Pythom - DAG Diagram Editor

A PyQt6-based application for creating and editing Directed Acyclic Graph (DAG) diagrams.

Features

• Node-based Architecture: Built with a clean class hierarchy

  • Node(QGraphicsObject) - Base class for all diagram elements
  • Object(Node) - Represents data/process nodes in the DAG
  • Arrow(Node) - Represents connections between objects

• Custom Scene and View:

  • DiagramScene(QGraphicsScene) - Custom scene with grid and object placement
  • DiagramView(QGraphicsView) - Enhanced view with zoom and pan capabilities

• Interactive Features:

  • Double-click canvas to place objects (snaps to 100x100 grid)
  • Drag objects to move them (snaps to grid)
  • Zoom in/out with mouse wheel or keyboard shortcuts
  • Pan with middle mouse button or keyboard
  • Selection highlighting

Usage

Run the application:

python main.py

Controls

• Double-click: Add a new object to the canvas
• Mouse wheel: Zoom in/out
• Middle mouse button: Pan the view
• Drag: Move selected objects
• Ctrl+Plus/Minus: Zoom in/out
• Ctrl+0: Reset zoom to 100%
• Ctrl+F: Fit all objects in view

Requirements

• Python 3.8+
• PyQt6

Install PyQt6:

pip install PyQt6

Project Structure

HomPy/
├── main.py              # Application entry point
├── main_window.py       # Main window with menus and toolbar
├── diagram_scene.py     # Custom QGraphicsScene
├── diagram_view.py      # Custom QGraphicsView with zoom/pan
├── node.py              # Base Node class
├── object_node.py       # Object node implementation
├── arrow.py             # Arrow node for connections
├── __init__.py          # Package initialization
└── README.md            # This file

Class Hierarchy

QGraphicsObject
└── Node (base class)
    ├── Object (rounded rectangle nodes)
    └── Arrow (connection arrows)

QGraphicsScene
└── DiagramScene (grid background, object placement)

QGraphicsView  
└── DiagramView (zoom, pan, keyboard shortcuts)

QMainWindow
└── MainWindow (menus, toolbar, status bar)

Future Enhancements

• Arrow creation by connecting objects
• Object property editing
• Save/load diagram files
• Export to image formats
• Undo/redo functionality
• Object types and styling
• Connection validation for DAG constraints