Introduce IsCaretAtEdgeOfInlineTextBox() to simplify ComputeInlineBoxPosition()

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

Index: third_party/WebKit/Source/core/editing/VisibleUnits.cpp
diff --git a/third_party/WebKit/Source/core/editing/VisibleUnits.cpp b/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
index 10d7bb2428cb8dcae515df30e6b47cfe308179ee..00d6b6ac4c461c5d98b4ea6929b006a89f2440d0 100644
--- a/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
+++ b/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
@@ -817,16 +817,20 @@ static InlineBoxPosition ComputeInlineBoxPositionTemplate(
       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() &&