Rename undo_buffer to revision tracker

Signed-off-by: Arjo Chakravarty <arjoc@google.com>

rmf_site_editor/src/interaction/gizmo.rs

@@ -19,7 +19,7 @@ use std::collections::HashMap;
 
 use crate::{
     interaction::*,
-    site::{UndoBuffer, UndoEvent},
+    site::{RevisionTracker, UndoEvent},
 };
 use bevy::{math::Affine3A, prelude::*, window::PrimaryWindow};
 use bevy_mod_raycast::{deferred::RaycastMesh, deferred::RaycastSource, primitives::rays::Ray3d};
@@ -391,14 +391,14 @@ pub fn update_gizmo_click_start(
 
 #[derive(Debug)]
 pub struct GizmoMoveChange {
-    entity: Entity,
-    prev_pos: Transform,
-    dest_pos: Transform,
+    pub entity: Entity,
+    pub prev_pos: Transform,
+    pub dest_pos: Transform,
 }
 
 #[derive(Resource, Default)]
 pub struct GizmoMoveUndoBuffer {
-    revisions: HashMap<usize, GizmoMoveChange>,
+    pub revisions: HashMap<usize, GizmoMoveChange>,
 }
 
 pub(crate) fn undo_gizmo_change(
@@ -429,7 +429,7 @@ pub fn update_gizmo_release(
     mut gizmo_state: ResMut<GizmoState>,
     mouse_button_input: Res<Input<MouseButton>>,
     mut picked: ResMut<Picked>,
-    mut version_tracker: ResMut<UndoBuffer>,
+    mut version_tracker: ResMut<RevisionTracker>,
     mut change_history: ResMut<GizmoMoveUndoBuffer>,
     last_dragged: Res<LastDraggedPos>,
 ) {

rmf_site_editor/src/site/change_plugin.rs

@@ -19,7 +19,7 @@ use crate::site::SiteUpdateSet;
 use bevy::prelude::*;
 use std::{fmt::Debug, sync::Arc};
 
-use super::{UndoBuffer, UndoEvent};
+use super::{RevisionTracker, UndoEvent};
 
 /// The Change component is used as an event to indicate that the value of a
 /// component should change for some entity. Using these events instead of
@@ -121,7 +121,7 @@ fn update_changed_values<T: Component + Clone + Debug>(
     mut commands: Commands,
     mut values: Query<&mut T>,
     mut changes: EventReader<Change<T>>,
-    mut undo_buffer: ResMut<UndoBuffer>,
+    mut undo_buffer: ResMut<RevisionTracker>,
     mut change_history: ResMut<ChangeHistory<T>>,
 ) {
     for change in changes.read() {

rmf_site_editor/src/site/undo_plugin.rs

@@ -4,15 +4,21 @@ use std::fmt::Debug;
 
 use crate::{EditMenu, MenuEvent, MenuItem};
 
+/// This represents an undo event. If you want to implement some form of undo-able
+/// action, your plugin should watch for this event. Specifically, we should be
 #[derive(Event, Debug, Clone, Copy)]
 pub struct UndoEvent {
+    /// The action id that should be reverted
     pub action_id: usize,
 }
 
+/// This struct represents the undo menu item.
 #[derive(Resource)]
 struct UndoMenu {
     menu_entity: Entity,
 }
+
+/// This is responsible for drawing the undo GUI menu
 ///TODO(arjo): Decouple
 impl FromWorld for UndoMenu {
     fn from_world(world: &mut World) -> Self {
@@ -25,10 +31,11 @@ impl FromWorld for UndoMenu {
     }
 }
 
+/// This item watches the GUI menu to detect if an undo action was clicked.
 fn watch_undo_click(
     mut reader: EventReader<MenuEvent>,
     menu_handle: Res<UndoMenu>,
-    mut undo_buffer: ResMut<UndoBuffer>,
+    mut undo_buffer: ResMut<RevisionTracker>,
     mut event_writer: EventWriter<UndoEvent>,
 ) {
     for menu_click in reader.read() {
@@ -43,20 +50,26 @@ fn watch_undo_click(
     }
 }
 
+/// The RevisionTracker resource is used to manage the undo
+/// stack. When a plugin wishes to commit an action it should request anew revision
+/// from the RevisionTracker. It is up to the plugin to maintain its
+/// own history of what state changes ocurred.
 #[derive(Resource, Default)]
-pub struct UndoBuffer {
-    pub prev_value: usize,
-    pub undo_stack: Vec<usize>,
+pub struct RevisionTracker {
+    pub(crate) prev_value: usize,
+    pub(crate) undo_stack: Vec<usize>,
 }
 
-impl UndoBuffer {
+impl RevisionTracker {
+    /// Request a new revision id. This is associated with the action you sent
     pub fn get_next_revision(&mut self) -> usize {
         self.prev_value += 1;
         self.undo_stack.push(self.prev_value);
         self.prev_value
     }
 
-    pub fn undo_last(&mut self) -> Option<usize> {
+    /// Get the last item that was supposed to be undone.
+    pub(crate) fn undo_last(&mut self) -> Option<usize> {
         self.undo_stack.pop()
     }
 }
@@ -68,7 +81,7 @@ impl Plugin for UndoPlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<EditMenu>()
             .init_resource::<UndoMenu>()
-            .init_resource::<UndoBuffer>()
+            .init_resource::<RevisionTracker>()
             .add_event::<UndoEvent>()
             .add_systems(Update, (watch_undo_click));
     }