frontend: the advoware GUI

Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>

frontend/examples/todo/state.rs

@@ -0,0 +1,92 @@
+use orbtk::prelude::*;
+
+use std::collections::VecDeque;
+
+#[derive(Debug)]
+pub enum Event {
+    Create(Entity),
+    Delete(Entity),
+}
+
+#[derive(AsAny, Default)]
+pub struct AppState {
+    events: VecDeque<Event>,
+    pub notes: Entity,
+    count: u32,
+}
+
+impl AppState {
+    fn append_note(&self, ctx: &mut Context, copy: String) {
+	let id = ctx.entity;
+	let bctx = &mut ctx.build_context();
+	let text = TextBox::create().text(copy);
+
+	let container = Stack::create()
+	    .orientation(Orientation::Horizontal)
+	    .vertical_alignment(Alignment::Start)
+	    .child(text.build(bctx))
+	    .build(bctx);
+
+	let button = Button::create()
+	    .horizontal_alignment(Alignment::End)
+	    .text("Delete")
+	    .on_click(move |ctxt, _| {
+		ctxt.get_mut::<AppState>(id)
+		    .events
+		    .push_back(Event::Delete(container));
+
+		true
+	    })
+	    .build(bctx);
+
+	bctx.append_child(container, button);
+	bctx.append_child(self.notes, container);
+    }
+
+    fn fetch_text(ctx: &mut Context, entity: Entity) -> Option<String> {
+	let mut widget = ctx.get_widget(entity);
+
+	let entry = widget.get_mut::<String16>("text");
+	if entry.is_empty() {
+	    return None;
+	}
+
+	let copy = entry.to_string();
+	entry.clear();
+	Some(copy)
+    }
+
+    pub fn send(&mut self, event: Event) {
+	self.events.push_back(event);
+    }
+}
+
+impl State for AppState {
+    fn update(&mut self, _: &mut Registry, ctx: &mut Context) {
+	if let Some(event) = self.events.pop_front() {
+	    match event {
+		// Create and append the note to the UI.
+		Event::Create(entity) => {
+		    if let Some(copy) = Self::fetch_text(ctx, entity) {
+			self.append_note(ctx, copy);
+			let count = self.count + 1;
+			self.count = count;
+			if count == 1 {
+			    ctx.widget().set::<f64>("spacing", 12.0);
+			}
+		    }
+		}
+
+		// Delete the note of the given ID from the UI.
+		Event::Delete(id) => {
+		    ctx.remove_child_from(id, self.notes);
+		    let count = self.count - 1;
+		    self.count = count;
+		    if count == 0 {
+			ctx.widget().set::<f64>("spacing", 0.0);
+		    }
+		}
+	    }
+	}
+    }
+}