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      1 /* libs/android_runtime/android/graphics/PathMeasure.cpp
      2 **
      3 ** Copyright 2007, 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 "jni.h"
     19 #include "GraphicsJNI.h"
     20 #include <android_runtime/AndroidRuntime.h>
     21 
     22 #include "SkPathMeasure.h"
     23 
     24 /*  We declare an explicit pair, so that we don't have to rely on the java
     25     client to be sure not to edit the path while we have an active measure
     26     object associated with it.
     27 
     28     This costs us the copy of the path, for the sake of not allowing a bad
     29     java client to randomly crash (since we can't detect the case where the
     30     native path has been modified).
     31 
     32     The C side does have this risk, but it chooses for speed over safety. If it
     33     later changes this, and is internally safe from changes to the path, then
     34     we can remove this explicit copy from our JNI code.
     35 
     36     Note that we do not have a reference on the java side to the java path.
     37     Were we to not need the native copy here, we would want to add a java
     38     reference, so that the java path would not get GD'd while the measure object
     39     was still alive.
     40 */
     41 struct PathMeasurePair {
     42     PathMeasurePair() {}
     43     PathMeasurePair(const SkPath& path, bool forceClosed)
     44         : fPath(path), fMeasure(fPath, forceClosed) {}
     45 
     46     SkPath          fPath;      // copy of the user's path
     47     SkPathMeasure   fMeasure;   // this guy points to fPath
     48 };
     49 
     50 namespace android {
     51 
     52 class SkPathMeasureGlue {
     53 public:
     54 
     55     static PathMeasurePair* create(JNIEnv* env, jobject clazz, const SkPath* path, jboolean forceClosed) {
     56         return path ? new PathMeasurePair(*path, forceClosed) : new PathMeasurePair;
     57     }
     58 
     59     static void setPath(JNIEnv* env, jobject clazz, PathMeasurePair* pair, const SkPath* path, jboolean forceClosed) {
     60         if (NULL == path) {
     61             pair->fPath.reset();
     62         } else {
     63             pair->fPath = *path;
     64         }
     65         pair->fMeasure.setPath(&pair->fPath, forceClosed);
     66     }
     67 
     68     static jfloat getLength(JNIEnv* env, jobject clazz, PathMeasurePair* pair) {
     69         return SkScalarToFloat(pair->fMeasure.getLength());
     70     }
     71 
     72     static void convertTwoElemFloatArray(JNIEnv* env, jfloatArray array, const SkScalar src[2]) {
     73         AutoJavaFloatArray autoArray(env, array, 2);
     74         jfloat* ptr = autoArray.ptr();
     75         ptr[0] = SkScalarToFloat(src[0]);
     76         ptr[1] = SkScalarToFloat(src[1]);
     77     }
     78 
     79     static jboolean getPosTan(JNIEnv* env, jobject clazz, PathMeasurePair* pair, jfloat dist, jfloatArray pos, jfloatArray tan) {
     80         SkScalar    tmpPos[2], tmpTan[2];
     81         SkScalar*   posPtr = pos ? tmpPos : NULL;
     82         SkScalar*   tanPtr = tan ? tmpTan : NULL;
     83 
     84         if (!pair->fMeasure.getPosTan(SkFloatToScalar(dist), (SkPoint*)posPtr, (SkVector*)tanPtr)) {
     85             return false;
     86         }
     87 
     88         if (pos) {
     89             convertTwoElemFloatArray(env, pos, tmpPos);
     90         }
     91         if (tan) {
     92             convertTwoElemFloatArray(env, tan, tmpTan);
     93         }
     94         return true;
     95     }
     96 
     97     static jboolean getMatrix(JNIEnv* env, jobject clazz, PathMeasurePair* pair, jfloat dist,
     98                           SkMatrix* matrix, int flags) {
     99         return pair->fMeasure.getMatrix(SkFloatToScalar(dist), matrix, (SkPathMeasure::MatrixFlags)flags);
    100     }
    101 
    102     static jboolean getSegment(JNIEnv* env, jobject clazz, PathMeasurePair* pair, jfloat startF,
    103                                jfloat stopF, SkPath* dst, jboolean startWithMoveTo) {
    104         return pair->fMeasure.getSegment(SkFloatToScalar(startF), SkFloatToScalar(stopF), dst, startWithMoveTo);
    105     }
    106 
    107     static jboolean isClosed(JNIEnv* env, jobject clazz, PathMeasurePair* pair) {
    108         return pair->fMeasure.isClosed();
    109     }
    110 
    111     static jboolean nextContour(JNIEnv* env, jobject clazz, PathMeasurePair* pair) {
    112         return pair->fMeasure.nextContour();
    113     }
    114 
    115     static void destroy(JNIEnv* env, jobject clazz, PathMeasurePair* pair) {
    116         delete pair;
    117     }
    118 };
    119 
    120 static JNINativeMethod methods[] = {
    121     {"native_create",       "(IZ)I",        (void*) SkPathMeasureGlue::create      },
    122     {"native_setPath",      "(IIZ)V",       (void*) SkPathMeasureGlue::setPath     },
    123     {"native_getLength",    "(I)F",         (void*) SkPathMeasureGlue::getLength   },
    124     {"native_getPosTan",    "(IF[F[F)Z",    (void*) SkPathMeasureGlue::getPosTan   },
    125     {"native_getMatrix",    "(IFII)Z",      (void*) SkPathMeasureGlue::getMatrix   },
    126     {"native_getSegment",   "(IFFIZ)Z",     (void*) SkPathMeasureGlue::getSegment  },
    127     {"native_isClosed",     "(I)Z",         (void*) SkPathMeasureGlue::isClosed    },
    128     {"native_nextContour",  "(I)Z",         (void*) SkPathMeasureGlue::nextContour },
    129     {"native_destroy",      "(I)V",         (void*) SkPathMeasureGlue::destroy     }
    130 };
    131 
    132 int register_android_graphics_PathMeasure(JNIEnv* env) {
    133     int result = AndroidRuntime::registerNativeMethods(env, "android/graphics/PathMeasure", methods,
    134         sizeof(methods) / sizeof(methods[0]));
    135     return result;
    136 }
    137 
    138 }
    139