82 lines
2.9 KiB
Rust
82 lines
2.9 KiB
Rust
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#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
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use eframe::{egui, epi};
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use poll_promise::Promise;
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fn main() {
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let options = eframe::NativeOptions::default();
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eframe::run_native(Box::new(MyApp::default()), options);
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}
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#[derive(Default)]
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struct MyApp {
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/// `None` when download hasn't started yet.
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promise: Option<Promise<ehttp::Result<egui::TextureHandle>>>,
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}
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impl epi::App for MyApp {
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fn name(&self) -> &str {
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"Download and show an image with eframe/egui"
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}
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fn update(&mut self, ctx: &egui::Context, frame: &epi::Frame) {
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let promise = self.promise.get_or_insert_with(|| {
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// Begin download.
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// We download the image using `ehttp`, a library that works both in WASM and on native.
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// We use the `poll-promise` library to communicate with the UI thread.
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let ctx = ctx.clone();
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let frame = frame.clone();
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let (sender, promise) = Promise::new();
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let request = ehttp::Request::get("https://picsum.photos/seed/1.759706314/1024");
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ehttp::fetch(request, move |response| {
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frame.request_repaint(); // wake up UI thread
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let texture = response.and_then(|response| parse_response(&ctx, response));
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sender.send(texture); // send the results back to the UI thread.
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});
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promise
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});
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egui::CentralPanel::default().show(ctx, |ui| match promise.ready() {
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None => {
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ui.add(egui::Spinner::new()); // still loading
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}
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Some(Err(err)) => {
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ui.colored_label(egui::Color32::RED, err); // something went wrong
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}
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Some(Ok(texture)) => {
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let mut size = texture.size_vec2();
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size *= (ui.available_width() / size.x).min(1.0);
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size *= (ui.available_height() / size.y).min(1.0);
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ui.image(texture, size);
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}
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});
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}
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}
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fn parse_response(
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ctx: &egui::Context,
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response: ehttp::Response,
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) -> Result<egui::TextureHandle, String> {
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let content_type = response.content_type().unwrap_or_default();
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if content_type.starts_with("image/") {
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let image = load_image(&response.bytes).map_err(|err| err.to_string())?;
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Ok(ctx.load_texture("my-image", image))
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} else {
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Err(format!(
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"Expected image, found content-type {:?}",
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content_type
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))
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}
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}
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fn load_image(image_data: &[u8]) -> Result<egui::ColorImage, image::ImageError> {
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let image = image::load_from_memory(image_data)?;
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let size = [image.width() as _, image.height() as _];
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let image_buffer = image.to_rgba8();
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let pixels = image_buffer.as_flat_samples();
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Ok(egui::ColorImage::from_rgba_unmultiplied(
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size,
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pixels.as_slice(),
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))
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}
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