| Flutter Impeller |

text_contents.cc
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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 #include "impeller/entity/contents/text_contents.h"
6
7 #include <cstring>
8 #include <optional>
9 #include <utility>
10
11 #include "impeller/core/buffer_view.h"
12 #include "impeller/core/formats.h"
13 #include "impeller/core/sampler_descriptor.h"
14 #include "impeller/entity/entity.h"
15 #include "impeller/geometry/color.h"
16 #include "impeller/geometry/point.h"
17 #include "impeller/renderer/render_pass.h"
18 #include "impeller/typographer/glyph_atlas.h"
19
20 namespace impeller {
21 Point SizeToPoint(Size size) {
22 return Point(size.width, size.height);
23 }
24
25 using VS = GlyphAtlasPipeline::VertexShader;
26 using FS = GlyphAtlasPipeline::FragmentShader;
27
28 TextContents::TextContents() = default;
29
30 TextContents::~TextContents() = default;
31
32 void TextContents::SetTextFrame(const std::shared_ptr<TextFrame>& frame) {
33 frame_ = frame;
34 }
35
36 void TextContents::SetColor(Color color) {
37 color_ = color;
38 }
39
40 Color TextContents::GetColor() const {
41 return color_.WithAlpha(color_.alpha * inherited_opacity_);
42 }
43
44 void TextContents::SetInheritedOpacity(Scalar opacity) {
45 inherited_opacity_ = opacity;
46 }
47
48 void TextContents::SetOffset(Vector2 offset) {
49 offset_ = offset;
50 }
51
52 void TextContents::SetForceTextColor(bool value) {
53 force_text_color_ = value;
54 }
55
56 std::optional<Rect> TextContents::GetCoverage(const Entity& entity) const {
57 return frame_->GetBounds().TransformBounds(entity.GetTransform());
58 }
59
60 void TextContents::SetTextProperties(Color color,
61 bool stroke,
62 Scalar stroke_width,
63 Cap stroke_cap,
64 Join stroke_join,
65 Scalar stroke_miter) {
66 if (frame_->HasColor()) {
67 // Alpha is always applied when rendering, remove it here so
68 // we do not double-apply the alpha.
69 properties_.color = color.WithAlpha(1.0);
70 }
71 if (stroke) {
72 properties_.stroke = true;
73 properties_.stroke_width = stroke_width;
74 properties_.stroke_cap = stroke_cap;
75 properties_.stroke_join = stroke_join;
76 properties_.stroke_miter = stroke_miter;
77 }
78 }
79
80 namespace {
81 Scalar AttractToOne(Scalar x) {
82 // Epsilon was decided by looking at the floating point inaccuracies in
83 // the ScaledK test.
84 const Scalar epsilon = 0.005f;
85 if (std::abs(x - 1.f) < epsilon) {
86 return 1.f;
87 }
88 if (std::abs(x + 1.f) < epsilon) {
89 return -1.f;
90 }
91 return x;
92 }
93
94 } // namespace
95
96 void TextContents::ComputeVertexData(
97 VS::PerVertexData* vtx_contents,
98 const std::shared_ptr<TextFrame>& frame,
99 Scalar scale,
100 const Matrix& entity_transform,
101 Vector2 offset,
102 std::optional<GlyphProperties> glyph_properties,
103 const std::shared_ptr<GlyphAtlas>& atlas) {
104 // Common vertex information for all glyphs.
105 // All glyphs are given the same vertex information in the form of a
106 // unit-sized quad. The size of the glyph is specified in per instance data
107 // and the vertex shader uses this to size the glyph correctly. The
108 // interpolated vertex information is also used in the fragment shader to
109 // sample from the glyph atlas.
110
111 constexpr std::array<Point, 6> unit_points = {Point{0, 0}, Point{1, 0},
112 Point{0, 1}, Point{1, 0},
113 Point{0, 1}, Point{1, 1}};
114
115 ISize atlas_size = atlas->GetTexture()->GetSize();
116 bool is_translation_scale = entity_transform.IsTranslationScaleOnly();
117 Matrix basis_transform = entity_transform.Basis();
118
119 VS::PerVertexData vtx;
120 size_t i = 0u;
121 size_t bounds_offset = 0u;
122 for (const TextRun& run : frame->GetRuns()) {
123 const Font& font = run.GetFont();
124 Scalar rounded_scale = frame->GetScale();
125 const Matrix transform = frame->GetOffsetTransform();
126 FontGlyphAtlas* font_atlas = nullptr;
127
128 // Adjust glyph position based on the subpixel rounding
129 // used by the font.
130 Point subpixel_adjustment(0.5, 0.5);
131 switch (font.GetAxisAlignment()) {
132 case AxisAlignment::kNone:
133 break;
134 case AxisAlignment::kX:
135 subpixel_adjustment.x = 0.125;
136 break;
137 case AxisAlignment::kY:
138 subpixel_adjustment.y = 0.125;
139 break;
140 case AxisAlignment::kAll:
141 subpixel_adjustment.x = 0.125;
142 subpixel_adjustment.y = 0.125;
143 break;
144 }
145
146 Point screen_offset = (entity_transform * Point(0, 0));
147 for (const TextRun::GlyphPosition& glyph_position :
148 run.GetGlyphPositions()) {
149 const FrameBounds& frame_bounds = frame->GetFrameBounds(bounds_offset);
150 bounds_offset++;
151 auto atlas_glyph_bounds = frame_bounds.atlas_bounds;
152 auto glyph_bounds = frame_bounds.glyph_bounds;
153
154 // If frame_bounds.is_placeholder is true, this is the first frame
155 // the glyph has been rendered and so its atlas position was not
156 // known when the glyph was recorded. Perform a slow lookup into the
157 // glyph atlas hash table.
158 if (frame_bounds.is_placeholder) {
159 if (!font_atlas) {
160 font_atlas =
161 atlas->GetOrCreateFontGlyphAtlas(ScaledFont{font, rounded_scale});
162 }
163
164 if (!font_atlas) {
165 VALIDATION_LOG << "Could not find font in the atlas.";
166 continue;
167 }
168 Point subpixel = TextFrame::ComputeSubpixelPosition(
169 glyph_position, font.GetAxisAlignment(), transform);
170
171 std::optional<FrameBounds> maybe_atlas_glyph_bounds =
172 font_atlas->FindGlyphBounds(SubpixelGlyph{
173 glyph_position.glyph, //
174 subpixel, //
175 glyph_properties //
176 });
177 if (!maybe_atlas_glyph_bounds.has_value()) {
178 VALIDATION_LOG << "Could not find glyph position in the atlas.";
179 continue;
180 }
181 atlas_glyph_bounds = maybe_atlas_glyph_bounds.value().atlas_bounds;
182 }
183
184 Scalar inverted_rounded_scale = 1.f / rounded_scale;
185 Rect scaled_bounds = glyph_bounds.Scale(inverted_rounded_scale);
186 // For each glyph, we compute two rectangles. One for the vertex
187 // positions and one for the texture coordinates (UVs). The atlas
188 // glyph bounds are used to compute UVs in cases where the
189 // destination and source sizes may differ due to clamping the sizes
190 // of large glyphs.
191 Point uv_origin = (atlas_glyph_bounds.GetLeftTop()) / atlas_size;
192 Point uv_size = SizeToPoint(atlas_glyph_bounds.GetSize()) / atlas_size;
193
194 Matrix unscaled_basis =
195 basis_transform * Matrix::MakeScale({inverted_rounded_scale,
196 inverted_rounded_scale, 1});
197
198 // In typical scales < 48x these values should be -1 or 1. We round to
199 // those to avoid inaccuracies.
200 unscaled_basis.m[0] = AttractToOne(unscaled_basis.m[0]);
201 unscaled_basis.m[5] = AttractToOne(unscaled_basis.m[5]);
202
203 Point unrounded_glyph_position =
204 // This is for RTL text.
205 unscaled_basis * glyph_bounds.GetLeftTop() +
206 (basis_transform * glyph_position.position);
207
208 Point screen_glyph_position =
209 (screen_offset + unrounded_glyph_position + subpixel_adjustment)
210 .Floor();
211 for (const Point& point : unit_points) {
212 Point position;
213 if (is_translation_scale) {
214 position = (screen_glyph_position +
215 (unscaled_basis * point * glyph_bounds.GetSize()))
216 .Round();
217 } else {
218 position = entity_transform *
219 (glyph_position.position + scaled_bounds.GetLeftTop() +
220 point * scaled_bounds.GetSize());
221 }
222 vtx.uv = uv_origin + (uv_size * point);
223 vtx.position = position;
224 vtx_contents[i++] = vtx;
225 }
226 }
227 }
228 }
229
230 bool TextContents::Render(const ContentContext& renderer,
231 const Entity& entity,
232 RenderPass& pass) const {
233 auto color = GetColor();
234 if (color.IsTransparent()) {
235 return true;
236 }
237
238 auto type = frame_->GetAtlasType();
239 const std::shared_ptr<GlyphAtlas>& atlas =
240 renderer.GetLazyGlyphAtlas()->CreateOrGetGlyphAtlas(
241 *renderer.GetContext(), renderer.GetTransientsBuffer(), type);
242
243 if (!atlas || !atlas->IsValid()) {
244 VALIDATION_LOG << "Cannot render glyphs without prepared atlas.";
245 return false;
246 }
247 if (!frame_->IsFrameComplete()) {
248 VALIDATION_LOG << "Failed to find font glyph bounds.";
249 return false;
250 }
251
252 // Information shared by all glyph draw calls.
253 pass.SetCommandLabel("TextFrame");
254 auto opts = OptionsFromPassAndEntity(pass, entity);
255 opts.primitive_type = PrimitiveType::kTriangle;
256 pass.SetPipeline(renderer.GetGlyphAtlasPipeline(opts));
257
258 // Common vertex uniforms for all glyphs.
259 VS::FrameInfo frame_info;
260 frame_info.mvp =
261 Entity::GetShaderTransform(entity.GetShaderClipDepth(), pass, Matrix());
262 bool is_translation_scale = entity.GetTransform().IsTranslationScaleOnly();
263 Matrix entity_transform = entity.GetTransform();
264
265 VS::BindFrameInfo(pass,
266 renderer.GetTransientsBuffer().EmplaceUniform(frame_info));
267
268 FS::FragInfo frag_info;
269 frag_info.use_text_color = force_text_color_ ? 1.0 : 0.0;
270 frag_info.text_color = ToVector(color.Premultiply());
271 frag_info.is_color_glyph = type == GlyphAtlas::Type::kColorBitmap;
272
273 FS::BindFragInfo(pass,
274 renderer.GetTransientsBuffer().EmplaceUniform(frag_info));
275
276 SamplerDescriptor sampler_desc;
277 if (is_translation_scale) {
278 sampler_desc.min_filter = MinMagFilter::kNearest;
279 sampler_desc.mag_filter = MinMagFilter::kNearest;
280 } else {
281 // Currently, we only propagate the scale of the transform to the atlas
282 // renderer, so if the transform has more than just a translation, we turn
283 // on linear sampling to prevent crunchiness caused by the pixel grid not
284 // being perfectly aligned.
285 // The downside is that this slightly over-blurs rotated/skewed text.
286 sampler_desc.min_filter = MinMagFilter::kLinear;
287 sampler_desc.mag_filter = MinMagFilter::kLinear;
288 }
289
290 // No mipmaps for glyph atlas (glyphs are generated at exact scales).
291 sampler_desc.mip_filter = MipFilter::kBase;
292
293 FS::BindGlyphAtlasSampler(
294 pass, // command
295 atlas->GetTexture(), // texture
296 renderer.GetContext()->GetSamplerLibrary()->GetSampler(
297 sampler_desc) // sampler
298 );
299
300 auto& host_buffer = renderer.GetTransientsBuffer();
301 size_t vertex_count = 0;
302 for (const auto& run : frame_->GetRuns()) {
303 vertex_count += run.GetGlyphPositions().size();
304 }
305 vertex_count *= 6;
306
307 BufferView buffer_view = host_buffer.Emplace(
308 vertex_count * sizeof(VS::PerVertexData), alignof(VS::PerVertexData),
309 [&](uint8_t* contents) {
310 VS::PerVertexData* vtx_contents =
311 reinterpret_cast<VS::PerVertexData*>(contents);
312 ComputeVertexData(vtx_contents, frame_, scale_,
313 /*entity_transform=*/entity_transform, offset_,
314 GetGlyphProperties(), atlas);
315 });
316
317 pass.SetVertexBuffer(std::move(buffer_view));
318 pass.SetIndexBuffer({}, IndexType::kNone);
319 pass.SetElementCount(vertex_count);
320
321 return pass.Draw().ok();
322 }
323
324 std::optional<GlyphProperties> TextContents::GetGlyphProperties() const {
325 return (properties_.stroke || frame_->HasColor())
326 ? std::optional<GlyphProperties>(properties_)
327 : std::nullopt;
328 }
329
330 } // namespace impeller
type
GLenum type
Definition: blit_command_gles.cc:151
buffer_view
BufferView buffer_view
Definition: blit_command_gles.cc:152
buffer_view.h
impeller::ContentContext
Definition: content_context.h:371
impeller::ContentContext::GetTransientsBuffer
HostBuffer & GetTransientsBuffer() const
Retrieve the currnent host buffer for transient storage.
Definition: content_context.h:866
impeller::ContentContext::GetLazyGlyphAtlas
const std::shared_ptr< LazyGlyphAtlas > & GetLazyGlyphAtlas() const
Definition: content_context.h:834
impeller::ContentContext::GetGlyphAtlasPipeline
PipelineRef GetGlyphAtlasPipeline(ContentContextOptions opts) const
Definition: content_context.h:518
impeller::ContentContext::GetContext
std::shared_ptr< Context > GetContext() const
Definition: content_context.cc:613
impeller::Entity
Definition: entity.h:20
impeller::Entity::GetShaderTransform
Matrix GetShaderTransform(const RenderPass &pass) const
Get the vertex shader transform used for drawing this Entity.
Definition: entity.cc:48
impeller::Entity::GetTransform
const Matrix & GetTransform() const
Get the global transform matrix for this Entity.
Definition: entity.cc:44
impeller::Entity::GetShaderClipDepth
float GetShaderClipDepth() const
Definition: entity.cc:88
impeller::FontGlyphAtlas
An object that can look up glyph locations within the GlyphAtlas for a particular typeface.
Definition: glyph_atlas.h:269
impeller::FontGlyphAtlas::FindGlyphBounds
std::optional< FrameBounds > FindGlyphBounds(const SubpixelGlyph &glyph) const
Find the location of a glyph in the atlas.
Definition: glyph_atlas.cc:131
impeller::Font
Describes a typeface along with any modifications to its intrinsic properties.
Definition: font.h:35
impeller::Font::GetAxisAlignment
AxisAlignment GetAxisAlignment() const
Definition: font.cc:41
impeller::GlyphAtlas::Type::kColorBitmap
@ kColorBitmap
impeller::HostBuffer::EmplaceUniform
BufferView EmplaceUniform(const UniformType &uniform)
Emplace uniform data onto the host buffer. Ensure that backend specific uniform alignment requirement...
Definition: host_buffer.h:48
impeller::RenderPass
Render passes encode render commands directed as one specific render target into an underlying comman...
Definition: render_pass.h:30
impeller::RenderPass::SetVertexBuffer
virtual bool SetVertexBuffer(VertexBuffer buffer)
Specify the vertex and index buffer to use for this command.
Definition: render_pass.cc:127
impeller::RenderPass::SetIndexBuffer
virtual bool SetIndexBuffer(BufferView index_buffer, IndexType index_type)
Specify an index buffer to use for this command. To unset the index buffer, pass IndexType::kNone to ...
Definition: render_pass.cc:164
impeller::RenderPass::SetPipeline
virtual void SetPipeline(PipelineRef pipeline)
The pipeline to use for this command.
Definition: render_pass.cc:86
impeller::RenderPass::Draw
virtual fml::Status Draw()
Record the currently pending command.
Definition: render_pass.cc:208
impeller::RenderPass::SetElementCount
virtual void SetElementCount(size_t count)
Definition: render_pass.cc:119
impeller::RenderPass::SetCommandLabel
virtual void SetCommandLabel(std::string_view label)
The debugging label to use for the command.
Definition: render_pass.cc:97
impeller::RenderPipelineHandle::VertexShader
VertexShader_ VertexShader
Definition: pipeline.h:113
impeller::RenderPipelineHandle::FragmentShader
FragmentShader_ FragmentShader
Definition: pipeline.h:114
impeller::TextContents::~TextContents
~TextContents()
impeller::TextContents::SetOffset
void SetOffset(Vector2 offset)
Definition: text_contents.cc:48
impeller::TextContents::SetTextProperties
void SetTextProperties(Color color, bool stroke, Scalar stroke_width, Cap stroke_cap, Join stroke_join, Scalar stroke_miter)
Must be set after text frame.
Definition: text_contents.cc:60
impeller::TextContents::SetInheritedOpacity
void SetInheritedOpacity(Scalar opacity) override
Inherit the provided opacity.
Definition: text_contents.cc:44
impeller::TextContents::SetForceTextColor
void SetForceTextColor(bool value)
Force the text color to apply to the rendered glyphs, even if those glyphs are bitmaps.
Definition: text_contents.cc:52
impeller::TextContents::Render
bool Render(const ContentContext &renderer, const Entity &entity, RenderPass &pass) const override
Definition: text_contents.cc:230
impeller::TextContents::GetCoverage
std::optional< Rect > GetCoverage(const Entity &entity) const override
Get the area of the render pass that will be affected when this contents is rendered.
Definition: text_contents.cc:56
impeller::TextContents::SetTextFrame
void SetTextFrame(const std::shared_ptr< TextFrame > &frame)
Definition: text_contents.cc:32
impeller::TextContents::SetColor
void SetColor(Color color)
Definition: text_contents.cc:36
impeller::TextContents::TextContents
TextContents()
impeller::TextContents::ComputeVertexData
static void ComputeVertexData(GlyphAtlasPipeline::VertexShader::PerVertexData *vtx_contents, const std::shared_ptr< TextFrame > &frame, Scalar scale, const Matrix &entity_transform, Vector2 offset, std::optional< GlyphProperties > glyph_properties, const std::shared_ptr< GlyphAtlas > &atlas)
Definition: text_contents.cc:96
impeller::TextContents::GetColor
Color GetColor() const
Definition: text_contents.cc:40
impeller::TextFrame::ComputeSubpixelPosition
static Point ComputeSubpixelPosition(const TextRun::GlyphPosition &glyph_position, AxisAlignment alignment, const Matrix &transform)
Definition: text_frame.cc:69
impeller::TextRun
Represents a collection of positioned glyphs from a specific font.
Definition: text_run.h:20
color.h
formats.h
value
int32_t value
Definition: dl_golden_unittests.cc:444
x
int32_t x
Definition: dl_golden_unittests.cc:443
entity.h
transform
Matrix transform
Definition: gaussian_blur_filter_contents.cc:214
glyph_atlas.h
impeller
Definition: allocation.cc:12
impeller::IndexType::kNone
@ kNone
Does not use the index buffer.
impeller::Join
Join
Definition: path.h:25
impeller::PrimitiveType::kTriangle
@ kTriangle
impeller::Scalar
float Scalar
Definition: scalar.h:18
impeller::VS
GlyphAtlasPipeline::VertexShader VS
Definition: text_contents.cc:25
impeller::Point
TPoint< Scalar > Point
Definition: point.h:327
impeller::Cap
Cap
Definition: path.h:19
impeller::AxisAlignment::kX
@ kX
impeller::AxisAlignment::kAll
@ kAll
impeller::AxisAlignment::kNone
@ kNone
impeller::AxisAlignment::kY
@ kY
impeller::MipFilter::kBase
@ kBase
The texture is sampled as if it only had a single mipmap level.
impeller::SizeToPoint
Point SizeToPoint(Size size)
Definition: text_contents.cc:21
impeller::ToVector
constexpr Vector4 ToVector(Color color)
Definition: shader_types.h:190
impeller::FS
GlyphAtlasPipeline::FragmentShader FS
Definition: text_contents.cc:26
impeller::OptionsFromPassAndEntity
ContentContextOptions OptionsFromPassAndEntity(const RenderPass &pass, const Entity &entity)
Definition: contents.cc:34
impeller::MinMagFilter::kLinear
@ kLinear
impeller::MinMagFilter::kNearest
@ kNearest
Select nearest to the sample point. Most widely supported.
std
Definition: comparable.h:95
point.h
render_pass.h
sampler_descriptor.h
vtx
SolidFillVertexShader::PerVertexData vtx
Definition: stroke_path_geometry.cc:320
stroke_width
const Scalar stroke_width
Definition: stroke_path_geometry.cc:312
scale
const Scalar scale
Definition: stroke_path_geometry.cc:316
offset
SeparatedVector2 offset
Definition: stroke_path_geometry.cc:319
impeller::BufferView
Definition: buffer_view.h:19
impeller::Color
Definition: color.h:123
impeller::Color::alpha
Scalar alpha
Definition: color.h:142
impeller::Color::WithAlpha
constexpr Color WithAlpha(Scalar new_alpha) const
Definition: color.h:277
impeller::FrameBounds
Definition: glyph_atlas.h:55
impeller::FrameBounds::atlas_bounds
Rect atlas_bounds
The bounds of the glyph within the glyph atlas.
Definition: glyph_atlas.h:57
impeller::FrameBounds::glyph_bounds
Rect glyph_bounds
The local glyph bounds.
Definition: glyph_atlas.h:59
impeller::FrameBounds::is_placeholder
bool is_placeholder
Definition: glyph_atlas.h:62
impeller::GlyphProperties::color
Color color
Definition: font_glyph_pair.h:17
impeller::GlyphProperties::stroke_cap
Cap stroke_cap
Definition: font_glyph_pair.h:19
impeller::GlyphProperties::stroke_width
Scalar stroke_width
Definition: font_glyph_pair.h:18
impeller::GlyphProperties::stroke_join
Join stroke_join
Definition: font_glyph_pair.h:20
impeller::GlyphProperties::stroke_miter
Scalar stroke_miter
Definition: font_glyph_pair.h:21
impeller::GlyphProperties::stroke
bool stroke
Definition: font_glyph_pair.h:22
impeller::Matrix
A 4x4 matrix using column-major storage.
Definition: matrix.h:37
impeller::Matrix::IsTranslationScaleOnly
constexpr bool IsTranslationScaleOnly() const
Returns true if the matrix has a scale-only basis and is non-projective. Note that an identity matrix...
Definition: matrix.h:427
impeller::Matrix::m
Scalar m[16]
Definition: matrix.h:39
impeller::Matrix::Basis
constexpr Matrix Basis() const
The Matrix without its w components (without translation).
Definition: matrix.h:239
impeller::Matrix::MakeScale
static constexpr Matrix MakeScale(const Vector3 &s)
Definition: matrix.h:104
impeller::SamplerDescriptor
Definition: sampler_descriptor.h:14
impeller::SamplerDescriptor::mip_filter
MipFilter mip_filter
Definition: sampler_descriptor.h:17
impeller::SamplerDescriptor::mag_filter
MinMagFilter mag_filter
Definition: sampler_descriptor.h:16
impeller::SamplerDescriptor::min_filter
MinMagFilter min_filter
Definition: sampler_descriptor.h:15
impeller::ScaledFont
A font and a scale. Used as a key that represents a typeface within a glyph atlas.
Definition: font_glyph_pair.h:40
impeller::SubpixelGlyph
A glyph and its subpixel position.
Definition: font_glyph_pair.h:60
impeller::SubpixelGlyph::glyph
Glyph glyph
Definition: font_glyph_pair.h:61
impeller::TPoint< Scalar >
impeller::TPoint::Round
static constexpr TPoint Round(const TPoint< U > &other)
Definition: point.h:49
impeller::TPoint::y
Type y
Definition: point.h:31
impeller::TPoint::x
Type x
Definition: point.h:30
impeller::TRect< Scalar >
impeller::TRect::GetSize
constexpr TSize< Type > GetSize() const
Returns the size of the rectangle which may be negative in either width or height and may have been c...
Definition: rect.h:331
impeller::TRect::Scale
constexpr TRect Scale(Type scale) const
Definition: rect.h:206
impeller::TRect::GetLeftTop
constexpr TPoint< T > GetLeftTop() const
Definition: rect.h:363
impeller::TSize< Scalar >
impeller::TSize::height
Type height
Definition: size.h:29
impeller::TSize::width
Type width
Definition: size.h:28
impeller::TextRun::GlyphPosition
Definition: text_run.h:22
text_contents.h
VALIDATION_LOG
#define VALIDATION_LOG
Definition: validation.h:91