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// Copyright 2012 The Chromium Authors
// 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 <stddef.h>
#include <utility>
#include <vector>
#include "base/check_op.h"
#include "ui/gfx/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_).
// |max_| is initially 0 and should be set to match the available ranged space.
// 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.
using Break = std::pair<size_t, T>;
using const_iterator = typename std::vector<Break>::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|.
// Returns whether or not the breaks changed while applying the |value|.
bool ClearAndSetInitialValue(T value);
// Adjust the breaks to apply |value| over the supplied |range|.
// Range |range| must be between [0, max_).
// Returns true if the breaks changed while applying the |value|.
bool ApplyValue(T value, const Range& range);
// Set the max position and trim any breaks at or beyond that position.
void SetMax(size_t max);
size_t max() const { return max_; }
// Get the break applicable to |position| (at or preceding |position|).
// |position| must be between [0, max_).
// Returns a valid iterator. Can't return |break_.end()|.
const_iterator GetBreak(size_t position) const;
// 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).
// Iterator |i| must be valid and must not be |break_.end()|.
Range GetRange(const const_iterator& i) const;
// Clears the breaks, and sets a break at position 0 with the value of the
// existing break at position 0. Only applicable on non-empty breaklists.
void Reset() {
DCHECK(breaks().size() > 0);
ClearAndSetInitialValue(breaks().front().second);
}
// 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_ = 0;
};
template <class T>
BreakList<T>::BreakList() : breaks_(1, Break(0, T())) {}
template <class T>
BreakList<T>::BreakList(T value) : breaks_(1, Break(0, value)) {}
template <class T>
bool BreakList<T>::ClearAndSetInitialValue(T value) {
// Return false if setting |value| does not change the breaks.
if (breaks_.size() == 1 && breaks_[0].second == value)
return false;
breaks_.clear();
breaks_.push_back(Break(0, value));
return true;
}
template <class T>
bool BreakList<T>::ApplyValue(T value, const Range& range) {
if (!range.IsValid() || range.is_empty())
return false;
DCHECK(!breaks_.empty());
DCHECK(!range.is_reversed());
DCHECK(Range(0, static_cast<uint32_t>(max_)).Contains(range));
// Return false if setting |value| does not change the breaks.
const_iterator start = GetBreak(range.start());
if (start->second == value && GetRange(start).Contains(range))
return false;
// Erase any breaks in |range|, then add start and end breaks as needed.
start += start->first < range.start() ? 1 : 0;
const_iterator end =
range.end() == max_ ? breaks_.cend() - 1 : GetBreak(range.end());
T trailing_value = end->second;
const_iterator i =
start == breaks_.cend() ? 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
return true;
}
template<class T>
void BreakList<T>::SetMax(size_t max) {
if (max < max_) {
const_iterator i = GetBreak(max);
if (i == breaks_.begin() || i->first < max)
i++;
breaks_.erase(i, breaks_.end());
}
max_ = max;
#ifndef NDEBUG
CheckBreaks();
#endif
}
template <class T>
typename BreakList<T>::const_iterator BreakList<T>::GetBreak(
size_t position) const {
DCHECK(!breaks_.empty());
DCHECK_LT(position, max_);
// Find the iterator with a 'strictly greater' position and return the
// previous one.
return std::upper_bound(breaks_.cbegin(), breaks_.cend(), position,
[](size_t offset, const Break& value) {
return offset < value.first;
}) -
1;
}
template<class T>
Range BreakList<T>::GetRange(
const typename BreakList<T>::const_iterator& i) const {
// BreakLists are never empty. Iterator should always be valid.
DCHECK(i != breaks_.end());
const const_iterator next = i + 1;
return 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(!breaks_.empty()) << "BreakList cannot be empty";
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_
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