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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 package android.webkit;
     17 
     18 import android.graphics.PointF;
     19 
     20 /**
     21  * A quadrilateral, determined by four points, clockwise order. Typically
     22  * p1 is "top-left" and p4 is "bottom-left" following webkit's rectangle-to-
     23  * FloatQuad conversion.
     24  */
     25 class QuadF {
     26     public PointF p1;
     27     public PointF p2;
     28     public PointF p3;
     29     public PointF p4;
     30 
     31     public QuadF() {
     32         p1 = new PointF();
     33         p2 = new PointF();
     34         p3 = new PointF();
     35         p4 = new PointF();
     36     }
     37 
     38     public void offset(float dx, float dy) {
     39         p1.offset(dx, dy);
     40         p2.offset(dx, dy);
     41         p3.offset(dx, dy);
     42         p4.offset(dx, dy);
     43     }
     44 
     45     /**
     46      * Determines if the quadrilateral contains the given point. This does
     47      * not work if the quadrilateral is self-intersecting or if any inner
     48      * angle is reflex (greater than 180 degrees).
     49      */
     50     public boolean containsPoint(float x, float y) {
     51         return isPointInTriangle(x, y, p1, p2, p3) ||
     52                 isPointInTriangle(x, y, p1, p3, p4);
     53     }
     54 
     55     @Override
     56     public String toString() {
     57         StringBuilder s = new StringBuilder("QuadF(");
     58         s.append(p1.x).append(",").append(p1.y);
     59         s.append(" - ");
     60         s.append(p2.x).append(",").append(p2.y);
     61         s.append(" - ");
     62         s.append(p3.x).append(",").append(p3.y);
     63         s.append(" - ");
     64         s.append(p4.x).append(",").append(p4.y);
     65         s.append(")");
     66         return s.toString();
     67     }
     68 
     69     private static boolean isPointInTriangle(float x0, float y0,
     70             PointF r1, PointF r2, PointF r3) {
     71         // Use the barycentric technique
     72         float x13 = r1.x - r3.x;
     73         float y13 = r1.y - r3.y;
     74         float x23 = r2.x - r3.x;
     75         float y23 = r2.y - r3.y;
     76         float x03 = x0 - r3.x;
     77         float y03 = y0 - r3.y;
     78 
     79         float determinant = (y23 * x13) - (x23 * y13);
     80         float lambda1 = ((y23 * x03) - (x23 * y03))/determinant;
     81         float lambda2 = ((x13 * y03) - (y13 * x03))/determinant;
     82         float lambda3 = 1 - lambda1 - lambda2;
     83         return lambda1 >= 0.0f && lambda2 >= 0.0f && lambda3 >= 0.0f;
     84     }
     85 }
     86