DEFINITION MODULE GR_Block;

    (*
    **  Author : Peter Jardine
    **
    **  Version:
    **  1.0      9 Mar 92   New file - based on the work of 
    **                      Michael McCarthy & John Pfitzner,
    **                      CSP-960 Project, Semester 2, 1991
    **      jrh 16-Jun-92   File save/restore from Malcolm Corney.
    **
    **
    **  A GPM Modula-2 graphics library module.
    **
    *)

FROM UxFiles IMPORT File;

TYPE
    BitMap; (* Opaque type used in Block Save and Restore routines *)

PROCEDURE FreeBlock(VAR b : BitMap);
    (*
    **  Deallocates the memory used to store an image via BlockSave.
    *)

PROCEDURE BlockRestore(bitmap : BitMap ; col, row : INTEGER);
PROCEDURE BlockNDCRestore(bitmap : BitMap ; x, y : REAL);
    (*
    **  Restores a previously saved region to the screen. Does not destroy
    **  or alter bitmap in any way, which means that we need some way of
    **  releasing memory when the image is no longer needed (FreeBlock).
    **  Note that of course the current video mode must be the same as that
    **  when the image was saved.
    *)

PROCEDURE BlockSave(col1, row1, col2, row2 : INTEGER; VAR bits : BitMap);
PROCEDURE BlockNDCSave(x1, y1, x2, y2 : REAL; VAR bits : BitMap);
    (*
    **  Save a rectangular region of the screen, returning a pointer to a
    **  structure that store the image data and some header details.
    *)

PROCEDURE BlockSaveToFile(file : File; col1, row1, col2, row2 : INTEGER;
                          VAR done : BOOLEAN);
PROCEDURE BlockNDCSaveToFile(file : File; x1, y1, x2, y2 : REAL;
                             VAR done : BOOLEAN);
    (*
    **  Save a rectangular region of the screen to the file.
    *)

PROCEDURE BlockRestoreFromFile(file : File; col1, row1 : INTEGER; 
                               VAR ok : BOOLEAN);
PROCEDURE BlockNDCRestoreFromFile(file : File; x1, y1 : REAL; 
                                  VAR done : BOOLEAN);
    (*
    **  Restore a previously saved region from file to the screen.
    **  The current video mode must be the same as that when the image was
    **  saved.
    *)

END GR_Block.