Make NGInlineItemsBuilder construct whitespace-collapsed offset mapping

third_party/WebKit/Source/core/layout/ng/inline/ng_offset_mapping_builder.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NGOffsetMappingBuilder_h
+#define NGOffsetMappingBuilder_h
+
+#include "core/CoreExport.h"
+#include "platform/wtf/Allocator.h"
+#include "platform/wtf/Vector.h"
+#include "platform/wtf/text/WTFString.h"
+
+namespace blink {
+
+// This is the helper class for constructing the DOM-to-TextContent offset
+// mapping. It holds an offset mapping, and provides APIs to modify the mapping
+// step by step until the construction is finished.
+// Design doc: https://goo.gl/CJbxky
+// TODO(xiaochengh): Change the mock implemetation to a real one.
+class CORE_EXPORT NGOffsetMappingBuilder {
+  STACK_ALLOCATED();
+
+ public:
+  NGOffsetMappingBuilder();
+
+  // TODO(xiaochengh): Add the following API when we implement the construction
+  // of the concatenated offset mapping.
+  // Associate the offset mapping with a simple annotation with the given node
+  // as its value.
+  // void Annotate(const Node&);
+
+  // Append an identity offset mapping of the specified length with null
+  // annotation to the builder.
+  void AppendIdentityMapping(unsigned length);
+
+  // Append a collapsed offset mapping from the specified length with null
+  // annotation to the builder.
+  void AppendCollapsedMapping(unsigned length);
+
+  // TODO(xiaochengh): Add the following API when we start to fix offset mapping
+  // for text-transform.
+  // Append an expanded offset mapping to the specified length with null
+  // annotation to the builder.
+  // void AppendExpandedMapping(unsigned length);
+
+  // This function should only be called by NGInlineItemsBuilder during
+  // whitespace collapsing, and in the case that the target string of the
+  // currently held mapping:
+  //   (i) has at least |skip_length + 1| characters,
+  //  (ii) has the last |skip_length| characters being non-text extra
+  //       characters, and
+  // (iii) has the |skip_length + 1|-st last character being a space.
+  // This function changes the space into collapsed.
+  void CollapseTrailingSpace(unsigned index);
+
+  // TODO(xiaochengh): Add the following API when we implement the construction
+  // of the concatenated offset mapping.
+  // Concatenate the offset mapping held by another builder to this builder.
+  // void Concatenate(const OffsetMappingBuilder&);
+
+  // TODO(xiaochengh): Add the following APIs when we implement the construction
+  // of the DOM-to-TextContent offset mapping.
+
+  // Composite the offset mapping held by another builder to this builder.
+  // void Composite(const OffsetMappingBuilder&);
+
+  // Finalize and return the offset mapping.
+  // OffsetMappingResult Build();
+
+  // Exposed for testing only.
+  Vector<unsigned> DumpOffsetMappingForTesting() const;
+
+ private:
+  // A mock implementation of the offset mapping builder that stores the mapping
+  // value of every offset in the plain way. This is simple but inefficient, and
+  // will be replaced by a real efficient implementation.
+  Vector<unsigned> mapping_;
+
+  DISALLOW_COPY_AND_ASSIGN(NGOffsetMappingBuilder);
+};
+
+}  // namespace blink
+
+#endif  // OffsetMappingBuilder_h