ThirdWay: A carefully modernised variant of MVC

The Model-View-Controller interface is the earliest GUI framework that found widespread interest. It was published together with Smalltalk and it is still available in Squeak. Most Squeak users moved to Morphic, a GUI framework that is both very powerful and very innovative. When compared with Morphic or with one of the commonly used GUI's, the MVC interface of Squeak looks now a bit old-fashioned. ThirdWay is an attempt to bring additional features to MVC.

ThirdWay was developed over a period of serveral years. To verify its useability, I wrote some same applications.

• TrussAnalyzer: a program to draw and to analyze planar trusses.

• TWFontEditor: a program to create and to modify StrikeFonts

• ODELaboratory: a program to numerically solve ordinary differential equations

Here are a few examples:

A text style displayer:

A dialog with a slider window and a stepper window:

Two notebook-like windows:

ThirdWay is a carefully modernised variant of MVC. It uses the controllers from MVC but not the views, which are replaced by a hierarchy of windows.

One of the most successful early Smalltalks was the Digitalk Smalltalk V/286. The success of Smalltalk V/286 had many reasons (price of the product, quality of the documentation etc.) but the simplicity of its Model-Dispatcher-Pane framework certainly helped its users to quickly create beautiful applications.

ThirdWay takes these features from various versions of Smalltalk V/286:

• A block is used to compute a window frame. It is, of course, possible to replace the block with a method. Class Framer is prepared to do this.
• The methods of most callbacks from a window take the window as a method argument. The advantage of this approach is that a callback can communicate with the calling window.

Advanced features include:

• SubModel, a subclass of model, is introduced as superclass for components. A component implements the mandatory protocol of both a model and a window. A component can be used as a visual element in a window. Class SubModelPresenter is used as a container for a component that can later be replaced by a different component.