diff --git a/core/java/android/text/Layout.java b/core/java/android/text/Layout.java
index 0bd5071..c94e489 100644
--- a/core/java/android/text/Layout.java
+++ b/core/java/android/text/Layout.java
@@ -824,6 +824,32 @@
         return TextUtils.packRangeInLong(0, getLineEnd(line));
     }
 
+    /**
+     * Checks if the trailing BiDi level should be used for an offset
+     *
+     * This method is useful when the offset is at the BiDi level transition point and determine
+     * which run need to be used. For example, let's think about following input: (L* denotes
+     * Left-to-Right characters, R* denotes Right-to-Left characters.)
+     * Input (Logical Order): L1 L2 L3 R1 R2 R3 L4 L5 L6
+     * Input (Display Order): L1 L2 L3 R3 R2 R1 L4 L5 L6
+     *
+     * Then, think about selecting the range (3, 6). The offset=3 and offset=6 are ambiguous here
+     * since they are at the BiDi transition point.  In Android, the offset is considered to be
+     * associated with the trailing run if the BiDi level of the trailing run is higher than of the
+     * previous run.  In this case, the BiDi level of the input text is as follows:
+     *
+     * Input (Logical Order): L1 L2 L3 R1 R2 R3 L4 L5 L6
+     *              BiDi Run: [ Run 0 ][ Run 1 ][ Run 2 ]
+     *            BiDi Level:  0  0  0  1  1  1  0  0  0
+     *
+     * Thus, offset = 3 is part of Run 1 and this method returns true for offset = 3, since the BiDi
+     * level of Run 1 is higher than the level of Run 0.  Similarly, the offset = 6 is a part of Run
+     * 1 and this method returns false for the offset = 6 since the BiDi level of Run 1 is higher
+     * than the level of Run 2.
+     *
+     * @returns true if offset is at the BiDi level transition point and trailing BiDi level is
+     *          higher than previous BiDi level. See above for the detail.
+     */
     private boolean primaryIsTrailingPrevious(int offset) {
         int line = getLineForOffset(offset);
         int lineStart = getLineStart(line);
@@ -874,6 +900,41 @@
     }
 
     /**
+     * Computes in linear time the results of calling
+     * #primaryIsTrailingPrevious for all offsets on a line.
+     * @param line The line giving the offsets we compute the information for
+     * @return The array of results, indexed from 0, where 0 corresponds to the line start offset
+     */
+    private boolean[] primaryIsTrailingPreviousAllLineOffsets(int line) {
+        int lineStart = getLineStart(line);
+        int lineEnd = getLineEnd(line);
+        int[] runs = getLineDirections(line).mDirections;
+
+        boolean[] trailing = new boolean[lineEnd - lineStart + 1];
+
+        byte[] level = new byte[lineEnd - lineStart + 1];
+        for (int i = 0; i < runs.length; i += 2) {
+            int start = lineStart + runs[i];
+            int limit = start + (runs[i + 1] & RUN_LENGTH_MASK);
+            if (limit > lineEnd) {
+                limit = lineEnd;
+            }
+            level[limit - lineStart - 1] =
+                    (byte) ((runs[i + 1] >>> RUN_LEVEL_SHIFT) & RUN_LEVEL_MASK);
+        }
+
+        for (int i = 0; i < runs.length; i += 2) {
+            int start = lineStart + runs[i];
+            byte currentLevel = (byte) ((runs[i + 1] >>> RUN_LEVEL_SHIFT) & RUN_LEVEL_MASK);
+            trailing[start - lineStart] = currentLevel > (start == lineStart
+                    ? (getParagraphDirection(line) == 1 ? 0 : 1)
+                    : level[start - lineStart - 1]);
+        }
+
+        return trailing;
+    }
+
+    /**
      * Get the primary horizontal position for the specified text offset.
      * This is the location where a new character would be inserted in
      * the paragraph's primary direction.
@@ -953,6 +1014,60 @@
     }
 
     /**
+     * Computes in linear time the results of calling
+     * #getHorizontal for all offsets on a line.
+     * @param line The line giving the offsets we compute information for
+     * @param clamped Whether to clamp the results to the width of the layout
+     * @param primary Whether the results should be the primary or the secondary horizontal
+     * @return The array of results, indexed from 0, where 0 corresponds to the line start offset
+     */
+    private float[] getLineHorizontals(int line, boolean clamped, boolean primary) {
+        int start = getLineStart(line);
+        int end = getLineEnd(line);
+        int dir = getParagraphDirection(line);
+        boolean hasTab = getLineContainsTab(line);
+        Directions directions = getLineDirections(line);
+
+        TabStops tabStops = null;
+        if (hasTab && mText instanceof Spanned) {
+            // Just checking this line should be good enough, tabs should be
+            // consistent across all lines in a paragraph.
+            TabStopSpan[] tabs = getParagraphSpans((Spanned) mText, start, end, TabStopSpan.class);
+            if (tabs.length > 0) {
+                tabStops = new TabStops(TAB_INCREMENT, tabs); // XXX should reuse
+            }
+        }
+
+        TextLine tl = TextLine.obtain();
+        tl.set(mPaint, mText, start, end, dir, directions, hasTab, tabStops);
+        boolean[] trailings = primaryIsTrailingPreviousAllLineOffsets(line);
+        if (!primary) {
+            for (int offset = 0; offset < trailings.length; ++offset) {
+                trailings[offset] = !trailings[offset];
+            }
+        }
+        float[] wid = tl.measureAllOffsets(trailings, null);
+        TextLine.recycle(tl);
+
+        if (clamped) {
+            for (int offset = 0; offset <= wid.length; ++offset) {
+                if (wid[offset] > mWidth) {
+                    wid[offset] = mWidth;
+                }
+            }
+        }
+        int left = getParagraphLeft(line);
+        int right = getParagraphRight(line);
+
+        int lineStartPos = getLineStartPos(line, left, right);
+        float[] horizontal = new float[end - start + 1];
+        for (int offset = 0; offset < horizontal.length; ++offset) {
+            horizontal[offset] = lineStartPos + wid[offset];
+        }
+        return horizontal;
+    }
+
+    /**
      * Get the leftmost position that should be exposed for horizontal
      * scrolling on the specified line.
      */
@@ -1167,6 +1282,8 @@
         // XXX: we don't care about tabs as we just use TextLine#getOffsetToLeftRightOf here.
         tl.set(mPaint, mText, lineStartOffset, lineEndOffset, getParagraphDirection(line), dirs,
                 false, null);
+        final HorizontalMeasurementProvider horizontal =
+                new HorizontalMeasurementProvider(line, primary);
 
         final int max;
         if (line == getLineCount() - 1) {
@@ -1176,7 +1293,7 @@
                     !isRtlCharAt(lineEndOffset - 1)) + lineStartOffset;
         }
         int best = lineStartOffset;
-        float bestdist = Math.abs(getHorizontal(best, primary) - horiz);
+        float bestdist = Math.abs(horizontal.get(lineStartOffset) - horiz);
 
         for (int i = 0; i < dirs.mDirections.length; i += 2) {
             int here = lineStartOffset + dirs.mDirections[i];
@@ -1192,7 +1309,7 @@
                 guess = (high + low) / 2;
                 int adguess = getOffsetAtStartOf(guess);
 
-                if (getHorizontal(adguess, primary) * swap >= horiz * swap)
+                if (horizontal.get(adguess) * swap >= horiz * swap)
                     high = guess;
                 else
                     low = guess;
@@ -1205,9 +1322,9 @@
                 int aft = tl.getOffsetToLeftRightOf(low - lineStartOffset, isRtl) + lineStartOffset;
                 low = tl.getOffsetToLeftRightOf(aft - lineStartOffset, !isRtl) + lineStartOffset;
                 if (low >= here && low < there) {
-                    float dist = Math.abs(getHorizontal(low, primary) - horiz);
+                    float dist = Math.abs(horizontal.get(low) - horiz);
                     if (aft < there) {
-                        float other = Math.abs(getHorizontal(aft, primary) - horiz);
+                        float other = Math.abs(horizontal.get(aft) - horiz);
 
                         if (other < dist) {
                             dist = other;
@@ -1222,7 +1339,7 @@
                 }
             }
 
-            float dist = Math.abs(getHorizontal(here, primary) - horiz);
+            float dist = Math.abs(horizontal.get(here) - horiz);
 
             if (dist < bestdist) {
                 bestdist = dist;
@@ -1230,7 +1347,7 @@
             }
         }
 
-        float dist = Math.abs(getHorizontal(max, primary) - horiz);
+        float dist = Math.abs(horizontal.get(max) - horiz);
 
         if (dist <= bestdist) {
             bestdist = dist;
@@ -1242,6 +1359,46 @@
     }
 
     /**
+     * Responds to #getHorizontal queries, by selecting the better strategy between:
+     * - calling #getHorizontal explicitly for each query
+     * - precomputing all #getHorizontal measurements, and responding to any query in constant time
+     * The first strategy is used for LTR-only text, while the second is used for all other cases.
+     * The class is currently only used in #getOffsetForHorizontal, so reuse with care in other
+     * contexts.
+     */
+    private class HorizontalMeasurementProvider {
+        private final int mLine;
+        private final boolean mPrimary;
+
+        private float[] mHorizontals;
+        private int mLineStartOffset;
+
+        HorizontalMeasurementProvider(final int line, final boolean primary) {
+            mLine = line;
+            mPrimary = primary;
+            init();
+        }
+
+        private void init() {
+            final Directions dirs = getLineDirections(mLine);
+            if (dirs == DIRS_ALL_LEFT_TO_RIGHT) {
+                return;
+            }
+
+            mHorizontals = getLineHorizontals(mLine, false, mPrimary);
+            mLineStartOffset = getLineStart(mLine);
+        }
+
+        float get(final int offset) {
+            if (mHorizontals == null) {
+                return getHorizontal(offset, mPrimary);
+            } else {
+                return mHorizontals[offset - mLineStartOffset];
+            }
+        }
+    }
+
+    /**
      * Return the text offset after the last character on the specified line.
      */
     public final int getLineEnd(int line) {
diff --git a/core/java/android/text/TextLine.java b/core/java/android/text/TextLine.java
index 2a52961..7933356 100644
--- a/core/java/android/text/TextLine.java
+++ b/core/java/android/text/TextLine.java
@@ -339,6 +339,98 @@
     }
 
     /**
+     * @see #measure(int, boolean, FontMetricsInt)
+     * @return The measure results for all possible offsets
+     */
+    float[] measureAllOffsets(boolean[] trailing, FontMetricsInt fmi) {
+        float[] measurement = new float[mLen + 1];
+
+        int[] target = new int[mLen + 1];
+        for (int offset = 0; offset < target.length; ++offset) {
+            target[offset] = trailing[offset] ? offset - 1 : offset;
+        }
+        if (target[0] < 0) {
+            measurement[0] = 0;
+        }
+
+        float h = 0;
+
+        if (!mHasTabs) {
+            if (mDirections == Layout.DIRS_ALL_LEFT_TO_RIGHT) {
+                for (int offset = 0; offset <= mLen; ++offset) {
+                    measurement[offset] = measureRun(0, offset, mLen, false, fmi);
+                }
+                return measurement;
+            }
+            if (mDirections == Layout.DIRS_ALL_RIGHT_TO_LEFT) {
+                for (int offset = 0; offset <= mLen; ++offset) {
+                    measurement[offset] = measureRun(0, offset, mLen, true, fmi);
+                }
+                return measurement;
+            }
+        }
+
+        char[] chars = mChars;
+        int[] runs = mDirections.mDirections;
+        for (int i = 0; i < runs.length; i += 2) {
+            int runStart = runs[i];
+            int runLimit = runStart + (runs[i + 1] & Layout.RUN_LENGTH_MASK);
+            if (runLimit > mLen) {
+                runLimit = mLen;
+            }
+            boolean runIsRtl = (runs[i + 1] & Layout.RUN_RTL_FLAG) != 0;
+
+            int segstart = runStart;
+            for (int j = mHasTabs ? runStart : runLimit; j <= runLimit; ++j) {
+                int codept = 0;
+                if (mHasTabs && j < runLimit) {
+                    codept = chars[j];
+                    if (codept >= 0xD800 && codept < 0xDC00 && j + 1 < runLimit) {
+                        codept = Character.codePointAt(chars, j);
+                        if (codept > 0xFFFF) {
+                            ++j;
+                            continue;
+                        }
+                    }
+                }
+
+                if (j == runLimit || codept == '\t') {
+                    float oldh = h;
+                    boolean advance = (mDir == Layout.DIR_RIGHT_TO_LEFT) == runIsRtl;
+                    float w = measureRun(segstart, j, j, runIsRtl, fmi);
+                    h += advance ? w : -w;
+
+                    float baseh = advance ? oldh : h;
+                    FontMetricsInt crtfmi = advance ? fmi : null;
+                    for (int offset = segstart; offset <= j && offset <= mLen; ++offset) {
+                        if (target[offset] >= segstart && target[offset] < j) {
+                            measurement[offset] =
+                                    baseh + measureRun(segstart, offset, j, runIsRtl, crtfmi);
+                        }
+                    }
+
+                    if (codept == '\t') {
+                        if (target[j] == j) {
+                            measurement[j] = h;
+                        }
+                        h = mDir * nextTab(h * mDir);
+                        if (target[j + 1] == j) {
+                            measurement[j + 1] =  h;
+                        }
+                    }
+
+                    segstart = j + 1;
+                }
+            }
+        }
+        if (target[mLen] == mLen) {
+            measurement[mLen] = h;
+        }
+
+        return measurement;
+    }
+
+    /**
      * Draws a unidirectional (but possibly multi-styled) run of text.
      *
      *