Design and Implementation of a General Purpose 2D CAD System

A general purpose 2D CAD system was established by Object-Oriented technology. Key technologies for realizing the system were introduced. The methods for forming shape container, manipulating shape container and constructing graph template library were described in detail. Basic shapes, such as line, rectangle, ellipse, polygon, B-Spline curve and textbox, can be grouped to be a shape container, and the shape containers can also be grouped to form a more complex one. The hierarchy of shape container is a Tree. Hence, to manipulate shape container is to access the container recursively. The Redo and Undo functions were realized by serializing canvas status to temporary files. And all of the canvas statuses were managed by undo-stack and redo-stack. The purposefully formed shape container can be reformed to a graph template, and the graph templates of the same type can be stored as a library. Different graph template library corresponds to different application. Various types of graph template library ensure the generality and flexibility of this system. Experimental results showed that the proposed methods are effective. This system can be applied to a lot of fields, such as construction, machinery and electronics. Index Terms CAD, graph element, Object-Oriented technology, tree structure, B-Spline curve