vello/src/scene.rs
Daniel McNab ff59839737
Move the vello crate to the workspace root (#231)
* Move the vello crate to the root of the crate

* Add warning that README is work in progress

* Add newline in warning

* Move the unlicense into the shader folder

* Fixup wgsl-analyzer include paths
2023-01-05 09:32:09 +00:00

633 lines
19 KiB
Rust

// Copyright 2022 The piet-gpu authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Also licensed under MIT license, at your choice.
use peniko::kurbo::{Affine, PathEl, Point, Rect, Shape};
use peniko::{BlendMode, BrushRef, ColorStop, Fill, Stroke};
use bytemuck::{Pod, Zeroable};
use std::ops::Range;
/// Raw data streams describing an encoded scene.
#[derive(Default)]
pub struct SceneData {
pub transform_stream: Vec<[f32; 6]>,
pub tag_stream: Vec<u8>,
pub pathseg_stream: Vec<u8>,
pub linewidth_stream: Vec<f32>,
pub drawtag_stream: Vec<u32>,
pub drawdata_stream: Vec<u8>,
pub n_path: u32,
pub n_pathseg: u32,
pub n_clip: u32,
pub resources: ResourceBundle,
}
impl SceneData {
fn is_empty(&self) -> bool {
self.pathseg_stream.is_empty()
}
fn reset(&mut self, is_fragment: bool) {
self.transform_stream.clear();
self.tag_stream.clear();
self.pathseg_stream.clear();
self.linewidth_stream.clear();
self.drawtag_stream.clear();
self.drawdata_stream.clear();
self.n_path = 0;
self.n_pathseg = 0;
self.n_clip = 0;
self.resources.clear();
if !is_fragment {
self.transform_stream.push([1.0, 0.0, 0.0, 1.0, 0.0, 0.0]);
self.linewidth_stream.push(-1.0);
}
}
fn append(&mut self, other: &SceneData, transform: &Option<Affine>) {
let stops_base = self.resources.stops.len();
let drawdata_base = self.drawdata_stream.len();
if let Some(transform) = *transform {
self.transform_stream.extend(
other
.transform_stream
.iter()
.map(|x| affine_to_f32(&(transform * affine_from_f32(x)))),
);
} else {
self.transform_stream
.extend_from_slice(&other.transform_stream);
}
self.tag_stream.extend_from_slice(&other.tag_stream);
self.pathseg_stream.extend_from_slice(&other.pathseg_stream);
self.linewidth_stream
.extend_from_slice(&other.linewidth_stream);
self.drawtag_stream.extend_from_slice(&other.drawtag_stream);
self.drawdata_stream
.extend_from_slice(&other.drawdata_stream);
self.n_path += other.n_path;
self.n_pathseg += other.n_pathseg;
self.n_clip += other.n_clip;
self.resources
.stops
.extend_from_slice(&other.resources.stops);
self.resources
.patches
.extend(other.resources.patches.iter().map(|patch| match patch {
ResourcePatch::Ramp { offset, stops } => {
let stops = stops.start + stops_base..stops.end + stops_base;
ResourcePatch::Ramp {
offset: drawdata_base + offset,
stops,
}
}
}));
}
}
/// Encoded definition of a scene and associated resources.
#[derive(Default)]
pub struct Scene {
data: SceneData,
}
impl Scene {
/// Creates a new scene.
pub fn new() -> Self {
Self::default()
}
/// Returns the raw encoded scene data streams.
pub fn data(&self) -> &SceneData {
&self.data
}
}
/// Encoded definition of a scene fragment and associated resources.
#[derive(Default)]
pub struct SceneFragment {
data: SceneData,
}
impl SceneFragment {
/// Creates a new scene fragment.
pub fn new() -> Self {
Self::default()
}
/// Returns true if the fragment does not contain any paths.
pub fn is_empty(&self) -> bool {
self.data.is_empty()
}
/// Returns the the entire sequence of points in the scene fragment.
pub fn points(&self) -> &[[f32; 2]] {
if self.is_empty() {
&[]
} else {
bytemuck::cast_slice(&self.data.pathseg_stream)
}
}
}
#[derive(Default)]
/// Collection of late bound resources for a scene or scene fragment.
pub struct ResourceBundle {
/// Sequence of resource patches.
pub patches: Vec<ResourcePatch>,
/// Cache of color stops, referenced by range from the patches.
pub stops: Vec<ColorStop>,
}
impl ResourceBundle {
/// Clears the resource set.
pub(crate) fn clear(&mut self) {
self.patches.clear();
self.stops.clear();
}
}
#[derive(Clone)]
/// Description of a late bound resource.
pub enum ResourcePatch {
/// Gradient ramp resource.
Ramp {
/// Byte offset to the ramp id in the draw data stream.
offset: usize,
/// Range of the gradient stops in the resource set.
stops: Range<usize>,
},
}
/// Builder for constructing a scene or scene fragment.
pub struct SceneBuilder<'a> {
scene: &'a mut SceneData,
layer_depth: u32,
}
impl<'a> SceneBuilder<'a> {
/// Creates a new builder for filling a scene. Any current content in the scene
/// will be cleared.
pub fn for_scene(scene: &'a mut Scene) -> Self {
Self::new(&mut scene.data, false)
}
/// Creates a new builder for filling a scene fragment. Any current content in
/// the fragment will be cleared.
pub fn for_fragment(fragment: &'a mut SceneFragment) -> Self {
Self::new(&mut fragment.data, true)
}
/// Creates a new builder for constructing a scene.
fn new(scene: &'a mut SceneData, is_fragment: bool) -> Self {
scene.reset(is_fragment);
Self {
scene,
layer_depth: 0,
}
}
/// Pushes a new layer bound by the specifed shape and composed with
/// previous layers using the specified blend mode.
pub fn push_layer(
&mut self,
blend: impl Into<BlendMode>,
alpha: f32,
transform: Affine,
shape: &impl Shape,
) {
let blend = blend.into();
self.maybe_encode_transform(transform);
self.linewidth(-1.0);
if !self.encode_path(shape, true) {
// If the layer shape is invalid, encode a valid empty path. This suppresses
// all drawing until the layer is popped.
self.encode_path(&Rect::new(0.0, 0.0, 0.0, 0.0), true);
}
self.begin_clip(blend, alpha.clamp(0.0, 1.0));
self.layer_depth += 1;
}
/// Pops the current layer.
pub fn pop_layer(&mut self) {
if self.layer_depth > 0 {
self.end_clip();
self.layer_depth -= 1;
}
}
/// Fills a shape using the specified style and brush.
pub fn fill<'b>(
&mut self,
_style: Fill,
transform: Affine,
brush: impl Into<BrushRef<'b>>,
brush_transform: Option<Affine>,
shape: &impl Shape,
) {
self.maybe_encode_transform(transform);
self.linewidth(-1.0);
if self.encode_path(shape, true) {
if let Some(brush_transform) = brush_transform {
self.encode_transform(transform * brush_transform);
self.swap_last_tags();
self.encode_brush(brush);
} else {
self.encode_brush(brush);
}
}
}
/// Strokes a shape using the specified style and brush.
pub fn stroke<'b>(
&mut self,
style: &Stroke,
transform: Affine,
brush: impl Into<BrushRef<'b>>,
brush_transform: Option<Affine>,
shape: &impl Shape,
) {
self.maybe_encode_transform(transform);
self.linewidth(style.width);
if self.encode_path(shape, false) {
if let Some(brush_transform) = brush_transform {
self.encode_transform(transform * brush_transform);
self.swap_last_tags();
self.encode_brush(brush);
} else {
self.encode_brush(brush);
}
}
}
/// Appends a fragment to the scene.
pub fn append(&mut self, fragment: &SceneFragment, transform: Option<Affine>) {
self.scene.append(&fragment.data, &transform);
}
/// Completes construction and finalizes the underlying scene.
pub fn finish(mut self) {
for _ in 0..self.layer_depth {
self.end_clip();
}
}
}
impl<'a> SceneBuilder<'a> {
/// Encodes a path for the specified shape.
///
/// When the `is_fill` parameter is true, closes any open subpaths by inserting
/// a line to the start point of the subpath with the end segment bit set.
fn encode_path(&mut self, shape: &impl Shape, is_fill: bool) -> bool {
let mut b = PathBuilder::new(
&mut self.scene.tag_stream,
&mut self.scene.pathseg_stream,
is_fill,
);
for el in shape.path_elements(0.1) {
match el {
PathEl::MoveTo(p0) => b.move_to(p0.x as f32, p0.y as f32),
PathEl::LineTo(p0) => b.line_to(p0.x as f32, p0.y as f32),
PathEl::QuadTo(p0, p1) => {
b.quad_to(p0.x as f32, p0.y as f32, p1.x as f32, p1.y as f32)
}
PathEl::CurveTo(p0, p1, p2) => b.cubic_to(
p0.x as f32,
p0.y as f32,
p1.x as f32,
p1.y as f32,
p2.x as f32,
p2.y as f32,
),
PathEl::ClosePath => b.close_path(),
}
}
b.finish();
if b.n_pathseg != 0 {
self.scene.n_path += 1;
self.scene.n_pathseg += b.n_pathseg;
true
} else {
false
}
}
fn maybe_encode_transform(&mut self, transform: Affine) {
if self.scene.transform_stream.last() != Some(&affine_to_f32(&transform)) {
self.encode_transform(transform);
}
}
fn encode_transform(&mut self, transform: Affine) {
self.scene.tag_stream.push(0x20);
self.scene.transform_stream.push(affine_to_f32(&transform));
}
// Swap the last two tags in the tag stream; used for transformed
// gradients.
fn swap_last_tags(&mut self) {
let len = self.scene.tag_stream.len();
self.scene.tag_stream.swap(len - 1, len - 2);
}
// -1.0 means "fill"
fn linewidth(&mut self, linewidth: f32) {
if self.scene.linewidth_stream.last() != Some(&linewidth) {
self.scene.tag_stream.push(0x40);
self.scene.linewidth_stream.push(linewidth);
}
}
fn encode_brush<'b>(&mut self, brush: impl Into<BrushRef<'b>>) {
match brush.into() {
BrushRef::Solid(color) => {
self.scene.drawtag_stream.push(DRAWTAG_FILLCOLOR);
let rgba_color = color.to_premul_u32();
self.scene
.drawdata_stream
.extend(bytemuck::bytes_of(&FillColor { rgba_color }));
}
BrushRef::LinearGradient(gradient) => {
let index = self.add_ramp(&gradient.stops);
self.scene.drawtag_stream.push(DRAWTAG_FILLLINGRADIENT);
self.scene
.drawdata_stream
.extend(bytemuck::bytes_of(&FillLinGradient {
index,
p0: point_to_f32(gradient.start),
p1: point_to_f32(gradient.end),
}));
}
BrushRef::RadialGradient(gradient) => {
let index = self.add_ramp(&gradient.stops);
self.scene.drawtag_stream.push(DRAWTAG_FILLRADGRADIENT);
self.scene
.drawdata_stream
.extend(bytemuck::bytes_of(&FillRadGradient {
index,
p0: point_to_f32(gradient.start_center),
p1: point_to_f32(gradient.end_center),
r0: gradient.start_radius,
r1: gradient.end_radius,
}));
}
BrushRef::SweepGradient(_gradient) => todo!("sweep gradients aren't done yet!"),
}
}
fn add_ramp(&mut self, stops: &[ColorStop]) -> u32 {
let offset = self.scene.drawdata_stream.len();
let resources = &mut self.scene.resources;
let stops_start = resources.stops.len();
resources.stops.extend_from_slice(stops);
resources.patches.push(ResourcePatch::Ramp {
offset,
stops: stops_start..stops_start + stops.len(),
});
0
}
/// Start a clip.
fn begin_clip(&mut self, blend: BlendMode, alpha: f32) {
self.scene.drawtag_stream.push(DRAWTAG_BEGINCLIP);
let element = Clip {
blend: encode_blend_mode(blend),
alpha,
};
self.scene
.drawdata_stream
.extend(bytemuck::bytes_of(&element));
self.scene.n_clip += 1;
}
fn end_clip(&mut self) {
self.scene.drawtag_stream.push(DRAWTAG_ENDCLIP);
// This is a dummy path, and will go away with the new clip impl.
self.scene.tag_stream.push(0x10);
self.scene.n_path += 1;
self.scene.n_clip += 1;
}
}
fn encode_blend_mode(mode: BlendMode) -> u32 {
(mode.mix as u32) << 8 | mode.compose as u32
}
// Tags for draw objects. See shader/shared/drawtag.wgsl for the authoritative source.
const DRAWTAG_FILLCOLOR: u32 = 0x44;
const DRAWTAG_FILLLINGRADIENT: u32 = 0x114;
const DRAWTAG_FILLRADGRADIENT: u32 = 0x2dc;
const DRAWTAG_BEGINCLIP: u32 = 0x9;
const DRAWTAG_ENDCLIP: u32 = 0x21;
#[repr(C)]
#[derive(Clone, Copy, Debug, Default, Zeroable, Pod)]
pub struct FillColor {
rgba_color: u32,
}
#[repr(C)]
#[derive(Clone, Copy, Debug, Default, Zeroable, Pod)]
pub struct FillLinGradient {
index: u32,
p0: [f32; 2],
p1: [f32; 2],
}
#[repr(C)]
#[derive(Clone, Copy, Debug, Default, Zeroable, Pod)]
pub struct FillRadGradient {
index: u32,
p0: [f32; 2],
p1: [f32; 2],
r0: f32,
r1: f32,
}
#[allow(unused)]
#[repr(C)]
#[derive(Clone, Copy, Debug, Default, Zeroable, Pod)]
pub struct FillImage {
index: u32,
// [i16; 2]
offset: u32,
}
#[repr(C)]
#[derive(Clone, Copy, Debug, Default, Zeroable, Pod)]
pub struct Clip {
blend: u32,
alpha: f32,
}
struct PathBuilder<'a> {
tag_stream: &'a mut Vec<u8>,
// If we're never going to use the i16 encoding, it might be
// slightly faster to store this as Vec<u32>, we'd get aligned
// stores on ARM etc.
pathseg_stream: &'a mut Vec<u8>,
first_pt: [f32; 2],
state: PathState,
n_pathseg: u32,
is_fill: bool,
}
#[derive(PartialEq)]
enum PathState {
Start,
MoveTo,
NonemptySubpath,
}
impl<'a> PathBuilder<'a> {
pub fn new(tags: &'a mut Vec<u8>, pathsegs: &'a mut Vec<u8>, is_fill: bool) -> PathBuilder<'a> {
PathBuilder {
tag_stream: tags,
pathseg_stream: pathsegs,
first_pt: [0.0, 0.0],
state: PathState::Start,
n_pathseg: 0,
is_fill,
}
}
pub fn move_to(&mut self, x: f32, y: f32) {
if self.is_fill {
self.close_path();
}
let buf = [x, y];
let bytes = bytemuck::bytes_of(&buf);
self.first_pt = buf;
if self.state == PathState::MoveTo {
let new_len = self.pathseg_stream.len() - 8;
self.pathseg_stream.truncate(new_len);
} else if self.state == PathState::NonemptySubpath {
if let Some(tag) = self.tag_stream.last_mut() {
*tag |= 4;
}
}
self.pathseg_stream.extend_from_slice(bytes);
self.state = PathState::MoveTo;
}
pub fn line_to(&mut self, x: f32, y: f32) {
if self.state == PathState::Start {
if self.n_pathseg == 0 {
// This copies the behavior of kurbo which treats an initial line, quad
// or curve as a move.
self.move_to(x, y);
return;
}
self.move_to(self.first_pt[0], self.first_pt[1]);
}
let buf = [x, y];
let bytes = bytemuck::bytes_of(&buf);
self.pathseg_stream.extend_from_slice(bytes);
self.tag_stream.push(9);
self.state = PathState::NonemptySubpath;
self.n_pathseg += 1;
}
pub fn quad_to(&mut self, x1: f32, y1: f32, x2: f32, y2: f32) {
if self.state == PathState::Start {
if self.n_pathseg == 0 {
self.move_to(x2, y2);
return;
}
self.move_to(self.first_pt[0], self.first_pt[1]);
}
let buf = [x1, y1, x2, y2];
let bytes = bytemuck::bytes_of(&buf);
self.pathseg_stream.extend_from_slice(bytes);
self.tag_stream.push(10);
self.state = PathState::NonemptySubpath;
self.n_pathseg += 1;
}
pub fn cubic_to(&mut self, x1: f32, y1: f32, x2: f32, y2: f32, x3: f32, y3: f32) {
if self.state == PathState::Start {
if self.n_pathseg == 0 {
self.move_to(x3, y3);
return;
}
self.move_to(self.first_pt[0], self.first_pt[1]);
}
let buf = [x1, y1, x2, y2, x3, y3];
let bytes = bytemuck::bytes_of(&buf);
self.pathseg_stream.extend_from_slice(bytes);
self.tag_stream.push(11);
self.state = PathState::NonemptySubpath;
self.n_pathseg += 1;
}
pub fn close_path(&mut self) {
match self.state {
PathState::Start => return,
PathState::MoveTo => {
let new_len = self.pathseg_stream.len() - 8;
self.pathseg_stream.truncate(new_len);
self.state = PathState::Start;
return;
}
PathState::NonemptySubpath => (),
}
let len = self.pathseg_stream.len();
if len < 8 {
// can't happen
return;
}
let first_bytes = bytemuck::bytes_of(&self.first_pt);
if &self.pathseg_stream[len - 8..len] != first_bytes {
self.pathseg_stream.extend_from_slice(first_bytes);
self.tag_stream.push(13);
self.n_pathseg += 1;
} else {
if let Some(tag) = self.tag_stream.last_mut() {
*tag |= 4;
}
}
self.state = PathState::Start;
}
pub fn finish(&mut self) {
if self.is_fill {
self.close_path();
}
if self.state == PathState::MoveTo {
let new_len = self.pathseg_stream.len() - 8;
self.pathseg_stream.truncate(new_len);
}
if self.n_pathseg != 0 {
if let Some(tag) = self.tag_stream.last_mut() {
*tag |= 4;
}
self.tag_stream.push(0x10);
}
}
}
fn affine_to_f32(affine: &Affine) -> [f32; 6] {
affine.as_coeffs().map(|value| value as f32)
}
fn affine_from_f32(coeffs: &[f32; 6]) -> Affine {
Affine::new(coeffs.map(|value| value as f64))
}
fn point_to_f32(point: Point) -> [f32; 2] {
[point.x as f32, point.y as f32]
}