,6 +694,11 @@ impl LayoutHolder for MenuBarMessageHandler {
 							.icon(if self.session_panel_open { "CheckboxChecked" } else { "CheckboxUnchecked" })
 							.on_commit(|_| WorkspaceMessage::ToggleSessionPanelOpen.into())
 							.disabled(self.focus_document),
+						MenuListEntry::new("History")
+							.label("History")
+							.icon(if self.history_panel_open { "CheckboxChecked" } else { "CheckboxUnchecked" })
+							.on_commit(|_| WorkspaceMessage::ToggleHistoryPanelOpen.into())
+							.disabled(self.focus_document),
 					],
 				])
 				.widget_instance(),

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

@@ -174,7 +174,9 @@ impl DocumentHistory {
 		}
 		match note {
 			UndoNote::Retracted(ops) => self.restage_ops(ops),
-			UndoNote::Dropped(rev) => self.redo_retired_step(rev),
+			UndoNote::Dropped(rev) => {
+				self.redo_retired_step(rev);
+			}
 			UndoNote::Cursor => {}
 		}
 		true
@@ -219,11 +221,30 @@ impl DocumentHistory {
 		self.storage.as_ref().map(|storage| storage.resource_gc_roots()).unwrap_or_default()
 	}
 
-	pub fn redo_retired_step(&mut self, rev: document_graph_storage::Rev) {
-		let Some(storage) = self.storage.as_mut() else { return };
-		if let Err(error) = storage.redo_retired_step(rev) {
-			log::error!("Redoing the dropped step failed: {error}");
-		}
+	pub fn redo_retired_step(&mut self, rev: document_graph_storage::Rev) -> bool {
+		self.change_line(|storage| storage.redo_retired_step(rev), "Redoing the dropped step failed")
+	}
+
+	pub fn drop_step(&mut self, rev: document_graph_storage::Rev) -> bool {
+		self.change_line(|storage| storage.drop_step(rev), "Removing the step failed")
+	}
+
+	pub fn move_head_to(&mut self, rev: document_graph_storage::Rev) -> bool {
+		self.change_line(|storage| storage.move_head(rev), "Moving the head failed")
+	}
+
+	fn change_line(&mut self, change: impl FnOnce(&mut document_format::GddV1) -> Result<(), document_format::Error>, failure: &str) -> bool {
+		let Some(storage) = self.storage.as_mut().filter(|storage| storage.can_change_line()) else {
+			return false;
+		};
+		change(storage).inspect_err(|error| log::error!("{failure}: {error}")).is_ok()
+	}
+
+	/// Forgets the legacy snapshots once the head has moved off their line.
+	pub fn clear_legacy(&mut self) {
+		self.legacy_undo_stack.clear();
+		self.legacy_redo_stack.clear();
+		self.undo_notes.clear();
 	}
 
 	pub fn retire_storage_interaction(&mut self) {

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

@@ -56,6 +56,17 @@ pub enum DocumentMessage {
 	DeselectAllLayers,
 	DocumentHistoryBackward,
 	DocumentHistoryForward,
+	/// Moves the shared head to an earlier interaction and keeps the later steps as a branch.
+	HistoryMoveHead {
+		rev: document_graph_storage::Rev,
+	},
+	/// Drops a retired interaction and mints the later ones again on its parent.
+	HistoryRemoveStep {
+		rev: document_graph_storage::Rev,
+	},
+	HistoryRestoreStep {
+		rev: document_graph_storage::Rev,
+	},
 	DocumentStructureChanged,
 	DrawArtboardOverlays {
 		context: OverlayContext,

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

@@ -473,6 +473,27 @@ impl MessageHandler<DocumentMessage, DocumentMessageContext<'_>> for DocumentMes
 				self.undo_with_history(document_id, viewport, preferences.validate_storage_round_trip, responses)
 			}
 			DocumentMessage::DocumentHistoryForward => self.redo_with_history(document_id, viewport, preferences.validate_storage_round_trip, responses),
+			DocumentMessage::HistoryMoveHead { rev } => self.apply_history_action(
+				document_id,
+				|history| history.move_head_to(rev),
+				&resource_storage.resources_mut(),
+				preferences.validate_storage_round_trip,
+				responses,
+			),
+			DocumentMessage::HistoryRemoveStep { rev } => self.apply_history_action(
+				document_id,
+				|history| history.drop_step(rev),
+				&resource_storage.resources_mut(),
+				preferences.validate_storage_round_trip,
+				responses,
+			),
+			DocumentMessage::HistoryRestoreStep { rev } => self.apply_history_action(
+				document_id,
+				|history| history.redo_retired_step(rev),
+				&resource_storage.resources_mut(),
+				preferences.validate_storage_round_trip,
+				responses,
+			),
 			DocumentMessage::DocumentStructureChanged => {
 				if layers_panel_open {
 					self.network_interface.load_structure();
@@ -2997,6 +3018,32 @@ impl DocumentMessageHandler {
 		self.drive_storage_undo_redo(document_id, legacy_applied, true, validate, responses);
 	}
 
+	/// Performs a History panel action in storage and drops the legacy snapshots, which are off the head's line.
+	fn apply_history_action(
+		&mut self,
+		document_id: DocumentId,
+		action: impl FnOnce(&mut DocumentHistory) -> bool,
+		byte_store: &dyn ResourceStorage,
+		validate: bool,
+		responses: &mut VecDeque<Message>,
+	) {
+		if self.network_interface.transaction_status() != TransactionStatus::Finished {
+			return;
+		}
+		responses.add(EventMessage::ToolAbort);
+		self.stage_edits_outside_transaction(byte_store, validate);
+		self.history.retire_storage_interaction();
+		let stored_name = self.stored_name().map(str::to_string);
+		if !action(&mut self.history) {
+			return;
+		}
+		self.history.clear_legacy();
+		self.follow_storage_changes(stored_name, responses);
+		responses.add(PortfolioMessage::AutoSaveDocument { document_id });
+		responses.add(OverlaysMessage::Draw);
+		responses.add(EventMessage::SelectionChanged);
+	}
+
 	/// Reconciles the interface with storage. The tab takes the stored name only if it changed from `name_before`.
 	fn follow_storage_changes(&mut self, name_before: Option<String>, responses: &mut VecDeque<Message>) {
 		if let Some(gdd) = self.history.storage_mut() {

editor/src/messages/portfolio/history/history_message.rs

@@ -0,0 +1,16 @@
+use crate::messages::prelude::*;
+
+#[impl_message(Message, PortfolioMessage, History)]
+#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
+pub enum HistoryMessage {
+	Refresh,
+	Tick,
+	Expand { id: String, expanded: bool },
+	LoadMore,
+	GoBack { id: String },
+	RemoveStep { id: String },
+	BringBack { id: String },
+	Follow { id: Option<String> },
+	Rename { id: String, label: String },
+	Tag { id: String, tag: String, on: bool },
+}