Qt CAD Vector Graphics Editor: A Lightweight CAD Solution

CAD (Computer-Aided Design) software has become an indispensable tool in various industries, from mechanical engineering to architecture. Typically, CAD software is resource-intensive and requires specialized hardware and software configurations. However, with the advent of modern frameworks like Qt, it is now possible to create lightweight CAD applications that offer similar functionalities but with a smaller footprint.

In this article, we’ll delve into the process of developing a basic CAD vector graphics editor using Qt. This software will allow users to create, modify, and delete geometric primitives such as lines, circles, rectangles, and polygons. It will also provide a mechanism for querying and manipulating these primitives, making it suitable for basic CAD tasks.

1. Setting Up the Project

To begin, we need to set up a new Qt Widgets Application project. Open Qt Creator and create a new project, selecting the ‘Widgets Application’ template. Configure the project settings as per your requirements and click ‘Finish’ to generate the basic project structure.

2. Designing the User Interface

The next step is to design the user interface for our CAD application. Open the ‘mainwindow.ui’ file in the Qt Designer and arrange the widgets as per your preference. You can use a combination of QLineEdit, QPushButton, QGraphicsView, and QGraphicsScene to create a functional user interface.

• QLineEdit: Used for entering numerical values for geometric primitives.
• QPushButton: Used for performing actions like adding, deleting, modifying, and querying primitives.
• QGraphicsView and QGraphicsScene: Used for displaying and manipulating the geometric primitives visually.

3. Implementing the Core Functionality

Once the user interface is designed, we need to implement the core functionality of adding, deleting, modifying, and querying geometric primitives.

• Adding Primitives: Implement a function that creates geometric primitives based on user input. For example, when the user clicks the ‘Add Line’ button, you can prompt them to enter the starting and ending points of the line using QLineEdit, and then create a QGraphicsLineItem and add it to the QGraphicsScene.
• Deleting Primitives: Implement a function that removes selected primitives from the QGraphicsScene. You can use the QGraphicsScene’s removeItem() function to achieve this.
• Modifying Primitives: Implement functions to modify the properties of selected primitives. For example, you can allow users to change the color, thickness, or position of a primitive by providing appropriate input fields and buttons.
• Querying Primitives: Implement a function that queries the properties of selected primitives. You can display the properties of a selected primitive in a separate widget or dialog box.

4. Connecting Signals and Slots

Connect the signals emitted by the user interface widgets (like button clicks) to the appropriate slots (functions) implemented in the previous step. This ensures that when the user performs an action, the corresponding functionality is executed.

5. Testing and Debugging

Once the implementation is complete, thoroughly test the application to ensure that all functionalities work as expected. Use the Qt Creator’s debugging tools to identify and fix any issues or bugs.

6. Packaging and Distribution

Once the application is stable and ready for distribution, you can package it using Qt’s deployment tools. This allows you to create a standalone executable that can be run on other systems without the need for a separate Qt installation.

In conclusion, developing a lightweight CAD vector graphics editor using Qt is a feasible task that can be accomplished with careful planning and execution. By leveraging Qt’s powerful widgets and graphics capabilities, you can create a functional and user-friendly CAD application suitable for basic design tasks.