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[Impeller] write glyphs to malloc buffer. #52937

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May 20, 2024
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[Impeller] write glyphs to malloc buffer. #52937

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65 changes: 11 additions & 54 deletions impeller/typographer/backends/skia/typographer_context_skia.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -46,56 +46,6 @@ namespace impeller {
// https://github.com/flutter/flutter/issues/114563
constexpr auto kPadding = 2;

namespace {

class HostBufferAllocator : public SkBitmap::Allocator {
public:
explicit HostBufferAllocator(HostBuffer& host_buffer)
: host_buffer_(host_buffer) {}

[[nodiscard]] BufferView TakeBufferView() {
buffer_view_.buffer->Flush();
return std::move(buffer_view_);
}

// |SkBitmap::Allocator|
bool allocPixelRef(SkBitmap* bitmap) override {
if (!bitmap) {
return false;
}
const SkImageInfo& info = bitmap->info();
if (kUnknown_SkColorType == info.colorType() || info.width() < 0 ||
info.height() < 0 || !info.validRowBytes(bitmap->rowBytes())) {
return false;
}

size_t required_bytes = bitmap->rowBytes() * bitmap->height();
BufferView buffer_view = host_buffer_.Emplace(nullptr, required_bytes,
DefaultUniformAlignment());

// The impeller host buffer is not cleared between frames and may contain
// stale data. The Skia software canvas does not write to pixels without
// any contents, which causes this data to leak through.
::memset(buffer_view.buffer->OnGetContents() + buffer_view.range.offset, 0,
required_bytes);

auto pixel_ref = sk_sp<SkPixelRef>(new SkPixelRef(
info.width(), info.height(),
buffer_view.buffer->OnGetContents() + buffer_view.range.offset,
bitmap->rowBytes()));

bitmap->setPixelRef(std::move(pixel_ref), 0, 0);
buffer_view_ = std::move(buffer_view);
return true;
}

private:
BufferView buffer_view_;
HostBuffer& host_buffer_;
};

} // namespace

std::shared_ptr<TypographerContext> TypographerContextSkia::Make() {
return std::make_shared<TypographerContextSkia>();
}
Expand Down Expand Up @@ -282,9 +232,8 @@ static bool UpdateAtlasBitmap(const GlyphAtlas& atlas,
}

SkBitmap bitmap;
HostBufferAllocator allocator(host_buffer);
bitmap.setInfo(GetImageInfo(atlas, size));
if (!bitmap.tryAllocPixels(&allocator)) {
if (!bitmap.tryAllocPixels()) {
return false;
}
auto surface = SkSurfaces::WrapPixels(bitmap.pixmap());
Expand All @@ -298,11 +247,19 @@ static bool UpdateAtlasBitmap(const GlyphAtlas& atlas,

DrawGlyph(canvas, pair.scaled_font, pair.glyph, has_color);

// Writing to a malloc'd buffer and then copying to the staging buffers
// benchmarks as substantially faster on a number of Android devices.
BufferView buffer_view = host_buffer.Emplace(
bitmap.getAddr(0, 0),
size.Area() * BytesPerPixelForPixelFormat(
atlas.GetTexture()->GetTextureDescriptor().format),
DefaultUniformAlignment());

// convert_to_read is set to false so that the texture remains in a transfer
// dst layout until we finish writing to it below. This only has an impact
// on Vulkan where we are responsible for managing image layouts.
if (!blit_pass->AddCopy(allocator.TakeBufferView(), //
texture, //
if (!blit_pass->AddCopy(std::move(buffer_view), //
texture, //
IRect::MakeXYWH(pos->GetLeft(), pos->GetTop(),
size.width, size.height), //
/*label=*/"", //
Expand Down