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},