Flexible Architecture

Essential Diagram is designed to be a high-performance, modular, easy-to-use and easy-to-customize engine. Many of the classes and components in the library can be sub-classed, providing users the ability to extend and customize the library to meet their needs.

Essential Diagram employs the MVC (Model-View-Controller) design to clearly separate data, presentation and user interaction.

Model

A Model is a collection of nodes that are rendered on a view and manipulated by a controller. The Diagram document represents the Model in this pattern.

View

A View is an object that draws the model in a rectangular area on the screen. A view also renders additional visual information that does not exist inside the model, such as bounding boxes, coordinate axes, and grids.

View also provides methods to perform hit testing. When a mouse event occurs, the point at which the event occurred is always provided in device coordinates. Since the View maps device coordinates and world coordinates, the View is the logical entry point for hit testing routines.

Controller

A Controller is an object that receives user input and translates it to actions and commands on the Model and View. A Controller contains one or more tools which are re-usable objects and these tools implement a slice of functionality for the controller.

The Model, View and Controller objects communicate with each other through well defined interfaces.

Benefits:

• A significant advantage to this design is that the model, view and controller components are interchangeable. Users may swap them with other components to build highly specialized applications.

• Another key benefit of this design is that it reduces the complexity of the product which, in turn, increases reliability.

Essential Diagram supports nesting of graphical objects and models. A node is a named-object in a hierarchy of objects. Node transformations are relative to parent-nodes. Users can also address nodes by name. There is also support for graph navigation using nodes and edges.

Parent-node properties can be inherited by child-nodes and users can apply property values to one or all nodes of the model. There is also support for adding custom properties at run-time.

Styling options are available for various regions and aspects of the diagram. Some of them are FillStyle, LineStyle, FontColorStyle, ShadowStyle and BackgroundStyle.

Essential Diagram lets users export their diagrams to a variety of data formats such as bitmaps, enhanced metafiles, and SVG format files. Alternatively, with a license of Essential PDF, diagrams can be exported as PDF documents as well. Diagrams can be directly saved as bitmaps or rendered to an external graphics device context to write out as an enhanced metafile image. SVG Export is a new feature introduced in the Essential Diagram version 4.1. This enables diagrams to be saved as Scalable Vector Graphics (SVG) format files.