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// Copyright 2015 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 THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_GRANULARITY_STRATEGY_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_GRANULARITY_STRATEGY_H_
#include "third_party/blink/renderer/core/editing/forward.h"
#include "third_party/blink/renderer/core/editing/selection_strategy.h"
#include "third_party/blink/renderer/platform/geometry/int_size.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
namespace blink {
class IntPoint;
class LocalFrame;
enum class TextGranularity;
class GranularityStrategy {
USING_FAST_MALLOC(GranularityStrategy);
public:
virtual ~GranularityStrategy();
virtual SelectionStrategy GetType() const = 0;
virtual void Clear() = 0;
// Calculates and returns the new selection based on the updated extent
// location in absolute coordinates.
virtual SelectionInDOMTree UpdateExtent(const IntPoint&, LocalFrame*) = 0;
protected:
GranularityStrategy();
};
// Always uses character granularity.
class CharacterGranularityStrategy final : public GranularityStrategy {
public:
CharacterGranularityStrategy();
~CharacterGranularityStrategy() final;
// GranularityStrategy:
SelectionStrategy GetType() const final;
void Clear() final;
SelectionInDOMTree UpdateExtent(const IntPoint&, LocalFrame*) final;
};
// "Expand by word, shrink by character" selection strategy.
// Uses character granularity when selection is shrinking. If the selection is
// expanding, granularity doesn't change until a word boundary is passed, after
// which the granularity switches to "word".
// In word granularity, the word is not selected until the extent point passes
// the middle of the word.
//
// The "offset" feature:
// The offset is the horizontal distance between the extent point (passed in
// updateExtent) and the end of the selection. In character granularity the
// offset is typically zero or near zero, however in word granularity it can be
// significant. When the offset is positive and the extent point moved to the
// left, the offset is preserved, i.e. the selection tracks the extent point
// with the constant offset. When the offset is positive and the extent point
// is moved to the right, the offset gets reduced. Selection will not grow
// until the offset is reduced all the way to zero.
//
// This behavior is best illustrated by an example:
//
// ^ marks base, | marks extent point, > marks selection end:
// Lorem ip^sum|> dolor sit amet, consectetur
//
// Move extent over the middle of "dolor". Granularity should change to word
// granularity and the selection end should jump to the end of the word.
// Lorem ip^sum dolo|r> sit amet, consectetur
//
// Move extent back one character. Granularity changes to "character". The
// selection end should move back one character as well. Note an offset between
// the extent and the selection end.
// Lorem ip^sum dol|o>r sit amet, consectetur
//
// Move extent forward one character. The offset is reduced to 0. Selection end
// doesn't change.
// Lorem ip^sum dolo|>r sit amet, consectetur
//
// Move forward one character. End moves with extent in character granularity.
// Lorem ip^sum dolor|> sit amet, consectetur
class DirectionGranularityStrategy final : public GranularityStrategy {
public:
DirectionGranularityStrategy();
~DirectionGranularityStrategy() final;
// GranularityStrategy:
SelectionStrategy GetType() const final;
void Clear() final;
SelectionInDOMTree UpdateExtent(const IntPoint&, LocalFrame*) final;
private:
enum class StrategyState {
// Starting state.
// Selection was cleared and there were no extent updates since then.
// One an update is performed, the strategy goes into the Expanding
// state unless the update shrinks the selection without changing
// relative base/extent order, in which case the strategy goes into the
// Shrinking state.
kCleared,
// Last time the selection was changed by updateExtent - it was expanded
// or the relative base/extent order was changed.
kExpanding,
// Last time the selection was changed by updateExtent - it was shrunk
// (without changing relative base/extent order).
kShrinking
};
StrategyState state_;
// Current selection granularity being used.
TextGranularity granularity_;
// Horizontal offset in pixels in absolute coordinates applied to the extent
// point.
int offset_;
// This defines location of the offset-adjusted extent point (from the
// latest updateExtent call) relative to the location of extent's
// VisiblePosition. It is used to detect sub-position extent movement.
IntSize diff_extent_point_from_extent_position_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_GRANULARITY_STRATEGY_H_
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