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James Gregory 2013-12-31 11:38:48 +11:00
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35-04.md
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@ -12,89 +12,91 @@ pages: 664-667
**LISTING 35.2 L35-2.C**
/*
* Sample program to illustrate EGA/VGA line drawing routines.
*
* Compiled with Borland C++
*
* By Michael Abrash
*/
```c
/*
* Sample program to illustrate EGA/VGA line drawing routines.
*
* Compiled with Borland C++
*
* By Michael Abrash
*/
#include <dos.h> /* contains geninterrupt */
#include <dos.h> /* contains geninterrupt */
#define GRAPHICS_MODE 0x10
#define TEXT_MODE 0x03
#define BIOS_VIDEO_INT 0x10
#define X_MAX 640 /* working screen width */
#define Y_MAX 348 /* working screen height */
#define GRAPHICS_MODE 0x10
#define TEXT_MODE 0x03
#define BIOS_VIDEO_INT 0x10
#define X_MAX 640 /* working screen width */
#define Y_MAX 348 /* working screen height */
extern void EVGALine();
extern void EVGALine();
/*
* Subroutine to draw a rectangle full of vectors, of the specified
* length and color, around the specified rectangle center.
*/
void VectorsUp(XCenter, YCenter, XLength, YLength, Color)
int XCenter, YCenter; /* center of rectangle to fill */
int XLength, YLength; /* distance from center to edge
of rectangle */
int Color; /* color to draw lines in */
{
int WorkingX, WorkingY;
/*
* Subroutine to draw a rectangle full of vectors, of the specified
* length and color, around the specified rectangle center.
*/
void VectorsUp(XCenter, YCenter, XLength, YLength, Color)
int XCenter, YCenter; /* center of rectangle to fill */
int XLength, YLength; /* distance from center to edge
of rectangle */
int Color; /* color to draw lines in */
{
int WorkingX, WorkingY;
/* Lines from center to top of rectangle */
WorkingX = XCenter - XLength;
WorkingY = YCenter - YLength;
for ( ; WorkingX < ( XCenter + XLength ); WorkingX++ )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color);
/* Lines from center to top of rectangle */
WorkingX = XCenter - XLength;
WorkingY = YCenter - YLength;
for ( ; WorkingX < ( XCenter + XLength ); WorkingX++ )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color);
/* Lines from center to right of rectangle */
WorkingX = XCenter + XLength - 1;
WorkingY = YCenter - YLength;
for ( ; WorkingY < ( YCenter + YLength ); WorkingY++ )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color);
/* Lines from center to right of rectangle */
WorkingX = XCenter + XLength - 1;
WorkingY = YCenter - YLength;
for ( ; WorkingY < ( YCenter + YLength ); WorkingY++ )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color);
/* Lines from center to bottom of rectangle */
WorkingX = XCenter + XLength - 1;
WorkingY = YCenter + YLength - 1;
for ( ; WorkingX >= ( XCenter - XLength ); WorkingX— )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color);
/* Lines from center to bottom of rectangle */
WorkingX = XCenter + XLength - 1;
WorkingY = YCenter + YLength - 1;
for ( ; WorkingX >= ( XCenter - XLength ); WorkingX— )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color);
/* Lines from center to left of rectangle */
WorkingX = XCenter - XLength;
WorkingY = YCenter + YLength - 1;
for ( ; WorkingY >= ( YCenter - YLength ); WorkingY— )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color );
}
/* Lines from center to left of rectangle */
WorkingX = XCenter - XLength;
WorkingY = YCenter + YLength - 1;
for ( ; WorkingY >= ( YCenter - YLength ); WorkingY— )
EVGALine(XCenter, YCenter, WorkingX, WorkingY, Color );
}
/*
* Sample program to draw four rectangles full of lines.
*/
void main()
{
char temp;
/*
* Sample program to draw four rectangles full of lines.
*/
void main()
{
char temp;
/* Set graphics mode */
_AX = GRAPHICS_MODE;
geninterrupt(BIOS_VIDEO_INT);
/* Set graphics mode */
_AX = GRAPHICS_MODE;
geninterrupt(BIOS_VIDEO_INT);
/* Draw each of four rectangles full of vectors */
VectorsUp(X_MAX / 4, Y_MAX / 4, X_MAX / 4,
Y_MAX / 4, 1);
VectorsUp(X_MAX * 3 / 4, Y_MAX / 4, X_MAX / 4,
Y_MAX / 4, 2);
VectorsUp(X_MAX / 4, Y_MAX * 3 / 4, X_MAX / 4,
Y_MAX / 4, 3);
VectorsUp(X_MAX * 3 / 4, Y_MAX * 3 / 4, X_MAX / 4,
Y_MAX / 4, 4);
/* Draw each of four rectangles full of vectors */
VectorsUp(X_MAX / 4, Y_MAX / 4, X_MAX / 4,
Y_MAX / 4, 1);
VectorsUp(X_MAX * 3 / 4, Y_MAX / 4, X_MAX / 4,
Y_MAX / 4, 2);
VectorsUp(X_MAX / 4, Y_MAX * 3 / 4, X_MAX / 4,
Y_MAX / 4, 3);
VectorsUp(X_MAX * 3 / 4, Y_MAX * 3 / 4, X_MAX / 4,
Y_MAX / 4, 4);
/* Wait for the enter key to be pressed */
scanf("%c", &temp);
/* Wait for the enter key to be pressed */
scanf("%c", &temp);
/* Return back to text mode */
_AX = TEXT_MODE;
geninterrupt(BIOS_VIDEO_INT);
}
/* Return back to text mode */
_AX = TEXT_MODE;
geninterrupt(BIOS_VIDEO_INT);
}
```
#### Looking at EVGALine {#Heading7}