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// Copyright 2013 The Flutter 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 FLUTTER_IMPELLER_TYPOGRAPHER_GLYPH_ATLAS_H_
#define FLUTTER_IMPELLER_TYPOGRAPHER_GLYPH_ATLAS_H_
#include <functional>
#include <memory>
#include <optional>
#include <unordered_map>
#include "flutter/fml/macros.h"
#include "impeller/core/texture.h"
#include "impeller/geometry/rect.h"
#include "impeller/renderer/pipeline.h"
#include "impeller/typographer/font_glyph_pair.h"
#include "impeller/typographer/rectangle_packer.h"
namespace impeller {
class FontGlyphAtlas;
//------------------------------------------------------------------------------
/// @brief A texture containing the bitmap representation of glyphs in
/// different fonts along with the ability to query the location of
/// specific font glyphs within the texture.
///
class GlyphAtlas {
public:
//----------------------------------------------------------------------------
/// @brief Describes how the glyphs are represented in the texture.
enum class Type {
//--------------------------------------------------------------------------
/// The glyphs are reprsented at their requested size using only an 8-bit
/// alpha channel.
///
kAlphaBitmap,
//--------------------------------------------------------------------------
/// The glyphs are reprsented at their requested size using N32 premul
/// colors.
///
kColorBitmap,
};
//----------------------------------------------------------------------------
/// @brief Create an empty glyph atlas.
///
/// @param[in] type How the glyphs are represented in the texture.
///
explicit GlyphAtlas(Type type);
~GlyphAtlas();
bool IsValid() const;
//----------------------------------------------------------------------------
/// @brief Describes how the glyphs are represented in the texture.
///
Type GetType() const;
//----------------------------------------------------------------------------
/// @brief Set the texture for the glyph atlas.
///
/// @param[in] texture The texture
///
void SetTexture(std::shared_ptr<Texture> texture);
//----------------------------------------------------------------------------
/// @brief Get the texture for the glyph atlas.
///
/// @return The texture.
///
const std::shared_ptr<Texture>& GetTexture() const;
//----------------------------------------------------------------------------
/// @brief Record the location of a specific font-glyph pair within the
/// atlas.
///
/// @param[in] pair The font-glyph pair
/// @param[in] rect The rectangle
///
void AddTypefaceGlyphPosition(const FontGlyphPair& pair, Rect rect);
//----------------------------------------------------------------------------
/// @brief Get the number of unique font-glyph pairs in this atlas.
///
/// @return The glyph count.
///
size_t GetGlyphCount() const;
//----------------------------------------------------------------------------
/// @brief Iterate of all the glyphs along with their locations in the
/// atlas.
///
/// @param[in] iterator The iterator. Return `false` from the iterator to
/// stop iterating.
///
/// @return The number of glyphs iterated over.
///
size_t IterateGlyphs(
const std::function<bool(const ScaledFont& scaled_font,
const Glyph& glyph,
const Rect& rect)>& iterator) const;
//----------------------------------------------------------------------------
/// @brief Find the location of a specific font-glyph pair in the atlas.
///
/// @param[in] pair The font-glyph pair
///
/// @return The location of the font-glyph pair in the atlas.
/// `std::nullopt` if the pair is not in the atlas.
///
std::optional<Rect> FindFontGlyphBounds(const FontGlyphPair& pair) const;
//----------------------------------------------------------------------------
/// @brief Obtain an interface for querying the location of glyphs in the
/// atlas for the given font and scale. This provides a more
/// efficient way to look up a run of glyphs in the same font.
///
/// @param[in] font The font
/// @param[in] scale The scale
///
/// @return A pointer to a FontGlyphAtlas, or nullptr if the font and
/// scale are not available in the atlas. The pointer is only
/// valid for the lifetime of the GlyphAtlas.
///
const FontGlyphAtlas* GetFontGlyphAtlas(const Font& font, Scalar scale) const;
private:
const Type type_;
std::shared_ptr<Texture> texture_;
std::unordered_map<ScaledFont, FontGlyphAtlas> font_atlas_map_;
GlyphAtlas(const GlyphAtlas&) = delete;
GlyphAtlas& operator=(const GlyphAtlas&) = delete;
};
//------------------------------------------------------------------------------
/// @brief A container for caching a glyph atlas across frames.
///
class GlyphAtlasContext {
public:
virtual ~GlyphAtlasContext();
//----------------------------------------------------------------------------
/// @brief Retrieve the current glyph atlas.
std::shared_ptr<GlyphAtlas> GetGlyphAtlas() const;
//----------------------------------------------------------------------------
/// @brief Retrieve the size of the current glyph atlas.
const ISize& GetAtlasSize() const;
//----------------------------------------------------------------------------
/// @brief Retrieve the previous (if any) rect packer.
std::shared_ptr<RectanglePacker> GetRectPacker() const;
//----------------------------------------------------------------------------
/// @brief Update the context with a newly constructed glyph atlas.
void UpdateGlyphAtlas(std::shared_ptr<GlyphAtlas> atlas, ISize size);
void UpdateRectPacker(std::shared_ptr<RectanglePacker> rect_packer);
protected:
GlyphAtlasContext();
private:
std::shared_ptr<GlyphAtlas> atlas_;
ISize atlas_size_;
std::shared_ptr<RectanglePacker> rect_packer_;
GlyphAtlasContext(const GlyphAtlasContext&) = delete;
GlyphAtlasContext& operator=(const GlyphAtlasContext&) = delete;
};
//------------------------------------------------------------------------------
/// @brief An object that can look up glyph locations within the GlyphAtlas
/// for a particular typeface.
///
class FontGlyphAtlas {
public:
FontGlyphAtlas() = default;
//----------------------------------------------------------------------------
/// @brief Find the location of a glyph in the atlas.
///
/// @param[in] glyph The glyph
///
/// @return The location of the glyph in the atlas.
/// `std::nullopt` if the glyph is not in the atlas.
///
std::optional<Rect> FindGlyphBounds(const Glyph& glyph) const;
private:
friend class GlyphAtlas;
std::unordered_map<Glyph, Rect> positions_;
FontGlyphAtlas(const FontGlyphAtlas&) = delete;
FontGlyphAtlas& operator=(const FontGlyphAtlas&) = delete;
};
} // namespace impeller
#endif // FLUTTER_IMPELLER_TYPOGRAPHER_GLYPH_ATLAS_H_