Introduce IsCaretAtEdgeOfInlineTextBox() to simplify ComputeInlineBoxPosition()

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

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
  * reserved.
  *
  * 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 799 matching lines @@
       int caret_min_offset = box->CaretMinOffset();
       int caret_max_offset = box->CaretMaxOffset();
 
       if (caret_offset < caret_min_offset || caret_offset > caret_max_offset ||
           (caret_offset == caret_max_offset && box->IsLineBreak()))
         continue;
 
       if (caret_offset > caret_min_offset && caret_offset < caret_max_offset)
         return InlineBoxPosition(box, caret_offset);
 
-      if (((caret_offset == caret_max_offset) ^
-           (affinity == TextAffinity::kDownstream)) ||
-          ((caret_offset == caret_min_offset) ^
-           (affinity == TextAffinity::kUpstream)) ||
-          (caret_offset == caret_max_offset && box->NextLeafChild() &&
-           box->NextLeafChild()->IsLineBreak())) {
+      if (caret_offset == caret_min_offset) {

[Xiaocheng, 2017/06/12 18:35:12]

I think it's better to use a wrapper function that evaluates the condition, so
that we don't have complicated control flow with interleaving breaks and
continues.

[yosin_UTC9, 2017/06/13 07:41:07]

You're right. Move the condition to another function.

+        if (affinity == TextAffinity::kDownstream) {
+          inline_box = box;
+          break;
+        }
+        candidate = box;
+        continue;
+      }
+      DCHECK_EQ(caret_offset, caret_max_offset);
+      if (affinity == TextAffinity::kUpstream ||
+          (box->NextLeafChild() && box->NextLeafChild()->IsLineBreak())) {
         inline_box = box;
         break;
       }
-
       candidate = box;
     }
     if (candidate && candidate == text_layout_object->LastTextBox() &&
         affinity == TextAffinity::kDownstream) {
       inline_box = SearchAheadForBetterMatch(text_layout_object);
       if (inline_box)
         caret_offset = inline_box->CaretMinOffset();
     }
     if (!inline_box)
       inline_box = candidate;
@@ skipping 1222 matching lines @@
 
 IntRect ComputeTextRect(const EphemeralRangeInFlatTree& range) {
   return EnclosingIntRect(ComputeTextRectTemplate(range));
 }
 
 FloatRect ComputeTextFloatRect(const EphemeralRange& range) {
   return ComputeTextRectTemplate(range);
 }
 
 }  // namespace blink