glyphon/examples/hello-world.rs

use glyphon::{
    Attrs, Buffer, Cache, Color, Family, FontSystem, Metrics, Resolution, Shaping, SwashCache,
    TextArea, TextAtlas, TextBounds, TextRenderer, Viewport,
};
use std::sync::Arc;
use wgpu::{
    CommandEncoderDescriptor, CompositeAlphaMode, DeviceDescriptor, Instance, InstanceDescriptor,
    LoadOp, MultisampleState, Operations, PresentMode, RenderPassColorAttachment,
    RenderPassDescriptor, RequestAdapterOptions, SurfaceConfiguration, TextureFormat,
    TextureUsages, TextureViewDescriptor,
};
use winit::{dpi::LogicalSize, event::WindowEvent, event_loop::EventLoop, window::Window};

fn main() {
    let event_loop = EventLoop::new().unwrap();
    event_loop
        .run_app(&mut Application { window_state: None })
        .unwrap();
}

struct WindowState {
    device: wgpu::Device,
    queue: wgpu::Queue,
    surface: wgpu::Surface<'static>,
    surface_config: SurfaceConfiguration,

    font_system: FontSystem,
    swash_cache: SwashCache,
    viewport: glyphon::Viewport,
    atlas: glyphon::TextAtlas,
    text_renderer: glyphon::TextRenderer,
    text_buffer: glyphon::Buffer,

    // Make sure that the winit window is last in the struct so that
    // it is dropped after the wgpu surface is dropped, otherwise the
    // program may crash when closed. This is probably a bug in wgpu.
    window: Arc<Window>,
}

impl WindowState {
    async fn new(window: Arc<Window>) -> Self {
        let physical_size = window.inner_size();
        let scale_factor = window.scale_factor();

        // Set up surface
        let instance = Instance::new(InstanceDescriptor::default());
        let adapter = instance
            .request_adapter(&RequestAdapterOptions::default())
            .await
            .unwrap();
        let (device, queue) = adapter
            .request_device(&DeviceDescriptor::default(), None)
            .await
            .unwrap();

        let surface = instance
            .create_surface(window.clone())
            .expect("Create surface");
        let swapchain_format = TextureFormat::Bgra8UnormSrgb;
        let surface_config = SurfaceConfiguration {
            usage: TextureUsages::RENDER_ATTACHMENT,
            format: swapchain_format,
            width: physical_size.width,
            height: physical_size.height,
            present_mode: PresentMode::Fifo,
            alpha_mode: CompositeAlphaMode::Opaque,
            view_formats: vec![],
            desired_maximum_frame_latency: 2,
        };
        surface.configure(&device, &surface_config);

        // Set up text renderer
        let mut font_system = FontSystem::new();
        let swash_cache = SwashCache::new();
        let cache = Cache::new(&device);
        let viewport = Viewport::new(&device, &cache);
        let mut atlas = TextAtlas::new(&device, &queue, &cache, swapchain_format);
        let text_renderer =
            TextRenderer::new(&mut atlas, &device, MultisampleState::default(), None);
        let mut text_buffer = Buffer::new(&mut font_system, Metrics::new(30.0, 42.0));

        let physical_width = (physical_size.width as f64 * scale_factor) as f32;
        let physical_height = (physical_size.height as f64 * scale_factor) as f32;

        text_buffer.set_size(
            &mut font_system,
            Some(physical_width),
            Some(physical_height),
        );
        text_buffer.set_text(&mut font_system, "Hello world! 👋\nThis is rendered with 🦅 glyphon 🦁\nThe text below should be partially clipped.\na b c d e f g h i j k l m n o p q r s t u v w x y z", Attrs::new().family(Family::SansSerif), Shaping::Advanced);
        text_buffer.shape_until_scroll(&mut font_system, false);

        Self {
            device,
            queue,
            surface,
            surface_config,
            font_system,
            swash_cache,
            viewport,
            atlas,
            text_renderer,
            text_buffer,
            window,
        }
    }
}

struct Application {
    window_state: Option<WindowState>,
}

impl winit::application::ApplicationHandler for Application {
    fn resumed(&mut self, event_loop: &winit::event_loop::ActiveEventLoop) {
        if self.window_state.is_some() {
            return;
        }

        // Set up window
        let (width, height) = (800, 600);
        let window_attributes = Window::default_attributes()
            .with_inner_size(LogicalSize::new(width as f64, height as f64))
            .with_title("glyphon hello world");
        let window = Arc::new(event_loop.create_window(window_attributes).unwrap());

        self.window_state = Some(pollster::block_on(WindowState::new(window)));
    }

    fn window_event(
        &mut self,
        event_loop: &winit::event_loop::ActiveEventLoop,
        _window_id: winit::window::WindowId,
        event: WindowEvent,
    ) {
        let Some(state) = &mut self.window_state else {
            return;
        };

        let WindowState {
            window,
            device,
            queue,
            surface,
            surface_config,
            font_system,
            swash_cache,
            viewport,
            atlas,
            text_renderer,
            text_buffer,
            ..
        } = state;

        match event {
            WindowEvent::Resized(size) => {
                surface_config.width = size.width;
                surface_config.height = size.height;
                surface.configure(&device, &surface_config);
                window.request_redraw();
            }
            WindowEvent::RedrawRequested => {
                viewport.update(
                    &queue,
                    Resolution {
                        width: surface_config.width,
                        height: surface_config.height,
                    },
                );

                text_renderer
                    .prepare(
                        device,
                        queue,
                        font_system,
                        atlas,
                        viewport,
                        [TextArea {
                            buffer: text_buffer,
                            left: 10.0,
                            top: 10.0,
                            scale: 1.0,
                            bounds: TextBounds {
                                left: 0,
                                top: 0,
                                right: 600,
                                bottom: 160,
                            },
                            default_color: Color::rgb(255, 255, 255),
                            custom_glyphs: &[],
                        }],
                        swash_cache,
                    )
                    .unwrap();

                let frame = surface.get_current_texture().unwrap();
                let view = frame.texture.create_view(&TextureViewDescriptor::default());
                let mut encoder =
                    device.create_command_encoder(&CommandEncoderDescriptor { label: None });
                {
                    let mut pass = encoder.begin_render_pass(&RenderPassDescriptor {
                        label: None,
                        color_attachments: &[Some(RenderPassColorAttachment {
                            view: &view,
                            resolve_target: None,
                            ops: Operations {
                                load: LoadOp::Clear(wgpu::Color::BLACK),
                                store: wgpu::StoreOp::Store,
                            },
                        })],
                        depth_stencil_attachment: None,
                        timestamp_writes: None,
                        occlusion_query_set: None,
                    });

                    text_renderer.render(&atlas, &viewport, &mut pass).unwrap();
                }

                queue.submit(Some(encoder.finish()));
                frame.present();

                atlas.trim();
            }
            WindowEvent::CloseRequested => event_loop.exit(),
            _ => {}
        }
    }
}