egui-glyphon/examples/hello-world.rs

#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release

use std::{ops::Deref, sync::Arc};

use eframe::{
    egui::{self, Slider},
    egui_wgpu,
    epaint::{
        mutex::{Mutex, RwLock},
        Rect, Vec2,
    },
    CreationContext,
};
use egui::{Align2, Pos2};
use egui_glyphon::{
    glyphon::{Attrs, Family, FontSystem, Metrics, Shaping},
    BufferWithTextArea, GlyphonRenderer, GlyphonRendererCallback,
};
use glyphon::{cosmic_text::Align, Buffer};

fn main() -> Result<(), eframe::Error> {
    env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).
    let options = eframe::NativeOptions {
        viewport: egui::ViewportBuilder::default().with_inner_size([320.0, 240.0]),
        ..Default::default()
    };
    eframe::run_native(
        "My egui App",
        options,
        Box::new(|cc| Box::new(MyApp::new(cc))),
    )
}

struct MyApp {
    font_system: Arc<Mutex<FontSystem>>,
    buffers: Vec<Arc<RwLock<Buffer>>>,
}

impl Default for MyApp {
    fn default() -> Self {
        let mut font_system = FontSystem::new();
        let buffers = cosmic_jotdown::jotdown_into_buffers(
            r#"# Header

Test _test_ *test* 'test' "`test`""#,
            &mut font_system,
            Metrics::new(30.0, 42.0),
            f32::MAX,
        )
        .map(|buffer| Arc::new(RwLock::new(buffer)))
        .collect();

        Self {
            font_system: Arc::new(Mutex::new(font_system)),
            buffers,
        }
    }
}

impl MyApp {
    fn new(cc: &CreationContext<'_>) -> Self {
        let app = Self::default();

        if let Some(ref wgpu) = cc.wgpu_render_state {
            GlyphonRenderer::insert(wgpu, Arc::clone(&app.font_system));
        }

        app
    }
}

pub fn measure_buffer(buffer: &Buffer, vb: Vec2) -> Rect {
    let mut rtl = false;
    let (width, total_lines) =
        buffer
            .layout_runs()
            .fold((0.0, 0usize), |(width, total_lines), run| {
                if run.rtl {
                    rtl = true;
                }
                (run.line_w.max(width), total_lines + 1)
            });

    let (max_width, max_height) = buffer.size();

    let size = Vec2::new(
        if rtl { vb.x } else { width.min(max_width) },
        (total_lines as f32 * buffer.metrics().line_height).min(max_height),
    );
    match buffer.lines[0].align() {
        Some(Align::Right) | Some(Align::End) => {
            Align2::RIGHT_TOP.align_size_within_rect(size, Rect::from_min_size(Pos2::ZERO, vb))
        }
        Some(Align::Center) | Some(Align::Justified) => {
            Align2::CENTER_TOP.align_size_within_rect(size, Rect::from_min_size(Pos2::ZERO, vb))
        }
        Some(Align::Left) | None => Rect::from_min_size(Pos2::ZERO, size),
    }
}

impl eframe::App for MyApp {
    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
        egui::CentralPanel::default().show(ctx, |ui| {
            let mut rect = Rect::from_min_size(ui.cursor().min, Vec2::INFINITY);
            let buffers: Vec<BufferWithTextArea> = self
                .buffers
                .iter()
                .cloned()
                .map(|buffer| {
                    let buffer_size = measure_buffer(buffer.read().deref(), ui.max_rect().size());
                    let this_rect = rect;
                    rect.min.y += buffer_size.height() + 48.0;
                    BufferWithTextArea::new(
                        buffer,
                        this_rect,
                        1.0,
                        egui_glyphon::glyphon::Color::rgb(255, 255, 255),
                        ui.ctx(),
                    )
                })
                .collect();
            ui.painter().add(egui_wgpu::Callback::new_paint_callback(
                ui.max_rect(),
                GlyphonRendererCallback { buffers },
            ));
        });
    }
}