Page840_Screen.cpp

#include "Page840_Screen.h"
// initialize static member
Screen::Action Screen::Menu[] = { &Screen::home,
                                  &Screen::forward,
                                  &Screen::back,
                                  &Screen::up,
                                  &Screen::down
                                };
Screen& Screen::move(Directions cm)
{
    // run the element indexed by cm on this object
    return (this->*Menu[cm])(); // Menu[cm] points to a member function
}
inline Screen& Screen::home()
{
    cursor = 0;
    return *this;
}
inline Screen& Screen::forward()
{
    if(cursor < height * width - 1)
        ++cursor;
    return *this;
}
inline Screen& Screen::back()
{
    if(cursor > 0)
        --cursor;
    else
        cursor = 0;
    return *this;
}
inline Screen& Screen::up()
{
    if(cursor - width > 0)
        cursor -= width;
    else
        cursor = 0;
    return *this;
}
inline Screen& Screen::down()
{
    if(cursor + width < height * width)
        cursor += width;
    else
        cursor = height * width - 1;
    return *this;
}
// Note: in this file, only home, forward, back, up and down are inline. We can't
// declare a function as inline if it's in a source file and it will be called
// by functions in other source files. Or the compiler would complain that it
// cannot find the definition of the function. See this link:
// https://stackoverflow.com/questions/7883022/inline-in-source-file