{TxtWin.inc doc-file by Kari Lammassaari }

Txtwin.inc creates a dynamic text windows with borders and header strings
on normal text screen (width 80), start address 0 in VRAM. 
The underlying screen is saved onto heap ans the screen is restored after 
the erasure of the window.
The windows can be scrolled up/down.
The windows can be written/cleared.
Each window stores their cursor positions during writing process.

The txtwin.inc NEEDS following inc. files (available at ftp.funet.fi and at
home page of Manuel Bilderbeek): 
 
 -  READVRAM.INC 
 -  WRTVRAM.INC
 -  FILLVRAM.INC

The txtwin.inc contains following global types, functions and procedures:

 -  Pointer   = ^Byte;              { Used with heap management) 
 -  String255 = String[255];
 -  String80  = String[80];

- Function  MakeWindow(Col,Row,Width,Height:Byte;Header:StringType):Pointer;

   Col,Row refers the column and the row of the upper left corner of the window.
   MakeWindow stores the underlying screen onto heap. NO checking of the 
   available memory. NO checking of the screen bounds ie. does the window spread
   over the screen borders.
   The structure of heap record:  offset 0  = column of the upper left corner
                                         1  = row    of the upper left corner
                                         2  = length of the window
                                         3  = height of the window
                                         4  = the cursor column of the window
                                         5  = the cursor row of the window
                                         6  = underlying screen data
                                         .
                                         .

 - Procedure EraseWindow(WindowPtr:Pointer);
  
    Removes window and restores underlying screen. Frees allocated heap memory.

 - Procedure ScrollWindowUp(WindowPtr:Pointer);

    Scrolls window up one row and writes an empty line on the bottom of 
    the window.

 - Procedure ScrollWindowDown(WindowPtr:Pointer);

    Scrolls window down one row and writes an empty line on the top of 
    the window.

 - Procedure WritelnWindow(WindowPtr:Pointer;St:String255);

    Writes a string with a linefeed on the window, updates the cursor 
    coordinates of the window . Scrolls window if necessary.

 - Procedure WriteWindow(WindowPtr:Pointer;St:String255);

    Writes a string without a linefeed on the window, updates the cursor 
    coordinates of the window . Scrolls window if necessary.

 - Procedure GotoWindowXY(WindowPtr:Pointer;Col,Row:Byte);

    Sets the window cursor position to Col,Row. NO checking of the validity
    of coordinates.

 - Procedure ClrEolWindow(WindowPtr:Pointer);

    Clears a window row from the current location of the window cursor.

- Procedure ClrWindow(WindowPtr:Pointer);

   Clears the window. (Does NOT remove window form the screen.)
   Set Window cursor coordinates at 1,1 = upper left corner.