Extract InlineBox handling from MostForwardCaretPosition()

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 2804 matching lines @@
     if (layout_object->IsText() &&
         ToLayoutText(layout_object)->FirstTextBox()) {
       LayoutText* const text_layout_object = ToLayoutText(layout_object);
       const unsigned text_start_offset = text_layout_object->TextStartOffset();
       if (current_node != start_node) {
         DCHECK(current_pos.AtStartOfNode());
         return PositionTemplate<Strategy>(
             current_node, layout_object->CaretMinOffset() + text_start_offset);
       }
 
-      // Map offset in DOM node to offset in InlineBox.
-      DCHECK_GE(current_pos.OffsetInLeafNode(),
-                static_cast<int>(text_start_offset));
-      const unsigned text_offset =
-          current_pos.OffsetInLeafNode() - text_start_offset;
-      InlineTextBox* last_text_box = text_layout_object->LastTextBox();
-      for (InlineTextBox* box = text_layout_object->FirstTextBox(); box;
-           box = box->NextTextBox()) {
-        if (text_offset <= box->end()) {
-          if (text_offset >= box->Start())
-            return current_pos.ComputePosition();
-          continue;
-        }
-
-        if (box == last_text_box || text_offset != box->Start() + box->Len())
-          continue;
-
-        // The text continues on the next line only if the last text box is not
-        // on this line and none of the boxes on this line have a larger start
-        // offset.
-
-        bool continues_on_next_line = true;
-        InlineBox* other_box = box;
-        while (continues_on_next_line) {
-          other_box = other_box->NextLeafChild();
-          if (!other_box)
-            break;
-          if (other_box == last_text_box ||
-              (LineLayoutAPIShim::LayoutObjectFrom(
-                   other_box->GetLineLayoutItem()) == text_layout_object &&
-               ToInlineTextBox(other_box)->Start() >= text_offset))
-            continues_on_next_line = false;
-        }
-
-        other_box = box;
-        while (continues_on_next_line) {
-          other_box = other_box->PrevLeafChild();
-          if (!other_box)
-            break;
-          if (other_box == last_text_box ||
-              (LineLayoutAPIShim::LayoutObjectFrom(
-                   other_box->GetLineLayoutItem()) == text_layout_object &&
-               ToInlineTextBox(other_box)->Start() >= text_offset))
-            continues_on_next_line = false;
-        }
-
-        if (continues_on_next_line)
-          return current_pos.ComputePosition();
+      if (CanForwardCaretPosition(text_layout_object,
+                                  current_pos.OffsetInLeafNode())) {
+        return current_pos.ComputePosition();
       }
     }
   }
-
   return last_visible.DeprecatedComputePosition();
 }
 
+// TODO(editing-dev): This function is just moved out from
+// |MostForwardCaretPosition()|. We should study this function more and
+// name it appropriately. See https://trac.webkit.org/changeset/32438/
+// which introduce this.
+static bool CanForwardCaretPosition(const LayoutText* text_layout_object,

[Xiaocheng, 2017/06/05 19:35:53]

nit: |CanBeForwardCaretPosition| seems a better name.

[yosin_UTC9, 2017/06/06 04:21:14]

Done. Thanks for providing good name.

+                                    int offset_in_node) {
+  const unsigned text_start_offset = text_layout_object->TextStartOffset();
+  DCHECK_GE(offset_in_node, static_cast<int>(text_start_offset));
+  const unsigned text_offset = offset_in_node - text_start_offset;
+  InlineTextBox* const last_text_box = text_layout_object->LastTextBox();
+  for (InlineTextBox* box = text_layout_object->FirstTextBox(); box;
+       box = box->NextTextBox()) {
+    if (text_offset <= box->end()) {
+      if (text_offset >= box->Start())
+        return true;
+      continue;
+    }
+
+    if (box == last_text_box || text_offset != box->Start() + box->Len())
+      continue;
+
+    // TODO(yosin): We should move below code fragment into
+    // |DoesContinueOnNextLine()|. Note: |MostForwardCaretPosition()| has

[Xiaocheng, 2017/06/05 19:35:53]

nit: s/Forward/Backward/

[yosin_UTC9, 2017/06/06 04:21:14]

Done. Thanks for catching this.

+    // same code fragment except for comparison on |text_offset|.
+    // Backward: other_box->Start() >  text_offset
+    // Forward:  other_box->Start() >= text_offset
+    // The text continues on the next line only if the last text box is not
+    // on this line and none of the boxes on this line have a larger start
+    // offset.
+    bool continues_on_next_line = true;
+    InlineBox* other_box = box;
+    while (continues_on_next_line) {
+      other_box = other_box->NextLeafChild();
+      if (!other_box)
+        break;
+      if (other_box == last_text_box ||
+          (LineLayoutAPIShim::LayoutObjectFrom(
+               other_box->GetLineLayoutItem()) == text_layout_object &&
+           ToInlineTextBox(other_box)->Start() >= text_offset))
+        continues_on_next_line = false;
+    }
+
+    other_box = box;
+    while (continues_on_next_line) {
+      other_box = other_box->PrevLeafChild();
+      if (!other_box)
+        break;
+      if (other_box == last_text_box ||
+          (LineLayoutAPIShim::LayoutObjectFrom(
+               other_box->GetLineLayoutItem()) == text_layout_object &&
+           ToInlineTextBox(other_box)->Start() >= text_offset))
+        continues_on_next_line = false;
+    }
+
+    if (continues_on_next_line)
+      return true;
+  }
+  return false;
+}
+
 Position MostForwardCaretPosition(const Position& position,
                                   EditingBoundaryCrossingRule rule) {
   return MostForwardCaretPosition<EditingStrategy>(position, rule);
 }
 
 PositionInFlatTree MostForwardCaretPosition(const PositionInFlatTree& position,
                                             EditingBoundaryCrossingRule rule) {
   return MostForwardCaretPosition<EditingInFlatTreeStrategy>(position, rule);
 }
 
@@ skipping 866 matching lines @@
 
 IntRect ComputeTextRect(const EphemeralRangeInFlatTree& range) {
   return EnclosingIntRect(ComputeTextRectTemplate(range));
 }
 
 FloatRect ComputeTextFloatRect(const EphemeralRange& range) {
   return ComputeTextRectTemplate(range);
 }
 
 }  // namespace blink