Introduction

This manual describes the MrEd GUI toolbox for programmers developing MrEd applications. It assumes familiarity with MzScheme as described in PLT MzScheme: Language Manual (particularly the class and interface system) and with basic GUI concepts (such as windows and events).

What is MrEd?

MrEd is a Scheme implementation based on MzScheme (see PLT MzScheme: Language Manual). MrEd embeds MzScheme and extends it with a graphical user interface (GUI) toolbox. GUI applications written with MrEd run without modification under Windows, MacOS, and Unix/X.

MrEd is not a graphical environment for developing Scheme programs. DrScheme, documented in PLT DrScheme: Development Environment Manual, is the development environment for producing MzScheme- and MrEd-based applications.

Toolbox Organization

For documentation purposes, the MrEd toolbox is organized into three parts:

• The windowing toolbox, for implementing form-filling GUI programs (such as a database query window) using buttons, menus, text fields, and events.
• The drawing toolbox, for drawing pictures or implementing dynamic GUI programs (such as a video game) using drawing canvases, pens, and brushes.
• The editor toolbox, for developing traditional text editors, editors that mix text and graphics, or free-form layout editors (such as a word processor, HTML editor, or icon-based file browser).

All three parts are immediately available when MrEd is started. MrEd's initial Scheme namespace contains bindings for all of the class, interface, and procedure names defined in this manual. In addition, the initial environment binds mred@ to a signed unit that exports all of the MrEd bindings (including mred@) and binds mred^ to the unit's signature (but no knowledge about units or signatures is required to understand this manual).