bool line_intersects_rect(const vector2& l_s, const vector2& l_e,
const vector2& r_s, const vector2& r_e)
{
//
// I translated this from intersectsLine in
// http://www.opensource.apple.com/source/gcc_os/
// gcc_os-1256/libjava/java/awt/geom/Rectangle2D.java
//
// Seeing as they're professionals, they might know what they're doing ;-)
//
enum { OUT_LEFT = 1, OUT_TOP = 2, OUT_RIGHT = 4, OUT_BOTTOM = 8 };
#define OUTCODE(x1, y1, x2, y2, w, h, v)\
do {\
if ((x1) < (x2)) {\
(v) |= OUT_LEFT;\
} else if ((x1) >= (x2) + (w)) {\
(v) |= OUT_RIGHT;\
}\
if ((y1) < (y2)) {\
(v) |= OUT_TOP;\
} else if ((y1) >= (y2) + (h)) {\
(v) |= OUT_BOTTOM;\
}\
} while (0)
double r_w = r_e[0] - r_s[0],
r_h = r_e[1] - r_s[1],
r_x = r_s[0],
r_y = r_s[1],
x1 = l_s[0],
y1 = l_s[1],
x2 = l_e[0],
y2 = l_e[1],
mx = r_x,
my = r_y,
mx2 = r_w,
my2 = r_h;
int o1 = 0,
o2 = 0;
OUTCODE(x1, y1, r_x, r_y, r_w, r_h, o1);
OUTCODE(x2, y2, r_x, r_y, r_w, r_h, o2);
x1 -= mx;
x2 -= mx;
y1 -= my;
y2 -= my;
// Here we handle all lines that stay entirely on one side of the
// rectangle. We also handle some lines that intersect the
// rectangle. All vertical and horizontal lines are handled here.
int x_or = o1 ^ o2;
int o_r = o1 | o2;
if ((x_or & (OUT_BOTTOM | OUT_TOP)) == 0) {
if ((o_r & (OUT_BOTTOM | OUT_TOP)) != 0) {
return false;
}
return ((o1 & (OUT_LEFT | OUT_RIGHT)) != 0
|| (o2 & (OUT_LEFT | OUT_RIGHT)) != 0);
} else if ((x_or & (OUT_LEFT | OUT_RIGHT)) == 0) {
if ((o_r & (OUT_LEFT | OUT_RIGHT)) != 0) {
return false;
}
return ((o1 & (OUT_BOTTOM | OUT_TOP)) != 0
|| (o2 & (OUT_BOTTOM | OUT_TOP)) != 0);
}
double dx = x2 - x1,
dy = y2 - y1,
t1l = - x1 / dx,
t1h = (mx2 - x1) / dx;
if (t1l >= t1h) {
return false;
}
double t2l = - y1 / dy,
t2h = (my2 - y1) / dy;
if (t2l >= t2h || t2l >= t1h || t2h < t1l) {
return false;
}
return true;
}
void DibBitmap::DrawLine(short x1, short y1, short x2, short y2, Color clr)
{
int xl = 0, yb = 0;
int xr = m_siz.cx - 1;
int yt = m_siz.cy - 1;
int adx, ady, adx2, ady2, sx, sy;
int out1, out2, type1, type2;
int ca, cb, r, diff, xs, ys, n, alt;
OUTCODE(x1, y1, out1, type1);
OUTCODE(x2, y2, out2, type2);
if (out1 & out2) return;
if ((type1 != 0 && type2 == 0) || (type1 == 2 && type2 == 1)){
SWAP(out1, out2);
SWAP(type1, type2);
SWAP(x1, x2);
SWAP(y1, y2);
}
xs = x1;
ys = y1;
sx = 1;
adx = x2 - x1;
if (adx < 0) { adx = -adx; sx = -1; }
sy = 1;
ady = y2 - y1;
if (ady < 0) { ady = -ady; sy = -1; }
adx2 = adx + adx;
ady2 = ady + ady;
if (adx >= ady) {
/*
* line is semi-horizontal
*/
r = ady2 - adx;
CLIP(x1, x2, y1, adx, adx2, ady2, xs, ys, sx, sy,
xl, LEFT, xr, RIGHT, yb, BOTTOM, yt, TOP);
diff = ady2 - adx2;
if (alt) {
for (;; xs += sx) { /* alternate Bresenham */
plot(xs, ys);
if (r >= 0 ) {
if (--n < 0) break;
r += diff;
ys += sy;
}
else r += ady2;
}
}
else{
for (;; xs += sx) { /* standard Bresenham */
plot(xs, ys);
if (--n < 0) break;
if (r >= 0 ) { r += diff; ys += sy; }
else r += ady2;
}
}
}
else {
/*
* line is semi-vertical
*/
r = adx2 - ady;
CLIP(y1, y2, x1, ady, ady2, adx2, ys, xs, sy, sx,
yb, BOTTOM, yt, TOP, xl, LEFT, xr, RIGHT);
diff = adx2 - ady2;
if (alt) {
for (;; ys += sy) { /* alternate Bresenham */
plot(xs, ys);
if (r >= 0 ) {
if (--n < 0) break;
r += diff;
xs += sx;
}
else r += adx2;
}
}
else {
for (;; ys += sy) { /* standard Bresenham */
plot(xs, ys);
if (--n < 0) break;
if (r >= 0 ) { r += diff; xs += sx; }
else r += adx2;
}
}
}
}
