#include <content_context.h>

Public Types
enum class	StencilMode : uint8_t { kIgnore , kStencilNonZeroFill , kStencilEvenOddFill , kCoverCompare , kCoverCompareInverted , kOverdrawPreventionIncrement , kOverdrawPreventionRestore }

Public Member Functions
constexpr uint64_t	ToKey () const

void	ApplyToPipelineDescriptor (PipelineDescriptor &desc) const

Public Attributes
SampleCount	sample_count = SampleCount::kCount1

BlendMode	blend_mode = BlendMode::kSrcOver

CompareFunction	depth_compare = CompareFunction::kAlways

StencilMode	stencil_mode = ContentContextOptions::StencilMode::kIgnore

PrimitiveType	primitive_type = PrimitiveType::kTriangle

PixelFormat	color_attachment_pixel_format = PixelFormat::kUnknown

bool	has_depth_stencil_attachments = true

bool	depth_write_enabled = false

bool	is_for_rrect_blur_clear = false

Detailed Description

Pipeline state configuration.

Each unique combination of these options requires a different pipeline state object to be built. This struct is used as a key for the per-pipeline variant cache.

When adding fields to this key, reliant features should take care to limit the combinatorical explosion of variations. A sufficiently complicated Flutter application may easily require building hundreds of PSOs in total, but they shouldn't require e.g. 10s of thousands.

Definition at line 40 of file content_context.h.

Member Enumeration Documentation

◆ StencilMode

enum class impeller::ContentContextOptions::StencilMode : uint8_t

strong

Enumerator
kIgnore	Turn the stencil test off. Used when drawing without stencil-then-cover or overdraw prevention.
kStencilNonZeroFill	Draw the stencil for the NonZero fill path rule. The stencil ref should always be 0 on commands using this mode.
kStencilEvenOddFill	Draw the stencil for the EvenOdd fill path rule. The stencil ref should always be 0 on commands using this mode.
kCoverCompare	Used for draw calls which fill in the stenciled area. Intended to be used after `kStencilNonZeroFill` or `kStencilEvenOddFill` is used to set up the stencil buffer. Also cleans up the stencil buffer by resetting everything to zero. The stencil ref should always be 0 on commands using this mode.
kCoverCompareInverted	The opposite of `kCoverCompare`. Used for draw calls which fill in the non-stenciled area (intersection clips). Intended to be used after `kStencilNonZeroFill` or `kStencilEvenOddFill` is used to set up the stencil buffer. Also cleans up the stencil buffer by resetting everything to zero. The stencil ref should always be 0 on commands using this mode.
kOverdrawPreventionIncrement	For each fragment, increment the stencil value if it's currently zero. Discard fragments when the value is non-zero. This prevents self-overlapping strokes from drawing over themselves. Note that this is done for rendering correctness, not performance. If a stroke is drawn with a backdrop-reliant blend and self-intersects, then the intersected geometry will render incorrectly when overdrawn because we don't adjust the geometry prevent self-intersection. The stencil ref should always be 0 on commands using this mode.
kOverdrawPreventionRestore	Reset the stencil to a new maximum value specified by the ref (currently always 0). The stencil ref should always be 0 on commands using this mode.

Definition at line 41 of file content_context.h.

                         : uint8_t {
    /// Turn the stencil test off. Used when drawing without stencil-then-cover
    /// or overdraw prevention.
    kIgnore,
 
    // Operations used for stencil-then-cover.
 
    /// Draw the stencil for the NonZero fill path rule.
    ///
    /// The stencil ref should always be 0 on commands using this mode.
    kStencilNonZeroFill,
    /// Draw the stencil for the EvenOdd fill path rule.
    ///
    /// The stencil ref should always be 0 on commands using this mode.
    kStencilEvenOddFill,
    /// Used for draw calls which fill in the stenciled area. Intended to be
    /// used after `kStencilNonZeroFill` or `kStencilEvenOddFill` is used to set
    /// up the stencil buffer. Also cleans up the stencil buffer by resetting
    /// everything to zero.
    ///
    /// The stencil ref should always be 0 on commands using this mode.
    kCoverCompare,
    /// The opposite of `kCoverCompare`. Used for draw calls which fill in the
    /// non-stenciled area (intersection clips). Intended to be used after
    /// `kStencilNonZeroFill` or `kStencilEvenOddFill` is used to set up the
    /// stencil buffer. Also cleans up the stencil buffer by resetting
    /// everything to zero.
    ///
    /// The stencil ref should always be 0 on commands using this mode.
    kCoverCompareInverted,
 
    // Operations used for the "overdraw prevention" mechanism. This is used for
    // drawing strokes.
 
    /// For each fragment, increment the stencil value if it's currently zero.
    /// Discard fragments when the value is non-zero. This prevents
    /// self-overlapping strokes from drawing over themselves.
    ///
    /// Note that this is done for rendering correctness, not performance. If a
    /// stroke is drawn with a backdrop-reliant blend and self-intersects, then
    /// the intersected geometry will render incorrectly when overdrawn because
    /// we don't adjust the geometry prevent self-intersection.
    ///
    /// The stencil ref should always be 0 on commands using this mode.
    kOverdrawPreventionIncrement,
    /// Reset the stencil to a new maximum value specified by the ref (currently
    /// always 0).
    ///
    /// The stencil ref should always be 0 on commands using this mode.
    kOverdrawPreventionRestore,
  };

Member Function Documentation

◆ ApplyToPipelineDescriptor()

void impeller::ContentContextOptions::ApplyToPipelineDescriptor ( PipelineDescriptor & desc ) const

Definition at line 313 of file content_context.cc.

                                    {
  auto pipeline_blend = blend_mode;
  if (blend_mode > Entity::kLastPipelineBlendMode) {
    VALIDATION_LOG << "Cannot use blend mode " << static_cast<int>(blend_mode)
                   << " as a pipeline blend.";
    pipeline_blend = BlendMode::kSrcOver;
  }
 
  desc.SetSampleCount(sample_count);
 
  ColorAttachmentDescriptor color0 = *desc.GetColorAttachmentDescriptor(0u);
  color0.format = color_attachment_pixel_format;
  color0.alpha_blend_op = BlendOperation::kAdd;
  color0.color_blend_op = BlendOperation::kAdd;
  color0.write_mask = ColorWriteMaskBits::kAll;
 
  switch (pipeline_blend) {
    case BlendMode::kClear:
      if (is_for_rrect_blur_clear) {
        color0.alpha_blend_op = BlendOperation::kReverseSubtract;
        color0.color_blend_op = BlendOperation::kReverseSubtract;
        color0.dst_alpha_blend_factor = BlendFactor::kOne;
        color0.dst_color_blend_factor = BlendFactor::kOne;
        color0.src_alpha_blend_factor = BlendFactor::kDestinationColor;
        color0.src_color_blend_factor = BlendFactor::kDestinationColor;
      } else {
        color0.dst_alpha_blend_factor = BlendFactor::kZero;
        color0.dst_color_blend_factor = BlendFactor::kZero;
        color0.src_alpha_blend_factor = BlendFactor::kZero;
        color0.src_color_blend_factor = BlendFactor::kZero;
      }
      break;
    case BlendMode::kSrc:
      color0.blending_enabled = false;
      color0.dst_alpha_blend_factor = BlendFactor::kZero;
      color0.dst_color_blend_factor = BlendFactor::kZero;
      color0.src_alpha_blend_factor = BlendFactor::kOne;
      color0.src_color_blend_factor = BlendFactor::kOne;
      break;
    case BlendMode::kDst:
      color0.dst_alpha_blend_factor = BlendFactor::kOne;
      color0.dst_color_blend_factor = BlendFactor::kOne;
      color0.src_alpha_blend_factor = BlendFactor::kZero;
      color0.src_color_blend_factor = BlendFactor::kZero;
      color0.write_mask = ColorWriteMaskBits::kNone;
      break;
    case BlendMode::kSrcOver:
      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.src_alpha_blend_factor = BlendFactor::kOne;
      color0.src_color_blend_factor = BlendFactor::kOne;
      break;
    case BlendMode::kDstOver:
      color0.dst_alpha_blend_factor = BlendFactor::kOne;
      color0.dst_color_blend_factor = BlendFactor::kOne;
      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      break;
    case BlendMode::kSrcIn:
      color0.dst_alpha_blend_factor = BlendFactor::kZero;
      color0.dst_color_blend_factor = BlendFactor::kZero;
      color0.src_alpha_blend_factor = BlendFactor::kDestinationAlpha;
      color0.src_color_blend_factor = BlendFactor::kDestinationAlpha;
      break;
    case BlendMode::kDstIn:
      color0.dst_alpha_blend_factor = BlendFactor::kSourceAlpha;
      color0.dst_color_blend_factor = BlendFactor::kSourceAlpha;
      color0.src_alpha_blend_factor = BlendFactor::kZero;
      color0.src_color_blend_factor = BlendFactor::kZero;
      break;
    case BlendMode::kSrcOut:
      color0.dst_alpha_blend_factor = BlendFactor::kZero;
      color0.dst_color_blend_factor = BlendFactor::kZero;
      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      break;
    case BlendMode::kDstOut:
      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.src_alpha_blend_factor = BlendFactor::kZero;
      color0.src_color_blend_factor = BlendFactor::kZero;
      break;
    case BlendMode::kSrcATop:
      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.src_alpha_blend_factor = BlendFactor::kDestinationAlpha;
      color0.src_color_blend_factor = BlendFactor::kDestinationAlpha;
      break;
    case BlendMode::kDstATop:
      color0.dst_alpha_blend_factor = BlendFactor::kSourceAlpha;
      color0.dst_color_blend_factor = BlendFactor::kSourceAlpha;
      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      break;
    case BlendMode::kXor:
      color0.dst_alpha_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.dst_color_blend_factor = BlendFactor::kOneMinusSourceAlpha;
      color0.src_alpha_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      color0.src_color_blend_factor = BlendFactor::kOneMinusDestinationAlpha;
      break;
    case BlendMode::kPlus:
      color0.dst_alpha_blend_factor = BlendFactor::kOne;
      color0.dst_color_blend_factor = BlendFactor::kOne;
      color0.src_alpha_blend_factor = BlendFactor::kOne;
      color0.src_color_blend_factor = BlendFactor::kOne;
      break;
    case BlendMode::kModulate:
      color0.dst_alpha_blend_factor = BlendFactor::kSourceAlpha;
      color0.dst_color_blend_factor = BlendFactor::kSourceColor;
      color0.src_alpha_blend_factor = BlendFactor::kZero;
      color0.src_color_blend_factor = BlendFactor::kZero;
      break;
    default:
      FML_UNREACHABLE();
  }
  desc.SetColorAttachmentDescriptor(0u, color0);
 
  if (!has_depth_stencil_attachments) {
    desc.ClearDepthAttachment();
    desc.ClearStencilAttachments();
  }
 
  auto maybe_stencil = desc.GetFrontStencilAttachmentDescriptor();
  auto maybe_depth = desc.GetDepthStencilAttachmentDescriptor();
  FML_DCHECK(has_depth_stencil_attachments == maybe_depth.has_value())
      << "Depth attachment doesn't match expected pipeline state. "
         "has_depth_stencil_attachments="
      << has_depth_stencil_attachments;
  FML_DCHECK(has_depth_stencil_attachments == maybe_stencil.has_value())
      << "Stencil attachment doesn't match expected pipeline state. "
         "has_depth_stencil_attachments="
      << has_depth_stencil_attachments;
  if (maybe_stencil.has_value()) {
    StencilAttachmentDescriptor front_stencil = maybe_stencil.value();
    StencilAttachmentDescriptor back_stencil = front_stencil;
 
    switch (stencil_mode) {
      case StencilMode::kIgnore:
        front_stencil.stencil_compare = CompareFunction::kAlways;
        front_stencil.depth_stencil_pass = StencilOperation::kKeep;
        desc.SetStencilAttachmentDescriptors(front_stencil);
        break;
      case StencilMode::kStencilNonZeroFill:
        // The stencil ref should be 0 on commands that use this mode.
        front_stencil.stencil_compare = CompareFunction::kAlways;
        front_stencil.depth_stencil_pass = StencilOperation::kIncrementWrap;
        back_stencil.stencil_compare = CompareFunction::kAlways;
        back_stencil.depth_stencil_pass = StencilOperation::kDecrementWrap;
        desc.SetStencilAttachmentDescriptors(front_stencil, back_stencil);
        break;
      case StencilMode::kStencilEvenOddFill:
        // The stencil ref should be 0 on commands that use this mode.
        front_stencil.stencil_compare = CompareFunction::kEqual;
        front_stencil.depth_stencil_pass = StencilOperation::kIncrementWrap;
        front_stencil.stencil_failure = StencilOperation::kDecrementWrap;
        desc.SetStencilAttachmentDescriptors(front_stencil);
        break;
      case StencilMode::kCoverCompare:
        // The stencil ref should be 0 on commands that use this mode.
        front_stencil.stencil_compare = CompareFunction::kNotEqual;
        front_stencil.depth_stencil_pass =
            StencilOperation::kSetToReferenceValue;
        desc.SetStencilAttachmentDescriptors(front_stencil);
        break;
      case StencilMode::kCoverCompareInverted:
        // The stencil ref should be 0 on commands that use this mode.
        front_stencil.stencil_compare = CompareFunction::kEqual;
        front_stencil.stencil_failure = StencilOperation::kSetToReferenceValue;
        desc.SetStencilAttachmentDescriptors(front_stencil);
        break;
      case StencilMode::kOverdrawPreventionIncrement:
        front_stencil.stencil_compare = CompareFunction::kEqual;
        front_stencil.depth_stencil_pass = StencilOperation::kIncrementClamp;
        desc.SetStencilAttachmentDescriptors(front_stencil);
        break;
      case StencilMode::kOverdrawPreventionRestore:
        front_stencil.stencil_compare = CompareFunction::kLess;
        front_stencil.depth_stencil_pass =
            StencilOperation::kSetToReferenceValue;
        desc.SetStencilAttachmentDescriptors(front_stencil);
        break;
    }
  }
  if (maybe_depth.has_value()) {
    DepthAttachmentDescriptor depth = maybe_depth.value();
    depth.depth_write_enabled = depth_write_enabled;
    depth.depth_compare = depth_compare;
    desc.SetDepthStencilAttachmentDescriptor(depth);
  }
 
  desc.SetPrimitiveType(primitive_type);
  desc.SetPolygonMode(PolygonMode::kFill);
}

◆ ToKey()

constexpr uint64_t impeller::ContentContextOptions::ToKey ( ) const

inlineconstexpr

Definition at line 103 of file content_context.h.

                                   {
    static_assert(sizeof(sample_count) == 1);
    static_assert(sizeof(blend_mode) == 1);
    static_assert(sizeof(sample_count) == 1);
    static_assert(sizeof(depth_compare) == 1);
    static_assert(sizeof(stencil_mode) == 1);
    static_assert(sizeof(primitive_type) == 1);
    static_assert(sizeof(color_attachment_pixel_format) == 1);
 
    return (is_for_rrect_blur_clear ? 1llu : 0llu) << 0 |
           (0) << 1 |  // // Unused, previously wireframe.
           (has_depth_stencil_attachments ? 1llu : 0llu) << 2 |
           (depth_write_enabled ? 1llu : 0llu) << 3 |
           // enums
           static_cast<uint64_t>(color_attachment_pixel_format) << 8 |
           static_cast<uint64_t>(primitive_type) << 16 |
           static_cast<uint64_t>(stencil_mode) << 24 |
           static_cast<uint64_t>(depth_compare) << 32 |
           static_cast<uint64_t>(blend_mode) << 40 |
           static_cast<uint64_t>(sample_count) << 48;
  }