Fix setComposingText when newCursorPosition != 1

third_party/WebKit/Source/core/editing/PlainTextRange.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 130 matching lines @@
                     resultEnd = textRunStartPosition;
                 else
                     resultEnd = textRunEndPosition;
             }
             docTextPosition += len;
             break;
         }
         docTextPosition += len;
     }
 
-    if (!startRangeFound)
-        return EphemeralRange();
+    if (!startRangeFound) {
+        // startRangeFound = start() >= docTextPosition && start() <= docTextPosition + len.
+        // The former condition is related to the left boundary, and the latter to the right boundary.
+        // Since we assert that end()>=start()>=0, and docTextPosition==0 before the loop starts,
+        // so startRangeFound is false if and only if new cursor position exceeds the right boundary.
+        // In that case, the cursor should stay at the right boundary, because EditText, the component
+        // in Android, behaves in that way.

[Changwan Ryu, 2016/04/05 07:50:37]

how about renaming startRangeFound as startOutOfBound and not adding any comment
here.

[yabinh, 2016/04/05 08:06:41]

Acknowledged.

+        resultStart = textRunEndPosition;
+        resultEnd = textRunEndPosition;
+    }
 
     if (length() && end() > docTextPosition) { // end() is out of bounds
         resultEnd = textRunEndPosition;
     }
 
     return EphemeralRange(resultStart.toOffsetInAnchor(), resultEnd.toOffsetInAnchor());
 }
 
 PlainTextRange PlainTextRange::create(const ContainerNode& scope, const EphemeralRange& range)
 {
@@ skipping 17 matching lines @@
 
     return PlainTextRange(start, end);
 }
 
 PlainTextRange PlainTextRange::create(const ContainerNode& scope, const Range& range)
 {
     return create(scope, EphemeralRange(&range));
 }
 
 } // namespace blink