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C/C++ Users Group Library 1996 July
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C-C++ Users Group Library July 1996.iso
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v_12_08
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egapixel.c
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1994-04-25
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/******************************************************
* EGAPIXEL.C - this is a hardware-specific function
* to examine and fill EGA/VGA pixels.
*
* for TurboC V2.0
*
* by Anton Treuenfels
* last revision: 04/11/94
*
* references:
* Stevens, Roger T., "Graphics Programming in C",
* M&T Books, 1988
* Wilton, Richard, "PC & PS/2 Video Systems",
* Microsoft Press, 1987
*****************************************************/
#include "usrdef.h"
/*******************************
* Header Section - EGAPIXEL.H *
*******************************/
#ifndef SEEN_EGAPIX
#define SEEN_EGAPIX
/* function prototype */
void egaflood(int, int, Boolean);
#endif
/*****************************
* Code Section - EGAPIXEL.C *
*****************************/
#include <stddef.h>
#include <dos.h>
#include <graphics.h>
#include "bgigrh.h"
#include "flood.h"
#include "uflood.h"
#define BRDRPIX WHITE
#define BACKPIX LIGHTBLUE
#define FOREPIX BLUE
/* screen dimension */
#define XMAX 639 /* highest supported by BGI */
/* video memory */
#define VBASE 0xa0000000L /* base address */
#define ROWSIZE 80 /* bytes per row */
#define COLMASK 0xfff8 /* column mask */
#define COLSHFT 3 /* column shift */
#define PIXMASK 0x07 /* pixel select */
/* graphics controller */
#define SETGRH(R, V) {outportb(0x3ce, (R)); \
outportb(0x3cf, (V));}
#define COMP 2 /* color compare register */
#define DFLTCMP 0x00
#define MODE 5 /* mode register */
#define DFLTMOD 0x00
#define R1W2 0x06 /* read mode 1, write mode 2 */
#define MASK 8 /* bitmask register */
#define DFLTMSK 0xff
/* pixel masks and pattern */
static Byte pixMask[] = {0x80, 0x40, 0x20, 0x10,
0x08, 0x04, 0x02, 0x01};
static Byte patMask[] = {0xcc, 0xcc, 0x33, 0x33,
0xcc, 0xcc, 0x33, 0x33};
#define PATMASK 0x07 /* pattern select */
/* screen variables */
static int currCol; /* current column */
static int currRow; /* current row */
static int colOffset; /* column offset */
static Byte far *rowPtr; /* row offset */
static Byte far *screenPtr; /* current screen byte */
static Byte rowPattern; /* row fill pattern */
/*****************************************************/
/* initialize current column and row */
static void initcurr(int ypos) {
currCol = ~COLMASK;
currRow = ypos - 1;
}
/* examine one pixel */
static int egapixel(int xpos, int ypos) {
Byte bitmask;
if (ypos != currRow) {
if ((ypos < 0) || (ypos > MaxYPos))
return(FALSE);
currRow = ypos;
rowPtr = (Byte far *)(VBASE + ypos * ROWSIZE);
screenPtr = rowPtr + colOffset;
rowPattern = patMask[ypos & PATMASK];
}
if ((xpos & COLMASK) != currCol) {
if ((xpos < 0) || (xpos > XMAX))
return(FALSE);
currCol = xpos & COLMASK;
colOffset = xpos >> COLSHFT;
screenPtr = rowPtr + colOffset;
}
bitmask = pixMask[xpos & PIXMASK];
if ((*screenPtr & bitmask) != 0)
return(FALSE);
SETGRH(MASK, bitmask);
*screenPtr =
(rowPattern & bitmask) ? FOREPIX : BACKPIX;
return(TRUE);
}
/* execute fill */
void egaflood(int xpos, int ypos, Boolean fastfill) {
abspoint(&xpos, &ypos);
initcurr(ypos);
SETGRH(COMP, BRDRPIX);
SETGRH(MODE, R1W2);
if (fastfill)
(void)flood(xpos, ypos, egapixel);
else
(void)uflood(xpos, ypos, egapixel);
SETGRH(MASK, DFLTMSK);
SETGRH(MODE, DFLTMOD);
SETGRH(COMP, DFLTCMP);
}