pathfinder/gpu/src/lib.rs

// pathfinder/gpu/src/lib.rs
//
// Copyright © 2019 The Pathfinder Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Minimal abstractions over GPU device capabilities.

use crate::resources::ResourceLoader;
use image::ImageFormat;
use pathfinder_geometry::basic::point::Point2DI;
use pathfinder_geometry::basic::rect::RectI;
use pathfinder_geometry::basic::transform3d::Transform3DF;
use pathfinder_geometry::color::ColorF;
use pathfinder_simd::default::F32x4;
use std::time::Duration;

pub mod resources;

static INCLUDES: [&str; 6] = [
    "tile_alpha_vertex",
    "tile_monochrome",
    "tile_multicolor",
    "tile_solid_vertex",
    "post_convolve",
    "post_gamma_correct",
];

pub trait Device {
    type Buffer;
    type Framebuffer;
    type Program;
    type Shader;
    type Texture;
    type TimerQuery;
    type Uniform;
    type VertexArray;
    type VertexAttr;

    fn create_texture(&self, format: TextureFormat, size: Point2DI) -> Self::Texture;
    fn create_texture_from_data(&self, size: Point2DI, data: &[u8]) -> Self::Texture;
    fn create_shader_from_source(
        &self,
        resources: &dyn ResourceLoader,
        name: &str,
        source: &[u8],
        kind: ShaderKind,
        includes: &[&str],
    ) -> Self::Shader;
    fn create_vertex_array(&self) -> Self::VertexArray;
    fn create_program_from_shaders(
        &self,
        resources: &dyn ResourceLoader,
        name: &str,
        vertex_shader: Self::Shader,
        fragment_shader: Self::Shader,
    ) -> Self::Program;
    fn get_vertex_attr(&self, program: &Self::Program, name: &str) -> Self::VertexAttr;
    fn get_uniform(&self, program: &Self::Program, name: &str) -> Self::Uniform;
    fn use_program(&self, program: &Self::Program);
    fn configure_vertex_attr(&self, attr: &Self::VertexAttr, descriptor: &VertexAttrDescriptor);
    fn set_uniform(&self, uniform: &Self::Uniform, data: UniformData);
    fn create_framebuffer(&self, texture: Self::Texture) -> Self::Framebuffer;
    fn create_buffer(&self) -> Self::Buffer;
    fn allocate_buffer<T>(
        &self,
        buffer: &Self::Buffer,
        data: BufferData<T>,
        target: BufferTarget,
        mode: BufferUploadMode,
    );
    fn framebuffer_texture<'f>(&self, framebuffer: &'f Self::Framebuffer) -> &'f Self::Texture;
    fn texture_size(&self, texture: &Self::Texture) -> Point2DI;
    fn upload_to_texture(&self, texture: &Self::Texture, size: Point2DI, data: &[u8]);
    fn read_pixels_from_default_framebuffer(&self, size: Point2DI) -> Vec<u8>;
    fn clear(&self, params: &ClearParams);
    fn draw_arrays(&self, primitive: Primitive, index_count: u32, render_state: &RenderState);
    fn draw_elements(&self, primitive: Primitive, index_count: u32, render_state: &RenderState);
    fn draw_elements_instanced(&self,
                               primitive: Primitive,
                               index_count: u32,
                               instance_count: u32,
                               render_state: &RenderState);
    fn create_timer_query(&self) -> Self::TimerQuery;
    fn begin_timer_query(&self, query: &Self::TimerQuery);
    fn end_timer_query(&self, query: &Self::TimerQuery);
    fn timer_query_is_available(&self, query: &Self::TimerQuery) -> bool;
    fn get_timer_query(&self, query: &Self::TimerQuery) -> Duration;

    // TODO(pcwalton): Go bindless...
    fn bind_vertex_array(&self, vertex_array: &Self::VertexArray);
    fn bind_buffer(&self, buffer: &Self::Buffer, target: BufferTarget);
    fn bind_default_framebuffer(&self, viewport: RectI);
    fn bind_framebuffer(&self, framebuffer: &Self::Framebuffer);
    fn bind_texture(&self, texture: &Self::Texture, unit: u32);

    fn create_texture_from_png(&self, resources: &dyn ResourceLoader, name: &str) -> Self::Texture {
        let data = resources.slurp(&format!("textures/{}.png", name)).unwrap();
        let image = image::load_from_memory_with_format(&data, ImageFormat::PNG)
            .unwrap()
            .to_luma();
        let size = Point2DI::new(image.width() as i32, image.height() as i32);
        self.create_texture_from_data(size, &image)
    }

    fn create_shader(
        &self,
        resources: &dyn ResourceLoader,
        name: &str,
        kind: ShaderKind,
    ) -> Self::Shader {
        let suffix = match kind {
            ShaderKind::Vertex => 'v',
            ShaderKind::Fragment => 'f',
        };
        let source = resources.slurp(&format!("shaders/{}.{}s.glsl", name, suffix)).unwrap();
        self.create_shader_from_source(resources, name, &source, kind, &INCLUDES)
    }

    fn create_program_from_shader_names(
        &self,
        resources: &dyn ResourceLoader,
        program_name: &str,
        vertex_shader_name: &str,
        fragment_shader_name: &str,
    ) -> Self::Program {
        let vertex_shader = self.create_shader(resources, vertex_shader_name, ShaderKind::Vertex);
        let fragment_shader =
            self.create_shader(resources, fragment_shader_name, ShaderKind::Fragment);
        self.create_program_from_shaders(resources, program_name, vertex_shader, fragment_shader)
    }

    fn create_program(&self, resources: &dyn ResourceLoader, name: &str) -> Self::Program {
        self.create_program_from_shader_names(resources, name, name, name)
    }

    fn load_shader_include(&self, resources: &dyn ResourceLoader, include_name: &str) -> Vec<u8> {
        resources.slurp(&format!("shaders/{}.inc.glsl", include_name)).unwrap()
    }
}

#[derive(Clone, Copy, Debug)]
pub enum TextureFormat {
    R8,
    R16F,
    RGBA8,
}

#[derive(Clone, Copy, Debug)]
pub enum VertexAttrType {
    F32,
    I16,
    I8,
    U16,
    U8,
}

#[derive(Clone, Copy, Debug)]
pub enum BufferData<'a, T> {
    Uninitialized(usize),
    Memory(&'a [T]),
}

#[derive(Clone, Copy, Debug)]
pub enum BufferTarget {
    Vertex,
    Index,
}

#[derive(Clone, Copy, Debug)]
pub enum BufferUploadMode {
    Static,
    Dynamic,
}

#[derive(Clone, Copy, Debug, PartialEq)]
pub enum ShaderKind {
    Vertex,
    Fragment,
}

#[derive(Clone, Copy)]
pub enum UniformData {
    Int(i32),
    Mat2(F32x4),
    Mat4([F32x4; 4]),
    Vec2(F32x4),
    Vec4(F32x4),
    TextureUnit(u32),
}

#[derive(Clone, Copy)]
pub enum Primitive {
    Triangles,
    Lines,
}

#[derive(Clone, Copy, Default)]
pub struct ClearParams {
    pub color: Option<ColorF>,
    pub rect: Option<RectI>,
    pub depth: Option<f32>,
    pub stencil: Option<u8>,
}

#[derive(Clone, Debug)]
pub struct RenderState {
    pub blend: BlendState,
    pub depth: Option<DepthState>,
    pub stencil: Option<StencilState>,
    pub color_mask: bool,
}

#[derive(Clone, Copy, Debug)]
pub enum BlendState {
    Off,
    RGBOneAlphaOne,
    RGBOneAlphaOneMinusSrcAlpha,
    RGBSrcAlphaAlphaOneMinusSrcAlpha,
}

#[derive(Clone, Copy, Default, Debug)]
pub struct DepthState {
    pub func: DepthFunc,
    pub write: bool,
}

#[derive(Clone, Copy, Debug)]
pub enum DepthFunc {
    Less,
    Always,
}

#[derive(Clone, Copy, Debug)]
pub struct StencilState {
    pub func: StencilFunc,
    pub reference: u32,
    pub mask: u32,
    pub write: bool,
}

#[derive(Clone, Copy, Debug)]
pub enum StencilFunc {
    Always,
    Equal,
    NotEqual,
}

impl Default for RenderState {
    #[inline]
    fn default() -> RenderState {
        RenderState {
            blend: BlendState::default(),
            depth: None,
            stencil: None,
            color_mask: true,
        }
    }
}

impl Default for BlendState {
    #[inline]
    fn default() -> BlendState {
        BlendState::Off
    }
}

impl Default for StencilState {
    #[inline]
    fn default() -> StencilState {
        StencilState {
            func: StencilFunc::default(),
            reference: 0,
            mask: !0,
            write: false,
        }
    }
}

impl Default for DepthFunc {
    #[inline]
    fn default() -> DepthFunc {
        DepthFunc::Less
    }
}

impl Default for StencilFunc {
    #[inline]
    fn default() -> StencilFunc {
        StencilFunc::Always
    }
}

impl UniformData {
    #[inline]
    pub fn from_transform_3d(transform: &Transform3DF) -> UniformData {
        UniformData::Mat4([transform.c0, transform.c1, transform.c2, transform.c3])
    }
}

#[derive(Clone, Copy, Debug)]
pub struct VertexAttrDescriptor {
    pub size: usize,
    pub class: VertexAttrClass,
    pub attr_type: VertexAttrType,
    pub stride: usize,
    pub offset: usize,
    pub divisor: u32,
}

#[derive(Clone, Copy, Debug, PartialEq)]
pub enum VertexAttrClass {
    Float,
    FloatNorm,
    Int,
}