Implement add popups (#63)

* Implement add popups

* Fix clippy errors

examples/tab_add_popup.rs

@@ -0,0 +1,137 @@
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
+
+use eframe::{egui, NativeOptions};
+
+use egui::{Color32, RichText};
+use egui_dock::{DockArea, NodeIndex, StyleBuilder, Tree};
+
+fn main() {
+    let options = NativeOptions::default();
+    eframe::run_native(
+        "My egui App",
+        options,
+        Box::new(|_cc| Box::new(MyApp::default())),
+    );
+}
+
+enum MyTabKind {
+    Regular,
+    Fancy,
+}
+
+struct MyTab {
+    kind: MyTabKind,
+    node: NodeIndex,
+}
+impl MyTab {
+    fn regular(node_index: usize) -> Self {
+        Self {
+            kind: MyTabKind::Regular,
+            node: NodeIndex(node_index),
+        }
+    }
+
+    fn fancy(node_index: usize) -> Self {
+        Self {
+            kind: MyTabKind::Fancy,
+            node: NodeIndex(node_index),
+        }
+    }
+
+    fn title(&self) -> String {
+        match self.kind {
+            MyTabKind::Regular => format!("Regular Tab {}", self.node.0),
+            MyTabKind::Fancy => format!("Fancy Tab {}", self.node.0),
+        }
+    }
+
+    fn content(&self) -> RichText {
+        match self.kind {
+            MyTabKind::Regular => {
+                RichText::new(format!("Content of {}. This tab is ho-hum.", self.title()))
+            }
+            MyTabKind::Fancy => RichText::new(format!(
+                "Content of {}. This tab sure is fancy!",
+                self.title()
+            ))
+            .italics()
+            .size(20.0)
+            .color(Color32::from_rgb(255, 128, 64)),
+        }
+    }
+}
+
+struct TabViewer<'a> {
+    added_nodes: &'a mut Vec<MyTab>,
+}
+
+impl egui_dock::TabViewer for TabViewer<'_> {
+    type Tab = MyTab;
+
+    fn ui(&mut self, ui: &mut egui::Ui, tab: &mut Self::Tab) {
+        ui.label(tab.content());
+    }
+
+    fn title(&mut self, tab: &mut Self::Tab) -> egui::WidgetText {
+        tab.title().into()
+    }
+
+    fn add_popup(&mut self, ui: &mut egui::Ui, node: NodeIndex) {
+        ui.set_min_width(120.0);
+        ui.style_mut().visuals.button_frame = false;
+
+        if ui.button("Regular tab").clicked() {
+            self.added_nodes.push(MyTab::regular(node.0));
+        }
+
+        if ui.button("Fancy tab").clicked() {
+            self.added_nodes.push(MyTab::fancy(node.0));
+        }
+    }
+}
+
+struct MyApp {
+    tree: Tree<MyTab>,
+    counter: usize,
+}
+
+impl Default for MyApp {
+    fn default() -> Self {
+        let mut tree = Tree::new(vec![MyTab::regular(1), MyTab::fancy(2)]);
+
+        // You can modify the tree before constructing the dock
+        let [a, b] = tree.split_left(NodeIndex::root(), 0.3, vec![MyTab::fancy(3)]);
+        let [_, _] = tree.split_below(a, 0.7, vec![MyTab::fancy(4)]);
+        let [_, _] = tree.split_below(b, 0.5, vec![MyTab::regular(5)]);
+
+        Self { tree, counter: 6 }
+    }
+}
+
+impl eframe::App for MyApp {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        let mut added_nodes = Vec::new();
+        DockArea::new(&mut self.tree)
+            .style(
+                StyleBuilder::from_egui(ctx.style().as_ref())
+                    .show_add_buttons(true)
+                    .show_add_popup(true)
+                    .build(),
+            )
+            .show(
+                ctx,
+                &mut TabViewer {
+                    added_nodes: &mut added_nodes,
+                },
+            );
+
+        added_nodes.drain(..).for_each(|node| {
+            self.tree.set_focused_node(node.node);
+            self.tree.push_to_focused_leaf(MyTab {
+                kind: node.kind,
+                node: NodeIndex(self.counter),
+            });
+            self.counter += 1;
+        });
+    }
+}