Create bevy_event.rs

Gives an example how to send a bevy event from a button event handler. It took me a while to figure this out so I thought others might find this helpful.

examples/bevy_event.rs

+use bevy::{
+    prelude::{App as BevyApp, AssetServer, Commands, Res, ResMut, EventWriter, EventReader},
+    window::WindowDescriptor,
+    DefaultPlugins,
+};
+use kayak_ui::bevy::{BevyContext, BevyKayakUIPlugin, FontMapping, UICameraBundle};
+use kayak_ui::core::{
+    render, rsx,
+    styles::{Style, StyleProp, Units},
+    use_state, widget, EventType, OnEvent,
+};
+use kayak_ui::widgets::{App, Button, Text, Window};
+
+pub struct MyEvent;
+
+#[widget]
+fn EventWindow() {
+    let text_styles = Style {
+        bottom: StyleProp::Value(Units::Stretch(1.0)),
+        left: StyleProp::Value(Units::Stretch(0.1)),
+        right: StyleProp::Value(Units::Stretch(0.1)),
+        top: StyleProp::Value(Units::Stretch(1.0)),
+        width: StyleProp::Value(Units::Stretch(1.0)),
+        height: StyleProp::Value(Units::Pixels(28.0)),
+        ..Default::default()
+    };
+
+    let button_text_styles = Style {
+        left: StyleProp::Value(Units::Stretch(1.0)),
+        right: StyleProp::Value(Units::Stretch(1.0)),
+        ..Default::default()
+    };
+
+    let on_event = OnEvent::new(move |ctx, event| match event.event_type {
+        EventType::Click(..) => {
+            ctx.query_world::<EventWriter<MyEvent>, _, ()>(|mut writer| writer.send(MyEvent));
+        },
+        _ => {}
+    });
+
+    rsx! {
+        <>
+            <Window draggable={true} position={(50.0, 50.0)} size={(300.0, 300.0)} title={"Bevy Event Example".to_string()}>
+                <Button on_event={Some(on_event)}>
+                    <Text styles={Some(button_text_styles)} line_height={Some(40.0)} size={24.0} content={"Send bevy event".to_string()}>{}</Text>
+                </Button>
+            </Window>
+        </>
+    }
+}
+
+fn startup(
+    mut commands: Commands,
+    mut font_mapping: ResMut<FontMapping>,
+    asset_server: Res<AssetServer>,
+) {
+    commands.spawn_bundle(UICameraBundle::new());
+
+    font_mapping.set_default(asset_server.load("roboto.kayak_font"));
+
+    let context = BevyContext::new(|context| {
+        render! {
+            <App>
+                <EventWindow />
+            </App>
+        }
+    });
+
+    commands.insert_resource(context);
+}
+
+fn on_my_event(mut reader: EventReader<MyEvent>) {
+    for _ in reader.iter() {
+        println!("MyEvent detected");
+    }
+}
+
+fn main() {
+    BevyApp::new()
+        .insert_resource(WindowDescriptor {
+            width: 1270.0,
+            height: 720.0,
+            title: String::from("UI Example"),
+            ..Default::default()
+        })
+        .add_plugins(DefaultPlugins)
+        .add_event::<MyEvent>()
+        .add_plugin(BevyKayakUIPlugin)
+        .add_startup_system(startup)
+        .add_system(on_my_event)
+        .run();
+}