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      1 /* libs/graphics/effects/SkCullPoints.cpp
      2 **
      3 ** Copyright 2006, The Android Open Source Project
      4 **
      5 ** Licensed under the Apache License, Version 2.0 (the "License");
      6 ** you may not use this file except in compliance with the License.
      7 ** You may obtain a copy of the License at
      8 **
      9 **     http://www.apache.org/licenses/LICENSE-2.0
     10 **
     11 ** Unless required by applicable law or agreed to in writing, software
     12 ** distributed under the License is distributed on an "AS IS" BASIS,
     13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14 ** See the License for the specific language governing permissions and
     15 ** limitations under the License.
     16 */
     17 
     18 #include "SkCullPoints.h"
     19 #include "Sk64.h"
     20 
     21 static bool cross_product_is_neg(const SkIPoint& v, int dx, int dy)
     22 {
     23 #if 0
     24     return v.fX * dy - v.fY * dx < 0;
     25 #else
     26     Sk64   tmp0, tmp1;
     27 
     28     tmp0.setMul(v.fX, dy);
     29     tmp1.setMul(dx, v.fY);
     30     tmp0.sub(tmp1);
     31     return tmp0.isNeg();
     32 #endif
     33 }
     34 
     35 bool SkCullPoints::sect_test(int x0, int y0, int x1, int y1) const
     36 {
     37     const SkIRect& r = fR;
     38 
     39     if (x0 < r.fLeft    && x1 < r.fLeft ||
     40         x0 > r.fRight   && x1 > r.fRight ||
     41         y0 < r.fTop     && y1 < r.fTop ||
     42         y0 > r.fBottom  && y1 > r.fBottom)
     43         return false;
     44 
     45     // since the crossprod test is a little expensive, check for easy-in cases first
     46     if (r.contains(x0, y0) || r.contains(x1, y1))
     47         return true;
     48 
     49     // At this point we're not sure, so we do a crossprod test
     50     SkIPoint           vec;
     51     const SkIPoint*    rAsQuad = fAsQuad;
     52 
     53     vec.set(x1 - x0, y1 - y0);
     54     bool isNeg = cross_product_is_neg(vec, x0 - rAsQuad[0].fX, y0 - rAsQuad[0].fY);
     55     for (int i = 1; i < 4; i++) {
     56         if (cross_product_is_neg(vec, x0 - rAsQuad[i].fX, y0 - rAsQuad[i].fY) != isNeg)
     57         {
     58             return true;
     59         }
     60     }
     61     return false;   // we didn't intersect
     62 }
     63 
     64 static void toQuad(const SkIRect& r, SkIPoint quad[4])
     65 {
     66     SkASSERT(quad);
     67 
     68     quad[0].set(r.fLeft, r.fTop);
     69     quad[1].set(r.fRight, r.fTop);
     70     quad[2].set(r.fRight, r.fBottom);
     71     quad[3].set(r.fLeft, r.fBottom);
     72 }
     73 
     74 SkCullPoints::SkCullPoints()
     75 {
     76     SkIRect    r;
     77     r.setEmpty();
     78     this->reset(r);
     79 }
     80 
     81 SkCullPoints::SkCullPoints(const SkIRect& r)
     82 {
     83     this->reset(r);
     84 }
     85 
     86 void SkCullPoints::reset(const SkIRect& r)
     87 {
     88     fR = r;
     89     toQuad(fR, fAsQuad);
     90     fPrevPt.set(0, 0);
     91     fPrevResult = kNo_Result;
     92 }
     93 
     94 void SkCullPoints::moveTo(int x, int y)
     95 {
     96     fPrevPt.set(x, y);
     97     fPrevResult = kNo_Result;   // so we trigger a movetolineto later
     98 }
     99 
    100 SkCullPoints::LineToResult SkCullPoints::lineTo(int x, int y, SkIPoint line[])
    101 {
    102     SkASSERT(line != NULL);
    103 
    104     LineToResult result = kNo_Result;
    105     int x0 = fPrevPt.fX;
    106     int y0 = fPrevPt.fY;
    107 
    108     // need to upgrade sect_test to chop the result
    109     // and to correctly return kLineTo_Result when the result is connected
    110     // to the previous call-out
    111     if (this->sect_test(x0, y0, x, y))
    112     {
    113         line[0].set(x0, y0);
    114         line[1].set(x, y);
    115 
    116         if (fPrevResult != kNo_Result && fPrevPt.equals(x0, y0))
    117             result = kLineTo_Result;
    118         else
    119             result = kMoveToLineTo_Result;
    120     }
    121 
    122     fPrevPt.set(x, y);
    123     fPrevResult = result;
    124 
    125     return result;
    126 }
    127 
    128 /////////////////////////////////////////////////////////////////////////////////////////////////
    129 
    130 #include "SkPath.h"
    131 
    132 SkCullPointsPath::SkCullPointsPath()
    133     : fCP(), fPath(NULL)
    134 {
    135 }
    136 
    137 SkCullPointsPath::SkCullPointsPath(const SkIRect& r, SkPath* dst)
    138     : fCP(r), fPath(dst)
    139 {
    140 }
    141 
    142 void SkCullPointsPath::reset(const SkIRect& r, SkPath* dst)
    143 {
    144     fCP.reset(r);
    145     fPath = dst;
    146 }
    147 
    148 void SkCullPointsPath::moveTo(int x, int y)
    149 {
    150     fCP.moveTo(x, y);
    151 }
    152 
    153 void SkCullPointsPath::lineTo(int x, int y)
    154 {
    155     SkIPoint   pts[2];
    156 
    157     switch (fCP.lineTo(x, y, pts)) {
    158     case SkCullPoints::kMoveToLineTo_Result:
    159         fPath->moveTo(SkIntToScalar(pts[0].fX), SkIntToScalar(pts[0].fY));
    160         // fall through to the lineto case
    161     case SkCullPoints::kLineTo_Result:
    162         fPath->lineTo(SkIntToScalar(pts[1].fX), SkIntToScalar(pts[1].fY));
    163         break;
    164     default:
    165         break;
    166     }
    167 }
    168 
    169