druid 0.8.2

// Copyright 2019 The Druid Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! This is a very small example of how to setup a Druid application.
//! It does the almost bare minimum while still being useful.

// On Windows platform, don't show a console when opening the app.
#![windows_subsystem = "windows"]

use druid::widget::prelude::*;
use druid::widget::{Flex, Label, TextBox};
use druid::{AppLauncher, Data, Lens, UnitPoint, WidgetExt, WindowDesc};

const VERTICAL_WIDGET_SPACING: f64 = 20.0;
const TEXT_BOX_WIDTH: f64 = 200.0;

#[derive(Clone, Data, Lens)]
struct HelloState {
    name: String,
}

pub fn main() {
    // describe the main window
    let main_window = WindowDesc::new(build_root_widget())
        .title("Hello World!")
        .window_size((400.0, 400.0));

    // create the initial app state
    let initial_state: HelloState = HelloState {
        name: "World".into(),
    };

    // start the application. Here we pass in the application state.
    AppLauncher::with_window(main_window)
        .log_to_console()
        .launch(initial_state)
        .expect("Failed to launch application");
}

fn build_root_widget() -> impl Widget<HelloState> {
    // a label that will determine its text based on the current app data.
    let label = Label::new(|data: &HelloState, _env: &Env| {
        if data.name.is_empty() {
            "Hello anybody!?".to_string()
        } else {
            format!("Hello {}!", data.name)
        }
    })
    .with_text_size(32.0);

    // a textbox that modifies `name`.
    let textbox = TextBox::new()
        .with_placeholder("Who are we greeting?")
        .with_text_size(18.0)
        .fix_width(TEXT_BOX_WIDTH)
        .lens(HelloState::name);

    // arrange the two widgets vertically, with some padding
    Flex::column()
        .with_child(label)
        .with_spacer(VERTICAL_WIDGET_SPACING)
        .with_child(textbox)
        .align_vertical(UnitPoint::CENTER)
}