83 lines
3.1 KiB
Markdown
83 lines
3.1 KiB
Markdown
Notwithstanding that it's not optimized, Listing 36.1 is reasonably
|
|
fast. If you run Listing 36.2 (a sample line-drawing program that you
|
|
can use to test-drive Listing 36.1), you may be as surprised as I was at
|
|
how quickly the screen fills with vectors, considering that Listing 36.1
|
|
is entirely in C and has some redundant divides. Or perhaps you won't be
|
|
surprised—in which case I suggest you *not* miss the next chapter.
|
|
|
|
**LISTING 36.2 L36-2.C**
|
|
|
|
/* Sample line-drawing program. Uses the optimized
|
|
line-drawing functions coded in LListing L36.1.C.
|
|
Tested with Borland C++ in the small model. */
|
|
|
|
#include <dos.h>
|
|
|
|
#define GRAPHICS_MODE 0x13
|
|
#define TEXT_MODE 0x03
|
|
#define BIOS_VIDEO_INT 0x10
|
|
#define X_MAX 320 /* working screen width */
|
|
#define Y_MAX 200 /* working screen height */
|
|
|
|
extern void LineDraw(int XStart, int YStart, int XEnd, int YEnd, int Color);
|
|
|
|
/* 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++ )
|
|
{
|
|
LineDraw(XCenter, YCenter, WorkingX, WorkingY, Color);
|
|
}
|
|
/* lines from center to right of rectangle */
|
|
WorkingX = XCenter + XLength - 1;
|
|
WorkingY = YCenter - YLength;
|
|
for ( ; WorkingY < ( YCenter + YLength ); WorkingY++ )
|
|
{
|
|
LineDraw(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-- )
|
|
{
|
|
LineDraw(XCenter, YCenter, WorkingX, WorkingY, Color);
|
|
}
|
|
/* lines from center to left of rectangle */
|
|
WorkingX = XCenter - XLength;
|
|
WorkingY = YCenter + YLength - 1;
|
|
for ( ; WorkingY >= ( YCenter - YLength ); WorkingY-- )
|
|
{
|
|
LineDraw(XCenter, YCenter, WorkingX, WorkingY, Color);
|
|
}
|
|
}
|
|
/* Sample program to draw four rectangles full of lines. */
|
|
int main()
|
|
{
|
|
union REGS regs;
|
|
|
|
/* Set graphics mode */
|
|
regs.x.ax = GRAPHICS_MODE;
|
|
int86(BIOS_VIDEO_INT, ®s, ®s);
|
|
|
|
/* 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 a key to be pressed */
|
|
getch();
|
|
|
|
/* Return back to text mode */
|
|
regs.x.ax = TEXT_MODE;
|
|
int86(BIOS_VIDEO_INT, ®s, ®s);
|
|
}
|