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/*
* Copyright 2022 Google LLC
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "src/gpu/graphite/render/AnalyticRRectRenderStep.h"
#include "src/base/SkVx.h"
#include "src/core/SkRRectPriv.h"
#include "src/gpu/graphite/DrawParams.h"
#include "src/gpu/graphite/DrawWriter.h"
#include "src/gpu/graphite/render/CommonDepthStencilSettings.h"
// This RenderStep is flexible and can draw filled rectangles, filled quadrilaterals with per-edge
// AA, filled rounded rectangles with arbitrary corner radii, stroked rectangles with any join,
// stroked lines with any cap, stroked rounded rectangles with circular corners (each corner can be
// different or square), hairline rectangles, hairline lines, and hairline rounded rectangles with
// arbitrary corners.
//
// We combine all of these together to maximize batching across simple geometric draws and reduce
// the number pipeline specializations. Additionally, these primitives are the most common
// operations and help us avoid triggering MSAA.
//
// Each of these "primitives" is represented by a single instance. The instance attributes are
// flexible enough to describe any of the above shapes without relying on uniforms to define its
// operation. The attributes encode shape as follows:
//
// float4 xRadiiOrFlags - if any components is > 0, the instance represents a filled round rect
// with elliptical corners and these values specify the X radii in top-left CW order.
// Otherwise, if .x < -1, the instance represents a stroked or hairline [round] rect or line,
// where .y differentiates hairline vs. stroke. If .y is negative, then it is a hairline [round]
// rect and xRadiiOrFlags stores (-2 - X radii); if .y is zero, it is a regular stroked [round]
// rect; if .y is positive, then it is a stroked *or* hairline line. For .y >= 0, .z holds the
// stroke radius and .w stores the join limit (matching StrokeStyle's conventions).
// Lastly, if -1 <= .x <= 0, it's a filled quadrilateral with per-edge AA defined by each by the
// component: aa != 0.
// float4 radiiOrQuadXs - if in filled round rect or hairline [round] rect mode, these values
// provide the Y radii in top-left CW order. If in stroked [round] rect mode, these values
// provide the circular corner radii (same order). Otherwise, when in per-edge quad mode, these
// values provide the X coordinates of the quadrilateral (same order).
// float4 ltrbOrQuadYs - if in filled round rect mode or stroked [round] rect mode, these values
// define the LTRB edge coordinates of the rectangle surrounding the round rect (or the
// rect itself when the radii are 0s). In stroked line mode, LTRB is treated as (x0,y0) and
// (x1,y1) that defines the line. Otherwise, in per-edge quad mode, these values provide
// the Y coordinates of the quadrilateral.
//
// From the other direction, shapes produce instance values like:
// - filled rect: [-1 -1 -1 -1] [L R R L] [T T B B]
// - stroked rect: [-2 0 stroke join] [0 0 0 0] [L T R B]
// - hairline rect: [-2 -2 -2 -2] [0 0 0 0] [L T R B]
// - filled rrect: [xRadii(tl,tr,br,bl)] [yRadii(tl,tr,br,bl)] [L T R B]
// - stroked rrect: [-2 0 stroke join] [radii(tl,tr,br,bl)] [L T R B]
// - hairline rrect: [-2-xRadii(tl,tr,br,bl)] [radii(tl,tr,br,bl)] [L T R B]
// - filled line: N/A, discarded higher in the stack
// - stroked line: [-2 1 stroke cap] [0 0 0 0] [x0,y0,x1,y1]
// - hairline line: [-2 1 0 1] [0 0 0 0] [x0,y0,x1,y1]
// - per-edge quad: [aa(t,r,b,l) ? -1 : 0] [xs(tl,tr,br,bl)] [ys(tl,tr,br,bl)]
//
// This encoding relies on the fact that a valid SkRRect with all x radii equal to 0 must have
// y radii equal to 0 (so it's a rectangle and we can treat it as a quadrilateral with
// all edges AA'ed). This avoids other encodings' inability to represent a quad with all edges
// anti-aliased (e.g. checking for negatives in xRadiiOrFlags to turn on per-edge mode).
//
// From this encoding, data can be unpacked for each corner, which are equivalent under
// rotational symmetry. A corner can have an outer curve, be mitered, or be beveled. It can
// have an inner curve, an inner miter, or fill the interior. Per-edge quads are always mitered
// and fill the interior, but the vertices are placed such that the edge coverage ramps can
// collapse to 0 area on non-AA edges.
//
// The vertices that describe each corner are placed so that edges, miters, and bevels calculate
// coverage by interpolating a varying and then clamping in the fragment shader. Triangles that
// cover the inner and outer curves calculate distance to the curve within the fragment shader.
//
// See https://docs.google.com/presentation/d/1MCPstNsSlDBhR8CrsJo0r-cZNbu-sEJEvU9W94GOJoY/edit?usp=sharing
// for diagrams and explanation of how the geometry is defined.
//
// AnalyticRRectRenderStep uses the common technique of approximating distance to the level set by
// one expansion of the Taylor's series for the level set's equation. Given a level set function
// C(x,y), this amounts to calculating C(px,py)/|∇C(px,py)|. For the straight edges the level set
// is linear and calculated in the vertex shader and then interpolated exactly over the rectangle.
// This provides distances to all four exterior edges within the fragment shader and allows it to
// reconstruct a relative position per elliptical corner. Unfortunately this requires the fragment
// shader to calculate the length of the gradient for straight edges instead of interpolating
// exact device-space distance.
//
// All four corner radii are potentially evaluated by the fragment shader although each corner's
// coverage is only calculated when the pixel is within the bounding box of its quadrant. For fills
// and simple strokes it's theoretically valid to have each pixel calculate a single corner's
// coverage that was controlled via the vertex shader. However, testing all four corners is
// necessary in order to correctly handle self-intersecting stroke interiors. Similarly, all four
// edges must be evaluated in order to handle extremely thin shapes; whereas often you could get
// away with tracking a single edge distance per pixel.
//
// Analytic derivatives are used so that a single pipeline can be used regardless of HW derivative
// support or for geometry that would prove difficult for forward differencing. The device-space
// gradient for ellipses is calculated per-pixel by transforming a per-pixel local gradient vector
// with the Jacobian of the inverse local-to-device transform:
//
// (px,py) is the projected point of (u,v) transformed by a 3x3 matrix, M:
// [x(u,v) / w(u,v)] [x] [m00 m01 m02] [u]
// (px,py) = [y(u,v) / w(u,v)] where [y] = [m10 m11 m12]X[v] = M*(u,v,1)
// [w] [m20 m21 m22] [1]
//
// C(px,py) can be defined in terms of a local Cl(u,v) as C(px,py) = Cl(p^-1(px,py)), where p^-1 =
//
// [x'(px,py) / w'(px,py)] [x'] [m00' m01' * m02'] [px]
// (u,v) = [y'(px,py) / w'(px,py)] where [y'] = [m10' m11' * m12']X[py] = M^-1*(px,py,0,1)
// [w'] [m20' m21' * m22'] [ 1]
//
// Note that if the 3x3 M was arrived by dropping the 3rd row and column from a 4x4 since we assume
// a local 3rd coordinate of 0, M^-1 is not equal to the 4x4 inverse with dropped rows and columns.
//
// Using the chain rule, then ∇C(px,py)
// = ∇Cl(u,v)X[1/w'(px,py) 0 -x'(px,py)/w'(px,py)^2] [m00' m01']
// [ 0 1/w'(px,py) -y'(px,py)/w'(px,py)^2]X[m10' m11']
// [m20' m21']
//
// = 1/w'(px,py)*∇Cl(u,v)X[1 0 -x'(px,py)/w'(px,py)] [m00' m01']
// [0 1 -y'(px,py)/w'(px,py)]X[m10' m11']
// [m20' m21']
//
// = w(u,v)*∇Cl(u,v)X[1 0 0 -u] [m00' m01']
// [0 1 0 -v]X[m10' m11']
// [m20' m21']
//
// = w(u,v)*∇Cl(u,v)X[m00'-m20'u m01'-m21'u]
// [m10'-m20'v m11'-m21'v]
//
// The vertex shader calculates the rightmost 2x2 matrix and interpolates it across the shape since
// each component is linear in (u,v). ∇Cl(u,v) is evaluated per pixel in the fragment shader and
// depends on which corner and edge being evaluated. w(u,v) is the device-space W coordinate, so
// its reciprocal is provided in sk_FragCoord.w.
namespace skgpu::graphite {
using AAFlags = EdgeAAQuad::Flags;
static skvx::float4 load_x_radii(const SkRRect& rrect) {
return skvx::float4{rrect.radii(SkRRect::kUpperLeft_Corner).fX,
rrect.radii(SkRRect::kUpperRight_Corner).fX,
rrect.radii(SkRRect::kLowerRight_Corner).fX,
rrect.radii(SkRRect::kLowerLeft_Corner).fX};
}
static skvx::float4 load_y_radii(const SkRRect& rrect) {
return skvx::float4{rrect.radii(SkRRect::kUpperLeft_Corner).fY,
rrect.radii(SkRRect::kUpperRight_Corner).fY,
rrect.radii(SkRRect::kLowerRight_Corner).fY,
rrect.radii(SkRRect::kLowerLeft_Corner).fY};
}
static bool opposite_insets_intersect(const SkRRect& rrect, float strokeRadius, float aaRadius) {
// One AA inset per side
const float maxInset = strokeRadius + 2.f * aaRadius;
return // Horizontal insets would intersect opposite corner's curve
maxInset >= rrect.width() - rrect.radii(SkRRect::kLowerLeft_Corner).fX ||
maxInset >= rrect.width() - rrect.radii(SkRRect::kLowerRight_Corner).fX ||
maxInset >= rrect.width() - rrect.radii(SkRRect::kUpperLeft_Corner).fX ||
maxInset >= rrect.width() - rrect.radii(SkRRect::kUpperRight_Corner).fX ||
// Vertical insets would intersect opposite corner's curve
maxInset >= rrect.height() - rrect.radii(SkRRect::kLowerLeft_Corner).fY ||
maxInset >= rrect.height() - rrect.radii(SkRRect::kLowerRight_Corner).fY ||
maxInset >= rrect.height() - rrect.radii(SkRRect::kUpperLeft_Corner).fY ||
maxInset >= rrect.height() - rrect.radii(SkRRect::kUpperRight_Corner).fY;
}
static bool opposite_insets_intersect(const Rect& rect, float strokeRadius, float aaRadius) {
return any(rect.size() <= 2.f * (strokeRadius + aaRadius));
}
static bool opposite_insets_intersect(const Geometry& geometry,
float strokeRadius,
float aaRadius) {
if (geometry.isEdgeAAQuad()) {
SkASSERT(strokeRadius == 0.f);
const EdgeAAQuad& quad = geometry.edgeAAQuad();
if (quad.edgeFlags() == AAFlags::kNone) {
// If all edges are non-AA, there won't be any insetting. This allows completely non-AA
// quads to use the fill triangles for simpler fragment shader work.
return false;
} else if (quad.isRect() && quad.edgeFlags() == AAFlags::kAll) {
return opposite_insets_intersect(quad.bounds(), 0.f, aaRadius);
} else {
// Quads with mixed AA edges are tiles where non-AA edges must seam perfectly together.
// If we were to inset along just the axis with AA at a corner, two adjacent quads could
// arrive at slightly different inset coordinates and then we wouldn't have a perfect
// mesh. Forcing insets to snap to the center means all non-AA edges are formed solely
// by the original quad coordinates and should seam perfectly assuming perfect input.
// The only downside to this is the fill triangles cannot be used since they would
// partially extend into the coverage ramp from adjacent AA edges.
return true;
}
} else {
const Shape& shape = geometry.shape();
if (shape.isLine()) {
return strokeRadius <= aaRadius;
} else if (shape.isRect()) {
return opposite_insets_intersect(shape.rect(), strokeRadius, aaRadius);
} else {
SkASSERT(shape.isRRect());
return opposite_insets_intersect(shape.rrect(), strokeRadius, aaRadius);
}
}
}
static bool is_clockwise(const EdgeAAQuad& quad) {
if (quad.isRect()) {
return true; // by construction, these are always locally clockwise
}
// This assumes that each corner has a consistent winding, which is the case for convex inputs,
// which is an assumption of the per-edge AA API. Check the sign of cross product between the
// first two edges.
const skvx::float4& xs = quad.xs();
const skvx::float4& ys = quad.ys();
float winding = (xs[0] - xs[3])*(ys[1] - ys[0]) - (ys[0] - ys[3])*(xs[1] - xs[0]);
if (winding == 0.f) {
// The input possibly forms a triangle with duplicate vertices, so check the opposite corner
winding = (xs[2] - xs[1])*(ys[3] - ys[2]) - (ys[2] - ys[1])*(xs[3] - xs[2]);
}
// At this point if winding is < 0, the quad's vertices are CCW. If it's still 0, the vertices
// form a line, in which case the vertex shader constructs a correct CW winding. Otherwise,
// the quad or triangle vertices produce a positive winding and are CW.
return winding >= 0.f;
}
static skvx::float2 quad_center(const EdgeAAQuad& quad) {
// The center of the bounding box is *not* a good center to use. Take the average of the
// four points instead (which is slightly biased if they form a triangle, but still okay).
return skvx::float2(dot(quad.xs(), skvx::float4(0.25f)),
dot(quad.ys(), skvx::float4(0.25f)));
}
// Represents the per-vertex attributes used in each instance.
struct Vertex {
SkV2 fPosition;
SkV2 fNormal;
float fNormalScale;
float fCenterWeight;
};
// Allowed values for the center weight instance value (selected at record time based on style
// and transform), and are defined such that when (insance-weight > vertex-weight) is true, the
// vertex should be snapped to the center instead of its regular calculation.
static constexpr float kSolidInterior = 1.f;
static constexpr float kStrokeInterior = 0.f;
static constexpr float kFilledStrokeInterior = -1.f;
// Special value for local AA radius to signal when the self-intersections of a stroke interior
// need extra calculations in the vertex shader.
static constexpr float kComplexAAInsets = -1.f;
static constexpr int kCornerVertexCount = 9; // sk_VertexID is divided by this in SkSL
static constexpr int kVertexCount = 4 * kCornerVertexCount;
static constexpr int kIndexCount = 69;
static void write_index_buffer(VertexWriter writer) {
static constexpr uint16_t kTL = 0 * kCornerVertexCount;
static constexpr uint16_t kTR = 1 * kCornerVertexCount;
static constexpr uint16_t kBR = 2 * kCornerVertexCount;
static constexpr uint16_t kBL = 3 * kCornerVertexCount;
static const uint16_t kIndices[kIndexCount] = {
// Exterior AA ramp outset
kTL+0,kTL+4,kTL+1,kTL+5,kTL+2,kTL+3,kTL+5,
kTR+0,kTR+4,kTR+1,kTR+5,kTR+2,kTR+3,kTR+5,
kBR+0,kBR+4,kBR+1,kBR+5,kBR+2,kBR+3,kBR+5,
kBL+0,kBL+4,kBL+1,kBL+5,kBL+2,kBL+3,kBL+5,
kTL+0,kTL+4, // close and jump to next strip
// Outer to inner edges
kTL+4,kTL+6,kTL+5,kTL+7,
kTR+4,kTR+6,kTR+5,kTR+7,
kBR+4,kBR+6,kBR+5,kBR+7,
kBL+4,kBL+6,kBL+5,kBL+7,
kTL+4,kTL+6, // close and jump to next strip
// Fill triangles
kTL+6,kTL+8,kTL+7, kTL+7,kTR+8,
kTR+6,kTR+8,kTR+7, kTR+7,kBR+8,
kBR+6,kBR+8,kBR+7, kBR+7,kBL+8,
kBL+6,kBL+8,kBL+7, kBL+7,kTL+8,
kTL+6 // close
};
if (writer) {
writer << kIndices;
} // otherwise static buffer creation failed, so do nothing; Context initialization will fail.
}
static void write_vertex_buffer(VertexWriter writer) {
// Allowed values for the normal scale attribute. +1 signals a device-space outset along the
// normal away from the outer edge of the stroke. 0 signals no outset, but placed on the outer
// edge of the stroke. -1 signals a local inset along the normal from the inner edge.
static constexpr float kOutset = 1.0;
static constexpr float kInset = -1.0;
static constexpr float kCenter = 1.f; // "true" as a float
// Zero, but named this way to help call out non-zero parameters.
static constexpr float _______ = 0.f;
static constexpr float kHR2 = 0.5f * SK_FloatSqrt2; // "half root 2"
// This template is repeated 4 times in the vertex buffer, for each of the four corners.
// The vertex ID is used to lookup per-corner instance properties such as corner radii or
// positions, but otherwise this vertex data produces a consistent clockwise mesh from
// TL -> TR -> BR -> BL.
static constexpr Vertex kCornerTemplate[kCornerVertexCount] = {
// Device-space AA outsets from outer curve
{ {1.0f, 0.0f}, {1.0f, 0.0f}, kOutset, _______ },
{ {1.0f, 0.0f}, {kHR2, kHR2}, kOutset, _______ },
{ {0.0f, 1.0f}, {kHR2, kHR2}, kOutset, _______ },
{ {0.0f, 1.0f}, {0.0f, 1.0f}, kOutset, _______ },
// Outer anchors (no local or device-space normal outset)
{ {1.0f, 0.0f}, {kHR2, kHR2}, _______, _______ },
{ {0.0f, 1.0f}, {kHR2, kHR2}, _______, _______ },
// Inner curve (with additional AA inset in the common case)
{ {1.0f, 0.0f}, {1.0f, 0.0f}, kInset, _______ },
{ {0.0f, 1.0f}, {0.0f, 1.0f}, kInset, _______ },
// Center filling vertices (equal to inner AA insets unless 'center' triggers a fill).
// TODO: On backends that support "cull" distances (and with SkSL support), these vertices
// and their corresponding triangles can be completely removed. The inset vertices can
// set their cull distance value to cause all filling triangles to be discarded or not
// depending on the instance's style.
{ {1.0f, 0.0f}, {1.0f, 0.0f}, kInset, kCenter },
};
if (writer) {
writer << kCornerTemplate // TL
<< kCornerTemplate // TR
<< kCornerTemplate // BR
<< kCornerTemplate; // BL
} // otherwise static buffer creation failed, so do nothing; Context initialization will fail.
}
AnalyticRRectRenderStep::AnalyticRRectRenderStep(StaticBufferManager* bufferManager)
: RenderStep("AnalyticRRectRenderStep",
"",
Flags::kPerformsShading | Flags::kEmitsCoverage | Flags::kOutsetBoundsForAA,
/*uniforms=*/{},
PrimitiveType::kTriangleStrip,
kDirectDepthGreaterPass,
/*vertexAttrs=*/{
{"position", VertexAttribType::kFloat2, SkSLType::kFloat2},
{"normal", VertexAttribType::kFloat2, SkSLType::kFloat2},
// TODO: These values are all +1/0/-1, or +1/0, so could be packed
// much more densely than as three floats.
{"normalScale", VertexAttribType::kFloat, SkSLType::kFloat},
{"centerWeight", VertexAttribType::kFloat, SkSLType::kFloat}
},
/*instanceAttrs=*/
{{"xRadiiOrFlags", VertexAttribType::kFloat4, SkSLType::kFloat4},
{"radiiOrQuadXs", VertexAttribType::kFloat4, SkSLType::kFloat4},
{"ltrbOrQuadYs", VertexAttribType::kFloat4, SkSLType::kFloat4},
// XY stores center of rrect in local coords. Z and W store values to
// control interior fill behavior. Z can be -1, 0, or 1:
// -1: A stroked interior where AA insets overlap, but isn't solid.
// 0: A stroked interior with no complications.
// 1: A solid interior (fill or sufficiently large stroke width).
// W specifies the size of the AA inset if it's >= 0, or signals that
// the inner curves intersect in a complex manner (rare).
{"center", VertexAttribType::kFloat4, SkSLType::kFloat4},
// TODO: pack depth and ssbo index into one 32-bit attribute, if we can
// go without needing both render step and paint ssbo index attributes.
{"depth", VertexAttribType::kFloat, SkSLType::kFloat},
{"ssboIndices", VertexAttribType::kUShort2, SkSLType::kUShort2},
{"mat0", VertexAttribType::kFloat3, SkSLType::kFloat3},
{"mat1", VertexAttribType::kFloat3, SkSLType::kFloat3},
{"mat2", VertexAttribType::kFloat3, SkSLType::kFloat3}},
/*varyings=*/{
// TODO: If the inverse transform is part of the draw's SSBO, we can
// reconstruct the Jacobian in the fragment shader using the existing
// local coordinates varying
{"jacobian", SkSLType::kFloat4}, // float2x2
// Distance to LTRB edges of unstroked shape. Depending on
// 'perPixelControl' these will either be local or device-space values.
{"edgeDistances", SkSLType::kFloat4}, // distance to LTRB edges
// TODO: These are constant for all fragments for a given instance,
// could we store them in the draw's SSBO?
{"xRadii", SkSLType::kFloat4},
{"yRadii", SkSLType::kFloat4},
// Matches the StrokeStyle struct (X is radius, Y < 0 is round join,
// Y = 0 is bevel, Y > 0 is miter join).
// TODO: These could easily be considered part of the draw's uniforms.
{"strokeParams", SkSLType::kFloat2},
// 'perPixelControl' is a tightly packed description of how to
// evaluate the possible edges that influence coverage in a pixel.
// The decision points and encoded values are spread across X and Y
// so that they are consistent regardless of whether or not MSAA is
// used and does not require centroid sampling.
//
// The signs of values are used to determine the type of coverage to
// calculate in the fragment shader and depending on the state, extra
// varying state is encoded in the fields:
// - A positive X value overrides all per-pixel coverage calculations
// and sets the pixel to full coverage. Y is ignored in this case.
// - A zero X value represents a solid interior shape.
// - X much less than 0 represents bidirectional coverage for a
// stroke, using a sufficiently negative value to avoid
// extrapolation from fill triangles. For actual shapes with
// bidirectional coverage, the fill triangles are zero area.
//
// - Y much greater than 0 takes precedence over the latter two X
// rules and signals that 'edgeDistances' holds device-space values
// and does not require additional per-pixel calculations. The
// coverage scale is encoded as (1+scale*w) and the bias is
// reconstructed from that. X is always 0 for non-fill triangles
// since device-space edge distance is only used for solid interiors
// - Otherwise, any negative Y value represents an additional
// reduction in coverage due to a device-space outset. It is clamped
// below 0 to avoid adding coverage from extrapolation.
{"perPixelControl", SkSLType::kFloat2},
}) {
// Initialize the static buffers we'll use when recording draw calls.
// NOTE: Each instance of this RenderStep gets its own copy of the data. Since there should only
// ever be one AnalyticRRectRenderStep at a time, this shouldn't be an issue.
write_vertex_buffer(bufferManager->getVertexWriter(sizeof(Vertex) * kVertexCount,
&fVertexBuffer));
write_index_buffer(bufferManager->getIndexWriter(sizeof(uint16_t) * kIndexCount,
&fIndexBuffer));
}
AnalyticRRectRenderStep::~AnalyticRRectRenderStep() {}
std::string AnalyticRRectRenderStep::vertexSkSL() const {
// Returns the body of a vertex function, which must define a float4 devPosition variable and
// must write to an already-defined float2 stepLocalCoords variable.
return "float4 devPosition = analytic_rrect_vertex_fn("
// Vertex Attributes
"position, normal, normalScale, centerWeight, "
// Instance Attributes
"xRadiiOrFlags, radiiOrQuadXs, ltrbOrQuadYs, center, depth, "
"float3x3(mat0, mat1, mat2), "
// Varyings
"jacobian, edgeDistances, xRadii, yRadii, strokeParams, perPixelControl, "
// Render Step
"stepLocalCoords);\n";
}
const char* AnalyticRRectRenderStep::fragmentCoverageSkSL() const {
// The returned SkSL must write its coverage into a 'half4 outputCoverage' variable (defined in
// the calling code) with the actual coverage splatted out into all four channels.
return "outputCoverage = analytic_rrect_coverage_fn(sk_FragCoord, "
"jacobian, "
"edgeDistances, "
"xRadii, "
"yRadii, "
"strokeParams, "
"perPixelControl);";
}
void AnalyticRRectRenderStep::writeVertices(DrawWriter* writer,
const DrawParams& params,
skvx::ushort2 ssboIndices) const {
SkASSERT(params.geometry().isShape() || params.geometry().isEdgeAAQuad());
DrawWriter::Instances instance{*writer, fVertexBuffer, fIndexBuffer, kIndexCount};
auto vw = instance.append(1);
// The bounds of a rect is the rect, and the bounds of a rrect is tight (== SkRRect::getRect()).
Rect bounds = params.geometry().bounds();
// aaRadius will be set to a negative value to signal a complex self-intersection that has to
// be calculated in the vertex shader.
float aaRadius = params.transform().localAARadius(bounds);
float strokeInset = 0.f;
float centerWeight = kSolidInterior;
if (params.isStroke()) {
// EdgeAAQuads are not stroked so we know it's a Shape, but we support rects, rrects, and
// lines that all need to be converted to the same form.
const Shape& shape = params.geometry().shape();
SkASSERT(params.strokeStyle().halfWidth() >= 0.f);
SkASSERT(shape.isRect() || shape.isLine() || params.strokeStyle().halfWidth() == 0.f ||
(shape.isRRect() && SkRRectPriv::AllCornersCircular(shape.rrect())));
float strokeRadius = params.strokeStyle().halfWidth();
skvx::float2 size = shape.isLine() ? skvx::float2(length(shape.p1() - shape.p0()), 0.f)
: bounds.size(); // rect or [r]rect
skvx::float2 innerGap = size - 2.f * params.strokeStyle().halfWidth();
if (any(innerGap <= 0.f) && strokeRadius > 0.f) {
// AA inset intersections are measured from the *outset* and remain marked as "solid"
strokeInset = -strokeRadius;
} else {
// This will be upgraded to kFilledStrokeInterior if insets intersect
centerWeight = kStrokeInterior;
strokeInset = strokeRadius;
}
skvx::float4 xRadii = shape.isRRect() ? load_x_radii(shape.rrect()) : skvx::float4(0.f);
if (strokeRadius > 0.f || shape.isLine()) {
// Regular strokes only need to upload 4 corner radii; hairline lines can be uploaded in
// the same manner since it has no real corner radii.
float joinStyle = params.strokeStyle().joinLimit();
float lineFlag = shape.isLine() ? 1.f : 0.f;
auto empty = size == 0.f;
// Points and lines produce caps instead of joins. However, the capped geometry is
// visually equivalent to a joined, stroked [r]rect of the paired join style.
if (shape.isLine() || all(empty)) {
// However, butt-cap points are defined not to produce any geometry, so that combo
// should have been rejected earlier.
SkASSERT(shape.isLine() || params.strokeStyle().cap() != SkPaint::kButt_Cap);
switch(params.strokeStyle().cap()) {
case SkPaint::kRound_Cap: joinStyle = -1.f; break; // round cap == round join
case SkPaint::kButt_Cap: joinStyle = 0.f; break; // butt cap == bevel join
case SkPaint::kSquare_Cap: joinStyle = 1.f; break; // square cap == miter join
}
} else if (params.strokeStyle().isMiterJoin()) {
// Normal corners are 90-degrees so become beveled if the miter limit is < sqrt(2).
// If the [r]rect has a width or height of 0, the corners are actually 180-degrees,
// so the must always be beveled (or, equivalently, butt-capped).
if (params.strokeStyle().miterLimit() < SK_ScalarSqrt2 || any(empty)) {
joinStyle = 0.f; // == bevel (or butt if width or height are zero)
} else {
// Discard actual miter limit because a 90-degree corner never exceeds it.
joinStyle = 1.f;
}
} // else no join style correction needed for non-empty geometry or round joins
// Write a negative value outside [-1, 0] to signal a stroked shape, the line flag, then
// the style params, followed by corner radii and coords.
vw << -2.f << lineFlag << strokeRadius << joinStyle << xRadii
<< (shape.isLine() ? shape.line() : bounds.ltrb());
} else {
// Write -2 - cornerRadii to encode the X radii in such a way to trigger stroking but
// guarantee the 2nd field is non-zero to signal hairline. Then we upload Y radii as
// well to allow for elliptical hairlines.
skvx::float4 yRadii = shape.isRRect() ? load_y_radii(shape.rrect()) : skvx::float4(0.f);
vw << (-2.f - xRadii) << yRadii << bounds.ltrb();
}
} else {
// Empty fills should not have been recorded at all.
SkASSERT(!bounds.isEmptyNegativeOrNaN());
if (params.geometry().isEdgeAAQuad()) {
// NOTE: If quad.isRect() && quad.edgeFlags() == kAll, the written data is identical to
// Shape.isRect() case below.
const EdgeAAQuad& quad = params.geometry().edgeAAQuad();
// If all edges are non-AA, set localAARadius to 0 so that the fill triangles cover the
// entire shape. Otherwise leave it as-is for the full AA rect case; in the event it's
// mixed-AA or a quad, it'll be converted to complex insets down below.
if (quad.edgeFlags() == EdgeAAQuad::Flags::kNone) {
aaRadius = 0.f;
}
// -1 for AA on, 0 for AA off
auto edgeSigns = skvx::float4{quad.edgeFlags() & AAFlags::kLeft ? -1.f : 0.f,
quad.edgeFlags() & AAFlags::kTop ? -1.f : 0.f,
quad.edgeFlags() & AAFlags::kRight ? -1.f : 0.f,
quad.edgeFlags() & AAFlags::kBottom ? -1.f : 0.f};
// The vertex shader expects points to be in clockwise order. EdgeAAQuad is the only
// shape that *might* have counter-clockwise input.
if (is_clockwise(quad)) {
vw << edgeSigns << quad.xs() << quad.ys();
} else {
vw << skvx::shuffle<2,1,0,3>(edgeSigns) // swap left and right AA bits
<< skvx::shuffle<1,0,3,2>(quad.xs()) // swap TL with TR, and BL with BR
<< skvx::shuffle<1,0,3,2>(quad.ys()); // ""
}
} else {
const Shape& shape = params.geometry().shape();
// Filled lines are empty by definition, so they shouldn't have been recorded
SkASSERT(!shape.isLine());
if (shape.isRect() || (shape.isRRect() && shape.rrect().isRect())) {
// Rectangles (or rectangles embedded in an SkRRect) are converted to the
// quadrilateral case, but with all edges anti-aliased (== -1).
skvx::float4 ltrb = bounds.ltrb();
vw << /*edge flags*/ skvx::float4(-1.f)
<< /*xs*/ skvx::shuffle<0,2,2,0>(ltrb)
<< /*ys*/ skvx::shuffle<1,1,3,3>(ltrb);
} else {
// A filled rounded rectangle, so make sure at least one corner radii > 0 or the
// shader won't detect it as a rounded rect.
SkASSERT(any(load_x_radii(shape.rrect()) > 0.f));
vw << load_x_radii(shape.rrect()) << load_y_radii(shape.rrect()) << bounds.ltrb();
}
}
}
if (opposite_insets_intersect(params.geometry(), strokeInset, aaRadius)) {
aaRadius = kComplexAAInsets;
if (centerWeight == kStrokeInterior) {
centerWeight = kFilledStrokeInterior;
}
}
// All instance types share the remaining instance attribute definitions
const SkM44& m = params.transform().matrix();
auto center = params.geometry().isEdgeAAQuad() ? quad_center(params.geometry().edgeAAQuad())
: bounds.center();
vw << center << centerWeight << aaRadius
<< params.order().depthAsFloat()
<< ssboIndices
<< m.rc(0,0) << m.rc(1,0) << m.rc(3,0) // mat0
<< m.rc(0,1) << m.rc(1,1) << m.rc(3,1) // mat1
<< m.rc(0,3) << m.rc(1,3) << m.rc(3,3); // mat2
}
void AnalyticRRectRenderStep::writeUniformsAndTextures(const DrawParams&,
PipelineDataGatherer*) const {
// All data is uploaded as instance attributes, so no uniforms are needed.
}
} // namespace skgpu::graphite