The /tests/pc folder is now /tests/pcx86 (to be consistent with the associated emulator)
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Jeff Parsons
parent
51b50382fb
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663343a1ad
68 changed files with 24 additions and 16 deletions
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/*
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* C implementation of Bresenham's line drawing algorithm
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* for the EGA and VGA. Works in modes 0xE, 0xF, 0x10, and 0x12.
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*
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* Compiled with Borland C++
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*
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* By Michael Abrash
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*/
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#include <dos.h> /* contains MK_FP macro */
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#include "regs.h"
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#define EVGA_SCREEN_WIDTH_IN_BYTES 80
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/* memory offset from start of
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one row to start of next */
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#define EVGA_SCREEN_SEGMENT 0xA000
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/* display memory segment */
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#define GC_INDEX 0x3CE
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/* Graphics Controller
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Index register port */
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#define GC_DATA 0x3CF
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/* Graphics Controller
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Data register port */
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#define SET_RESET_INDEX 0 /* indexes of needed */
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#define ENABLE_SET_RESET_INDEX 1 /* Graphics Controller */
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#define BIT_MASK_INDEX 8 /* registers */
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/*
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* Draws a dot at (X0,Y0) in whatever color the EGA/VGA hardware is
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* set up for. Leaves the bit mask set to whatever value the
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* dot required.
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*/
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void EVGADot(X0, Y0)
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unsigned int X0; /* coordinates at which to draw dot, with */
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unsigned int Y0; /* (0,0) at the upper left of the screen */
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{
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unsigned char far *PixelBytePtr;
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unsigned char PixelMask;
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/* Calculate the offset in the screen segment of the byte in
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which the pixel lies */
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PixelBytePtr = MK_FP(EVGA_SCREEN_SEGMENT,
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( Y0 * EVGA_SCREEN_WIDTH_IN_BYTES ) + ( X0 / 8 ));
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/* Generate a mask with a 1 bit in the pixel's position within the
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screen byte */
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PixelMask = 0x80 >> ( X0 & 0x07 );
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/* Set up the Graphics Controller's Bit Mask register to allow
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only the bit corresponding to the pixel being drawn to
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be modified */
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outportb(GC_INDEX, BIT_MASK_INDEX);
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outportb(GC_DATA, PixelMask);
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/* Draw the pixel. Because of the operation of the set/reset
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feature of the EGA/VGA, the value written doesn't matter.
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The screen byte is ORed in order to perform a read to latch the
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display memory, then perform a write in order to modify it. */
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*PixelBytePtr |= 0xFE;
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}
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/*
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* Draws a line in octant 0 or 3 ( |DeltaX| >= DeltaY ).
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*/
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void Octant0(X0, Y0, DeltaX, DeltaY, XDirection)
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unsigned int X0, Y0; /* coordinates of start of the line */
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unsigned int DeltaX, DeltaY; /* length of the line (both > 0) */
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int XDirection; /* 1 if line is drawn left to right,
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-1 if drawn right to left */
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{
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int DeltaYx2;
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int DeltaYx2MinusDeltaXx2;
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int ErrorTerm;
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/* Set up initial error term and values used inside drawing loop */
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DeltaYx2 = DeltaY * 2;
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DeltaYx2MinusDeltaXx2 = DeltaYx2 - (int) ( DeltaX * 2 );
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ErrorTerm = DeltaYx2 - (int) DeltaX;
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/* Draw the line */
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EVGADot(X0, Y0); /* draw the first pixel */
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while ( DeltaX-- ) {
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/* See if it's time to advance the Y coordinate */
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if ( ErrorTerm >= 0 ) {
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/* Advance the Y coordinate & adjust the error term
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back down */
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Y0++;
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ErrorTerm += DeltaYx2MinusDeltaXx2;
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} else {
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/* Add to the error term */
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ErrorTerm += DeltaYx2;
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}
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X0 += XDirection; /* advance the X coordinate */
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EVGADot(X0, Y0); /* draw a pixel */
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}
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}
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/*
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* Draws a line in octant 1 or 2 ( |DeltaX| < DeltaY ).
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*/
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void Octant1(X0, Y0, DeltaX, DeltaY, XDirection)
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unsigned int X0, Y0; /* coordinates of start of the line */
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unsigned int DeltaX, DeltaY; /* length of the line (both > 0) */
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int XDirection; /* 1 if line is drawn left to right,
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-1 if drawn right to left */
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{
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int DeltaXx2;
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int DeltaXx2MinusDeltaYx2;
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int ErrorTerm;
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/* Set up initial error term and values used inside drawing loop */
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DeltaXx2 = DeltaX * 2;
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DeltaXx2MinusDeltaYx2 = DeltaXx2 - (int) ( DeltaY * 2 );
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ErrorTerm = DeltaXx2 - (int) DeltaY;
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EVGADot(X0, Y0); /* draw the first pixel */
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while ( DeltaY-- ) {
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/* See if it's time to advance the X coordinate */
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if ( ErrorTerm >= 0 ) {
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/* Advance the X coordinate & adjust the error term
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back down */
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X0 += XDirection;
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ErrorTerm += DeltaXx2MinusDeltaYx2;
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} else {
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/* Add to the error term */
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ErrorTerm += DeltaXx2;
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}
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Y0++; /* advance the Y coordinate */
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EVGADot(X0, Y0); /* draw a pixel */
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}
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}
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/*
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* Draws a line on the EGA or VGA.
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*/
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void EVGALine(X0, Y0, X1, Y1, Color)
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int X0, Y0; /* coordinates of one end of the line */
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int X1, Y1; /* coordinates of the other end of the line */
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char Color; /* color to draw line in */
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{
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int DeltaX, DeltaY;
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int Temp;
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/* Set the drawing color */
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/* Put the drawing color in the Set/Reset register */
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outportb(GC_INDEX, SET_RESET_INDEX);
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outportb(GC_DATA, Color);
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/* Cause all planes to be forced to the Set/Reset color */
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outportb(GC_INDEX, ENABLE_SET_RESET_INDEX);
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outportb(GC_DATA, 0xF);
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/* Save half the line-drawing cases by swapping Y0 with Y1
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and X0 with X1 if Y0 is greater than Y1. As a result, DeltaY
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is always > 0, and only the octant 0-3 cases need to be
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handled. */
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if ( Y0 > Y1 ) {
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Temp = Y0;
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Y0 = Y1;
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Y1 = Temp;
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Temp = X0;
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X0 = X1;
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X1 = Temp;
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}
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/* Handle as four separate cases, for the four octants in which
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Y1 is greater than Y0 */
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DeltaX = X1 - X0; /* calculate the length of the line
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in each coordinate */
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DeltaY = Y1 - Y0;
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if ( DeltaX > 0 ) {
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if ( DeltaX > DeltaY ) {
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Octant0(X0, Y0, DeltaX, DeltaY, 1);
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} else {
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Octant1(X0, Y0, DeltaX, DeltaY, 1);
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}
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} else {
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DeltaX = -DeltaX; /* absolute value of DeltaX */
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if ( DeltaX > DeltaY ) {
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Octant0(X0, Y0, DeltaX, DeltaY, -1);
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} else {
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Octant1(X0, Y0, DeltaX, DeltaY, -1);
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}
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}
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/* Return the state of the EGA/VGA to normal */
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outportb(GC_INDEX, ENABLE_SET_RESET_INDEX);
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outportb(GC_DATA, 0);
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outportb(GC_INDEX, BIT_MASK_INDEX);
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outportb(GC_DATA, 0xFF);
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}
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