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* Copyright 2021 Google LLC
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef skgpu_DrawList_DEFINED
#define skgpu_DrawList_DEFINED
#include "include/core/SkPaint.h"
#include "src/core/SkTBlockList.h"
#include "src/gpu/graphite/DrawOrder.h"
#include "src/gpu/graphite/DrawParams.h"
#include "src/gpu/graphite/PaintParams.h"
#include "src/gpu/graphite/geom/Geometry.h"
#include "src/gpu/graphite/geom/Transform_graphite.h"
#include <limits>
#include <optional>
namespace skgpu::graphite {
class Renderer;
* A DrawList represents a collection of drawing commands (and related clip/shading state) in
* a form that closely mirrors what can be rendered efficiently and directly by the GPU backend
* (while balancing how much pre-processing to do for draws that might get eliminated later due to
* occlusion culling).
* A draw command combines:
* - a shape
* - a transform
* - a primitive clip (not affected by the transform)
* - optional shading description (shader, color filter, blend mode, etc)
* - a draw ordering (compressed painters index, stencil set, and write/test depth)
* Commands are accumulated in an arbitrary order and then sorted by increasing sort z when the list
* is prepared into an actual command buffer. The result of a draw command is the rasterization of
* the transformed shape, restricted by its primitive clip (e.g. a scissor rect) and a depth test
* of "GREATER" vs. its write/test z. (A test of GREATER, as opposed to GEQUAL, avoids double hits
* for draws that may have overlapping geometry, e.g. stroking.) If the command has a shading
* description, the color buffer will be modified; if not, it will be a depth-only draw.
* In addition to sorting the collected commands, the command list can be optimized during
* preparation. Commands that are fully occluded by later operations can be skipped entirely without
* affecting the final results. Adjacent commands (post sort) that would use equivalent GPU
* pipelines are merged to produce fewer (but larger) operations on the GPU.
* Other than flush-time optimizations (sort, cull, and merge), the command list does what you tell
* it to. Draw-specific simplification, style application, and advanced clipping should be handled
* at a higher layer.
class DrawList {
// The maximum number of draw calls that can be recorded into a DrawList before it must be
// converted to a DrawPass. The true fundamental limit is imposed by the limits of the depth
// attachment and precision of CompressedPaintersOrder and PaintDepth. These values can be
// shared by multiple draw calls so it's more difficult to reason about how much room is left
// in a DrawList. Limiting it to this keeps tracking simple and ensures that the sequences in
// DrawOrder cannot overflow since they are always less than or equal to the number of draws.
static constexpr int kMaxDraws = std::numeric_limits<uint16_t>::max();
// DrawList requires that all Transforms be valid and asserts as much; invalid transforms should
// be detected at the Device level or similar. The provided Renderer must be compatible with the
// 'shape' and 'stroke' parameters. If the renderer uses coverage AA, 'ordering' must have a
// compressed painters order that reflects that. If the renderer uses stencil, the 'ordering'
// must have a valid stencil index as well.
void recordDraw(const Renderer& renderer,
const Transform& localToDevice,
const Geometry& geometry,
const Clip& clip,
DrawOrder ordering,
const PaintParams* paint,
const StrokeStyle* stroke);
int drawCount() const { return fDraws.count(); }
int renderStepCount() const { return fRenderStepCount; }
friend class DrawPass;
struct Draw {
const Renderer& fRenderer; // Statically defined by function that recorded the Draw
DrawParams fDrawParams; // The DrawParam's transform is owned by fTransforms of the DrawList
std::optional<PaintParams> fPaintParams; // Not present implies depth-only draw
Draw(const Renderer& renderer, const Transform& transform, const Geometry& geometry,
const Clip& clip, DrawOrder order, const PaintParams* paint,
const StrokeStyle* stroke)
: fRenderer(renderer)
, fDrawParams(transform, geometry, clip, order, stroke)
, fPaintParams(paint ? std::optional<PaintParams>(*paint) : std::nullopt) {}
// The returned Transform reference remains valid for the lifetime of the DrawList.
const Transform& deduplicateTransform(const Transform&);
SkTBlockList<Transform, 16> fTransforms;
SkTBlockList<Draw, 16> fDraws;
// Running total of RenderSteps for all draws, assuming nothing is culled
int fRenderStepCount;
} // namespace skgpu
#endif // skgpu_DrawList_DEFINED