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/*
* L.PolyUtil contains utilify functions for polygons (clipping, etc.).
*/
L.PolyUtil = {};
/*
* Sutherland-Hodgeman polygon clipping algorithm.
* Used to avoid rendering parts of a polygon that are not currently visible.
*/
L.PolyUtil.clipPolygon = function(points, bounds) {
var min = bounds.min,
max = bounds.max,
clippedPoints,
edges = [1, 4, 2, 8],
i, j, k,
a, b,
len, edge, p,
lu = L.LineUtil;
for (i = 0, len = points.length; i < len; i++) {
points[i]._code = lu._getBitCode(points[i], bounds);
}
// for each edge (left, bottom, right, top)
for (k = 0; k < 4; k++) {
edge = edges[k];
clippedPoints = [];
for (i = 0, len = points.length, j = len - 1; i < len; j = i++) {
a = points[i];
b = points[j];
// if a is inside the clip window
if (!(a._code & edge)) {
// if b is outside the clip window (a->b goes out of screen)
if (b._code & edge) {
p = lu._getEdgeIntersection(b, a, edge, bounds);
p._code = lu._getBitCode(p, bounds);
clippedPoints.push(p);
}
clippedPoints.push(a);
// else if b is inside the clip window (a->b enters the screen)
} else if (!(b._code & edge)) {
p = lu._getEdgeIntersection(b, a, edge, bounds);
p._code = lu._getBitCode(p, bounds);
clippedPoints.push(p);
}
}
points = clippedPoints;
}
return points;
};
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