How to drag the window using mouse in egui?

Question

So I have this simple egui app written in Rust and I want to drag my window around the screen when I left click my mouse over the window and drag.

This is my window:

fn main() {
    let nativeoption = eframe::NativeOptions {
        always_on_top: false,
        maximized: false,
        decorated: true,
        fullscreen: false,
        drag_and_drop_support: true,
        initial_window_size: Option::from(egui::Vec2::new(300f32, 300f32)),
        min_window_size: None,
        max_window_size: None,
        resizable: true,
        ..Default::default()
    };
    eframe::run_native(
        "my egui app",
        nativeoption,
        Box::new(|cc| Box::new(MyEguiApp::new(cc))),
    )
    .expect("TODO: panic message");
}
#[derive(Default)]
struct MyEguiApp {
    name: String,
}

impl MyEguiApp {
    fn new(cc: &eframe::CreationContext<'_>) -> Self {
        MyEguiApp {
            name: String::new(),
        };
        Self::default()
    }
}

impl eframe::App for MyEguiApp {
    fn update(&mut self, ctx: &egui::Context, frame: &mut eframe::Frame) {
        egui::CentralPanel::default().show(ctx, |ui| {
            ui.heading("hello welcome to egui");
            ui.separator();
            ui.horizontal(|ui| {
                ui.label("Enter your name");
                let res = ui.text_edit_singleline(&mut self.name);
            });
            ui.label(format!("my name is {}", &self.name));
        });
    }
}

I want to be able to drag this anywhere using my mouse/cursor.

Answer 1

You can have portions of your UI drag the window around by adding a drag sense and calling frame.drag_window(). Here's an example with your heading:

// use more verbose definition so we can add `.sense()`
let res = Label::new(RichText::new("hello welcome to egui").heading())
    .sense(Sense::drag())
    .ui(ui);

// if heading is dragged, drag the whole window
if res.dragged() {
    frame.drag_window();
}

If you do want the whole window to be drag-able, try this:

if ui.interact(ui.max_rect(), Id::new("window-drag"), Sense::drag()).dragged() {
    frame.drag_window();
}