Extremely Fast Line Algorithm Variation D (Addition Fixed Point)

Copyright 2001-2, By Po-Han Lin
The following is the source for the Extremely Fast Line Algorithm Variation D (Addition Fixed Point).

```// Extremely Fast Line Algorithm Var D (Addition Fixed Point)
// Copyright 2001, By Po-Han Lin
// Freely useable in non-commercial applications as long as
// credits to Po-Han Lin and link to http://www.edepot.com is
// provided in source code and can been seen in compiled executable.
// Commercial applications please inquire about licensing the algorithms.
//
// Lastest version at http://www.edepot.com/phl.html

// used by myLine
void myPixel(SURFACE* surface, int x,int y) {
// PLOT x,y point on surface

}

// THE EXTREMELY FAST LINE ALGORITHM Variation D (Addition Fixed Point)
void myLine(SURFACE* surface, int x, int y, int x2, int y2) {
bool yLonger=false;
int incrementVal, endVal;
int shortLen=y2-y;
int longLen=x2-x;
if (abs(shortLen)>abs(longLen)) {
int swap=shortLen;
shortLen=longLen;
longLen=swap;
yLonger=true;
}
endVal=longLen;
if (longLen<0) {
incrementVal=-1;
longLen=-longLen;
} else incrementVal=1;
int decInc;
if (longLen==0) decInc=0;
else decInc = (shortLen << 16) / longLen;
int j=0;
if (yLonger) {
for (int i=0;i!=endVal;i+=incrementVal) {
myPixel(surface,x+(j >> 16),y+i);
j+=decInc;
}
} else {
for (int i=0;i!=endVal;i+=incrementVal) {
myPixel(surface,x+i,y+(j >> 16));
j+=decInc;
}
}

}

void mySquare(SURFACE* surface,int x, int y, int x2, int y2) {
myLine(surface,x,y,x2,y2);
myLine(surface,x2,y2,x2+(y-y2),y2+(x2-x));
myLine(surface,x,y,x+(y-y2),y+(x2-x));
myLine(surface,x+(y-y2),y+(x2-x),x2+(y-y2),y2+(x2-x));
}

void myRect(SURFACE* surface, int x, int y, int x2, int y2) {
myLine(surface,x,y,x2,y);
myLine(surface,x2,y,x2,y2);
myLine(surface,x2,y2,x,y2);
myLine(surface,x,y2,x,y);
}

```