| Flutter Impeller |

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

`#include <typographer_context_stb.h>`

Inheritance diagram for impeller::TypographerContextSTB:

## Public Member Functions
| TypographerContextSTB ()
| ~TypographerContextSTB () 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 FontGlyphMap &font_glyph_map) const override
Public Member Functions inherited from impeller::TypographerContext
virtual | ~TypographerContext ()
virtual bool | IsValid () const

## Static Public Member Functions
static std::unique_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 15 of file typographer_context_stb.h.

## Constructor & Destructor Documentation

## ◆ TypographerContextSTB()

impeller::TypographerContextSTB::TypographerContextSTB | ( |  | ) |

Definition at line 36 of file typographer_context_stb.cc.

36 : TypographerContext() {}

## ◆ ~TypographerContextSTB()

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

## Member Function Documentation

## ◆ CreateGlyphAtlas()

std::shared_ptr< GlyphAtlas > impeller::TypographerContextSTB::CreateGlyphAtlas | ( | Context & | context,
|  | GlyphAtlas::Type | type,
|  | HostBuffer & | host_buffer,
|  | const std::shared_ptr< GlyphAtlasContext > & | atlas_context,
|  | const FontGlyphMap & | font_glyph_map
| ) |  | const
| override virtual

Implements impeller::TypographerContext.

Definition at line 399 of file typographer_context_stb.cc.

404 {
405 TRACE_EVENT0("impeller", __FUNCTION__);
406 if (!IsValid()) {
407 return nullptr;
408 }
409 auto& atlas_context_stb = GlyphAtlasContextSTB::Cast(*atlas_context);
410 std::shared_ptr<GlyphAtlas> last_atlas = atlas_context->GetGlyphAtlas();
411
412 if (font_glyph_map.empty()) {
413 return last_atlas;
414 }
415
416 // ---------------------------------------------------------------------------
417 // Step 1: Determine if the atlas type and font glyph pairs are compatible
418 // with the current atlas and reuse if possible.
419 // ---------------------------------------------------------------------------
420 std::vector<FontGlyphPair> new_glyphs;
421 std::vector<Rect> new_sizes;
422 for (const auto& font_value : font_glyph_map) {
423 const ScaledFont& scaled_font = font_value.first;
424 const FontGlyphAtlas* font_glyph_atlas =
425 last_atlas->GetFontGlyphAtlas(scaled_font.font, scaled_font.scale);
426 if (font_glyph_atlas) {
427 for (const SubpixelGlyph& glyph : font_value.second) {
428 if (!font_glyph_atlas->FindGlyphBounds(glyph)) {
429 new_glyphs.emplace_back(scaled_font, glyph);
430 new_sizes.push_back(ComputeGlyphSize(scaled_font, glyph));
431 }
432 }
433 } else {
434 for (const SubpixelGlyph& glyph : font_value.second) {
435 new_glyphs.emplace_back(scaled_font, glyph);
436 new_sizes.push_back(ComputeGlyphSize(scaled_font, glyph));
437 }
438 }
439 }
440
441 if (last_atlas->GetType() == type && new_glyphs.size() == 0) {
442 return last_atlas;
443 }
444
445 std::shared_ptr<CommandBuffer> cmd_buffer = context.CreateCommandBuffer();
446 std::shared_ptr<BlitPass> blit_pass = cmd_buffer->CreateBlitPass();
447
448 fml::ScopedCleanupClosure closure([&cmd_buffer, &context]() {
449 context.GetCommandQueue()->Submit({std::move(cmd_buffer)});
450 });
451
452 // ---------------------------------------------------------------------------
453 // Step 2: Determine if the additional missing glyphs can be appended to the
454 // existing bitmap without recreating the atlas. This requires that
455 // the type is identical.
456 // ---------------------------------------------------------------------------
457 std::vector<Rect> glyph_positions;
458 if (last_atlas->GetType() == type &&
459 CanAppendToExistingAtlas(last_atlas, new_glyphs, glyph_positions,
460 atlas_context->GetAtlasSize(),
461 atlas_context->GetRectPacker())) {
462 // The old bitmap will be reused and only the additional glyphs will be
463 // added.
464
465 // ---------------------------------------------------------------------------
466 // Step 3a: Record the positions in the glyph atlas of the newly added
467 // glyphs.
468 // ---------------------------------------------------------------------------
469 for (size_t i = 0, count = glyph_positions.size(); i < count; i++) {
470 last_atlas->AddTypefaceGlyphPositionAndBounds(
471 new_glyphs[i], glyph_positions[i], new_sizes[i]);
472 }
473
474 // ---------------------------------------------------------------------------
475 // Step 4a: Draw new font-glyph pairs into the existing bitmap.
476 // ---------------------------------------------------------------------------
477 // auto bitmap = atlas_context->GetBitmap();
478 auto bitmap = atlas_context_stb.GetBitmap();
479 if (!UpdateAtlasBitmap(*last_atlas, bitmap, new_glyphs)) {
480 return nullptr;
481 }
482
483 // ---------------------------------------------------------------------------
484 // Step 5a: Update the existing texture with the updated bitmap.
485 // ---------------------------------------------------------------------------
486 if (!UpdateGlyphTextureAtlas(bitmap, context.GetResourceAllocator(),
487 blit_pass, last_atlas->GetTexture())) {
488 return nullptr;
489 }
490 return last_atlas;
491 }
492 // A new glyph atlas must be created.
493
494 // ---------------------------------------------------------------------------
495 // Step 3b: Get the optimum size of the texture atlas.
496 // ---------------------------------------------------------------------------
497 std::vector<FontGlyphPair> font_glyph_pairs;
498 font_glyph_pairs.reserve(std::accumulate(
499 font_glyph_map.begin(), font_glyph_map.end(), 0,
500 [](const int a, const auto& b) { return a + b.second.size(); }));
501 for (const auto& font_value : font_glyph_map) {
502 const ScaledFont& scaled_font = font_value.first;
503 for (const SubpixelGlyph& glyph : font_value.second) {
504 font_glyph_pairs.push_back({scaled_font, glyph});
505 }
506 }
507 auto glyph_atlas = std::make_shared<GlyphAtlas>(type);
508 auto atlas_size = OptimumAtlasSizeForFontGlyphPairs(
509 font_glyph_pairs, //
510 glyph_positions, //
511 atlas_context, //
512 type, //
513 context.GetResourceAllocator()->GetMaxTextureSizeSupported() //
514 );
515
516 atlas_context->UpdateGlyphAtlas(glyph_atlas, atlas_size, 0);
517 if (atlas_size.IsEmpty()) {
518 return nullptr;
519 }
520
521 // ---------------------------------------------------------------------------
522 // Step 4b: Find location of font-glyph pairs in the atlas. We have this from
523 // the last step. So no need to do create another rect packer. But just do a
524 // sanity check of counts. This could also be just an assertion as only a
525 // construction issue would cause such a failure.
526 // ---------------------------------------------------------------------------
527 if (glyph_positions.size() != font_glyph_pairs.size()) {
528 return nullptr;
529 }
530
531 // ---------------------------------------------------------------------------
532 // Step 5b: Record the positions in the glyph atlas.
533 // ---------------------------------------------------------------------------
534 {
535 size_t i = 0;
536 for (auto it = font_glyph_pairs.begin(); it != font_glyph_pairs.end();
537 ++i, ++it) {
538 glyph_atlas->AddTypefaceGlyphPositionAndBounds(*it, glyph_positions[i],
539 new_sizes[i]);
540 }
541 }
542
543 // ---------------------------------------------------------------------------
544 // Step 6b: Draw font-glyph pairs in the correct spot in the atlas.
545 // ---------------------------------------------------------------------------
546 auto bitmap = CreateAtlasBitmap(*glyph_atlas, atlas_size);
547 if (!bitmap) {
548 return nullptr;
549 }
550 atlas_context_stb.UpdateBitmap(bitmap);
551
552 // ---------------------------------------------------------------------------
553 // Step 7b: Upload the atlas as a texture.
554 // ---------------------------------------------------------------------------
555 PixelFormat format;
556 switch (type) {
557 case GlyphAtlas::Type::kAlphaBitmap:
558 format = context.GetCapabilities()->GetDefaultGlyphAtlasFormat();
559 break;
560 case GlyphAtlas::Type::kColorBitmap:
561 format = DISABLE_COLOR_FONT_SUPPORT
562 ? context.GetCapabilities()->GetDefaultGlyphAtlasFormat()
563 : PixelFormat::kR8G8B8A8UNormInt;
564 break;
565 }
566 auto texture = UploadGlyphTextureAtlas(context.GetResourceAllocator(),
567 blit_pass, bitmap, atlas_size, format);
568 if (!texture) {
569 return nullptr;
570 }
571
572 // ---------------------------------------------------------------------------
573 // Step 8b: Record the texture in the glyph atlas.
574 // ---------------------------------------------------------------------------
575 glyph_atlas->SetTexture(std::move(texture));
576
577 return glyph_atlas;
578 }

References impeller::saturated::b, impeller::CanAppendToExistingAtlas(), impeller::BackendCast< GlyphAtlasContextSTB, GlyphAtlasContext >::Cast(), impeller::ComputeGlyphSize(), impeller::CreateAtlasBitmap(), impeller::Context::CreateCommandBuffer(), DISABLE_COLOR_FONT_SUPPORT, impeller::FontGlyphAtlas::FindGlyphBounds(), impeller::ScaledFont::font, impeller::Context::GetCapabilities(), impeller::Context::GetCommandQueue(), impeller::Context::GetResourceAllocator(), impeller::TypographerContext::IsValid(), impeller::GlyphAtlas::kAlphaBitmap, impeller::GlyphAtlas::kColorBitmap, impeller::kR8G8B8A8UNormInt, impeller::OptimumAtlasSizeForFontGlyphPairs(), impeller::ScaledFont::scale, type, impeller::UpdateAtlasBitmap(), impeller::UpdateGlyphTextureAtlas(), and impeller::UploadGlyphTextureAtlas().

## ◆ CreateGlyphAtlasContext()

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

Implements impeller::TypographerContext.

Definition at line 41 of file typographer_context_stb.cc.

41 {
42 return std::make_shared<GlyphAtlasContextSTB>(type);
43 }

References type.

## ◆ Make()

std::unique_ptr< TypographerContext > impeller::TypographerContextSTB::Make | ( |  | ) |
| static

Definition at line 32 of file typographer_context_stb.cc.

32 {
33 return std::make_unique<TypographerContextSTB>();
34 }

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

- impeller/typographer/backends/stb/typographer_context_stb.h
- impeller/typographer/backends/stb/typographer_context_stb.cc

impeller::CreateAtlasBitmap
static std::shared_ptr< BitmapSTB > CreateAtlasBitmap(const GlyphAtlas &atlas, const ISize &atlas_size)
Definition: typographer_context_stb.cc:291
impeller::GlyphAtlas::Type::kColorBitmap
@ kColorBitmap
impeller::UpdateGlyphTextureAtlas
static bool UpdateGlyphTextureAtlas(std::shared_ptr< BitmapSTB > &bitmap, const std::shared_ptr< Allocator > &allocator, std::shared_ptr< BlitPass > &blit_pass, const std::shared_ptr< Texture > &texture)
Definition: typographer_context_stb.cc:316
impeller::GlyphAtlas::Type::kAlphaBitmap
@ kAlphaBitmap
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:311
impeller::PixelFormat::kR8G8B8A8UNormInt
@ kR8G8B8A8UNormInt
impeller::UploadGlyphTextureAtlas
static std::shared_ptr< Texture > UploadGlyphTextureAtlas(const std::shared_ptr< Allocator > &allocator, std::shared_ptr< BlitPass > &blit_pass, std::shared_ptr< BitmapSTB > &bitmap, const ISize &atlas_size, PixelFormat format)
Definition: typographer_context_stb.cc:340
impeller::TypographerContext::TypographerContext
TypographerContext()
Create a new context to render text that talks to an underlying graphics context.
Definition: typographer_context.cc:11
impeller::PixelFormat
PixelFormat
The Pixel formats supported by Impeller. The naming convention denotes the usage of the component,...
Definition: formats.h:99
impeller::CanAppendToExistingAtlas
static bool CanAppendToExistingAtlas(const std::shared_ptr< GlyphAtlas > &atlas, const std::vector< FontGlyphPair > &extra_pairs, std::vector< Rect > &glyph_positions, ISize atlas_size, const std::shared_ptr< RectanglePacker > &rect_packer)
Definition: typographer_context_stb.cc:102
type
GLenum type
Definition: blit_command_gles.cc:127
DISABLE_COLOR_FONT_SUPPORT
#define DISABLE_COLOR_FONT_SUPPORT
Definition: typographer_context_stb.cc:21
impeller::saturated::b
SI b
Definition: saturated_math.h:87
impeller::BackendCast< GlyphAtlasContextSTB, GlyphAtlasContext >::Cast
static GlyphAtlasContextSTB & Cast(GlyphAtlasContext &base)
Definition: backend_cast.h:13
impeller::OptimumAtlasSizeForFontGlyphPairs
static ISize OptimumAtlasSizeForFontGlyphPairs(const std::vector< FontGlyphPair > &pairs, std::vector< Rect > &glyph_positions, const std::shared_ptr< GlyphAtlasContext > &atlas_context, GlyphAtlas::Type type, const ISize &max_texture_size)
Definition: typographer_context_stb.cc:160
impeller::ComputeGlyphSize
static Rect ComputeGlyphSize(const SkFont &font, const SubpixelGlyph &glyph, Scalar scale)
Definition: typographer_context_skia.cc:381
impeller::TypographerContext::IsValid
virtual bool IsValid() const
Definition: typographer_context.cc:17