| Flutter Impeller |

Public Member Functions | Static Public Member Functions | List of all members
impeller::TypographerContextSkia Class Reference

`#include <typographer_context_skia.h>`

Inheritance diagram for impeller::TypographerContextSkia:

## Public Member Functions
| TypographerContextSkia ()
| ~TypographerContextSkia () override
std::shared_ptr< GlyphAtlasContext > | CreateGlyphAtlasContext (GlyphAtlas::Type type) const override
std::shared_ptr< GlyphAtlas > | CreateGlyphAtlas (Context &context, GlyphAtlas::Type type, HostBuffer &host_buffer, const std::shared_ptr< GlyphAtlasContext > &atlas_context, const std::vector< std::shared_ptr< TextFrame >> &text_frames) const override
Public Member Functions inherited from impeller::TypographerContext
virtual | ~TypographerContext ()
virtual bool | IsValid () const

## Static Public Member Functions
static std::shared_ptr< TypographerContext > | Make ()

## Additional Inherited Members
Protected Member Functions inherited from impeller::TypographerContext
| TypographerContext ()
| Create a new context to render text that talks to an underlying graphics context. More...

## Detailed Description

Definition at line 12 of file typographer_context_skia.h.

## Constructor & Destructor Documentation

## ◆ TypographerContextSkia()

impeller::TypographerContextSkia::TypographerContextSkia | ( |  | ) |
| default

## ◆ ~TypographerContextSkia()

impeller::TypographerContextSkia::~TypographerContextSkia | ( |  | ) |
| override default

## Member Function Documentation

## ◆ CreateGlyphAtlas()

std::shared_ptr< GlyphAtlas > impeller::TypographerContextSkia::CreateGlyphAtlas | ( | Context & | context,
|  | GlyphAtlas::Type | type,
|  | HostBuffer & | host_buffer,
|  | const std::shared_ptr< GlyphAtlasContext > & | atlas_context,
|  | const std::vector< std::shared_ptr< TextFrame >> & | text_frames
| ) |  | const
| override virtual

Implements impeller::TypographerContext.

Definition at line 498 of file typographer_context_skia.cc.

503 {
504 TRACE_EVENT0("impeller", __FUNCTION__);
505 if (!IsValid()) {
506 return nullptr;
507 }
508 std::shared_ptr<GlyphAtlas> last_atlas = atlas_context->GetGlyphAtlas();
509 FML_DCHECK(last_atlas->GetType() == type);
510
511 if (text_frames.empty()) {
512 return last_atlas;
513 }
514
515 // ---------------------------------------------------------------------------
516 // Step 1: Determine if the atlas type and font glyph pairs are compatible
517 // with the current atlas and reuse if possible. For each new font and
518 // glyph pair, compute the glyph size at scale.
519 // ---------------------------------------------------------------------------
520 auto [new_glyphs, glyph_sizes] = CollectNewGlyphs(last_atlas, text_frames);
521 if (new_glyphs.size() == 0) {
522 return last_atlas;
523 }
524
525 // ---------------------------------------------------------------------------
526 // Step 2: Determine if the additional missing glyphs can be appended to the
527 // existing bitmap without recreating the atlas.
528 // ---------------------------------------------------------------------------
529 std::vector<Rect> glyph_positions;
530 glyph_positions.reserve(new_glyphs.size());
531 size_t first_missing_index = 0;
532
533 if (last_atlas->GetTexture()) {
534 // Append all glyphs that fit into the current atlas.
535 first_missing_index = AppendToExistingAtlas(
536 last_atlas, new_glyphs, glyph_positions, glyph_sizes,
537 atlas_context->GetAtlasSize(), atlas_context->GetHeightAdjustment(),
538 atlas_context->GetRectPacker());
539
540 // ---------------------------------------------------------------------------
541 // Step 3a: Record the positions in the glyph atlas of the newly added
542 // glyphs.
543 // ---------------------------------------------------------------------------
544 for (size_t i = 0; i < first_missing_index; i++) {
545 last_atlas->AddTypefaceGlyphPositionAndBounds(
546 new_glyphs[i], glyph_positions[i], glyph_sizes[i]);
547 }
548
549 std::shared_ptr<CommandBuffer> cmd_buffer = context.CreateCommandBuffer();
550 std::shared_ptr<BlitPass> blit_pass = cmd_buffer->CreateBlitPass();
551
552 fml::ScopedCleanupClosure closure([&]() {
553 blit_pass->EncodeCommands();
554 if (!context.EnqueueCommandBuffer(std::move(cmd_buffer))) {
555 VALIDATION_LOG << "Failed to submit glyph atlas command buffer";
556 }
557 });
558
559 // ---------------------------------------------------------------------------
560 // Step 4a: Draw new font-glyph pairs into the a host buffer and encode
561 // the uploads into the blit pass.
562 // ---------------------------------------------------------------------------
563 if (!UpdateAtlasBitmap(*last_atlas, blit_pass, host_buffer,
564 last_atlas->GetTexture(), new_glyphs, 0,
565 first_missing_index)) {
566 return nullptr;
567 }
568
569 // If all glyphs fit, just return the old atlas.
570 if (first_missing_index == new_glyphs.size()) {
571 return last_atlas;
572 }
573 }
574
575 int64_t height_adjustment = atlas_context->GetAtlasSize().height;
576 const int64_t max_texture_height =
577 context.GetResourceAllocator()->GetMaxTextureSizeSupported().height;
578
579 // IF the current atlas size is as big as it can get, then "GC" and create an
580 // atlas with only the required glyphs. OpenGLES cannot reliably perform the
581 // blit required here, as 1) it requires attaching textures as read and write
582 // framebuffers which has substantially smaller size limits that max textures
583 // and 2) is missing a GLES 2.0 implementation and cap check.
584 bool blit_old_atlas = true;
585 std::shared_ptr<GlyphAtlas> new_atlas = last_atlas;
586 if (atlas_context->GetAtlasSize().height >= max_texture_height ||
587 context.GetBackendType() == Context::BackendType::kOpenGLES) {
588 blit_old_atlas = false;
589 new_atlas = std::make_shared<GlyphAtlas>(
590 type, /*initial_generation=*/last_atlas->GetAtlasGeneration() + 1);
591
592 auto [update_glyphs, update_sizes] =
593 CollectNewGlyphs(new_atlas, text_frames);
594 new_glyphs = std::move(update_glyphs);
595 glyph_sizes = std::move(update_sizes);
596
597 glyph_positions.clear();
598 glyph_positions.reserve(new_glyphs.size());
599 first_missing_index = 0;
600
601 height_adjustment = 0;
602 atlas_context->UpdateRectPacker(nullptr);
603 atlas_context->UpdateGlyphAtlas(new_atlas, {0, 0}, 0);
604 }
605
606 // A new glyph atlas must be created.
607 ISize atlas_size = ComputeNextAtlasSize(atlas_context, //
608 new_glyphs, //
609 glyph_positions, //
610 glyph_sizes, //
611 first_missing_index, //
612 max_texture_height //
613 );
614
615 atlas_context->UpdateGlyphAtlas(new_atlas, atlas_size, height_adjustment);
616 if (atlas_size.IsEmpty()) {
617 return nullptr;
618 }
619 FML_DCHECK(new_glyphs.size() == glyph_positions.size());
620
621 TextureDescriptor descriptor;
622 switch (type) {
623 case GlyphAtlas::Type::kAlphaBitmap:
624 descriptor.format =
625 context.GetCapabilities()->GetDefaultGlyphAtlasFormat();
626 break;
627 case GlyphAtlas::Type::kColorBitmap:
628 descriptor.format = PixelFormat::kR8G8B8A8UNormInt;
629 break;
630 }
631 descriptor.size = atlas_size;
632 descriptor.storage_mode = StorageMode::kDevicePrivate;
633 descriptor.usage = TextureUsage::kShaderRead;
634 std::shared_ptr<Texture> new_texture =
635 context.GetResourceAllocator()->CreateTexture(descriptor);
636 if (!new_texture) {
637 return nullptr;
638 }
639
640 new_texture->SetLabel("GlyphAtlas");
641
642 std::shared_ptr<CommandBuffer> cmd_buffer = context.CreateCommandBuffer();
643 std::shared_ptr<BlitPass> blit_pass = cmd_buffer->CreateBlitPass();
644
645 fml::ScopedCleanupClosure closure([&]() {
646 blit_pass->EncodeCommands();
647 if (!context.EnqueueCommandBuffer(std::move(cmd_buffer))) {
648 VALIDATION_LOG << "Failed to submit glyph atlas command buffer";
649 }
650 });
651
652 // Now append all remaining glyphs. This should never have any missing data...
653 auto old_texture = new_atlas->GetTexture();
654 new_atlas->SetTexture(std::move(new_texture));
655
656 // ---------------------------------------------------------------------------
657 // Step 3a: Record the positions in the glyph atlas of the newly added
658 // glyphs.
659 // ---------------------------------------------------------------------------
660 for (size_t i = first_missing_index; i < glyph_positions.size(); i++) {
661 new_atlas->AddTypefaceGlyphPositionAndBounds(
662 new_glyphs[i], glyph_positions[i], glyph_sizes[i]);
663 }
664
665 // ---------------------------------------------------------------------------
666 // Step 4a: Draw new font-glyph pairs into the a host buffer and encode
667 // the uploads into the blit pass.
668 // ---------------------------------------------------------------------------
669 if (!BulkUpdateAtlasBitmap(*new_atlas, blit_pass, host_buffer,
670 new_atlas->GetTexture(), new_glyphs,
671 first_missing_index, new_glyphs.size())) {
672 return nullptr;
673 }
674
675 // Blit the old texture to the top left of the new atlas.
676 if (blit_old_atlas && old_texture) {
677 blit_pass->AddCopy(old_texture, new_atlas->GetTexture(),
678 IRect::MakeSize(new_atlas->GetTexture()->GetSize()),
679 {0, 0});
680 }
681
682 // ---------------------------------------------------------------------------
683 // Step 8b: Record the texture in the glyph atlas.
684 // ---------------------------------------------------------------------------
685
686 return new_atlas;
687 }
type
GLenum type
Definition: blit_command_gles.cc:151
impeller::Context::BackendType::kOpenGLES
@ kOpenGLES
impeller::GlyphAtlas::Type::kAlphaBitmap
@ kAlphaBitmap
impeller::GlyphAtlas::Type::kColorBitmap
@ kColorBitmap
impeller::TypographerContext::IsValid
virtual bool IsValid() const
Definition: typographer_context.cc:17
impeller::BulkUpdateAtlasBitmap
static bool BulkUpdateAtlasBitmap(const GlyphAtlas &atlas, std::shared_ptr< BlitPass > &blit_pass, HostBuffer &host_buffer, const std::shared_ptr< Texture > &texture, const std::vector< FontGlyphPair > &new_pairs, size_t start_index, size_t end_index)
Batch render to a single surface.
Definition: typographer_context_skia.cc:261
impeller::StorageMode::kDevicePrivate
@ kDevicePrivate
impeller::AppendToExistingAtlas
static size_t AppendToExistingAtlas(const std::shared_ptr< GlyphAtlas > &atlas, const std::vector< FontGlyphPair > &extra_pairs, std::vector< Rect > &glyph_positions, const std::vector< Rect > &glyph_sizes, ISize atlas_size, int64_t height_adjustment, const std::shared_ptr< RectanglePacker > &rect_packer)
Definition: typographer_context_skia.cc:103
impeller::ComputeNextAtlasSize
static ISize ComputeNextAtlasSize(const std::shared_ptr< GlyphAtlasContext > &atlas_context, const std::vector< FontGlyphPair > &extra_pairs, std::vector< Rect > &glyph_positions, const std::vector< Rect > &glyph_sizes, size_t glyph_index_start, int64_t max_texture_height)
Definition: typographer_context_skia.cc:167
impeller::PixelFormat::kR8G8B8A8UNormInt
@ kR8G8B8A8UNormInt
impeller::ISize
ISize64 ISize
Definition: size.h:162
impeller::UpdateAtlasBitmap
static bool UpdateAtlasBitmap(const GlyphAtlas &atlas, std::shared_ptr< BlitPass > &blit_pass, HostBuffer &host_buffer, const std::shared_ptr< Texture > &texture, const std::vector< FontGlyphPair > &new_pairs, size_t start_index, size_t end_index)
Definition: typographer_context_skia.cc:320
impeller::TextureUsage::kShaderRead
@ kShaderRead
impeller::TRect::MakeSize
constexpr static TRect MakeSize(const TSize< U > &size)
Definition: rect.h:150

References impeller::AppendToExistingAtlas(), impeller::BulkUpdateAtlasBitmap(), impeller::ComputeNextAtlasSize(), impeller::Context::CreateCommandBuffer(), impeller::Context::EnqueueCommandBuffer(), impeller::TextureDescriptor::format, impeller::Context::GetBackendType(), impeller::Context::GetCapabilities(), impeller::Context::GetResourceAllocator(), impeller::TSize< T >::IsEmpty(), impeller::TypographerContext::IsValid(), impeller::GlyphAtlas::kAlphaBitmap, impeller::GlyphAtlas::kColorBitmap, impeller::kDevicePrivate, impeller::Context::kOpenGLES, impeller::kR8G8B8A8UNormInt, impeller::kShaderRead, impeller::TRect< T >::MakeSize(), impeller::TextureDescriptor::size, impeller::TextureDescriptor::storage_mode, type, impeller::UpdateAtlasBitmap(), and impeller::TextureDescriptor::usage.

## ◆ CreateGlyphAtlasContext()

std::shared_ptr< GlyphAtlasContext > impeller::TypographerContextSkia::CreateGlyphAtlasContext | ( | GlyphAtlas::Type | type | ) | const
| override virtual

Implements impeller::TypographerContext.

Definition at line 86 of file typographer_context_skia.cc.

86 {
87 return std::make_shared<GlyphAtlasContext>(type);
88 }

References type.

## ◆ Make()

std::shared_ptr< TypographerContext > impeller::TypographerContextSkia::Make | ( |  | ) |
| static

Definition at line 77 of file typographer_context_skia.cc.

77 {
78 return std::make_shared<TypographerContextSkia>();
79 }

Referenced by impeller::DlPlayground::OpenPlaygroundHere(), and impeller::testing::TEST_P().

The documentation for this class was generated from the following files:

- impeller/typographer/backends/skia/typographer_context_skia.h
- impeller/typographer/backends/skia/typographer_context_skia.cc