Move MotionEvent#split implementation to native

There is already a native implementation of split in InputDispatcher.
Prevent code duplication by moving the Java impl to native. The Java
impl is not correct, because it cannot access all values like the
transforms to initialize the split event with.

Bug: 326171104
Test: atest libinput_tests
Change-Id: I4be8799724e07a322099d2fb16901fa748656cec

2 files changed, 27 insertions, 75 deletions

diff --git a/core/java/android/view/MotionEvent.java b/core/java/android/view/MotionEvent.java
index 68e8c726a209..67a397828fa0 100644
--- a/core/java/android/view/MotionEvent.java
+++ b/core/java/android/view/MotionEvent.java
@@ -1733,6 +1733,8 @@ public final class MotionEvent extends InputEvent implements Parcelable {
     private static native long nativeCopy(long destNativePtr, long sourceNativePtr,
             boolean keepHistory);
     @CriticalNative
+    private static native long nativeSplit(long destNativePtr, long sourceNativePtr, int idBits);
+    @CriticalNative
     private static native int nativeGetId(long nativePtr);
     @CriticalNative
     private static native int nativeGetDeviceId(long nativePtr);
@@ -3767,86 +3769,23 @@ public final class MotionEvent extends InputEvent implements Parcelable {
     }
 
     /**
-     * Splits a motion event such that it includes only a subset of pointer ids.
+     * Splits a motion event such that it includes only a subset of pointer IDs.
+     * @param idBits the bitset indicating all of the pointer IDs from this motion event that should
+     *               be in the new split event. idBits must be a non-empty subset of the pointer IDs
+     *               contained in this event.
      * @hide
      */
+    // TODO(b/327503168): Pass downTime as a parameter to split.
     @UnsupportedAppUsage
+    @NonNull
     public final MotionEvent split(int idBits) {
-        MotionEvent ev = obtain();
-        synchronized (gSharedTempLock) {
-            final int oldPointerCount = nativeGetPointerCount(mNativePtr);
-            ensureSharedTempPointerCapacity(oldPointerCount);
-            final PointerProperties[] pp = gSharedTempPointerProperties;
-            final PointerCoords[] pc = gSharedTempPointerCoords;
-            final int[] map = gSharedTempPointerIndexMap;
-
-            final int oldAction = nativeGetAction(mNativePtr);
-            final int oldActionMasked = oldAction & ACTION_MASK;
-            final int oldActionPointerIndex = (oldAction & ACTION_POINTER_INDEX_MASK)
-                    >> ACTION_POINTER_INDEX_SHIFT;
-            int newActionPointerIndex = -1;
-            int newPointerCount = 0;
-            for (int i = 0; i < oldPointerCount; i++) {
-                nativeGetPointerProperties(mNativePtr, i, pp[newPointerCount]);
-                final int idBit = 1 << pp[newPointerCount].id;
-                if ((idBit & idBits) != 0) {
-                    if (i == oldActionPointerIndex) {
-                        newActionPointerIndex = newPointerCount;
-                    }
-                    map[newPointerCount] = i;
-                    newPointerCount += 1;
-                }
-            }
-
-            if (newPointerCount == 0) {
-                throw new IllegalArgumentException("idBits did not match any ids in the event");
-            }
-
-            final int newAction;
-            if (oldActionMasked == ACTION_POINTER_DOWN || oldActionMasked == ACTION_POINTER_UP) {
-                if (newActionPointerIndex < 0) {
-                    // An unrelated pointer changed.
-                    newAction = ACTION_MOVE;
-                } else if (newPointerCount == 1) {
-                    // The first/last pointer went down/up.
-                    newAction = oldActionMasked == ACTION_POINTER_DOWN
-                            ? ACTION_DOWN
-                            : (getFlags() & FLAG_CANCELED) == 0 ? ACTION_UP : ACTION_CANCEL;
-                } else {
-                    // A secondary pointer went down/up.
-                    newAction = oldActionMasked
-                            | (newActionPointerIndex << ACTION_POINTER_INDEX_SHIFT);
-                }
-            } else {
-                // Simple up/down/cancel/move or other motion action.
-                newAction = oldAction;
-            }
-
-            final int historySize = nativeGetHistorySize(mNativePtr);
-            for (int h = 0; h <= historySize; h++) {
-                final int historyPos = h == historySize ? HISTORY_CURRENT : h;
-
-                for (int i = 0; i < newPointerCount; i++) {
-                    nativeGetPointerCoords(mNativePtr, map[i], historyPos, pc[i]);
-                }
-
-                final long eventTimeNanos = nativeGetEventTimeNanos(mNativePtr, historyPos);
-                if (h == 0) {
-                    ev.initialize(nativeGetDeviceId(mNativePtr), nativeGetSource(mNativePtr),
-                            nativeGetDisplayId(mNativePtr),
-                            newAction, nativeGetFlags(mNativePtr),
-                            nativeGetEdgeFlags(mNativePtr), nativeGetMetaState(mNativePtr),
-                            nativeGetButtonState(mNativePtr), nativeGetClassification(mNativePtr),
-                            nativeGetXOffset(mNativePtr), nativeGetYOffset(mNativePtr),
-                            nativeGetXPrecision(mNativePtr), nativeGetYPrecision(mNativePtr),
-                            nativeGetDownTimeNanos(mNativePtr), eventTimeNanos,
-                            newPointerCount, pp, pc);
-                } else {
-                    nativeAddBatch(ev.mNativePtr, eventTimeNanos, pc, 0);
-                }
-            }
-            return ev;
+        if (idBits == 0) {
+            throw new IllegalArgumentException(
+                    "idBits must contain at least one pointer from this motion event");
         }
+        MotionEvent event = obtain();
+        event.mNativePtr = nativeSplit(event.mNativePtr, this.mNativePtr, idBits);
+        return event;
     }
 
     /**
diff --git a/core/jni/android_view_MotionEvent.cpp b/core/jni/android_view_MotionEvent.cpp
index 285dee364bb0..d5928f444fbd 100644
--- a/core/jni/android_view_MotionEvent.cpp
+++ b/core/jni/android_view_MotionEvent.cpp
@@ -607,6 +607,18 @@ static jlong android_view_MotionEvent_nativeCopy(jlong destNativePtr, jlong sour
     return reinterpret_cast<jlong>(destEvent);
 }
 
+static jlong android_view_MotionEvent_nativeSplit(jlong destNativePtr, jlong sourceNativePtr,
+                                                  jint idBits) {
+    MotionEvent* destEvent = reinterpret_cast<MotionEvent*>(destNativePtr);
+    if (!destEvent) {
+        destEvent = new MotionEvent();
+    }
+    MotionEvent* sourceEvent = reinterpret_cast<MotionEvent*>(sourceNativePtr);
+    destEvent->splitFrom(*sourceEvent, static_cast<std::bitset<MAX_POINTER_ID + 1>>(idBits),
+                         InputEvent::nextId());
+    return reinterpret_cast<jlong>(destEvent);
+}
+
 static jint android_view_MotionEvent_nativeGetId(jlong nativePtr) {
     MotionEvent* event = reinterpret_cast<MotionEvent*>(nativePtr);
     return event->getId();
@@ -822,6 +834,7 @@ static const JNINativeMethod gMotionEventMethods[] = {
         // --------------- @CriticalNative ------------------
 
         {"nativeCopy", "(JJZ)J", (void*)android_view_MotionEvent_nativeCopy},
+        {"nativeSplit", "(JJI)J", (void*)android_view_MotionEvent_nativeSplit},
         {"nativeGetId", "(J)I", (void*)android_view_MotionEvent_nativeGetId},
         {"nativeGetDeviceId", "(J)I", (void*)android_view_MotionEvent_nativeGetDeviceId},
         {"nativeGetSource", "(J)I", (void*)android_view_MotionEvent_nativeGetSource},