```/* <![CDATA[ */
function get_sym_list(){return [["Macro","xm",[["DEBUG_BEZIER_CLIP",11]]],["Function","xf",[["bezier_clip",15]]]];} /* ]]> */1/*
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7#include "CurveIntersection.h"
8#include "CurveUtilities.h"
9#include "LineParameters.h"
10
11#define DEBUG_BEZIER_CLIP 1
12
13// return false if unable to clip (e.g., unable to create implicit line)
14// caller should subdivide, or create degenerate if the values are too small
15bool bezier_clip(const Quadratic& q1, const Quadratic& q2, double& minT, double& maxT) {
16    minT = 1;
17    maxT = 0;
18    // determine normalized implicit line equation for pt[0] to pt[3]
19    //   of the form ax + by + c = 0, where a*a + b*b == 1
20
21    // find the implicit line equation parameters
22    LineParameters endLine;
24    if (!endLine.normalize()) {
25        printf("line cannot be normalized: need more code here\n");
26        SkASSERT(0);
27        return false;
28    }
29
30    double distance = endLine.controlPtDistance(q1);
31
32    // find fat line
33    double top = 0;
34    double bottom = distance / 2; // http://students.cs.byu.edu/~tom/557/text/cic.pdf (7.6)
35    if (top > bottom) {
36        SkTSwap(top, bottom);
37    }
38
39    // compute intersecting candidate distance
40    Quadratic distance2y; // points with X of (0, 1/2, 1)
42
43    int flags = 0;
44    if (approximately_lesser_or_equal(distance2y[0].y, top)) {
45        flags |= kFindTopMin;
46    } else if (approximately_greater_or_equal(distance2y[0].y, bottom)) {
47        flags |= kFindBottomMin;
48    } else {
49        minT = 0;
50    }
51
52    if (approximately_lesser_or_equal(distance2y[2].y, top)) {
53        flags |= kFindTopMax;
54    } else if (approximately_greater_or_equal(distance2y[2].y, bottom)) {
55        flags |= kFindBottomMax;
56    } else {
57        maxT = 1;
58    }
59    // Find the intersection of distance convex hull and fat line.
60    int idx = 0;
61    do {
62        int next = idx + 1;
63        if (next == 3) {
64            next = 0;
65        }
66        x_at(distance2y[idx], distance2y[next], top, bottom, flags, minT, maxT);
67        idx = next;
68    } while (idx);
69#if DEBUG_BEZIER_CLIP
70    _Rect r1, r2;
71    r1.setBounds(q1);
72    r2.setBounds(q2);
73    _Point testPt = {0.487, 0.337};
74    if (r1.contains(testPt) && r2.contains(testPt)) {
75        printf("%s q1=(%1.9g,%1.9g %1.9g,%1.9g %1.9g,%1.9g)"
76                " q2=(%1.9g,%1.9g %1.9g,%1.9g %1.9g,%1.9g) minT=%1.9g maxT=%1.9g\n",
77                __FUNCTION__, q1[0].x, q1[0].y, q1[1].x, q1[1].y, q1[2].x, q1[2].y,
78                q2[0].x, q2[0].y, q2[1].x, q2[1].y, q2[2].x, q2[2].y, minT, maxT);
79    }
80#endif
81    return minT < maxT; // returns false if distance shows no intersection
82}
83```