iris/src/layout/text.rs

use std::simd::{Simd, num::SimdUint};

use crate::layout::{Align, RegionAlign, TextureHandle, Textures, UiColor, Vec2};
use cosmic_text::{
    Attrs, AttrsList, Buffer, CacheKey, Color, Family, FontSystem, Metrics, Placement, SwashCache,
    SwashContent,
};
use image::{GenericImageView, RgbaImage};

/// TODO: properly wrap this
pub mod text_lib {
    pub use cosmic_text::*;
}

pub struct TextData {
    pub font_system: FontSystem,
    pub swash_cache: SwashCache,
    glyph_cache: Vec<(Placement, CacheKey, Color)>,
}

impl Default for TextData {
    fn default() -> Self {
        Self {
            font_system: FontSystem::new(),
            swash_cache: SwashCache::new(),
            glyph_cache: Default::default(),
        }
    }
}

#[derive(Clone, Copy)]
pub struct TextAttrs {
    pub color: UiColor,
    pub font_size: f32,
    pub line_height: f32,
    pub family: Family<'static>,
    pub wrap: bool,
    /// inner alignment of text region (within where it's drawn)
    pub align: RegionAlign,
}

impl TextAttrs {
    pub fn apply(&self, font_system: &mut FontSystem, buf: &mut Buffer, width: Option<f32>) {
        buf.set_metrics_and_size(
            font_system,
            Metrics::new(self.font_size, self.line_height),
            width,
            None,
        );
        let attrs = Attrs::new().family(self.family);
        let list = AttrsList::new(&attrs);
        for line in &mut buf.lines {
            line.set_attrs_list(list.clone());
        }
    }
}

pub type TextBuffer = Buffer;

impl Default for TextAttrs {
    fn default() -> Self {
        let size = 14.0;
        Self {
            color: UiColor::WHITE,
            font_size: size,
            line_height: size * 1.2,
            family: Family::SansSerif,
            wrap: false,
            align: Align::CENTER_LEFT,
        }
    }
}

impl TextData {
    pub fn draw(
        &mut self,
        buffer: &mut TextBuffer,
        attrs: &TextAttrs,
        textures: &mut Textures,
    ) -> RenderedText {
        // TODO: either this or the layout stuff (or both) is super slow,
        // should probably do texture packing and things if possible.
        // very visible if you add just a couple of wrapping texts and resize window
        // should also be timed to figure out exactly what points need to be sped up
        // let mut pixels = HashMap::<_, [u8; 4]>::default();
        let mut min_x = 0;
        let mut min_y = 0;
        let mut max_x = 0;
        let mut max_y = 0;
        let text_color = {
            let c = attrs.color;
            cosmic_text::Color::rgba(c.r, c.g, c.b, c.a)
        };
        let mut max_width = 0.0f32;
        let mut height = 0.0;

        for run in buffer.layout_runs() {
            for glyph in run.glyphs.iter() {
                let physical_glyph = glyph.physical((0., 0.), 1.0);

                let glyph_color = match glyph.color_opt {
                    Some(some) => some,
                    None => text_color,
                };

                if let Some(img) = self
                    .swash_cache
                    .get_image(&mut self.font_system, physical_glyph.cache_key)
                {
                    let mut pos = img.placement;
                    pos.left += physical_glyph.x;
                    pos.top = physical_glyph.y + run.line_y as i32 - pos.top;
                    min_x = min_x.min(pos.left);
                    min_y = min_y.min(pos.top);
                    max_x = max_x.max(pos.left + pos.width as i32);
                    max_y = max_y.max(pos.top + pos.height as i32);
                    self.glyph_cache
                        .push((pos, physical_glyph.cache_key, glyph_color));
                }
            }
            max_width = max_width.max(run.line_w);
            height += run.line_height;
        }
        let img_width = (max_x - min_x + 1) as u32;
        let img_height = (max_y - min_y + 1) as u32;
        let mut image = RgbaImage::new(img_width, img_height);

        for (pos, key, color) in self.glyph_cache.drain(..) {
            let img = self
                .swash_cache
                .get_image(&mut self.font_system, key)
                .as_ref()
                .unwrap();
            let mut merge = |i, color: [u8; 4]| {
                let i = i as i32;
                let x = (i % pos.width as i32 + pos.left - min_x) as u32;
                let y = (i / pos.width as i32 + pos.top - min_y) as u32;
                let pixel = &mut image[(x, y)].0;
                // TODO: no clue if proper alpha blending should be done
                *pixel = Simd::from(color).saturating_add(Simd::from(*pixel)).into();
            };

            match img.content {
                SwashContent::Mask => {
                    for (i, a) in img.data.iter().enumerate() {
                        let mut color = color.as_rgba();
                        color[3] = ((color[3] as u32 * *a as u32) / u8::MAX as u32) as u8;
                        merge(i, color);
                    }
                }
                SwashContent::SubpixelMask => todo!("subpixel mask text rendering"),
                SwashContent::Color => {
                    let (colors, _) = img.data.as_chunks::<4>();
                    for (i, color) in colors.iter().enumerate() {
                        merge(i, *color);
                    }
                }
            }
        }

        let max_dim = 8192;
        if image.width() > max_dim || image.height() > max_dim {
            let width = image.width().min(max_dim);
            let height = image.height().min(max_dim);
            eprintln!(
                "WARNING: image of size {:?} cropped to {:?} (texture too big)",
                image.dimensions(),
                (width, height)
            );
            image = image.view(0, 0, width, height).to_image();
        }

        RenderedText {
            handle: textures.add(image),
            top_left_offset: Vec2::new(min_x as f32, min_y as f32),
            size: Vec2::new(max_width, height),
        }
    }
}

#[derive(Clone)]
pub struct RenderedText {
    pub handle: TextureHandle,
    pub top_left_offset: Vec2,
    pub size: Vec2,
}