thib8956/new-shapes

Table of Contents

Plan: Undo/Redo Stack

Overview
Current State
Implementation Plan

1. Command pattern
2. CommandManager class
3. Controller integration
4. Keyboard shortcuts
5. Menu additions

Files to create/modify
Edge cases

Plan: Undo/Redo Stack

Overview

Implement undo/redo functionality with a command history stack.

Current State

Controller handles shape operations (add, delete, move, color change)
No command history exists
Selection system tracks selected shapes

Implementation Plan

1. Command pattern

Create Command interface with execute() and undo() methods
Create concrete commands:
- AddShapeCommand - stores shape reference, removes on undo
- DeleteShapesCommand - stores shapes list, re-adds on undo
- MoveShapeCommand - stores shape, original pos, new pos
- ChangeColorCommand - stores shape, old/new colors
- ResizeCommand - stores shape, old/new bounds
- GroupCommand - composite for batch operations

2. CommandManager class

Maintains two stacks: undoStack, redoStack
execute(Command): push to undoStack, clear redoStack
undo(): pop from undoStack, call undo(), push to redoStack
redo(): pop from redoStack, call execute(), push to undoStack
Limit stack size (e.g., 50 commands)

3. Controller integration

Replace direct shape operations with commands
Example: instead of collection.add(shape), do commandManager.execute(new AddShapeCommand(shape, collection))

4. Keyboard shortcuts

Ctrl+Z: undo
Ctrl+Y: redo (or Ctrl+Shift+Z)
Update menu with these shortcuts

Add Edit menu items: Undo, Redo
Enable/disable based on stack state

Files to create/modify

Create: commands/Command.java, commands/CommandManager.java
Create: commands/AddShapeCommand.java, commands/DeleteShapesCommand.java, commands/MoveShapeCommand.java, etc.
Modify: ui/Controller.java, App.java (menu)

Edge cases

Copy/paste after undo: clear redo stack
Multi-select delete: single compound command
Application close: no persistence needed (in-memory only)