Replace StyleRange with BreakList; update RenderText, etc.

ui/gfx/break_list.h

+// Copyright (c) 2012 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 UI_GFX_BREAK_LIST_H_
+#define UI_GFX_BREAK_LIST_H_
+
+#include <utility>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "ui/base/range/range.h"
+
+namespace gfx {
+
+// BreakLists manage ordered, non-overlapping, and non-repeating ranged values.
+// These may be used to apply ranged colors and styles to text, for an example.
+//
+// Each break stores the start position and value of its associated range.
+// A solitary break at position 0 applies to the entire space [0, max_).

[Alexei Svitkine (slow), 2013/01/31 21:25:07]

Can you document what happens if max_ is not specified?

If it's required, document it and mention what the two constructors set it to
(in the comments for the constructors).

[msw, 2013/02/01 00:08:08]

Done.

+// The first break always has position 0, to ensure all positions have a value.
+// The value of the terminal break applies to the range [break.first, max_).
+// The value of other breaks apply to the range [break.first, (break+1).first).
+template <typename T>
+class BreakList {
+ public:
+  // The break type and const iterator, typedef'ed for convenience.
+  typedef std::pair<size_t, T> Break;
+  typedef typename std::vector<Break>::const_iterator const_iterator;
+
+  // Initialize a break at position 0 with the default or supplied |value|.
+  BreakList();
+  explicit BreakList(T value);
+
+  const std::vector<Break>& breaks() const { return breaks_; }
+
+  // Clear the breaks and set a break at position 0 with the supplied |value|.
+  void SetValue(T value);
+
+  // Adjust the breaks to apply |value| over the supplied |range|.
+  void ApplyValue(T value, const ui::Range& range);
+
+  // Set the max position and trim any breaks at or beyond that position.
+  void SetMax(size_t max);
+
+  // Get the break applicable to |position| (at or preceeding |position|).
+  typename std::vector<Break>::iterator GetBreak(size_t position);
+
+  // Get the range of the supplied break; returns the break's start position and
+  // the next break's start position (or |max_| for the terminal break).
+  ui::Range GetRange(const typename BreakList<T>::const_iterator& i) const;
+
+  // Comparison functions for testing purposes.
+  bool EqualsValueForTesting(T value) const;
+  bool EqualsForTesting(const std::vector<Break>& breaks) const;
+
+ private:
+#ifndef NDEBUG
+  // Check for ordered breaks [0, |max_|) with no adjacent equivalent values.
+  void CheckBreaks();
+#endif
+
+  std::vector<Break> breaks_;
+  size_t max_;
+};
+
+template<class T>
+  BreakList<T>::BreakList() : breaks_(1, Break(0, T())), max_(0) {

[Alexei Svitkine (slow), 2013/01/31 21:25:07]

Nit: Remove spurious indent.

[msw, 2013/02/01 00:08:08]

Done.

+}
+
+template<class T>
+BreakList<T>::BreakList(T value) : breaks_(1, Break(0, value)), max_(0) {
+}
+
+template<class T>
+void BreakList<T>::SetValue(T value) {
+  breaks_.clear();
+  breaks_.push_back(Break(0, value));
+}
+
+template<class T>
+void BreakList<T>::ApplyValue(T value, const ui::Range& range) {
+  if (!range.IsValid() || range.is_empty())
+    return;
+  DCHECK(!breaks_.empty());
+  DCHECK(!range.is_reversed());
+  DCHECK(ui::Range(0, max_).Contains(range));
+
+  // Erase any breaks in |range|, then add start and end breaks as needed.
+  typename std::vector<Break>::iterator start = GetBreak(range.start());
+  start += start->first < range.start() ? 1 : 0;
+  typename std::vector<Break>::iterator end = GetBreak(range.end());
+  T trailing_value = end->second;
+  typename std::vector<Break>::iterator i =
+      start == breaks_.end() ? start : breaks_.erase(start, end + 1);
+  if (range.start() == 0 || (i - 1)->second != value)
+    i = breaks_.insert(i, Break(range.start(), value)) + 1;
+  if (trailing_value != value && range.end() != max_)
+    breaks_.insert(i, Break(range.end(), trailing_value));
+
+#ifndef NDEBUG
+  CheckBreaks();
+#endif
+}
+
+template<class T>
+void BreakList<T>::SetMax(size_t max) {
+  typename std::vector<Break>::iterator i = GetBreak(max);
+  i += (i == breaks_.begin() || i->first < max) ? 1 : 0;
+  breaks_.erase(i, breaks_.end());
+  max_ = max;
+
+#ifndef NDEBUG
+  CheckBreaks();
+#endif
+}
+
+template<class T>
+typename std::vector<std::pair<size_t, T> >::iterator BreakList<T>::GetBreak(
+    size_t position) {
+  typename std::vector<Break>::iterator i = breaks_.end() - 1;
+  for (; i != breaks_.begin() && i->first > position; --i);
+  return i;
+}
+
+template<class T>
+ui::Range BreakList<T>::GetRange(
+    const typename BreakList<T>::const_iterator& i) const {
+  const typename BreakList<T>::const_iterator next = i + 1;
+  return ui::Range(i->first, next == breaks_.end() ? max_ : next->first);
+}
+
+template<class T>
+bool BreakList<T>::EqualsValueForTesting(T value) const {
+  return breaks_.size() == 1 && breaks_[0] == Break(0, value);
+}
+
+template<class T>
+bool BreakList<T>::EqualsForTesting(const std::vector<Break>& breaks) const {
+  if (breaks_.size() != breaks.size())
+    return false;
+  for (size_t i = 0; i < breaks.size(); ++i)
+    if (breaks_[i] != breaks[i])
+      return false;
+  return true;
+}
+
+#ifndef NDEBUG
+template <class T>
+void BreakList<T>::CheckBreaks() {
+  DCHECK_EQ(breaks_[0].first, 0U) << "The first break must be at position 0.";
+  for (size_t i = 0; i < breaks_.size() - 1; ++i) {
+    DCHECK_LT(breaks_[i].first, breaks_[i + 1].first) << "Break out of order.";
+    DCHECK_NE(breaks_[i].second, breaks_[i + 1].second) << "Redundant break.";
+  }
+  if (max_ > 0)
+    DCHECK_LT(breaks_.back().first, max_) << "Break beyond max position.";
+}
+#endif
+
+}  // namespace gfx
+
+#endif  // UI_GFX_BREAK_LIST_H_