// screen.h
//
// This is the specification for a screen class - an abstraction of an
// old-fashioned character display.  The screen supports some useful 
// operations, such as displaying text and drawing lines and rectangles.
//
// The coordinate system for the screen is as follows: the origin is
// at the top left corner of the screen, and has coordinates (0,0).  
// The column number grows as you move to the right and the row number grows
// as you move down.  The width of the screen is given by the constant
// SCREEN_WIDTH and the height is given by the constant SCREEN_HEIGHT.
// That means that the lower-right corner is at 
// (SCREEN_WIDTH-1,SCREEN_HEIGHT-1).
// 
// For the member functions below that return a bool, the return value is
// a status code indicating whether the operation succeeded.  If true is
// returned, the operation completed successfully.  If false is returned, 
// the operation could not run and _nothing changed on the screen_.  In 
// other words, all operations check _ahead of time_ whether they can
// complete.  If they can't, they stop before modifying the screen.  An
// operation is unable to complete if any part of what would get drawn
// is outside the dimensions of the screen instance.

#ifndef __SCREEN_H__
#define __SCREEN_H__

#include <iostream.h>

// The width and height of the screen are given by these two constants.  The
// class should work no matter what values are placed here.
const int SCREEN_WIDTH = 78;
const int SCREEN_HEIGHT = 24;

class Screen
{
public:
	// Construct a new screen, initialize it to be blank.
	Screen();

	// Construct a new screen, initialize it to the char 'ch'.
	Screen( char ch );


	// Put the character 'ch' at position (col, row).
	bool putChar( int col, int row, char ch );

	// Get the contents of the screen at position (col, row);
	bool getChar( int col, int row, char& ch );

	// Draw a horizontal line starting at position (col, row), 
	// extending to the right 'length' units, made out of the character 'ch'.
	bool horizontalLine( int col, int row, int length, char ch );

	// Draw a vertical line starting at position (col, row), 
	// extending down 'length' units, made out of the character 'ch'.
	bool verticalLine( int col, int row, int length, char ch );

	// Draw a rectangle, with top left corner at position (col, row),
	// of dimension 'width' x 'height' units.  The vertical lines in the
	// border are made out of '|'.  The horizontal lines are made out of
	// '-'.  The corners are made out of '+'.  The rectangle is filled
	// with the character 'fill'.
	bool rectangle( int col, int row, int width, int height, char fill );

	// Draw the text contained in the buffer, starting at position (col, row)
	bool putText( int col, int row, char text[] );

	// Draw the text contained in the buffer, centered on line 'row'.
	bool putCenteredText( int row, char text[] );

	// Fill the whole screen with the character 'ch'.
	void fill( char ch );

	// Write the contents of the screen to the output stream 'os'.
	ostream& print( ostream& os );

	// Fill in the screen by reading in an existing screen from
	// a file.  The file should contain SCREEN_HEIGHT lines of text,
	// each line exactly SCREEN_WIDTH characters in length.
	istream& read( istream& is );

private:
};

#endif // __SCREEN_H__