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node_modules/d3-geo/src/clip/rectangle.js

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+import {abs, epsilon} from "../math.js";
+import clipBuffer from "./buffer.js";
+import clipLine from "./line.js";
+import clipRejoin from "./rejoin.js";
+import {merge} from "d3-array";
+
+var clipMax = 1e9, clipMin = -clipMax;
+
+// TODO Use d3-polygon’s polygonContains here for the ring check?
+// TODO Eliminate duplicate buffering in clipBuffer and polygon.push?
+
+export default function clipRectangle(x0, y0, x1, y1) {
+
+  function visible(x, y) {
+    return x0 <= x && x <= x1 && y0 <= y && y <= y1;
+  }
+
+  function interpolate(from, to, direction, stream) {
+    var a = 0, a1 = 0;
+    if (from == null
+        || (a = corner(from, direction)) !== (a1 = corner(to, direction))
+        || comparePoint(from, to) < 0 ^ direction > 0) {
+      do stream.point(a === 0 || a === 3 ? x0 : x1, a > 1 ? y1 : y0);
+      while ((a = (a + direction + 4) % 4) !== a1);
+    } else {
+      stream.point(to[0], to[1]);
+    }
+  }
+
+  function corner(p, direction) {
+    return abs(p[0] - x0) < epsilon ? direction > 0 ? 0 : 3
+        : abs(p[0] - x1) < epsilon ? direction > 0 ? 2 : 1
+        : abs(p[1] - y0) < epsilon ? direction > 0 ? 1 : 0
+        : direction > 0 ? 3 : 2; // abs(p[1] - y1) < epsilon
+  }
+
+  function compareIntersection(a, b) {
+    return comparePoint(a.x, b.x);
+  }
+
+  function comparePoint(a, b) {
+    var ca = corner(a, 1),
+        cb = corner(b, 1);
+    return ca !== cb ? ca - cb
+        : ca === 0 ? b[1] - a[1]
+        : ca === 1 ? a[0] - b[0]
+        : ca === 2 ? a[1] - b[1]
+        : b[0] - a[0];
+  }
+
+  return function(stream) {
+    var activeStream = stream,
+        bufferStream = clipBuffer(),
+        segments,
+        polygon,
+        ring,
+        x__, y__, v__, // first point
+        x_, y_, v_, // previous point
+        first,
+        clean;
+
+    var clipStream = {
+      point: point,
+      lineStart: lineStart,
+      lineEnd: lineEnd,
+      polygonStart: polygonStart,
+      polygonEnd: polygonEnd
+    };
+
+    function point(x, y) {
+      if (visible(x, y)) activeStream.point(x, y);
+    }
+
+    function polygonInside() {
+      var winding = 0;
+
+      for (var i = 0, n = polygon.length; i < n; ++i) {
+        for (var ring = polygon[i], j = 1, m = ring.length, point = ring[0], a0, a1, b0 = point[0], b1 = point[1]; j < m; ++j) {
+          a0 = b0, a1 = b1, point = ring[j], b0 = point[0], b1 = point[1];
+          if (a1 <= y1) { if (b1 > y1 && (b0 - a0) * (y1 - a1) > (b1 - a1) * (x0 - a0)) ++winding; }
+          else { if (b1 <= y1 && (b0 - a0) * (y1 - a1) < (b1 - a1) * (x0 - a0)) --winding; }
+        }
+      }
+
+      return winding;
+    }
+
+    // Buffer geometry within a polygon and then clip it en masse.
+    function polygonStart() {
+      activeStream = bufferStream, segments = [], polygon = [], clean = true;
+    }
+
+    function polygonEnd() {
+      var startInside = polygonInside(),
+          cleanInside = clean && startInside,
+          visible = (segments = merge(segments)).length;
+      if (cleanInside || visible) {
+        stream.polygonStart();
+        if (cleanInside) {
+          stream.lineStart();
+          interpolate(null, null, 1, stream);
+          stream.lineEnd();
+        }
+        if (visible) {
+          clipRejoin(segments, compareIntersection, startInside, interpolate, stream);
+        }
+        stream.polygonEnd();
+      }
+      activeStream = stream, segments = polygon = ring = null;
+    }
+
+    function lineStart() {
+      clipStream.point = linePoint;
+      if (polygon) polygon.push(ring = []);
+      first = true;
+      v_ = false;
+      x_ = y_ = NaN;
+    }
+
+    // TODO rather than special-case polygons, simply handle them separately.
+    // Ideally, coincident intersection points should be jittered to avoid
+    // clipping issues.
+    function lineEnd() {
+      if (segments) {
+        linePoint(x__, y__);
+        if (v__ && v_) bufferStream.rejoin();
+        segments.push(bufferStream.result());
+      }
+      clipStream.point = point;
+      if (v_) activeStream.lineEnd();
+    }
+
+    function linePoint(x, y) {
+      var v = visible(x, y);
+      if (polygon) ring.push([x, y]);
+      if (first) {
+        x__ = x, y__ = y, v__ = v;
+        first = false;
+        if (v) {
+          activeStream.lineStart();
+          activeStream.point(x, y);
+        }
+      } else {
+        if (v && v_) activeStream.point(x, y);
+        else {
+          var a = [x_ = Math.max(clipMin, Math.min(clipMax, x_)), y_ = Math.max(clipMin, Math.min(clipMax, y_))],
+              b = [x = Math.max(clipMin, Math.min(clipMax, x)), y = Math.max(clipMin, Math.min(clipMax, y))];
+          if (clipLine(a, b, x0, y0, x1, y1)) {
+            if (!v_) {
+              activeStream.lineStart();
+              activeStream.point(a[0], a[1]);
+            }
+            activeStream.point(b[0], b[1]);
+            if (!v) activeStream.lineEnd();
+            clean = false;
+          } else if (v) {
+            activeStream.lineStart();
+            activeStream.point(x, y);
+            clean = false;
+          }
+        }
+      }
+      x_ = x, y_ = y, v_ = v;
+    }
+
+    return clipStream;
+  };
+}