/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.text;

import android.annotation.FloatRange;
import android.annotation.IntRange;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.graphics.Paint;
import android.graphics.Rect;
import android.text.AutoGrowArray.ByteArray;
import android.text.AutoGrowArray.FloatArray;
import android.text.AutoGrowArray.IntArray;
import android.text.Layout.Directions;
import android.text.style.MetricAffectingSpan;
import android.text.style.ReplacementSpan;
import android.util.Pools.SynchronizedPool;

import dalvik.annotation.optimization.CriticalNative;

import libcore.util.NativeAllocationRegistry;

import java.util.Arrays;

MeasuredParagraph provides text information for rendering purpose.
The first motivation of this class is identify the text directions and retrieving individual
character widths. However retrieving character widths is slower than identifying text directions.
Thus, this class provides several builder methods for specific purposes.
- buildForBidi:
  Compute only text directions.
- buildForMeasurement:
  Compute text direction and all character widths.
- buildForStaticLayout:
  This is bit special. StaticLayout also needs to know text direction and character widths for
  line breaking, but all things are done in native code. Similarly, text measurement is done
  in native code. So instead of storing result to Java array, this keeps the result in native
  code since there is no good reason to move the results to Java layer.
In addition to the character widths, some additional information is computed for each purposes,
e.g. whole text length for measurement or font metrics for static layout.
MeasuredParagraph is NOT a thread safe object.
@hide
/**
 * MeasuredParagraph provides text information for rendering purpose.
 *
 * The first motivation of this class is identify the text directions and retrieving individual
 * character widths. However retrieving character widths is slower than identifying text directions.
 * Thus, this class provides several builder methods for specific purposes.
 *
 * - buildForBidi:
 *   Compute only text directions.
 * - buildForMeasurement:
 *   Compute text direction and all character widths.
 * - buildForStaticLayout:
 *   This is bit special. StaticLayout also needs to know text direction and character widths for
 *   line breaking, but all things are done in native code. Similarly, text measurement is done
 *   in native code. So instead of storing result to Java array, this keeps the result in native
 *   code since there is no good reason to move the results to Java layer.
 *
 * In addition to the character widths, some additional information is computed for each purposes,
 * e.g. whole text length for measurement or font metrics for static layout.
 *
 * MeasuredParagraph is NOT a thread safe object.
 * @hide
 */
public class MeasuredParagraph {
    private static final char OBJECT_REPLACEMENT_CHARACTER = '\uFFFC';

    private static final NativeAllocationRegistry sRegistry = new NativeAllocationRegistry(
            MeasuredParagraph.class.getClassLoader(), nGetReleaseFunc(), 1024);

    private MeasuredParagraph() {}  // Use build static functions instead.

    private static final SynchronizedPool<MeasuredParagraph> sPool = new SynchronizedPool<>(1);

    private static @NonNull MeasuredParagraph obtain() { // Use build static functions instead.
        final MeasuredParagraph mt = sPool.acquire();
        return mt != null ? mt : new MeasuredParagraph();
    }

    
Recycle the MeasuredParagraph.
Do not call any methods after you call this method.
/**
     * Recycle the MeasuredParagraph.
     *
     * Do not call any methods after you call this method.
     */
    public void recycle() {
        release();
        sPool.release(this);
    }

    // The casted original text.
    //
    // This may be null if the passed text is not a Spanned.
    private @Nullable Spanned mSpanned;

    // The start offset of the target range in the original text (mSpanned);
    private @IntRange(from = 0) int mTextStart;

    // The length of the target range in the original text.
    private @IntRange(from = 0) int mTextLength;

    // The copied character buffer for measuring text.
    //
    // The length of this array is mTextLength.
    private @Nullable char[] mCopiedBuffer;

    // The whole paragraph direction.
    private @Layout.Direction int mParaDir;

    // True if the text is LTR direction and doesn't contain any bidi characters.
    private boolean mLtrWithoutBidi;

    // The bidi level for individual characters.
    //
    // This is empty if mLtrWithoutBidi is true.
    private @NonNull ByteArray mLevels = new ByteArray();

    // The whole width of the text.
    // See getWholeWidth comments.
    private @FloatRange(from = 0.0f) float mWholeWidth;

    // Individual characters' widths.
    // See getWidths comments.
    private @Nullable FloatArray mWidths = new FloatArray();

    // The span end positions.
    // See getSpanEndCache comments.
    private @Nullable IntArray mSpanEndCache = new IntArray(4);

    // The font metrics.
    // See getFontMetrics comments.
    private @Nullable IntArray mFontMetrics = new IntArray(4 * 4);

    // The native MeasuredParagraph.
    // See getNativePtr comments.
    // Do not modify these members directly. Use bindNativeObject/unbindNativeObject instead.
    private /* Maybe Zero */ long mNativePtr = 0;
    private @Nullable Runnable mNativeObjectCleaner;

    // Associate the native object to this Java object.
    private void bindNativeObject(/* Non Zero*/ long nativePtr) {
        mNativePtr = nativePtr;
        mNativeObjectCleaner = sRegistry.registerNativeAllocation(this, nativePtr);
    }

    // Decouple the native object from this Java object and release the native object.
    private void unbindNativeObject() {
        if (mNativePtr != 0) {
            mNativeObjectCleaner.run();
            mNativePtr = 0;
        }
    }

    // Following two objects are for avoiding object allocation.
    private @NonNull TextPaint mCachedPaint = new TextPaint();
    private @Nullable Paint.FontMetricsInt mCachedFm;

    
Releases internal buffers.
/**
     * Releases internal buffers.
     */
    public void release() {
        reset();
        mLevels.clearWithReleasingLargeArray();
        mWidths.clearWithReleasingLargeArray();
        mFontMetrics.clearWithReleasingLargeArray();
        mSpanEndCache.clearWithReleasingLargeArray();
    }

    
Resets the internal state for starting new text.
/**
     * Resets the internal state for starting new text.
     */
    private void reset() {
        mSpanned = null;
        mCopiedBuffer = null;
        mWholeWidth = 0;
        mLevels.clear();
        mWidths.clear();
        mFontMetrics.clear();
        mSpanEndCache.clear();
        unbindNativeObject();
    }

    
Returns the length of the paragraph.
This is always available.
/**
     * Returns the length of the paragraph.
     *
     * This is always available.
     */
    public int getTextLength() {
        return mTextLength;
    }

    
Returns the characters to be measured.
This is always available.
/**
     * Returns the characters to be measured.
     *
     * This is always available.
     */
    public @NonNull char[] getChars() {
        return mCopiedBuffer;
    }

    
Returns the paragraph direction.
This is always available.
/**
     * Returns the paragraph direction.
     *
     * This is always available.
     */
    public @Layout.Direction int getParagraphDir() {
        return mParaDir;
    }

    
Returns the directions.
This is always available.
/**
     * Returns the directions.
     *
     * This is always available.
     */
    public Directions getDirections(@IntRange(from = 0) int start,  // inclusive
                                    @IntRange(from = 0) int end) {  // exclusive
        if (mLtrWithoutBidi) {
            return Layout.DIRS_ALL_LEFT_TO_RIGHT;
        }

        final int length = end - start;
        return AndroidBidi.directions(mParaDir, mLevels.getRawArray(), start, mCopiedBuffer, start,
                length);
    }

    
Returns the whole text width.
This is available only if the MeasuredParagraph is computed with buildForMeasurement.
Returns 0 in other cases.
/**
     * Returns the whole text width.
     *
     * This is available only if the MeasuredParagraph is computed with buildForMeasurement.
     * Returns 0 in other cases.
     */
    public @FloatRange(from = 0.0f) float getWholeWidth() {
        return mWholeWidth;
    }

    
Returns the individual character's width.
This is available only if the MeasuredParagraph is computed with buildForMeasurement.
Returns empty array in other cases.
/**
     * Returns the individual character's width.
     *
     * This is available only if the MeasuredParagraph is computed with buildForMeasurement.
     * Returns empty array in other cases.
     */
    public @NonNull FloatArray getWidths() {
        return mWidths;
    }

    
Returns the MetricsAffectingSpan end indices.
If the input text is not a spanned string, this has one value that is the length of the text.
This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
Returns empty array in other cases.
/**
     * Returns the MetricsAffectingSpan end indices.
     *
     * If the input text is not a spanned string, this has one value that is the length of the text.
     *
     * This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
     * Returns empty array in other cases.
     */
    public @NonNull IntArray getSpanEndCache() {
        return mSpanEndCache;
    }

    
Returns the int array which holds FontMetrics.
This array holds the repeat of top, bottom, ascent, descent of font metrics value.
This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
Returns empty array in other cases.
/**
     * Returns the int array which holds FontMetrics.
     *
     * This array holds the repeat of top, bottom, ascent, descent of font metrics value.
     *
     * This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
     * Returns empty array in other cases.
     */
    public @NonNull IntArray getFontMetrics() {
        return mFontMetrics;
    }

    
Returns the native ptr of the MeasuredParagraph.
This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
Returns 0 in other cases.
/**
     * Returns the native ptr of the MeasuredParagraph.
     *
     * This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
     * Returns 0 in other cases.
     */
    public /* Maybe Zero */ long getNativePtr() {
        return mNativePtr;
    }

    
Returns the width of the given range.
This is not available if the MeasuredParagraph is computed with buildForBidi.
Returns 0 if the MeasuredParagraph is computed with buildForBidi.
Params:
start – the inclusive start offset of the target region in the text
end – the exclusive end offset of the target region in the text/**
     * Returns the width of the given range.
     *
     * This is not available if the MeasuredParagraph is computed with buildForBidi.
     * Returns 0 if the MeasuredParagraph is computed with buildForBidi.
     *
     * @param start the inclusive start offset of the target region in the text
     * @param end the exclusive end offset of the target region in the text
     */
    public float getWidth(int start, int end) {
        if (mNativePtr == 0) {
            // We have result in Java.
            final float[] widths = mWidths.getRawArray();
            float r = 0.0f;
            for (int i = start; i < end; ++i) {
                r += widths[i];
            }
            return r;
        } else {
            // We have result in native.
            return nGetWidth(mNativePtr, start, end);
        }
    }

    
Retrieves the bounding rectangle that encloses all of the characters, with an implied origin
at (0, 0).
This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
/**
     * Retrieves the bounding rectangle that encloses all of the characters, with an implied origin
     * at (0, 0).
     *
     * This is available only if the MeasuredParagraph is computed with buildForStaticLayout.
     */
    public void getBounds(@IntRange(from = 0) int start, @IntRange(from = 0) int end,
            @NonNull Rect bounds) {
        nGetBounds(mNativePtr, mCopiedBuffer, start, end, bounds);
    }

    
Generates new MeasuredParagraph for Bidi computation.
If recycle is null, this returns new instance. If recycle is not null, this fills computed
result to recycle and returns recycle.
Params:
text – the character sequence to be measured
start – the inclusive start offset of the target region in the text
end – the exclusive end offset of the target region in the text
textDir – the text direction
recycle – pass existing MeasuredParagraph if you want to recycle it.
Returns:
measured text/**
     * Generates new MeasuredParagraph for Bidi computation.
     *
     * If recycle is null, this returns new instance. If recycle is not null, this fills computed
     * result to recycle and returns recycle.
     *
     * @param text the character sequence to be measured
     * @param start the inclusive start offset of the target region in the text
     * @param end the exclusive end offset of the target region in the text
     * @param textDir the text direction
     * @param recycle pass existing MeasuredParagraph if you want to recycle it.
     *
     * @return measured text
     */
    public static @NonNull MeasuredParagraph buildForBidi(@NonNull CharSequence text,
                                                     @IntRange(from = 0) int start,
                                                     @IntRange(from = 0) int end,
                                                     @NonNull TextDirectionHeuristic textDir,
                                                     @Nullable MeasuredParagraph recycle) {
        final MeasuredParagraph mt = recycle == null ? obtain() : recycle;
        mt.resetAndAnalyzeBidi(text, start, end, textDir);
        return mt;
    }

    
Generates new MeasuredParagraph for measuring texts.
If recycle is null, this returns new instance. If recycle is not null, this fills computed
result to recycle and returns recycle.
Params:
paint – the paint to be used for rendering the text.
text – the character sequence to be measured
start – the inclusive start offset of the target region in the text
end – the exclusive end offset of the target region in the text
textDir – the text direction
recycle – pass existing MeasuredParagraph if you want to recycle it.
Returns:
measured text/**
     * Generates new MeasuredParagraph for measuring texts.
     *
     * If recycle is null, this returns new instance. If recycle is not null, this fills computed
     * result to recycle and returns recycle.
     *
     * @param paint the paint to be used for rendering the text.
     * @param text the character sequence to be measured
     * @param start the inclusive start offset of the target region in the text
     * @param end the exclusive end offset of the target region in the text
     * @param textDir the text direction
     * @param recycle pass existing MeasuredParagraph if you want to recycle it.
     *
     * @return measured text
     */
    public static @NonNull MeasuredParagraph buildForMeasurement(@NonNull TextPaint paint,
                                                            @NonNull CharSequence text,
                                                            @IntRange(from = 0) int start,
                                                            @IntRange(from = 0) int end,
                                                            @NonNull TextDirectionHeuristic textDir,
                                                            @Nullable MeasuredParagraph recycle) {
        final MeasuredParagraph mt = recycle == null ? obtain() : recycle;
        mt.resetAndAnalyzeBidi(text, start, end, textDir);

        mt.mWidths.resize(mt.mTextLength);
        if (mt.mTextLength == 0) {
            return mt;
        }

        if (mt.mSpanned == null) {
            // No style change by MetricsAffectingSpan. Just measure all text.
            mt.applyMetricsAffectingSpan(
                    paint, null /* spans */, start, end, 0 /* native static layout ptr */);
        } else {
            // There may be a MetricsAffectingSpan. Split into span transitions and apply styles.
            int spanEnd;
            for (int spanStart = start; spanStart < end; spanStart = spanEnd) {
                spanEnd = mt.mSpanned.nextSpanTransition(spanStart, end, MetricAffectingSpan.class);
                MetricAffectingSpan[] spans = mt.mSpanned.getSpans(spanStart, spanEnd,
                        MetricAffectingSpan.class);
                spans = TextUtils.removeEmptySpans(spans, mt.mSpanned, MetricAffectingSpan.class);
                mt.applyMetricsAffectingSpan(
                        paint, spans, spanStart, spanEnd, 0 /* native static layout ptr */);
            }
        }
        return mt;
    }

    
Generates new MeasuredParagraph for StaticLayout.
If recycle is null, this returns new instance. If recycle is not null, this fills computed
result to recycle and returns recycle.
Params:
paint – the paint to be used for rendering the text.
text – the character sequence to be measured
start – the inclusive start offset of the target region in the text
end – the exclusive end offset of the target region in the text
textDir – the text direction
recycle – pass existing MeasuredParagraph if you want to recycle it.
Returns:
measured text/**
     * Generates new MeasuredParagraph for StaticLayout.
     *
     * If recycle is null, this returns new instance. If recycle is not null, this fills computed
     * result to recycle and returns recycle.
     *
     * @param paint the paint to be used for rendering the text.
     * @param text the character sequence to be measured
     * @param start the inclusive start offset of the target region in the text
     * @param end the exclusive end offset of the target region in the text
     * @param textDir the text direction
     * @param recycle pass existing MeasuredParagraph if you want to recycle it.
     *
     * @return measured text
     */
    public static @NonNull MeasuredParagraph buildForStaticLayout(
            @NonNull TextPaint paint,
            @NonNull CharSequence text,
            @IntRange(from = 0) int start,
            @IntRange(from = 0) int end,
            @NonNull TextDirectionHeuristic textDir,
            boolean computeHyphenation,
            boolean computeLayout,
            @Nullable MeasuredParagraph recycle) {
        final MeasuredParagraph mt = recycle == null ? obtain() : recycle;
        mt.resetAndAnalyzeBidi(text, start, end, textDir);
        if (mt.mTextLength == 0) {
            // Need to build empty native measured text for StaticLayout.
            // TODO: Stop creating empty measured text for empty lines.
            long nativeBuilderPtr = nInitBuilder();
            try {
                mt.bindNativeObject(
                        nBuildNativeMeasuredParagraph(nativeBuilderPtr, mt.mCopiedBuffer,
                              computeHyphenation, computeLayout));
            } finally {
                nFreeBuilder(nativeBuilderPtr);
            }
            return mt;
        }

        long nativeBuilderPtr = nInitBuilder();
        try {
            if (mt.mSpanned == null) {
                // No style change by MetricsAffectingSpan. Just measure all text.
                mt.applyMetricsAffectingSpan(paint, null /* spans */, start, end, nativeBuilderPtr);
                mt.mSpanEndCache.append(end);
            } else {
                // There may be a MetricsAffectingSpan. Split into span transitions and apply
                // styles.
                int spanEnd;
                for (int spanStart = start; spanStart < end; spanStart = spanEnd) {
                    spanEnd = mt.mSpanned.nextSpanTransition(spanStart, end,
                                                             MetricAffectingSpan.class);
                    MetricAffectingSpan[] spans = mt.mSpanned.getSpans(spanStart, spanEnd,
                            MetricAffectingSpan.class);
                    spans = TextUtils.removeEmptySpans(spans, mt.mSpanned,
                                                       MetricAffectingSpan.class);
                    mt.applyMetricsAffectingSpan(paint, spans, spanStart, spanEnd,
                                                 nativeBuilderPtr);
                    mt.mSpanEndCache.append(spanEnd);
                }
            }
            mt.bindNativeObject(nBuildNativeMeasuredParagraph(nativeBuilderPtr, mt.mCopiedBuffer,
                      computeHyphenation, computeLayout));
        } finally {
            nFreeBuilder(nativeBuilderPtr);
        }

        return mt;
    }

    
Reset internal state and analyzes text for bidirectional runs.
Params:
text – the character sequence to be measured
start – the inclusive start offset of the target region in the text
end – the exclusive end offset of the target region in the text
textDir – the text direction/**
     * Reset internal state and analyzes text for bidirectional runs.
     *
     * @param text the character sequence to be measured
     * @param start the inclusive start offset of the target region in the text
     * @param end the exclusive end offset of the target region in the text
     * @param textDir the text direction
     */
    private void resetAndAnalyzeBidi(@NonNull CharSequence text,
                                     @IntRange(from = 0) int start,  // inclusive
                                     @IntRange(from = 0) int end,  // exclusive
                                     @NonNull TextDirectionHeuristic textDir) {
        reset();
        mSpanned = text instanceof Spanned ? (Spanned) text : null;
        mTextStart = start;
        mTextLength = end - start;

        if (mCopiedBuffer == null || mCopiedBuffer.length != mTextLength) {
            mCopiedBuffer = new char[mTextLength];
        }
        TextUtils.getChars(text, start, end, mCopiedBuffer, 0);

        // Replace characters associated with ReplacementSpan to U+FFFC.
        if (mSpanned != null) {
            ReplacementSpan[] spans = mSpanned.getSpans(start, end, ReplacementSpan.class);

            for (int i = 0; i < spans.length; i++) {
                int startInPara = mSpanned.getSpanStart(spans[i]) - start;
                int endInPara = mSpanned.getSpanEnd(spans[i]) - start;
                // The span interval may be larger and must be restricted to [start, end)
                if (startInPara < 0) startInPara = 0;
                if (endInPara > mTextLength) endInPara = mTextLength;
                Arrays.fill(mCopiedBuffer, startInPara, endInPara, OBJECT_REPLACEMENT_CHARACTER);
            }
        }

        if ((textDir == TextDirectionHeuristics.LTR
                || textDir == TextDirectionHeuristics.FIRSTSTRONG_LTR
                || textDir == TextDirectionHeuristics.ANYRTL_LTR)
                && TextUtils.doesNotNeedBidi(mCopiedBuffer, 0, mTextLength)) {
            mLevels.clear();
            mParaDir = Layout.DIR_LEFT_TO_RIGHT;
            mLtrWithoutBidi = true;
        } else {
            final int bidiRequest;
            if (textDir == TextDirectionHeuristics.LTR) {
                bidiRequest = Layout.DIR_REQUEST_LTR;
            } else if (textDir == TextDirectionHeuristics.RTL) {
                bidiRequest = Layout.DIR_REQUEST_RTL;
            } else if (textDir == TextDirectionHeuristics.FIRSTSTRONG_LTR) {
                bidiRequest = Layout.DIR_REQUEST_DEFAULT_LTR;
            } else if (textDir == TextDirectionHeuristics.FIRSTSTRONG_RTL) {
                bidiRequest = Layout.DIR_REQUEST_DEFAULT_RTL;
            } else {
                final boolean isRtl = textDir.isRtl(mCopiedBuffer, 0, mTextLength);
                bidiRequest = isRtl ? Layout.DIR_REQUEST_RTL : Layout.DIR_REQUEST_LTR;
            }
            mLevels.resize(mTextLength);
            mParaDir = AndroidBidi.bidi(bidiRequest, mCopiedBuffer, mLevels.getRawArray());
            mLtrWithoutBidi = false;
        }
    }

    private void applyReplacementRun(@NonNull ReplacementSpan replacement,
                                     @IntRange(from = 0) int start,  // inclusive, in copied buffer
                                     @IntRange(from = 0) int end,  // exclusive, in copied buffer
                                     /* Maybe Zero */ long nativeBuilderPtr) {
        // Use original text. Shouldn't matter.
        // TODO: passing uninitizlied FontMetrics to developers. Do we need to keep this for
        //       backward compatibility? or Should we initialize them for getFontMetricsInt?
        final float width = replacement.getSize(
                mCachedPaint, mSpanned, start + mTextStart, end + mTextStart, mCachedFm);
        if (nativeBuilderPtr == 0) {
            // Assigns all width to the first character. This is the same behavior as minikin.
            mWidths.set(start, width);
            if (end > start + 1) {
                Arrays.fill(mWidths.getRawArray(), start + 1, end, 0.0f);
            }
            mWholeWidth += width;
        } else {
            nAddReplacementRun(nativeBuilderPtr, mCachedPaint.getNativeInstance(), start, end,
                               width);
        }
    }

    private void applyStyleRun(@IntRange(from = 0) int start,  // inclusive, in copied buffer
                               @IntRange(from = 0) int end,  // exclusive, in copied buffer
                               /* Maybe Zero */ long nativeBuilderPtr) {

        if (mLtrWithoutBidi) {
            // If the whole text is LTR direction, just apply whole region.
            if (nativeBuilderPtr == 0) {
                mWholeWidth += mCachedPaint.getTextRunAdvances(
                        mCopiedBuffer, start, end - start, start, end - start, false /* isRtl */,
                        mWidths.getRawArray(), start);
            } else {
                nAddStyleRun(nativeBuilderPtr, mCachedPaint.getNativeInstance(), start, end,
                        false /* isRtl */);
            }
        } else {
            // If there is multiple bidi levels, split into individual bidi level and apply style.
            byte level = mLevels.get(start);
            // Note that the empty text or empty range won't reach this method.
            // Safe to search from start + 1.
            for (int levelStart = start, levelEnd = start + 1;; ++levelEnd) {
                if (levelEnd == end || mLevels.get(levelEnd) != level) {  // transition point
                    final boolean isRtl = (level & 0x1) != 0;
                    if (nativeBuilderPtr == 0) {
                        final int levelLength = levelEnd - levelStart;
                        mWholeWidth += mCachedPaint.getTextRunAdvances(
                                mCopiedBuffer, levelStart, levelLength, levelStart, levelLength,
                                isRtl, mWidths.getRawArray(), levelStart);
                    } else {
                        nAddStyleRun(nativeBuilderPtr, mCachedPaint.getNativeInstance(), levelStart,
                                levelEnd, isRtl);
                    }
                    if (levelEnd == end) {
                        break;
                    }
                    levelStart = levelEnd;
                    level = mLevels.get(levelEnd);
                }
            }
        }
    }

    private void applyMetricsAffectingSpan(
            @NonNull TextPaint paint,
            @Nullable MetricAffectingSpan[] spans,
            @IntRange(from = 0) int start,  // inclusive, in original text buffer
            @IntRange(from = 0) int end,  // exclusive, in original text buffer
            /* Maybe Zero */ long nativeBuilderPtr) {
        mCachedPaint.set(paint);
        // XXX paint should not have a baseline shift, but...
        mCachedPaint.baselineShift = 0;

        final boolean needFontMetrics = nativeBuilderPtr != 0;

        if (needFontMetrics && mCachedFm == null) {
            mCachedFm = new Paint.FontMetricsInt();
        }

        ReplacementSpan replacement = null;
        if (spans != null) {
            for (int i = 0; i < spans.length; i++) {
                MetricAffectingSpan span = spans[i];
                if (span instanceof ReplacementSpan) {
                    // The last ReplacementSpan is effective for backward compatibility reasons.
                    replacement = (ReplacementSpan) span;
                } else {
                    // TODO: No need to call updateMeasureState for ReplacementSpan as well?
                    span.updateMeasureState(mCachedPaint);
                }
            }
        }

        final int startInCopiedBuffer = start - mTextStart;
        final int endInCopiedBuffer = end - mTextStart;

        if (nativeBuilderPtr != 0) {
            mCachedPaint.getFontMetricsInt(mCachedFm);
        }

        if (replacement != null) {
            applyReplacementRun(replacement, startInCopiedBuffer, endInCopiedBuffer,
                                nativeBuilderPtr);
        } else {
            applyStyleRun(startInCopiedBuffer, endInCopiedBuffer, nativeBuilderPtr);
        }

        if (needFontMetrics) {
            if (mCachedPaint.baselineShift < 0) {
                mCachedFm.ascent += mCachedPaint.baselineShift;
                mCachedFm.top += mCachedPaint.baselineShift;
            } else {
                mCachedFm.descent += mCachedPaint.baselineShift;
                mCachedFm.bottom += mCachedPaint.baselineShift;
            }

            mFontMetrics.append(mCachedFm.top);
            mFontMetrics.append(mCachedFm.bottom);
            mFontMetrics.append(mCachedFm.ascent);
            mFontMetrics.append(mCachedFm.descent);
        }
    }

    
Returns the maximum index that the accumulated width not exceeds the width.
If forward=false is passed, returns the minimum index from the end instead.
This only works if the MeasuredParagraph is computed with buildForMeasurement.
Undefined behavior in other case.
/**
     * Returns the maximum index that the accumulated width not exceeds the width.
     *
     * If forward=false is passed, returns the minimum index from the end instead.
     *
     * This only works if the MeasuredParagraph is computed with buildForMeasurement.
     * Undefined behavior in other case.
     */
    @IntRange(from = 0) int breakText(int limit, boolean forwards, float width) {
        float[] w = mWidths.getRawArray();
        if (forwards) {
            int i = 0;
            while (i < limit) {
                width -= w[i];
                if (width < 0.0f) break;
                i++;
            }
            while (i > 0 && mCopiedBuffer[i - 1] == ' ') i--;
            return i;
        } else {
            int i = limit - 1;
            while (i >= 0) {
                width -= w[i];
                if (width < 0.0f) break;
                i--;
            }
            while (i < limit - 1 && (mCopiedBuffer[i + 1] == ' ' || w[i + 1] == 0.0f)) {
                i++;
            }
            return limit - i - 1;
        }
    }

    
Returns the length of the substring.
This only works if the MeasuredParagraph is computed with buildForMeasurement.
Undefined behavior in other case.
/**
     * Returns the length of the substring.
     *
     * This only works if the MeasuredParagraph is computed with buildForMeasurement.
     * Undefined behavior in other case.
     */
    @FloatRange(from = 0.0f) float measure(int start, int limit) {
        float width = 0;
        float[] w = mWidths.getRawArray();
        for (int i = start; i < limit; ++i) {
            width += w[i];
        }
        return width;
    }

    
This only works if the MeasuredParagraph is computed with buildForStaticLayout.
/**
     * This only works if the MeasuredParagraph is computed with buildForStaticLayout.
     */
    public @IntRange(from = 0) int getMemoryUsage() {
        return nGetMemoryUsage(mNativePtr);
    }

    private static native /* Non Zero */ long nInitBuilder();

    
Apply style to make native measured text.
Params:
nativeBuilderPtr – The native MeasuredParagraph builder pointer.
paintPtr – The native paint pointer to be applied.
start – The start offset in the copied buffer.
end – The end offset in the copied buffer.
isRtl – True if the text is RTL./**
     * Apply style to make native measured text.
     *
     * @param nativeBuilderPtr The native MeasuredParagraph builder pointer.
     * @param paintPtr The native paint pointer to be applied.
     * @param start The start offset in the copied buffer.
     * @param end The end offset in the copied buffer.
     * @param isRtl True if the text is RTL.
     */
    private static native void nAddStyleRun(/* Non Zero */ long nativeBuilderPtr,
                                            /* Non Zero */ long paintPtr,
                                            @IntRange(from = 0) int start,
                                            @IntRange(from = 0) int end,
                                            boolean isRtl);

    
Apply ReplacementRun to make native measured text.
Params:
nativeBuilderPtr – The native MeasuredParagraph builder pointer.
paintPtr – The native paint pointer to be applied.
start – The start offset in the copied buffer.
end – The end offset in the copied buffer.
width – The width of the replacement./**
     * Apply ReplacementRun to make native measured text.
     *
     * @param nativeBuilderPtr The native MeasuredParagraph builder pointer.
     * @param paintPtr The native paint pointer to be applied.
     * @param start The start offset in the copied buffer.
     * @param end The end offset in the copied buffer.
     * @param width The width of the replacement.
     */
    private static native void nAddReplacementRun(/* Non Zero */ long nativeBuilderPtr,
                                                  /* Non Zero */ long paintPtr,
                                                  @IntRange(from = 0) int start,
                                                  @IntRange(from = 0) int end,
                                                  @FloatRange(from = 0) float width);

    private static native long nBuildNativeMeasuredParagraph(/* Non Zero */ long nativeBuilderPtr,
                                                 @NonNull char[] text,
                                                 boolean computeHyphenation,
                                                 boolean computeLayout);

    private static native void nFreeBuilder(/* Non Zero */ long nativeBuilderPtr);

    @CriticalNative
    private static native float nGetWidth(/* Non Zero */ long nativePtr,
                                         @IntRange(from = 0) int start,
                                         @IntRange(from = 0) int end);

    @CriticalNative
    private static native /* Non Zero */ long nGetReleaseFunc();

    @CriticalNative
    private static native int nGetMemoryUsage(/* Non Zero */ long nativePtr);

    private static native void nGetBounds(long nativePtr, char[] buf, int start, int end,
            Rect rect);
}