myheyj / et-plus-plus

ET++ is used to study the Design Patterns book of GOF

Patterns introduced in Design Patterns

ET++ is referenced in Abstract Factory (p97), Builder, Factory Method, Prototype, Adapter, Bridge (p151), Composite, Decorator, Facade, Flyweight, Chain of Responsibility, Command, Iterator, Mediator, Observer, and Strategy in Design Patterns (ISBN-13: 9787111095071).

Abstract Factory

Factories:

• WindowSystem (abstract)

  • NeWSWindowSystem

  • ServerWindowSystem

  • SunWindowSystem

  • XWindowSystem

Products:

• WindowPort (abstract)

  • NeWSWindowPort

  • ServerPort

  • SunWindowPort

  • XWindowPort

• FontManager (abstract)

  • NeWSFontManager

  • ServerFontManager

  • SunFontManager

  • XFontManager

• DevBitmap (abstract)

  • SunBitmap

  • XBitmap

• ClipBoard (abstract)

  • SunClipBoard

  • XClipBoard

How does et++ decide which concrete factory to use?

In InitWindowSystem, it uses macros to choose the concrete factory.

WindowSystem    *gWindowSystem= 0;

void InitWindowSystem()
{
    // ...

#ifdef WS_SUNSERVER
    if (gWindowSystem == 0)
	gWindowSystem= NewServerWindowSystem(); // try to connect to SunWindow server
#endif WS_SUNSERVER

#ifdef WS_X
    if (gWindowSystem == 0)
	gWindowSystem= NewXWindowSystem();      // try to connect to X server
#endif WS_X

#ifdef WS_NEWS
    if (gWindowSystem == 0)
	gWindowSystem= NewNeWSWindowSystem();   // try to connect to NeWS server
#endif WS_NEWS
    
#ifdef WS_SUNWINDOW
    if (gWindowSystem == 0)
	gWindowSystem= NewSunWindowSystem();    // try SunWindow System
#endif WS_SUNWINDOW
    
    // ...
}

Bridge

• BlankWin (Abstraction)

  • Window (Refined Abstraction)

  • Icon (Refined Abstraction)

• WindowPort (Implementor)

  • NeWSWindowPort (Concrete Implementor)

  • ServerPort (Concrete Implementor)

  • SunWindowPort (Concrete Implementor)

  • XWindowPort (Concrete Implementor)

This pattern is combined with Abstract Factory to make a concrete WindowPort object.

class WindowPort *BlankWin::MakePort()
{
    if (portDesc == 0) {
        portDesc= gWindowSystem->MakeWindow((InpHandlerFun) &BlankWin::input, this,
                        TestFlag(eBWinOverlay), TestFlag(eBWinBlock), FALSE);
        portDesc->cursor= cursor;
    }
    return portDesc;
}