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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 #if 0
     23     return v.fX * dy - v.fY * dx < 0;
     24 #else
     25     Sk64   tmp0, tmp1;
     26 
     27     tmp0.setMul(v.fX, dy);
     28     tmp1.setMul(dx, v.fY);
     29     tmp0.sub(tmp1);
     30     return tmp0.isNeg() != 0;
     31 #endif
     32 }
     33 
     34 bool SkCullPoints::sect_test(int x0, int y0, int x1, int y1) const {
     35     const SkIRect& r = fR;
     36 
     37     if ((x0 < r.fLeft    && x1 < r.fLeft) ||
     38         (x0 > r.fRight   && x1 > r.fRight) ||
     39         (y0 < r.fTop     && y1 < r.fTop) ||
     40         (y0 > r.fBottom  && y1 > r.fBottom)) {
     41         return false;
     42     }
     43 
     44     // since the crossprod test is a little expensive, check for easy-in cases first
     45     if (r.contains(x0, y0) || r.contains(x1, y1)) {
     46         return true;
     47     }
     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             return true;
     58         }
     59     }
     60     return false;   // we didn't intersect
     61 }
     62 
     63 static void toQuad(const SkIRect& r, SkIPoint quad[4]) {
     64     SkASSERT(quad);
     65 
     66     quad[0].set(r.fLeft, r.fTop);
     67     quad[1].set(r.fRight, r.fTop);
     68     quad[2].set(r.fRight, r.fBottom);
     69     quad[3].set(r.fLeft, r.fBottom);
     70 }
     71 
     72 SkCullPoints::SkCullPoints() {
     73     SkIRect    r;
     74     r.setEmpty();
     75     this->reset(r);
     76 }
     77 
     78 SkCullPoints::SkCullPoints(const SkIRect& r) {
     79     this->reset(r);
     80 }
     81 
     82 void SkCullPoints::reset(const SkIRect& r) {
     83     fR = r;
     84     toQuad(fR, fAsQuad);
     85     fPrevPt.set(0, 0);
     86     fPrevResult = kNo_Result;
     87 }
     88 
     89 void SkCullPoints::moveTo(int x, int y) {
     90     fPrevPt.set(x, y);
     91     fPrevResult = kNo_Result;   // so we trigger a movetolineto later
     92 }
     93 
     94 SkCullPoints::LineToResult SkCullPoints::lineTo(int x, int y, SkIPoint line[]) {
     95     SkASSERT(line != NULL);
     96 
     97     LineToResult result = kNo_Result;
     98     int x0 = fPrevPt.fX;
     99     int y0 = fPrevPt.fY;
    100 
    101     // need to upgrade sect_test to chop the result
    102     // and to correctly return kLineTo_Result when the result is connected
    103     // to the previous call-out
    104     if (this->sect_test(x0, y0, x, y)) {
    105         line[0].set(x0, y0);
    106         line[1].set(x, y);
    107 
    108         if (fPrevResult != kNo_Result && fPrevPt.equals(x0, y0)) {
    109             result = kLineTo_Result;
    110         } else {
    111             result = kMoveToLineTo_Result;
    112         }
    113     }
    114 
    115     fPrevPt.set(x, y);
    116     fPrevResult = result;
    117 
    118     return result;
    119 }
    120 
    121 /////////////////////////////////////////////////////////////////////////////////////////////////
    122 
    123 #include "SkPath.h"
    124 
    125 SkCullPointsPath::SkCullPointsPath()
    126     : fCP(), fPath(NULL) {
    127 }
    128 
    129 SkCullPointsPath::SkCullPointsPath(const SkIRect& r, SkPath* dst)
    130     : fCP(r), fPath(dst) {
    131 }
    132 
    133 void SkCullPointsPath::reset(const SkIRect& r, SkPath* dst) {
    134     fCP.reset(r);
    135     fPath = dst;
    136 }
    137 
    138 void SkCullPointsPath::moveTo(int x, int y) {
    139     fCP.moveTo(x, y);
    140 }
    141 
    142 void SkCullPointsPath::lineTo(int x, int y) {
    143     SkIPoint   pts[2];
    144 
    145     switch (fCP.lineTo(x, y, pts)) {
    146     case SkCullPoints::kMoveToLineTo_Result:
    147         fPath->moveTo(SkIntToScalar(pts[0].fX), SkIntToScalar(pts[0].fY));
    148         // fall through to the lineto case
    149     case SkCullPoints::kLineTo_Result:
    150         fPath->lineTo(SkIntToScalar(pts[1].fX), SkIntToScalar(pts[1].fY));
    151         break;
    152     default:
    153         break;
    154     }
    155 }
    156 
    157