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// 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 in the LICENSE-APACHE file or at:
//     https://www.apache.org/licenses/LICENSE-2.0

//! Drawing API for `kas_wgpu`
//!
//! Extensions to the API of [`kas::draw`], plus some utility types.

mod custom;
mod draw_pipe;
mod draw_text;
mod flat_round;
mod shaded_round;
mod shaded_square;
mod shaders;

use kas::geom::Rect;
use wgpu::{CompareFunction, DepthStencilState, TextureFormat};
use wgpu_glyph::ab_glyph::FontRef;

pub(crate) use shaders::ShaderManager;

pub use custom::{CustomPipe, CustomPipeBuilder, CustomWindow, DrawCustom};

const DEPTH_FORMAT: TextureFormat = TextureFormat::Depth32Float;
pub(crate) const TEX_FORMAT: TextureFormat = TextureFormat::Bgra8UnormSrgb;

const fn new_depth_desc(depth_compare: CompareFunction) -> DepthStencilState {
    DepthStencilState {
        format: DEPTH_FORMAT,
        depth_write_enabled: true,
        depth_compare,
        stencil: wgpu::StencilState {
            front: wgpu::StencilFaceState::IGNORE,
            back: wgpu::StencilFaceState::IGNORE,
            read_mask: 0,
            write_mask: 0,
        },
        bias: wgpu::DepthBiasState {
            constant: 0,
            slope_scale: 0.0,
            clamp: 0.0,
        },
        clamp_depth: false,
    }
}
const DEPTH_DESC: DepthStencilState = new_depth_desc(CompareFunction::Always);
const GLPYH_DEPTH_DESC: DepthStencilState = new_depth_desc(CompareFunction::GreaterEqual);

/// 3-part colour data
#[repr(C)]
#[derive(Clone, Copy, Debug)]
pub(crate) struct Rgb {
    pub r: f32,
    pub g: f32,
    pub b: f32,
}

impl From<kas::draw::Colour> for Rgb {
    fn from(c: kas::draw::Colour) -> Self {
        Rgb {
            r: c.r,
            g: c.g,
            b: c.b,
        }
    }
}

/// Shared pipeline data
pub struct DrawPipe<C> {
    local_pool: futures::executor::LocalPool,
    staging_belt: wgpu::util::StagingBelt,
    shaded_square: shaded_square::Pipeline,
    shaded_round: shaded_round::Pipeline,
    flat_round: flat_round::Pipeline,
    custom: C,
}

type GlyphBrush = wgpu_glyph::GlyphBrush<DepthStencilState, FontRef<'static>>;

/// Per-window pipeline data
pub struct DrawWindow<CW: CustomWindow> {
    depth: Option<wgpu::TextureView>,
    clip_regions: Vec<Rect>,
    shaded_square: shaded_square::Window,
    shaded_round: shaded_round::Window,
    flat_round: flat_round::Window,
    custom: CW,
    glyph_brush: GlyphBrush, // TODO: should be in DrawPipe
    pub(crate) dur_text: std::time::Duration,
}