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glyph_atlas.h
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef FLUTTER_IMPELLER_TYPOGRAPHER_GLYPH_ATLAS_H_
6 #define FLUTTER_IMPELLER_TYPOGRAPHER_GLYPH_ATLAS_H_
7
8 #include <functional>
9 #include <memory>
10 #include <optional>
11 #include <unordered_map>
12
13 #include "impeller/core/texture.h"
14 #include "impeller/geometry/rect.h"
15 #include "impeller/renderer/pipeline.h"
16 #include "impeller/typographer/font_glyph_pair.h"
17 #include "impeller/typographer/rectangle_packer.h"
18
19 namespace impeller {
20
21 class FontGlyphAtlas;
22
23 //------------------------------------------------------------------------------
24 /// @brief A texture containing the bitmap representation of glyphs in
25 /// different fonts along with the ability to query the location of
26 /// specific font glyphs within the texture.
27 ///
28 class GlyphAtlas {
29 public:
30 //----------------------------------------------------------------------------
31 /// @brief Describes how the glyphs are represented in the texture.
32 enum class Type {
33 //--------------------------------------------------------------------------
34 /// The glyphs are reprsented at their requested size using only an 8-bit
35 /// color channel.
36 ///
37 /// This might be backed by a grey or red single channel texture, depending
38 /// on the backend capabilities.
39 kAlphaBitmap,
40
41 //--------------------------------------------------------------------------
42 /// The glyphs are reprsented at their requested size using N32 premul
43 /// colors.
44 ///
45 kColorBitmap,
46 };
47
48 //----------------------------------------------------------------------------
49 /// @brief Create an empty glyph atlas.
50 ///
51 /// @param[in] type How the glyphs are represented in the texture.
52 ///
53 explicit GlyphAtlas(Type type);
54
55 ~GlyphAtlas();
56
57 bool IsValid() const;
58
59 //----------------------------------------------------------------------------
60 /// @brief Describes how the glyphs are represented in the texture.
61 ///
62 Type GetType() const;
63
64 //----------------------------------------------------------------------------
65 /// @brief Set the texture for the glyph atlas.
66 ///
67 /// @param[in] texture The texture
68 ///
69 void SetTexture(std::shared_ptr<Texture> texture);
70
71 //----------------------------------------------------------------------------
72 /// @brief Get the texture for the glyph atlas.
73 ///
74 /// @return The texture.
75 ///
76 const std::shared_ptr<Texture>& GetTexture() const;
77
78 //----------------------------------------------------------------------------
79 /// @brief Record the location of a specific font-glyph pair within the
80 /// atlas.
81 ///
82 /// @param[in] pair The font-glyph pair
83 /// @param[in] rect The rectangle
84 ///
85 void AddTypefaceGlyphPosition(const FontGlyphPair& pair, Rect rect);
86
87 //----------------------------------------------------------------------------
88 /// @brief Get the number of unique font-glyph pairs in this atlas.
89 ///
90 /// @return The glyph count.
91 ///
92 size_t GetGlyphCount() const;
93
94 //----------------------------------------------------------------------------
95 /// @brief Iterate of all the glyphs along with their locations in the
96 /// atlas.
97 ///
98 /// @param[in] iterator The iterator. Return `false` from the iterator to
99 /// stop iterating.
100 ///
101 /// @return The number of glyphs iterated over.
102 ///
103 size_t IterateGlyphs(
104 const std::function<bool(const ScaledFont& scaled_font,
105 const Glyph& glyph,
106 const Rect& rect)>& iterator) const;
107
108 //----------------------------------------------------------------------------
109 /// @brief Find the location of a specific font-glyph pair in the atlas.
110 ///
111 /// @param[in] pair The font-glyph pair
112 ///
113 /// @return The location of the font-glyph pair in the atlas.
114 /// `std::nullopt` if the pair is not in the atlas.
115 ///
116 std::optional<Rect> FindFontGlyphBounds(const FontGlyphPair& pair) const;
117
118 //----------------------------------------------------------------------------
119 /// @brief Obtain an interface for querying the location of glyphs in the
120 /// atlas for the given font and scale. This provides a more
121 /// efficient way to look up a run of glyphs in the same font.
122 ///
123 /// @param[in] font The font
124 /// @param[in] scale The scale
125 ///
126 /// @return A pointer to a FontGlyphAtlas, or nullptr if the font and
127 /// scale are not available in the atlas. The pointer is only
128 /// valid for the lifetime of the GlyphAtlas.
129 ///
130 const FontGlyphAtlas* GetFontGlyphAtlas(const Font& font, Scalar scale) const;
131
132 private:
133 const Type type_;
134 std::shared_ptr<Texture> texture_;
135
136 std::unordered_map<ScaledFont, FontGlyphAtlas> font_atlas_map_;
137
138 GlyphAtlas(const GlyphAtlas&) = delete;
139
140 GlyphAtlas& operator=(const GlyphAtlas&) = delete;
141 };
142
143 //------------------------------------------------------------------------------
144 /// @brief A container for caching a glyph atlas across frames.
145 ///
146 class GlyphAtlasContext {
147 public:
148 virtual ~GlyphAtlasContext();
149
150 //----------------------------------------------------------------------------
151 /// @brief Retrieve the current glyph atlas.
152 std::shared_ptr<GlyphAtlas> GetGlyphAtlas() const;
153
154 //----------------------------------------------------------------------------
155 /// @brief Retrieve the size of the current glyph atlas.
156 const ISize& GetAtlasSize() const;
157
158 //----------------------------------------------------------------------------
159 /// @brief Retrieve the previous (if any) rect packer.
160 std::shared_ptr<RectanglePacker> GetRectPacker() const;
161
162 //----------------------------------------------------------------------------
163 /// @brief Update the context with a newly constructed glyph atlas.
164 void UpdateGlyphAtlas(std::shared_ptr<GlyphAtlas> atlas, ISize size);
165
166 void UpdateRectPacker(std::shared_ptr<RectanglePacker> rect_packer);
167
168 protected:
169 GlyphAtlasContext();
170
171 private:
172 std::shared_ptr<GlyphAtlas> atlas_;
173 ISize atlas_size_;
174 std::shared_ptr<RectanglePacker> rect_packer_;
175
176 GlyphAtlasContext(const GlyphAtlasContext&) = delete;
177
178 GlyphAtlasContext& operator=(const GlyphAtlasContext&) = delete;
179 };
180
181 //------------------------------------------------------------------------------
182 /// @brief An object that can look up glyph locations within the GlyphAtlas
183 /// for a particular typeface.
184 ///
185 class FontGlyphAtlas {
186 public:
187 FontGlyphAtlas() = default;
188
189 //----------------------------------------------------------------------------
190 /// @brief Find the location of a glyph in the atlas.
191 ///
192 /// @param[in] glyph The glyph
193 ///
194 /// @return The location of the glyph in the atlas.
195 /// `std::nullopt` if the glyph is not in the atlas.
196 ///
197 std::optional<Rect> FindGlyphBounds(const Glyph& glyph) const;
198
199 private:
200 friend class GlyphAtlas;
201 std::unordered_map<Glyph, Rect> positions_;
202
203 FontGlyphAtlas(const FontGlyphAtlas&) = delete;
204
205 FontGlyphAtlas& operator=(const FontGlyphAtlas&) = delete;
206 };
207
208 } // namespace impeller
209
210 #endif // FLUTTER_IMPELLER_TYPOGRAPHER_GLYPH_ATLAS_H_
impeller::GlyphAtlas::Type::kColorBitmap
@ kColorBitmap
impeller::GlyphAtlas::GetGlyphCount
size_t GetGlyphCount() const
Get the number of unique font-glyph pairs in this atlas.
Definition: glyph_atlas.cc:84
pipeline.h
impeller::Scalar
float Scalar
Definition: scalar.h:18
impeller::GlyphAtlasContext::GetRectPacker
std::shared_ptr< RectanglePacker > GetRectPacker() const
Retrieve the previous (if any) rect packer.
Definition: glyph_atlas.cc:26
impeller::Font
Describes a typeface along with any modifications to its intrinsic properties.
Definition: font.h:22
impeller::GlyphAtlas::Type::kAlphaBitmap
@ kAlphaBitmap
impeller::GlyphAtlas::FindFontGlyphBounds
std::optional< Rect > FindFontGlyphBounds(const FontGlyphPair &pair) const
Find the location of a specific font-glyph pair in the atlas.
Definition: glyph_atlas.cc:66
impeller::GlyphAtlasContext::GetGlyphAtlas
std::shared_ptr< GlyphAtlas > GetGlyphAtlas() const
Retrieve the current glyph atlas.
Definition: glyph_atlas.cc:18
impeller::GlyphAtlas::GetFontGlyphAtlas
const FontGlyphAtlas * GetFontGlyphAtlas(const Font &font, Scalar scale) const
Obtain an interface for querying the location of glyphs in the atlas for the given font and scale....
Definition: glyph_atlas.cc:75
impeller::FontGlyphAtlas::FontGlyphAtlas
FontGlyphAtlas()=default
impeller::FontGlyphAtlas
An object that can look up glyph locations within the GlyphAtlas for a particular typeface.
Definition: glyph_atlas.h:185
impeller::GlyphAtlas::SetTexture
void SetTexture(std::shared_ptr< Texture > texture)
Set the texture for the glyph atlas.
Definition: glyph_atlas.cc:57
impeller::GlyphAtlasContext::GlyphAtlasContext
GlyphAtlasContext()
Definition: glyph_atlas.cc:12
impeller::GlyphAtlasContext::~GlyphAtlasContext
virtual ~GlyphAtlasContext()
Definition: glyph_atlas.cc:16
impeller::GlyphAtlas::IterateGlyphs
size_t IterateGlyphs(const std::function< bool(const ScaledFont &scaled_font, const Glyph &glyph, const Rect &rect)> &iterator) const
Iterate of all the glyphs along with their locations in the atlas.
Definition: glyph_atlas.cc:91
impeller::GlyphAtlas::GlyphAtlas
GlyphAtlas(Type type)
Create an empty glyph atlas.
Definition: glyph_atlas.cc:41
impeller::Glyph
The glyph index in the typeface.
Definition: glyph.h:20
impeller::TSize< int64_t >
impeller::GlyphAtlasContext::GetAtlasSize
const ISize & GetAtlasSize() const
Retrieve the size of the current glyph atlas.
Definition: glyph_atlas.cc:22
rectangle_packer.h
impeller::GlyphAtlas::GetType
Type GetType() const
Describes how the glyphs are represented in the texture.
Definition: glyph_atlas.cc:49
impeller::GlyphAtlas::~GlyphAtlas
~GlyphAtlas()
impeller::GlyphAtlas::GetTexture
const std::shared_ptr< Texture > & GetTexture() const
Get the texture for the glyph atlas.
Definition: glyph_atlas.cc:53
impeller::GlyphAtlas::Type
Type
Describes how the glyphs are represented in the texture.
Definition: glyph_atlas.h:32
font_glyph_pair.h
impeller::GlyphAtlas::AddTypefaceGlyphPosition
void AddTypefaceGlyphPosition(const FontGlyphPair &pair, Rect rect)
Record the location of a specific font-glyph pair within the atlas.
Definition: glyph_atlas.cc:61
impeller::GlyphAtlasContext
A container for caching a glyph atlas across frames.
Definition: glyph_atlas.h:146
impeller::FontGlyphPair
A font along with a glyph in that font rendered at a particular scale.
Definition: font_glyph_pair.h:35
impeller::GlyphAtlas
A texture containing the bitmap representation of glyphs in different fonts along with the ability to...
Definition: glyph_atlas.h:28
rect.h
texture.h
scale
const Scalar scale
Definition: stroke_path_geometry.cc:297
impeller::FontGlyphAtlas::FindGlyphBounds
std::optional< Rect > FindGlyphBounds(const Glyph &glyph) const
Find the location of a glyph in the atlas.
Definition: glyph_atlas.cc:111
impeller::GlyphAtlas::IsValid
bool IsValid() const
Definition: glyph_atlas.cc:45
impeller
Definition: aiks_blur_unittests.cc:20
impeller::TRect
Definition: rect.h:122
impeller::ScaledFont
A font and a scale. Used as a key that represents a typeface within a glyph atlas.
Definition: font_glyph_pair.h:24
impeller::GlyphAtlasContext::UpdateGlyphAtlas
void UpdateGlyphAtlas(std::shared_ptr< GlyphAtlas > atlas, ISize size)
Update the context with a newly constructed glyph atlas.
Definition: glyph_atlas.cc:30
impeller::GlyphAtlasContext::UpdateRectPacker
void UpdateRectPacker(std::shared_ptr< RectanglePacker > rect_packer)
Definition: glyph_atlas.cc:36