Support surrogate pairs when layouting text

The current framework does not consider surrogate pairs
when getting the index of the character. This bug becomes
visible when creating the text including Emojis. For
example cursor breaks up when it moves around the Emojis.

Our proposed solution will consider the surrogate pairs
when calculating the index. It will fix not only the Emoji
case, but also the letters that use surrogate pairs.

Change-Id: I4983f2e4df933c8af9d5f0cc27df871e8e10fed4

3 files changed, 35 insertions, 10 deletions

diff --git a/core/java/android/text/Layout.java b/core/java/android/text/Layout.java
index 38ac9b7..4e197cd 100644..100755
--- a/core/java/android/text/Layout.java
+++ b/core/java/android/text/Layout.java
@@ -749,6 +749,9 @@ public abstract class Layout {
         if (line == getLineCount() - 1)
             max++;
 
+        if (line != getLineCount() - 1)
+            max = TextUtils.getOffsetBefore(mText, getLineEnd(line));
+
         int best = min;
         float bestdist = Math.abs(getPrimaryHorizontal(best) - horiz);
 
@@ -893,7 +896,7 @@ public abstract class Layout {
         Directions dirs = getLineDirections(line);
 
         if (line != getLineCount() - 1)
-            end--;
+            end = TextUtils.getOffsetBefore(mText, end);
 
         float horiz = getPrimaryHorizontal(offset);
 
@@ -993,7 +996,7 @@ public abstract class Layout {
         Directions dirs = getLineDirections(line);
 
         if (line != getLineCount() - 1)
-            end--;
+            end = TextUtils.getOffsetBefore(mText, end);
 
         float horiz = getPrimaryHorizontal(offset);
 
@@ -1564,7 +1567,8 @@ public abstract class Layout {
                         h = dir * nextTab(text, start, end, h * dir, tabs);
                     }
 
-                    if (bm != null) {
+                    if (j != there && bm != null) {
+                        if (offset == start + j) return h;
                         workPaint.set(paint);
                         Styled.measureText(paint, workPaint, text,
                                            j, j + 2, null);
@@ -1958,4 +1962,3 @@ public abstract class Layout {
                                        new Directions(new short[] { 0, 32767 });
 
 }
-
diff --git a/core/java/android/text/StaticLayout.java b/core/java/android/text/StaticLayout.java
index f02ad2a..d0d2482 100644..100755
--- a/core/java/android/text/StaticLayout.java
+++ b/core/java/android/text/StaticLayout.java
@@ -313,7 +313,9 @@ extends Layout
                                                       class);
 
                 if (spanned == null) {
-                    paint.getTextWidths(sub, i, next, widths);
+                    final int actualNum = paint.getTextWidths(sub, i, next, widths);
+                    if (next - i > actualNum)
+                        adjustTextWidths(widths, sub, i, next, actualNum);
                     System.arraycopy(widths, 0, widths,
                                      end - start + (i - start), next - i);
                                      
@@ -321,9 +323,11 @@ extends Layout
                 } else {
                     mWorkPaint.baselineShift = 0;
 
-                    Styled.getTextWidths(paint, mWorkPaint,
-                                         spanned, i, next,
-                                         widths, fm);
+                    final int actualNum = Styled.getTextWidths(paint, mWorkPaint,
+                            spanned, i, next,
+                            widths, fm);
+                    if (next - i > actualNum)
+                        adjustTextWidths(widths, spanned, i, next, actualNum);
                     System.arraycopy(widths, 0, widths,
                                      end - start + (i - start), next - i);
 
@@ -966,6 +970,22 @@ extends Layout
             return low;
     }
 
+    private static void adjustTextWidths(float[] widths, CharSequence text,
+                              int curPos, int nextPos, int actualNum) {
+        try {
+            int dstIndex = nextPos - curPos - 1;
+            for (int srcIndex = actualNum - 1; srcIndex >= 0; srcIndex--) {
+                final char c = text.charAt(dstIndex + curPos);
+                if (c >= 0xD800 && c <= 0xDFFF) {
+                    widths[dstIndex--] = 0.0f;
+                }
+                widths[dstIndex--] = widths[srcIndex];
+            }
+        } catch (IndexOutOfBoundsException e) {
+            Log.e("text", "adjust text widths failed");
+        }
+    }
+
     private int out(CharSequence text, int start, int end,
                       int above, int below, int top, int bottom, int v,
                       float spacingmult, float spacingadd,
diff --git a/core/java/android/text/Styled.java b/core/java/android/text/Styled.java
index 513b2cd..13cc42c 100644..100755
--- a/core/java/android/text/Styled.java
+++ b/core/java/android/text/Styled.java
@@ -203,9 +203,10 @@ public class Styled
 			}
 		}
 	
+        int result;
         if (replacement == null) {
             workPaint.getFontMetricsInt(fmi);
-            workPaint.getTextWidths(text, start, end, widths);
+            result = workPaint.getTextWidths(text, start, end, widths);
         } else {
             int wid = replacement.getSize(workPaint, text, start, end, fmi);
 
@@ -214,8 +215,9 @@ public class Styled
                 for (int i = start + 1; i < end; i++)
                     widths[i - start] = 0;
             }
+            result = end - start;
         }
-        return end - start;
+        return result;
     }
 
     /**