[2nd] Add cluster count API

This is a preparation of the inter character justification

This is a 2nd attempt. The previous attempt was reverted due to
SystemUIGoogleRoboRNGTests failure which assumes the JNI signature has
not been changed. The proper fix is update the Robolectric artifacts
used by SystemUIGoogleRoboRNGTest but it cannot be done in the Android
repo, so add a workaround of calling JNI of old signature on Robolectric
environment.

Bug: 283193133
Test: CtsTextTestCases
Test: minikin_tests
Test: SystemUIGoogleRoboRNGTests
Change-Id: I0eb14f432065d4fc87de4e6e8766ef561f879697
diff --git a/core/api/current.txt b/core/api/current.txt
index e0b224e..0c90f7c 100644
--- a/core/api/current.txt
+++ b/core/api/current.txt
@@ -47292,6 +47292,7 @@
     method public int getLineForOffset(int);
     method public int getLineForVertical(int);
     method public float getLineLeft(int);
+    method @FlaggedApi("com.android.text.flags.inter_character_justification") @IntRange(from=0) public int getLineLetterSpacingUnitCount(@IntRange(from=0) int, boolean);
     method public float getLineMax(int);
     method public float getLineRight(int);
     method @FlaggedApi("com.android.text.flags.use_bounds_for_width") public final float getLineSpacingAmount();
diff --git a/core/java/android/text/BoringLayout.java b/core/java/android/text/BoringLayout.java
index 4c81888..a6d3bb4 100644
--- a/core/java/android/text/BoringLayout.java
+++ b/core/java/android/text/BoringLayout.java
@@ -454,7 +454,7 @@
             line.set(paint, source, 0, source.length(), Layout.DIR_LEFT_TO_RIGHT,
                     Layout.DIRS_ALL_LEFT_TO_RIGHT, false, null,
                     mEllipsizedStart, mEllipsizedStart + mEllipsizedCount, useFallbackLineSpacing);
-            mMax = (int) Math.ceil(line.metrics(null, null, false));
+            mMax = (int) Math.ceil(line.metrics(null, null, false, null));
             TextLine.recycle(line);
         }
 
@@ -603,7 +603,7 @@
                 0 /* ellipsisStart, 0 since text has not been ellipsized at this point */,
                 0 /* ellipsisEnd, 0 since text has not been ellipsized at this point */,
                 useFallbackLineSpacing);
-        fm.width = (int) Math.ceil(line.metrics(fm, fm.mDrawingBounds, false));
+        fm.width = (int) Math.ceil(line.metrics(fm, fm.mDrawingBounds, false, null));
         TextLine.recycle(line);
 
         return fm;
diff --git a/core/java/android/text/Layout.java b/core/java/android/text/Layout.java
index c9906cc..eca848a 100644
--- a/core/java/android/text/Layout.java
+++ b/core/java/android/text/Layout.java
@@ -18,6 +18,7 @@
 
 import static com.android.text.flags.Flags.FLAG_FIX_LINE_HEIGHT_FOR_LOCALE;
 import static com.android.text.flags.Flags.FLAG_USE_BOUNDS_FOR_WIDTH;
+import static com.android.text.flags.Flags.FLAG_INTER_CHARACTER_JUSTIFICATION;
 
 import android.annotation.FlaggedApi;
 import android.annotation.FloatRange;
@@ -50,8 +51,10 @@
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.text.BreakIterator;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * A base class that manages text layout in visual elements on
@@ -669,7 +672,8 @@
             int start = previousLineEnd;
             previousLineEnd = getLineStart(lineNum + 1);
             final boolean justify = isJustificationRequired(lineNum);
-            int end = getLineVisibleEnd(lineNum, start, previousLineEnd);
+            int end = getLineVisibleEnd(lineNum, start, previousLineEnd,
+                    true /* trailingSpaceAtLastLineIsVisible */);
             paint.setStartHyphenEdit(getStartHyphenEdit(lineNum));
             paint.setEndHyphenEdit(getEndHyphenEdit(lineNum));
 
@@ -1056,7 +1060,7 @@
             if (isJustificationRequired(line)) {
                 tl.justify(getJustifyWidth(line));
             }
-            tl.metrics(null, rectF, false);
+            tl.metrics(null, rectF, false, null);
 
             float lineLeft = rectF.left;
             float lineRight = rectF.right;
@@ -1456,7 +1460,7 @@
         tl.set(mPaint, mText, start, end, dir, directions, hasTab, tabStops,
                 getEllipsisStart(line), getEllipsisStart(line) + getEllipsisCount(line),
                 isFallbackLineSpacingEnabled());
-        float wid = tl.measure(offset - start, trailing, null, null);
+        float wid = tl.measure(offset - start, trailing, null, null, null);
         TextLine.recycle(tl);
 
         if (clamped && wid > mWidth) {
@@ -1792,12 +1796,69 @@
         if (isJustificationRequired(line)) {
             tl.justify(getJustifyWidth(line));
         }
-        final float width = tl.metrics(null, null, mUseBoundsForWidth);
+        final float width = tl.metrics(null, null, mUseBoundsForWidth, null);
         TextLine.recycle(tl);
         return width;
     }
 
     /**
+     * Returns the number of letter spacing unit in the line.
+     *
+     * <p>
+     * This API returns a number of letters that is a target of letter spacing. The letter spacing
+     * won't be added to the middle of the characters that are needed to be treated as a single,
+     * e.g., ligatured or conjunct form. Note that this value is different from the number of]
+     * grapheme clusters that is calculated by {@link BreakIterator#getCharacterInstance(Locale)}.
+     * For example, if the "fi" is ligatured, the ligatured form is treated as single uni and letter
+     * spacing is not added, but it has two separate grapheme cluster.
+     *
+     * <p>
+     * This value is used for calculating the letter spacing amount for the justification because
+     * the letter spacing is applied between clusters. For example, if extra {@code W} pixels needed
+     * to be filled by letter spacing, the amount of letter spacing to be applied is
+     * {@code W}/(letter spacing unit count - 1) px.
+     *
+     * @param line the index of the line
+     * @param includeTrailingWhitespace whether to include trailing whitespace
+     * @return the number of cluster count in the line.
+     */
+    @IntRange(from = 0)
+    @FlaggedApi(FLAG_INTER_CHARACTER_JUSTIFICATION)
+    public int getLineLetterSpacingUnitCount(@IntRange(from = 0) int line,
+            boolean includeTrailingWhitespace) {
+        final int start = getLineStart(line);
+        final int end = includeTrailingWhitespace ? getLineEnd(line)
+                : getLineVisibleEnd(line, getLineStart(line), getLineStart(line + 1),
+                        false  // trailingSpaceAtLastLineIsVisible: Treating trailing whitespaces at
+                               // the last line as a invisible chars for single line justification.
+                );
+
+        final Directions directions = getLineDirections(line);
+        // Returned directions can actually be null
+        if (directions == null) {
+            return 0;
+        }
+        final int dir = getParagraphDirection(line);
+
+        final TextLine tl = TextLine.obtain();
+        final TextPaint paint = mWorkPaint;
+        paint.set(mPaint);
+        paint.setStartHyphenEdit(getStartHyphenEdit(line));
+        paint.setEndHyphenEdit(getEndHyphenEdit(line));
+        tl.set(paint, mText, start, end, dir, directions,
+                false, null, // tab width is not used for cluster counting.
+                getEllipsisStart(line), getEllipsisStart(line) + getEllipsisCount(line),
+                isFallbackLineSpacingEnabled());
+        if (mLineInfo == null) {
+            mLineInfo = new TextLine.LineInfo();
+        }
+        mLineInfo.setClusterCount(0);
+        tl.metrics(null, null, mUseBoundsForWidth, mLineInfo);
+        TextLine.recycle(tl);
+        return mLineInfo.getClusterCount();
+    }
+
+    /**
      * Returns the signed horizontal extent of the specified line, excluding
      * leading margin.  If full is false, excludes trailing whitespace.
      * @param line the index of the line
@@ -1823,7 +1884,7 @@
         if (isJustificationRequired(line)) {
             tl.justify(getJustifyWidth(line));
         }
-        final float width = tl.metrics(null, null, mUseBoundsForWidth);
+        final float width = tl.metrics(null, null, mUseBoundsForWidth, null);
         TextLine.recycle(tl);
         return width;
     }
@@ -2432,14 +2493,21 @@
      * is not counted) on the specified line.
      */
     public int getLineVisibleEnd(int line) {
-        return getLineVisibleEnd(line, getLineStart(line), getLineStart(line+1));
+        return getLineVisibleEnd(line, getLineStart(line), getLineStart(line + 1),
+                true /* trailingSpaceAtLastLineIsVisible */);
     }
 
-    private int getLineVisibleEnd(int line, int start, int end) {
+    private int getLineVisibleEnd(int line, int start, int end,
+            boolean trailingSpaceAtLastLineIsVisible) {
         CharSequence text = mText;
         char ch;
-        if (line == getLineCount() - 1) {
-            return end;
+
+        // Historically, trailing spaces at the last line is counted as visible. However, this
+        // doesn't work well for justification.
+        if (trailingSpaceAtLastLineIsVisible) {
+            if (line == getLineCount() - 1) {
+                return end;
+            }
         }
 
         for (; end > start; end--) {
@@ -2939,7 +3007,7 @@
             tl.set(paint, text, start, end, dir, directions, hasTabs, tabStops,
                     0 /* ellipsisStart */, 0 /* ellipsisEnd */,
                     false /* use fallback line spacing. unused */);
-            return margin + Math.abs(tl.metrics(null, null, useBoundsForWidth));
+            return margin + Math.abs(tl.metrics(null, null, useBoundsForWidth, null));
         } finally {
             TextLine.recycle(tl);
             if (mt != null) {
@@ -3337,6 +3405,8 @@
     private boolean mUseBoundsForWidth;
     private @Nullable Paint.FontMetrics mMinimumFontMetrics;
 
+    private TextLine.LineInfo mLineInfo = null;
+
     /** @hide */
     @IntDef(prefix = { "DIR_" }, value = {
             DIR_LEFT_TO_RIGHT,
diff --git a/core/java/android/text/TextLine.java b/core/java/android/text/TextLine.java
index f9abec0..135935c 100644
--- a/core/java/android/text/TextLine.java
+++ b/core/java/android/text/TextLine.java
@@ -76,6 +76,21 @@
     private RectF mTmpRectForPaintAPI;
     private Rect mTmpRectForPrecompute;
 
+    // Recycling object for Paint APIs. Do not use outside getRunAdvances method.
+    private Paint.RunInfo mRunInfo;
+
+    public static final class LineInfo {
+        private int mClusterCount;
+
+        public int getClusterCount() {
+            return mClusterCount;
+        }
+
+        public void setClusterCount(int clusterCount) {
+            mClusterCount = clusterCount;
+        }
+    };
+
     private boolean mUseFallbackExtent = false;
 
     // The start and end of a potentially existing ellipsis on this text line.
@@ -270,7 +285,7 @@
             // width.
             return;
         }
-        final float width = Math.abs(measure(end, false, null, null));
+        final float width = Math.abs(measure(end, false, null, null, null));
         mAddedWidthForJustify = (justifyWidth - width) / spaces;
         mIsJustifying = true;
     }
@@ -315,10 +330,12 @@
      * @param drawBounds output parameter for drawing bounding box. optional.
      * @param returnDrawWidth true for returning width of the bounding box, false for returning
      *                       total advances.
+     * @param lineInfo an optional output parameter for filling line information.
      * @return the signed width of the line
      */
     @VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)
-    public float metrics(FontMetricsInt fmi, @Nullable RectF drawBounds, boolean returnDrawWidth) {
+    public float metrics(FontMetricsInt fmi, @Nullable RectF drawBounds, boolean returnDrawWidth,
+            @Nullable LineInfo lineInfo) {
         if (returnDrawWidth) {
             if (drawBounds == null) {
                 if (mTmpRectForMeasure == null) {
@@ -327,7 +344,7 @@
                 drawBounds = mTmpRectForMeasure;
             }
             drawBounds.setEmpty();
-            float w = measure(mLen, false, fmi, drawBounds);
+            float w = measure(mLen, false, fmi, drawBounds, lineInfo);
             float boundsWidth = drawBounds.width();
             if (Math.abs(w) > boundsWidth) {
                 return w;
@@ -337,7 +354,7 @@
                 return Math.signum(w) * boundsWidth;
             }
         } else {
-            return measure(mLen, false, fmi, drawBounds);
+            return measure(mLen, false, fmi, drawBounds, lineInfo);
         }
     }
 
@@ -407,12 +424,13 @@
      *                 the edge of the preceding run's edge. See example above.
      * @param fmi receives metrics information about the requested character, can be null
      * @param drawBounds output parameter for drawing bounding box. optional.
+     * @param lineInfo an optional output parameter for filling line information.
      * @return the signed graphical offset from the leading margin to the requested character edge.
      *         The positive value means the offset is right from the leading edge. The negative
      *         value means the offset is left from the leading edge.
      */
     public float measure(@IntRange(from = 0) int offset, boolean trailing,
-            @NonNull FontMetricsInt fmi, @Nullable RectF drawBounds) {
+            @NonNull FontMetricsInt fmi, @Nullable RectF drawBounds, @Nullable LineInfo lineInfo) {
         if (offset > mLen) {
             throw new IndexOutOfBoundsException(
                     "offset(" + offset + ") should be less than line limit(" + mLen + ")");
@@ -437,16 +455,16 @@
 
                     if (targetIsInThisSegment && sameDirection) {
                         return h + measureRun(segStart, offset, j, runIsRtl, fmi, drawBounds, null,
-                                0, h);
+                                0, h, lineInfo);
                     }
 
                     final float segmentWidth = measureRun(segStart, j, j, runIsRtl, fmi, drawBounds,
-                            null, 0, h);
+                            null, 0, h, lineInfo);
                     h += sameDirection ? segmentWidth : -segmentWidth;
 
                     if (targetIsInThisSegment) {
                         return h + measureRun(segStart, offset, j, runIsRtl, null, null,  null, 0,
-                                h);
+                                h, lineInfo);
                     }
 
                     if (j != runLimit) {  // charAt(j) == TAB_CHAR
@@ -537,7 +555,8 @@
                     final boolean sameDirection = (mDir == Layout.DIR_RIGHT_TO_LEFT) == runIsRtl;
 
                     final float segmentWidth =
-                            measureRun(segStart, j, j, runIsRtl, null, null, advances, segStart, 0);
+                            measureRun(segStart, j, j, runIsRtl, null, null, advances, segStart, 0,
+                                    null);
 
                     final float oldh = h;
                     h += sameDirection ? segmentWidth : -segmentWidth;
@@ -578,7 +597,7 @@
     }
 
     /**
-     * @see #measure(int, boolean, FontMetricsInt, RectF)
+     * @see #measure(int, boolean, FontMetricsInt, RectF, LineInfo)
      * @return The measure results for all possible offsets
      */
     @VisibleForTesting
@@ -610,7 +629,7 @@
                     final float previousSegEndHorizontal = measurement[segStart];
                     final float width =
                             measureRun(segStart, j, j, runIsRtl, fmi, null, measurement, segStart,
-                                    0);
+                                    0, null);
                     horizontal += sameDirection ? width : -width;
 
                     float currHorizontal = sameDirection ? oldHorizontal : horizontal;
@@ -675,14 +694,14 @@
             boolean needWidth) {
 
         if ((mDir == Layout.DIR_LEFT_TO_RIGHT) == runIsRtl) {
-            float w = -measureRun(start, limit, limit, runIsRtl, null, null, null, 0, 0);
+            float w = -measureRun(start, limit, limit, runIsRtl, null, null, null, 0, 0, null);
             handleRun(start, limit, limit, runIsRtl, c, null, x + w, top,
-                    y, bottom, null, null, false, null, 0);
+                    y, bottom, null, null, false, null, 0, null);
             return w;
         }
 
         return handleRun(start, limit, limit, runIsRtl, c, null, x, top,
-                y, bottom, null, null, needWidth, null, 0);
+                y, bottom, null, null, needWidth, null, 0, null);
     }
 
     /**
@@ -698,19 +717,20 @@
      * @param advances receives the advance information about the requested run, can be null.
      * @param advancesIndex the start index to fill in the advance information.
      * @param x horizontal offset of the run.
+     * @param lineInfo an optional output parameter for filling line information.
      * @return the signed width from the start of the run to the leading edge
      * of the character at offset, based on the run (not paragraph) direction
      */
     private float measureRun(int start, int offset, int limit, boolean runIsRtl,
             @Nullable FontMetricsInt fmi, @Nullable RectF drawBounds, @Nullable float[] advances,
-            int advancesIndex, float x) {
+            int advancesIndex, float x, @Nullable LineInfo lineInfo) {
         if (drawBounds != null && (mDir == Layout.DIR_LEFT_TO_RIGHT) == runIsRtl) {
-            float w = -measureRun(start, offset, limit, runIsRtl, null, null, null, 0, 0);
+            float w = -measureRun(start, offset, limit, runIsRtl, null, null, null, 0, 0, null);
             return handleRun(start, offset, limit, runIsRtl, null, null, x + w, 0, 0, 0, fmi,
-                    drawBounds, true, advances, advancesIndex);
+                    drawBounds, true, advances, advancesIndex, lineInfo);
         }
         return handleRun(start, offset, limit, runIsRtl, null, null, x, 0, 0, 0, fmi, drawBounds,
-                true, advances, advancesIndex);
+                true, advances, advancesIndex, lineInfo);
     }
 
     /**
@@ -729,14 +749,14 @@
             int limit, boolean runIsRtl, float x, boolean needWidth) {
 
         if ((mDir == Layout.DIR_LEFT_TO_RIGHT) == runIsRtl) {
-            float w = -measureRun(start, limit, limit, runIsRtl, null, null, null, 0, 0);
+            float w = -measureRun(start, limit, limit, runIsRtl, null, null, null, 0, 0, null);
             handleRun(start, limit, limit, runIsRtl, null, consumer, x + w, 0, 0, 0, null, null,
-                    false, null, 0);
+                    false, null, 0, null);
             return w;
         }
 
         return handleRun(start, limit, limit, runIsRtl, null, consumer, x, 0, 0, 0, null, null,
-                needWidth, null, 0);
+                needWidth, null, 0, null);
     }
 
 
@@ -1077,16 +1097,35 @@
 
     private float getRunAdvance(TextPaint wp, int start, int end, int contextStart, int contextEnd,
             boolean runIsRtl, int offset, @Nullable float[] advances, int advancesIndex,
-            RectF drawingBounds) {
+            RectF drawingBounds, @Nullable LineInfo lineInfo) {
+        if (lineInfo != null) {
+            if (mRunInfo == null) {
+                mRunInfo = new Paint.RunInfo();
+            }
+            mRunInfo.setClusterCount(0);
+        } else {
+            mRunInfo = null;
+        }
         if (mCharsValid) {
-            return wp.getRunCharacterAdvance(mChars, start, end, contextStart, contextEnd,
-                    runIsRtl, offset, advances, advancesIndex, drawingBounds);
+            float r = wp.getRunCharacterAdvance(mChars, start, end, contextStart, contextEnd,
+                    runIsRtl, offset, advances, advancesIndex, drawingBounds, mRunInfo);
+            if (lineInfo != null) {
+                lineInfo.setClusterCount(lineInfo.getClusterCount() + mRunInfo.getClusterCount());
+            }
+            return r;
         } else {
             final int delta = mStart;
-            if (mComputed == null || advances != null) {
-                return wp.getRunCharacterAdvance(mText, delta + start, delta + end,
+            // TODO: Add cluster information to the PrecomputedText for better performance of
+            // justification.
+            if (mComputed == null || advances != null || lineInfo != null) {
+                float r = wp.getRunCharacterAdvance(mText, delta + start, delta + end,
                         delta + contextStart, delta + contextEnd, runIsRtl,
-                        delta + offset, advances, advancesIndex, drawingBounds);
+                        delta + offset, advances, advancesIndex, drawingBounds, mRunInfo);
+                if (lineInfo != null) {
+                    lineInfo.setClusterCount(
+                            lineInfo.getClusterCount() + mRunInfo.getClusterCount());
+                }
+                return r;
             } else {
                 if (drawingBounds != null) {
                     if (mTmpRectForPrecompute == null) {
@@ -1120,6 +1159,7 @@
      * @param decorations the list of locations and paremeters for drawing decorations
      * @param advances receives the advance information about the requested run, can be null.
      * @param advancesIndex the start index to fill in the advance information.
+     * @param lineInfo an optional output parameter for filling line information.
      * @return the signed width of the run based on the run direction; only
      * valid if needWidth is true
      */
@@ -1128,7 +1168,7 @@
             Canvas c, TextShaper.GlyphsConsumer consumer, float x, int top, int y, int bottom,
             FontMetricsInt fmi, RectF drawBounds, boolean needWidth, int offset,
             @Nullable ArrayList<DecorationInfo> decorations,
-            @Nullable float[] advances, int advancesIndex) {
+            @Nullable float[] advances, int advancesIndex, @Nullable LineInfo lineInfo) {
 
         if (mIsJustifying) {
             wp.setWordSpacing(mAddedWidthForJustify);
@@ -1155,7 +1195,8 @@
                 mTmpRectForPaintAPI = new RectF();
             }
             totalWidth = getRunAdvance(wp, start, end, contextStart, contextEnd, runIsRtl, offset,
-                    advances, advancesIndex, drawBounds == null ? null : mTmpRectForPaintAPI);
+                    advances, advancesIndex, drawBounds == null ? null : mTmpRectForPaintAPI,
+                    lineInfo);
             if (drawBounds != null) {
                 if (runIsRtl) {
                     mTmpRectForPaintAPI.offset(x - totalWidth, 0);
@@ -1206,9 +1247,9 @@
                     final int decorationStart = Math.max(info.start, start);
                     final int decorationEnd = Math.min(info.end, offset);
                     float decorationStartAdvance = getRunAdvance(wp, start, end, contextStart,
-                            contextEnd, runIsRtl, decorationStart, null, 0, null);
+                            contextEnd, runIsRtl, decorationStart, null, 0, null, null);
                     float decorationEndAdvance = getRunAdvance(wp, start, end, contextStart,
-                            contextEnd, runIsRtl, decorationEnd, null, 0, null);
+                            contextEnd, runIsRtl, decorationEnd, null, 0, null, null);
                     final float decorationXLeft, decorationXRight;
                     if (runIsRtl) {
                         decorationXLeft = rightX - decorationEndAdvance;
@@ -1377,6 +1418,7 @@
      * @param needWidth true if the width is required
      * @param advances receives the advance information about the requested run, can be null.
      * @param advancesIndex the start index to fill in the advance information.
+     * @param lineInfo an optional output parameter for filling line information.
      * @return the signed width of the run based on the run direction; only
      * valid if needWidth is true
      */
@@ -1384,7 +1426,7 @@
             int limit, boolean runIsRtl, Canvas c,
             TextShaper.GlyphsConsumer consumer, float x, int top, int y,
             int bottom, FontMetricsInt fmi, RectF drawBounds, boolean needWidth,
-            @Nullable float[] advances, int advancesIndex) {
+            @Nullable float[] advances, int advancesIndex, @Nullable LineInfo lineInfo) {
 
         if (measureLimit < start || measureLimit > limit) {
             throw new IndexOutOfBoundsException("measureLimit (" + measureLimit + ") is out of "
@@ -1431,7 +1473,7 @@
             wp.setEndHyphenEdit(adjustEndHyphenEdit(limit, wp.getEndHyphenEdit()));
             return handleText(wp, start, limit, start, limit, runIsRtl, c, consumer, x, top,
                     y, bottom, fmi, drawBounds, needWidth, measureLimit, null, advances,
-                    advancesIndex);
+                    advancesIndex, lineInfo);
         }
 
         // Shaping needs to take into account context up to metric boundaries,
@@ -1523,7 +1565,7 @@
                             consumer, x, top, y, bottom, fmi, drawBounds,
                             needWidth || activeEnd < measureLimit,
                             Math.min(activeEnd, mlimit), mDecorations,
-                            advances, advancesIndex + activeStart - start);
+                            advances, advancesIndex + activeStart - start, lineInfo);
 
                     activeStart = j;
                     activePaint.set(wp);
@@ -1551,7 +1593,7 @@
             x += handleText(activePaint, activeStart, activeEnd, i, inext, runIsRtl, c, consumer, x,
                     top, y, bottom, fmi, drawBounds, needWidth || activeEnd < measureLimit,
                     Math.min(activeEnd, mlimit), mDecorations,
-                    advances, advancesIndex + activeStart - start);
+                    advances, advancesIndex + activeStart - start, lineInfo);
         }
 
         return x - originalX;
diff --git a/core/tests/coretests/src/android/graphics/PaintTest.java b/core/tests/coretests/src/android/graphics/PaintTest.java
index bf56df1..0dec756 100644
--- a/core/tests/coretests/src/android/graphics/PaintTest.java
+++ b/core/tests/coretests/src/android/graphics/PaintTest.java
@@ -19,6 +19,7 @@
 import static org.junit.Assert.assertNotEquals;
 
 import android.test.InstrumentationTestCase;
+import android.text.TextUtils;
 
 import androidx.test.filters.SmallTest;
 
@@ -362,4 +363,44 @@
         //    = 30
         assertEquals(30.0f, p.getUnderlineThickness(), 0.5f);
     }
+
+    private int getClusterCount(Paint p, String text) {
+        Paint.RunInfo runInfo = new Paint.RunInfo();
+        p.getRunCharacterAdvance(text, 0, text.length(), 0, text.length(), false, 0, null, 0, null,
+                runInfo);
+        int ccByString = runInfo.getClusterCount();
+        runInfo.setClusterCount(0);
+        char[] buf = new char[text.length()];
+        TextUtils.getChars(text, 0, text.length(), buf, 0);
+        p.getRunCharacterAdvance(buf, 0, buf.length, 0, buf.length, false, 0, null, 0, null,
+                runInfo);
+        int ccByChars = runInfo.getClusterCount();
+        assertEquals(ccByChars, ccByString);
+        return ccByChars;
+    }
+
+    public void testCluster() {
+        final Paint p = new Paint();
+        p.setTextSize(100);
+
+        // Regular String
+        assertEquals(1, getClusterCount(p, "A"));
+        assertEquals(2, getClusterCount(p, "AB"));
+
+        // Ligature is in the same cluster
+        assertEquals(1, getClusterCount(p, "fi"));  // Ligature
+        p.setFontFeatureSettings("'liga' off");
+        assertEquals(2, getClusterCount(p, "fi"));  // Ligature is disabled
+        p.setFontFeatureSettings("");
+
+        // Combining character
+        assertEquals(1, getClusterCount(p, "\u0061\u0300"));  // A + COMBINING GRAVE ACCENT
+
+        // BiDi
+        final String rtlStr = "\u05D0\u05D1\u05D2";
+        final String ltrStr = "abc";
+        assertEquals(3, getClusterCount(p, rtlStr));
+        assertEquals(6, getClusterCount(p, rtlStr + ltrStr));
+        assertEquals(9, getClusterCount(p, ltrStr + rtlStr + ltrStr));
+    }
 }
diff --git a/core/tests/coretests/src/android/text/TextLineTest.java b/core/tests/coretests/src/android/text/TextLineTest.java
index 34842a0..a31992c 100644
--- a/core/tests/coretests/src/android/text/TextLineTest.java
+++ b/core/tests/coretests/src/android/text/TextLineTest.java
@@ -50,11 +50,11 @@
         tl.set(paint, line, 0, line.length(), Layout.DIR_LEFT_TO_RIGHT,
                 Layout.DIRS_ALL_LEFT_TO_RIGHT, false /* hasTabs */, null /* tabStops */,
                 0, 0 /* no ellipsis */, false /* useFallbackLinespace */);
-        final float originalWidth = tl.metrics(null, null, false);
+        final float originalWidth = tl.metrics(null, null, false, null);
         final float expandedWidth = 2 * originalWidth;
 
         tl.justify(expandedWidth);
-        final float newWidth = tl.metrics(null, null, false);
+        final float newWidth = tl.metrics(null, null, false, null);
         TextLine.recycle(tl);
         return Math.abs(newWidth - expandedWidth) < 0.5;
     }
@@ -128,7 +128,7 @@
     private void assertMeasurements(final TextLine tl, final int length, boolean trailing,
             final float[] expected) {
         for (int offset = 0; offset <= length; ++offset) {
-            assertEquals(expected[offset], tl.measure(offset, trailing, null, null), 0.0f);
+            assertEquals(expected[offset], tl.measure(offset, trailing, null, null, null), 0.0f);
         }
 
         final boolean[] trailings = new boolean[length + 1];
@@ -318,7 +318,7 @@
         tl.set(new TextPaint(), text, 0, text.length(), 1, Layout.DIRS_ALL_LEFT_TO_RIGHT,
                 false /* hasTabs */, null /* tabStops */, 9, 12,
                 false /* useFallbackLineSpacing */);
-        tl.measure(text.length(), false /* trailing */, null /* fmi */, null);
+        tl.measure(text.length(), false /* trailing */, null /* fmi */, null, null);
 
         assertFalse(span.mIsUsed);
     }
@@ -335,7 +335,7 @@
         tl.set(new TextPaint(), text, 0, text.length(), 1, Layout.DIRS_ALL_LEFT_TO_RIGHT,
                 false /* hasTabs */, null /* tabStops */, 9, 12,
                 false /* useFallbackLineSpacing */);
-        tl.measure(text.length(), false /* trailing */, null /* fmi */, null);
+        tl.measure(text.length(), false /* trailing */, null /* fmi */, null, null);
 
         assertTrue(span.mIsUsed);
     }
@@ -352,7 +352,7 @@
         tl.set(new TextPaint(), text, 0, text.length(), 1, Layout.DIRS_ALL_LEFT_TO_RIGHT,
                 false /* hasTabs */, null /* tabStops */, 9, 12,
                 false /* useFallbackLineSpacing */);
-        tl.measure(text.length(), false /* trailing */, null /* fmi */, null);
+        tl.measure(text.length(), false /* trailing */, null /* fmi */, null, null);
         assertTrue(span.mIsUsed);
     }
 
diff --git a/graphics/java/android/graphics/Paint.java b/graphics/java/android/graphics/Paint.java
index f10cdb8..c5a2f98 100644
--- a/graphics/java/android/graphics/Paint.java
+++ b/graphics/java/android/graphics/Paint.java
@@ -65,6 +65,8 @@
     private long mNativeShader;
     private long mNativeColorFilter;
 
+    private static boolean sIsRobolectric = Build.FINGERPRINT.equals("robolectric");
+
     // Use a Holder to allow static initialization of Paint in the boot image.
     private static class NoImagePreloadHolder {
         public static final NativeAllocationRegistry sRegistry =
@@ -2474,6 +2476,19 @@
         nGetFontMetricsInt(mNativePaint, metrics, true);
     }
 
+    /** @hide */
+    public static final class RunInfo {
+        private int mClusterCount = 0;
+
+        public int getClusterCount() {
+            return mClusterCount;
+        }
+
+        public void setClusterCount(int clusterCount) {
+            mClusterCount = clusterCount;
+        }
+    }
+
     /**
      * Return the recommend line spacing based on the current typeface and
      * text size.
@@ -3320,7 +3335,7 @@
             int contextEnd, boolean isRtl, int offset,
             @Nullable float[] advances, int advancesIndex) {
         return getRunCharacterAdvance(text, start, end, contextStart, contextEnd, isRtl, offset,
-                advances, advancesIndex, null);
+                advances, advancesIndex, null, null);
     }
 
     /**
@@ -3339,12 +3354,14 @@
      * @param advances the array that receives the computed character advances
      * @param advancesIndex the start index from which the advances array is filled
      * @param drawBounds the output parameter for the bounding box of drawing text, optional
+     * @param runInfo the output parameter for storing run information.
      * @return width measurement between start and offset
-     * @hide
+     * @hide TODO: Reorganize APIs
      */
     public float getRunCharacterAdvance(@NonNull char[] text, int start, int end, int contextStart,
             int contextEnd, boolean isRtl, int offset,
-            @Nullable float[] advances, int advancesIndex, @Nullable RectF drawBounds) {
+            @Nullable float[] advances, int advancesIndex, @Nullable RectF drawBounds,
+            @Nullable RunInfo runInfo) {
         if (text == null) {
             throw new IllegalArgumentException("text cannot be null");
         }
@@ -3370,11 +3387,19 @@
         }
 
         if (end == start) {
+            if (runInfo != null) {
+                runInfo.setClusterCount(0);
+            }
             return 0.0f;
         }
 
-        return nGetRunCharacterAdvance(mNativePaint, text, start, end, contextStart, contextEnd,
-                isRtl, offset, advances, advancesIndex, drawBounds);
+        if (sIsRobolectric) {
+            return nGetRunCharacterAdvance(mNativePaint, text, start, end,
+                    contextStart, contextEnd, isRtl, offset, advances, advancesIndex, drawBounds);
+        } else {
+            return nGetRunCharacterAdvance(mNativePaint, text, start, end, contextStart, contextEnd,
+                    isRtl, offset, advances, advancesIndex, drawBounds, runInfo);
+        }
     }
 
     /**
@@ -3402,7 +3427,7 @@
             int contextStart, int contextEnd, boolean isRtl, int offset,
             @Nullable float[] advances, int advancesIndex) {
         return getRunCharacterAdvance(text, start, end, contextStart, contextEnd, isRtl, offset,
-                advances, advancesIndex, null);
+                advances, advancesIndex, null, null);
     }
 
     /**
@@ -3418,12 +3443,14 @@
      * @param advances the array that receives the computed character advances
      * @param advancesIndex the start index from which the advances array is filled
      * @param drawBounds the output parameter for the bounding box of drawing text, optional
+     * @param runInfo an optional output parameter for filling run information.
      * @return width measurement between start and offset
-     * @hide
+     * @hide  TODO: Reorganize APIs
      */
     public float getRunCharacterAdvance(@NonNull CharSequence text, int start, int end,
             int contextStart, int contextEnd, boolean isRtl, int offset,
-            @Nullable float[] advances, int advancesIndex, @Nullable RectF drawBounds) {
+            @Nullable float[] advances, int advancesIndex, @Nullable RectF drawBounds,
+            @Nullable RunInfo runInfo) {
         if (text == null) {
             throw new IllegalArgumentException("text cannot be null");
         }
@@ -3456,7 +3483,7 @@
         TextUtils.getChars(text, contextStart, contextEnd, buf, 0);
         final float result = getRunCharacterAdvance(buf, start - contextStart, end - contextStart,
                 0, contextEnd - contextStart, isRtl, offset - contextStart,
-                advances, advancesIndex, drawBounds);
+                advances, advancesIndex, drawBounds, runInfo);
         TemporaryBuffer.recycle(buf);
         return result;
     }
@@ -3574,7 +3601,7 @@
             int contextStart, int contextEnd, boolean isRtl, int offset);
     private static native float nGetRunCharacterAdvance(long paintPtr, char[] text, int start,
             int end, int contextStart, int contextEnd, boolean isRtl, int offset, float[] advances,
-            int advancesIndex, RectF drawingBounds);
+            int advancesIndex, RectF drawingBounds, RunInfo runInfo);
     private static native int nGetOffsetForAdvance(long paintPtr, char[] text, int start, int end,
             int contextStart, int contextEnd, boolean isRtl, float advance);
     private static native void nGetFontMetricsIntForText(long paintPtr, char[] text,
@@ -3729,4 +3756,11 @@
     private static native void nSetTextSize(long paintPtr, float textSize);
     @CriticalNative
     private static native boolean nEqualsForTextMeasurement(long leftPaintPtr, long rightPaintPtr);
+
+
+    // Following Native methods are kept for old Robolectric JNI signature used by
+    // SystemUIGoogleRoboRNGTests
+    private static native float nGetRunCharacterAdvance(long paintPtr, char[] text,
+            int start, int end, int contextStart, int contextEnd, boolean isRtl, int offset,
+            float[] advances, int advancesIndex, RectF drawingBounds);
 }
diff --git a/libs/hwui/hwui/MinikinUtils.cpp b/libs/hwui/hwui/MinikinUtils.cpp
index 7552b56d..833069f 100644
--- a/libs/hwui/hwui/MinikinUtils.cpp
+++ b/libs/hwui/hwui/MinikinUtils.cpp
@@ -96,7 +96,7 @@
 float MinikinUtils::measureText(const Paint* paint, minikin::Bidi bidiFlags,
                                 const Typeface* typeface, const uint16_t* buf, size_t start,
                                 size_t count, size_t bufSize, float* advances,
-                                minikin::MinikinRect* bounds) {
+                                minikin::MinikinRect* bounds, uint32_t* clusterCount) {
     minikin::MinikinPaint minikinPaint = prepareMinikinPaint(paint, typeface);
     const minikin::U16StringPiece textBuf(buf, bufSize);
     const minikin::Range range(start, start + count);
@@ -104,7 +104,7 @@
     const minikin::EndHyphenEdit endHyphen = paint->getEndHyphenEdit();
 
     return minikin::Layout::measureText(textBuf, range, bidiFlags, minikinPaint, startHyphen,
-                                        endHyphen, advances, bounds);
+                                        endHyphen, advances, bounds, clusterCount);
 }
 
 minikin::MinikinExtent MinikinUtils::getFontExtent(const Paint* paint, minikin::Bidi bidiFlags,
diff --git a/libs/hwui/hwui/MinikinUtils.h b/libs/hwui/hwui/MinikinUtils.h
index 61bc881..f8574ee 100644
--- a/libs/hwui/hwui/MinikinUtils.h
+++ b/libs/hwui/hwui/MinikinUtils.h
@@ -53,7 +53,7 @@
 
     static float measureText(const Paint* paint, minikin::Bidi bidiFlags, const Typeface* typeface,
                              const uint16_t* buf, size_t start, size_t count, size_t bufSize,
-                             float* advances, minikin::MinikinRect* bounds);
+                             float* advances, minikin::MinikinRect* bounds, uint32_t* clusterCount);
 
     static minikin::MinikinExtent getFontExtent(const Paint* paint, minikin::Bidi bidiFlags,
                                                 const Typeface* typeface, const uint16_t* buf,
diff --git a/libs/hwui/jni/Graphics.cpp b/libs/hwui/jni/Graphics.cpp
index 7cc4866..8315c4c 100644
--- a/libs/hwui/jni/Graphics.cpp
+++ b/libs/hwui/jni/Graphics.cpp
@@ -247,6 +247,9 @@
 static jfieldID gFontMetricsInt_bottom;
 static jfieldID gFontMetricsInt_leading;
 
+static jclass gRunInfo_class;
+static jfieldID gRunInfo_clusterCount;
+
 ///////////////////////////////////////////////////////////////////////////////
 
 void GraphicsJNI::get_jrect(JNIEnv* env, jobject obj, int* L, int* T, int* R, int* B)
@@ -511,6 +514,10 @@
     return descent - ascent + leading;
 }
 
+void GraphicsJNI::set_cluster_count_to_run_info(JNIEnv* env, jobject runInfo, jint clusterCount) {
+    env->SetIntField(runInfo, gRunInfo_clusterCount, clusterCount);
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////
 
 jobject GraphicsJNI::createBitmapRegionDecoder(JNIEnv* env, BitmapRegionDecoderWrapper* bitmap) {
@@ -834,5 +841,10 @@
     gFontMetricsInt_bottom = GetFieldIDOrDie(env, gFontMetricsInt_class, "bottom", "I");
     gFontMetricsInt_leading = GetFieldIDOrDie(env, gFontMetricsInt_class, "leading", "I");
 
+    gRunInfo_class = FindClassOrDie(env, "android/graphics/Paint$RunInfo");
+    gRunInfo_class = MakeGlobalRefOrDie(env, gRunInfo_class);
+
+    gRunInfo_clusterCount = GetFieldIDOrDie(env, gRunInfo_class, "mClusterCount", "I");
+
     return 0;
 }
diff --git a/libs/hwui/jni/GraphicsJNI.h b/libs/hwui/jni/GraphicsJNI.h
index b9fff36..b0a1074 100644
--- a/libs/hwui/jni/GraphicsJNI.h
+++ b/libs/hwui/jni/GraphicsJNI.h
@@ -77,6 +77,8 @@
     static SkRect* jrect_to_rect(JNIEnv*, jobject jrect, SkRect*);
     static void rect_to_jrectf(const SkRect&, JNIEnv*, jobject jrectf);
 
+    static void set_cluster_count_to_run_info(JNIEnv* env, jobject runInfo, jint clusterCount);
+
     static void set_jpoint(JNIEnv*, jobject jrect, int x, int y);
 
     static SkIPoint* jpoint_to_ipoint(JNIEnv*, jobject jpoint, SkIPoint* point);
diff --git a/libs/hwui/jni/Paint.cpp b/libs/hwui/jni/Paint.cpp
index d84b73d..58d9d8b 100644
--- a/libs/hwui/jni/Paint.cpp
+++ b/libs/hwui/jni/Paint.cpp
@@ -114,7 +114,7 @@
 
         std::unique_ptr<float[]> advancesArray(new float[count]);
         MinikinUtils::measureText(&paint, static_cast<minikin::Bidi>(bidiFlags), typeface, text, 0,
-                                  count, count, advancesArray.get(), nullptr);
+                                  count, count, advancesArray.get(), nullptr, nullptr);
 
         for (int i = 0; i < count; i++) {
             // traverse in the given direction
@@ -206,7 +206,7 @@
         }
         const float advance = MinikinUtils::measureText(
                 paint, static_cast<minikin::Bidi>(bidiFlags), typeface, text, start, count,
-                contextCount, advancesArray.get(), nullptr);
+                contextCount, advancesArray.get(), nullptr, nullptr);
         if (advances) {
             env->SetFloatArrayRegion(advances, advancesIndex, count, advancesArray.get());
         }
@@ -244,7 +244,7 @@
         minikin::Bidi bidiFlags = dir == 1 ? minikin::Bidi::FORCE_RTL : minikin::Bidi::FORCE_LTR;
         std::unique_ptr<float[]> advancesArray(new float[count]);
         MinikinUtils::measureText(paint, bidiFlags, typeface, text, start, count, start + count,
-                                  advancesArray.get(), nullptr);
+                                  advancesArray.get(), nullptr, nullptr);
         size_t result = minikin::GraphemeBreak::getTextRunCursor(advancesArray.get(), text,
                 start, count, offset, moveOpt);
         return static_cast<jint>(result);
@@ -508,7 +508,7 @@
     static jfloat doRunAdvance(JNIEnv* env, const Paint* paint, const Typeface* typeface,
                                const jchar buf[], jint start, jint count, jint bufSize,
                                jboolean isRtl, jint offset, jfloatArray advances,
-                               jint advancesIndex, SkRect* drawBounds) {
+                               jint advancesIndex, SkRect* drawBounds, uint32_t* clusterCount) {
         if (advances) {
             size_t advancesLength = env->GetArrayLength(advances);
             if ((size_t)(count + advancesIndex) > advancesLength) {
@@ -519,9 +519,9 @@
         minikin::Bidi bidiFlags = isRtl ? minikin::Bidi::FORCE_RTL : minikin::Bidi::FORCE_LTR;
         minikin::MinikinRect bounds;
         if (offset == start + count && advances == nullptr) {
-            float result =
-                    MinikinUtils::measureText(paint, bidiFlags, typeface, buf, start, count,
-                                              bufSize, nullptr, drawBounds ? &bounds : nullptr);
+            float result = MinikinUtils::measureText(paint, bidiFlags, typeface, buf, start, count,
+                                                     bufSize, nullptr,
+                                                     drawBounds ? &bounds : nullptr, clusterCount);
             if (drawBounds) {
                 copyMinikinRectToSkRect(bounds, drawBounds);
             }
@@ -529,7 +529,8 @@
         }
         std::unique_ptr<float[]> advancesArray(new float[count]);
         MinikinUtils::measureText(paint, bidiFlags, typeface, buf, start, count, bufSize,
-                                  advancesArray.get(), drawBounds ? &bounds : nullptr);
+                                  advancesArray.get(), drawBounds ? &bounds : nullptr,
+                                  clusterCount);
 
         if (drawBounds) {
             copyMinikinRectToSkRect(bounds, drawBounds);
@@ -549,7 +550,7 @@
         ScopedCharArrayRO textArray(env, text);
         jfloat result = doRunAdvance(env, paint, typeface, textArray.get() + contextStart,
                                      start - contextStart, end - start, contextEnd - contextStart,
-                                     isRtl, offset - contextStart, nullptr, 0, nullptr);
+                                     isRtl, offset - contextStart, nullptr, 0, nullptr, nullptr);
         return result;
     }
 
@@ -558,27 +559,41 @@
                                                         jint contextStart, jint contextEnd,
                                                         jboolean isRtl, jint offset,
                                                         jfloatArray advances, jint advancesIndex,
-                                                        jobject drawBounds) {
+                                                        jobject drawBounds, jobject runInfo) {
         const Paint* paint = reinterpret_cast<Paint*>(paintHandle);
         const Typeface* typeface = paint->getAndroidTypeface();
         ScopedCharArrayRO textArray(env, text);
         SkRect skDrawBounds;
+        uint32_t clusterCount = 0;
         jfloat result = doRunAdvance(env, paint, typeface, textArray.get() + contextStart,
                                      start - contextStart, end - start, contextEnd - contextStart,
                                      isRtl, offset - contextStart, advances, advancesIndex,
-                                     drawBounds ? &skDrawBounds : nullptr);
+                                     drawBounds ? &skDrawBounds : nullptr, &clusterCount);
         if (drawBounds != nullptr) {
             GraphicsJNI::rect_to_jrectf(skDrawBounds, env, drawBounds);
         }
+        if (runInfo) {
+            GraphicsJNI::set_cluster_count_to_run_info(env, runInfo, clusterCount);
+        }
         return result;
     }
 
+    // This method is kept for old Robolectric JNI signature used by SystemUIGoogleRoboRNGTests.
+    static jfloat getRunCharacterAdvance___CIIIIZI_FI_F_ForRobolectric(
+            JNIEnv* env, jclass cls, jlong paintHandle, jcharArray text, jint start, jint end,
+            jint contextStart, jint contextEnd, jboolean isRtl, jint offset, jfloatArray advances,
+            jint advancesIndex, jobject drawBounds) {
+        return getRunCharacterAdvance___CIIIIZI_FI_F(env, cls, paintHandle, text, start, end,
+                                                     contextStart, contextEnd, isRtl, offset,
+                                                     advances, advancesIndex, drawBounds, nullptr);
+    }
+
     static jint doOffsetForAdvance(const Paint* paint, const Typeface* typeface, const jchar buf[],
             jint start, jint count, jint bufSize, jboolean isRtl, jfloat advance) {
         minikin::Bidi bidiFlags = isRtl ? minikin::Bidi::FORCE_RTL : minikin::Bidi::FORCE_LTR;
         std::unique_ptr<float[]> advancesArray(new float[count]);
         MinikinUtils::measureText(paint, bidiFlags, typeface, buf, start, count, bufSize,
-                                  advancesArray.get(), nullptr);
+                                  advancesArray.get(), nullptr, nullptr);
         return minikin::getOffsetForAdvance(advancesArray.get(), buf, start, count, advance);
     }
 
@@ -1145,8 +1160,11 @@
          (void*)PaintGlue::getCharArrayBounds},
         {"nHasGlyph", "(JILjava/lang/String;)Z", (void*)PaintGlue::hasGlyph},
         {"nGetRunAdvance", "(J[CIIIIZI)F", (void*)PaintGlue::getRunAdvance___CIIIIZI_F},
-        {"nGetRunCharacterAdvance", "(J[CIIIIZI[FILandroid/graphics/RectF;)F",
+        {"nGetRunCharacterAdvance",
+         "(J[CIIIIZI[FILandroid/graphics/RectF;Landroid/graphics/Paint$RunInfo;)F",
          (void*)PaintGlue::getRunCharacterAdvance___CIIIIZI_FI_F},
+        {"nGetRunCharacterAdvance", "(J[CIIIIZI[FILandroid/graphics/RectF;)F",
+         (void*)PaintGlue::getRunCharacterAdvance___CIIIIZI_FI_F_ForRobolectric},
         {"nGetOffsetForAdvance", "(J[CIIIIZF)I", (void*)PaintGlue::getOffsetForAdvance___CIIIIZF_I},
         {"nGetFontMetricsIntForText", "(J[CIIIIZLandroid/graphics/Paint$FontMetricsInt;)V",
          (void*)PaintGlue::getFontMetricsIntForText___C},