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Commit c7bd2073 authored by Michael Hoisie's avatar Michael Hoisie
Browse files

Add an alternative to PathIterator.nNext for host 

PathIterator uses VMRuntime.newNonMovableArray and VMRuntime.addressOf
to create a region of memory for iterating over path segments.

However, VMRuntime.newNonMovableArray and VMRuntime.addressOf are
libcore-only and not supported on the host JVM. This causes problems
when Compose animations run on host runtimes such as LayoutLib,
Ravenwood, and Robolectric.

Add a variant method PathIterator.nNextHost that passes the float array
(not just the address) to a regular JNI method.

An alternative to this would be to convert `nNext` to a `FastNative`,
but that would slow it down on Android.

Another alternative would be to require LayoutLib/Ravenwood/Robolectric
to use some DirectByteBuffer hacks to simulate a non-movable address,
but that would require each framework to delegate/fake/shadow parts of
PathIterator. This approach solves it in one fell swoop.

Flag: NONE host-only change
Bug: 354621198
Bug: 357624564
Test: cts PathIteratorTest
Change-Id: Idfd2b6e41b499efffbbf5cbef343183981edd7b2
parent 6b09d0b0

graphics/java/android/graphics/PathIterator.java

+15 −4
Original line number Diff line number Diff line
@@ -44,6 +44,8 @@ public class PathIterator implements Iterator<PathIterator.Segment> { 
    private final Path mPath;

    private final int mPathGenerationId;

    private static final int POINT_ARRAY_SIZE = 8;

    private static final boolean IS_DALVIK = "dalvik".equalsIgnoreCase(

            System.getProperty("java.vm.name"));



    private static final NativeAllocationRegistry sRegistry =

            NativeAllocationRegistry.createMalloced(
@@ -80,9 +82,14 @@ public class PathIterator implements Iterator<PathIterator.Segment> { 
        mPath = path;

        mNativeIterator = nCreate(mPath.mNativePath);

        mPathGenerationId = mPath.getGenerationId();

        if (IS_DALVIK) {

            final VMRuntime runtime = VMRuntime.getRuntime();

            mPointsArray = (float[]) runtime.newNonMovableArray(float.class, POINT_ARRAY_SIZE);

            mPointsAddress = runtime.addressOf(mPointsArray);

        } else {

            mPointsArray = new float[POINT_ARRAY_SIZE];

            mPointsAddress = 0;

        }

        sRegistry.registerNativeAllocation(this, mNativeIterator);

    }
@@ -177,7 +184,8 @@ public class PathIterator implements Iterator<PathIterator.Segment> { 
            throw new ConcurrentModificationException(

                    "Iterator cannot be used on modified Path");

        }

        @Verb int verb = nNext(mNativeIterator, mPointsAddress);

        @Verb int verb = IS_DALVIK

            ? nNext(mNativeIterator, mPointsAddress) : nNextHost(mNativeIterator, mPointsArray);

        if (verb == VERB_DONE) {

            mDone = true;

        }
@@ -287,6 +295,9 @@ public class PathIterator implements Iterator<PathIterator.Segment> { 
    private static native long nCreate(long nativePath);

    private static native long nGetFinalizer();



    /* nNextHost should be used for host runtimes, e.g. LayoutLib */

    private static native int nNextHost(long nativeIterator, float[] points);



    // ------------------ Critical JNI ------------------------



    @CriticalNative

libs/hwui/jni/PathIterator.cpp

+14 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include "GraphicsJNI.h"

#include "SkPath.h"

#include "SkPoint.h"

#include "graphics_jni_helpers.h"



namespace android {
@@ -36,6 +37,18 @@ public: 
        return reinterpret_cast<jlong>(new SkPath::RawIter(*path));

    }



    // A variant of 'next' (below) that is compatible with the host JVM.

    static jint nextHost(JNIEnv* env, jclass clazz, jlong iteratorHandle, jfloatArray pointsArray) {

        jfloat* points = env->GetFloatArrayElements(pointsArray, 0);

#ifdef __ANDROID__

        jint result = next(iteratorHandle, reinterpret_cast<jlong>(points));

#else

        jint result = next(env, clazz, iteratorHandle, reinterpret_cast<jlong>(points));

#endif

        env->ReleaseFloatArrayElements(pointsArray, points, 0);

        return result;

    }



    // ---------------- @CriticalNative -------------------------



    static jint peek(CRITICAL_JNI_PARAMS_COMMA jlong iteratorHandle) {
@@ -72,6 +85,7 @@ static const JNINativeMethod methods[] = { 


        {"nPeek", "(J)I", (void*)SkPathIteratorGlue::peek},

        {"nNext", "(JJ)I", (void*)SkPathIteratorGlue::next},

        {"nNextHost", "(J[F)I", (void*)SkPathIteratorGlue::nextHost},

};



int register_android_graphics_PathIterator(JNIEnv* env) {