impeller::ContentContextOptions Struct Reference

#include <content_context.h>

Classes
struct	Equal
struct	Hash

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

Public Member Functions
void	ApplyToPipelineDescriptor (PipelineDescriptor &desc) const

Public Attributes
SampleCount	sample_count = SampleCount::kCount1
BlendMode	blend_mode = BlendMode::kSourceOver
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	wireframe = 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 263 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 264 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 28 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::kSourceOver;
  }
 
  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;
 
  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::kSource:
      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::kDestination:
      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;
      break;
    case BlendMode::kSourceOver:
      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::kDestinationOver:
      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::kSourceIn:
      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::kDestinationIn:
      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::kSourceOut:
      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::kDestinationOut:
      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::kSourceATop:
      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::kDestinationATop:
      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(wireframe ? PolygonMode::kLine : PolygonMode::kFill);
}

Member Data Documentation

blend_mode

BlendMode impeller::ContentContextOptions::blend_mode = BlendMode::kSourceOver

Definition at line 317 of file content_context.h.

color_attachment_pixel_format

PixelFormat impeller::ContentContextOptions::color_attachment_pixel_format = PixelFormat::kUnknown

Definition at line 321 of file content_context.h.

depth_compare

CompareFunction impeller::ContentContextOptions::depth_compare = CompareFunction::kAlways

Definition at line 318 of file content_context.h.

depth_write_enabled

bool impeller::ContentContextOptions::depth_write_enabled = false

Definition at line 323 of file content_context.h.

has_depth_stencil_attachments

bool impeller::ContentContextOptions::has_depth_stencil_attachments = true

Definition at line 322 of file content_context.h.

is_for_rrect_blur_clear

bool impeller::ContentContextOptions::is_for_rrect_blur_clear = false

Definition at line 325 of file content_context.h.

primitive_type

PrimitiveType impeller::ContentContextOptions::primitive_type = PrimitiveType::kTriangle

Definition at line 320 of file content_context.h.

sample_count

SampleCount impeller::ContentContextOptions::sample_count = SampleCount::kCount1

Definition at line 316 of file content_context.h.

stencil_mode

StencilMode impeller::ContentContextOptions::stencil_mode = ContentContextOptions::StencilMode::kIgnore

Definition at line 319 of file content_context.h.

wireframe

bool impeller::ContentContextOptions::wireframe = false

Definition at line 324 of file content_context.h.

---

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

• impeller/entity/contents/content_context.h
• impeller/entity/contents/content_context.cc