Add rudimentary support for gui windows that you can move around

emigui/src/window.rs

@@ -0,0 +1,98 @@
+use std::sync::Arc;
+
+use crate::{
+    layout::{make_id, Data, Direction},
+    widgets::Label,
+    *,
+};
+
+#[derive(Clone, Copy, Debug)]
+pub struct WindowState {
+    /// Last known pos/size
+    pub rect: Rect,
+}
+
+pub struct Window {
+    /// The title of the window and by default the source of its identity.
+    title: String,
+}
+
+impl Window {
+    pub fn new<S: Into<String>>(title: S) -> Self {
+        Self {
+            title: title.into(),
+        }
+    }
+
+    pub fn show<F>(self, data: Arc<Data>, add_contents: F)
+    where
+        F: FnOnce(&mut Region),
+    {
+        let id = make_id(&self.title);
+
+        let mut state = data.memory.lock().unwrap().get_or_create_window(
+            id,
+            Rect::from_min_size(
+                vec2(400.0, 200.0), // TODO
+                vec2(200.0, 200.0), // TODO
+            ),
+        );
+
+        let layer = Layer::Window(id);
+        let where_to_put_background = data.graphics.lock().unwrap().layer(layer).len();
+
+        let style = data.style();
+        let window_padding = style.window_padding;
+
+        let mut contents_region = Region {
+            data: data.clone(),
+            layer: Layer::Popup,
+            style,
+            id: Default::default(),
+            dir: Direction::Vertical,
+            align: Align::Min,
+            cursor: state.rect.min() + window_padding,
+            bounding_size: vec2(0.0, 0.0),
+            available_space: vec2(data.input.screen_size.x.min(350.0), std::f32::INFINITY), // TODO: window.width
+        };
+
+        // Show top bar:
+        contents_region.add(Label::new(self.title).text_style(TextStyle::Heading));
+
+        add_contents(&mut contents_region);
+
+        // Now insert window background:
+
+        // TODO: handle the last item_spacing in a nicer way
+        let inner_size = contents_region.bounding_size - style.item_spacing;
+        let outer_size = inner_size + 2.0 * window_padding;
+
+        state.rect = Rect::from_min_size(state.rect.min(), outer_size);
+
+        let mut graphics = data.graphics.lock().unwrap();
+        let graphics = graphics.layer(layer);
+        graphics.insert(
+            where_to_put_background,
+            PaintCmd::Rect {
+                corner_radius: 5.0,
+                fill_color: Some(style.background_fill_color()),
+                outline: Some(Outline {
+                    color: color::WHITE,
+                    width: 1.0,
+                }),
+                rect: state.rect,
+            },
+        );
+
+        let interact = data.interact(layer, state.rect, Some(id));
+        if interact.active {
+            state.rect = state.rect.translate(data.input().mouse_move);
+        }
+
+        let mut memory = data.memory.lock().unwrap();
+        if interact.active || interact.clicked {
+            memory.move_window_to_top(id);
+        }
+        memory.set_window_state(id, state);
+    }
+}