Add proper select popup placement

Added a popup select to the `list_view` example

examples/list_view.rs

@@ -2,30 +2,44 @@ extern crate cursive;
 
 use cursive::Cursive;
 use cursive::With;
-use cursive::view::{ListView, Checkbox, Dialog, EditView, TextView, LinearLayout};
+use cursive::view::{Checkbox, Dialog, EditView, LinearLayout, ListView,
+                    TextView, SelectView};
 
 fn main() {
     let mut siv = Cursive::new();
 
     siv.add_layer(Dialog::new(ListView::new()
             .child("Name", EditView::new().min_length(10))
-                              .child("Email", LinearLayout::horizontal()
-                                    .child(EditView::new().min_length(15).disabled().with_id("email1"))
+            .child("Email",
+                   LinearLayout::horizontal()
+                       .child(EditView::new()
+                           .min_length(15)
+                           .disabled()
+                           .with_id("email1"))
                        .child(TextView::new("@"))
-                                    .child(EditView::new().min_length(10).disabled().with_id("email2")))
-                              .child("Receive spam?", Checkbox::new().on_change(|s, checked| {
+                       .child(EditView::new()
+                           .min_length(10)
+                           .disabled()
+                           .with_id("email2")))
+            .child("Receive spam?",
+                   Checkbox::new().on_change(|s, checked| {
                        for name in &["email1", "email2"] {
                            let view: &mut EditView = s.find_id(name).unwrap();
                            view.set_enabled(checked);
                        }
                    }))
             .delimiter()
+            .child("Age",
+                   SelectView::new().popup()
+                       .item_str("0-18")
+                       .item_str("19-30")
+                       .item_str("31-40")
+                       .item_str("41+"))
             .with(|list| {
                 for i in 0..50 {
                     list.add_child(&format!("Item {}", i), EditView::new());
                 }
-                              })
-                              )
+            }))
         .title("Please fill out this form")
         .button("Ok", |s| s.quit()));
 

src/lib.rs

@@ -200,6 +200,12 @@ impl Cursive {
         B::set_refresh_rate(fps)
     }
 
+    /// Returns a reference to the currently active screen.
+    pub fn screen(&self) -> &StackView {
+        let id = self.active_screen;
+        &self.screens[id]
+    }
+
     /// Returns a mutable reference to the currently active screen.
     pub fn screen_mut(&mut self) -> &mut StackView {
         let id = self.active_screen;

src/view/menu_popup.rs

@@ -1,8 +1,10 @@
 use std::rc::Rc;
+use std::cmp::min;
 
 use unicode_width::UnicodeWidthStr;
 
 use Cursive;
+use With;
 use menu::{MenuItem, MenuTree};
 use Printer;
 use view::View;
@@ -36,6 +38,18 @@ impl MenuPopup {
         }
     }
 
+    /// Sets the currently focused element.
+    pub fn set_focus(&mut self, focus: usize) {
+        self.focus = min(focus, self.menu.len());
+    }
+
+    /// Sets the currently focused element.
+    ///
+    /// Chainable variant.
+    pub fn focus(self, focus: usize) -> Self {
+        self.with(|s| s.set_focus(focus))
+    }
+
     fn item_width(item: &MenuItem) -> usize {
         match *item {
             MenuItem::Delimiter => 1,

src/view/select_view.rs

@@ -7,6 +7,7 @@ use menu::MenuTree;
 use view::MenuPopup;
 use With;
 use direction::Direction;
+use view::position::Position;
 use view::{IdView, View};
 use align::{Align, HAlign, VAlign};
 use view::scroll::ScrollBase;
@@ -45,6 +46,10 @@ pub struct SelectView<T = String> {
     align: Align,
     // `true` if we show a one-line view, with popup on selection.
     popup: bool,
+    // We need the last offset to place the popup window
+    // We "cache" it during the draw, so we need interior mutability.
+    last_offset: Cell<Vec2>,
+    last_size: Vec2,
 }
 
 impl<T: 'static> SelectView<T> {
@@ -58,6 +63,8 @@ impl<T: 'static> SelectView<T> {
             select_cb: None,
             align: Align::top_left(),
             popup: false,
+            last_offset: Cell::new(Vec2::zero()),
+            last_size: Vec2::zero(),
         }
     }
 
@@ -210,6 +217,8 @@ impl SelectView<String> {
 
 impl<T: 'static> View for SelectView<T> {
     fn draw(&self, printer: &Printer) {
+        self.last_offset.set(printer.offset);
+
         if self.popup {
             let style = if !self.enabled {
                 ColorStyle::Secondary
@@ -218,15 +227,15 @@ impl<T: 'static> View for SelectView<T> {
             } else {
                 ColorStyle::Highlight
             };
-            let x = printer.size.x - 1;
+            let x = printer.size.x;
 
 
             printer.with_color(style, |printer| {
                 // Prepare the entire background
-                printer.print_hline((0, 0), x, " ");
+                printer.print_hline((1, 0), x - 1, " ");
                 // Draw the borders
                 printer.print((0, 0), "<");
-                printer.print((x, 0), ">");
+                printer.print((x-1, 0), ">");
 
                 let label = &self.items[self.focus()].label;
 
@@ -287,6 +296,8 @@ impl<T: 'static> View for SelectView<T> {
         if self.popup {
             match event {
                 Event::Key(Key::Enter) => {
+                    // Build a shallow menu tree to mimick the items array.
+                    // TODO: cache it?
                     let mut tree = MenuTree::new();
                     for (i, item) in self.items.iter().enumerate() {
                         let focus = self.focus.clone();
@@ -299,10 +310,38 @@ impl<T: 'static> View for SelectView<T> {
                             }
                         });
                     }
+                    // Let's keep the tree around,
+                    // the callback will want to use it.
                     let tree = Rc::new(tree);
+
+                    let focus = self.focus();
+                    // This is the offset for the label text.
+                    // We'll want to show the popup so that the text matches.
+                    // It'll be soo cool.
+                    let text_offset =
+                        (self.last_size.x - self.items[focus].label.len()) / 2;
+                    // The total offset for the window is:
+                    // * the last absolute offset at which we drew this view
+                    // * shifted to the top of the focus (so the line matches)
+                    // * shifted to the right of the text offset
+                    // * shifted top-left of the border+padding of the popup
+                    let offset = self.last_offset.get() - (0, focus) +
+                                 (text_offset, 0) -
+                                 (2, 1);
+                    // And now, we can return the callback.
                     EventResult::with_cb(move |s| {
+                        // The callback will want to work with a fresh Rc
                         let tree = tree.clone();
-                        s.add_layer(MenuPopup::new(tree));
+                        // We'll relativise the absolute position,
+                        // So that we are locked to the parent view.
+                        // A nice effect is that window resizes will keep both
+                        // layers together.
+                        let current_offset = s.screen().offset();
+                        let offset = offset - current_offset;
+                        // And finally, put the view in view!
+                        s.screen_mut()
+                            .add_layer_at(Position::parent(offset),
+                                          MenuPopup::new(tree).focus(focus));
                     })
                 }
                 _ => EventResult::Ignored,
@@ -354,6 +393,8 @@ impl<T: 'static> View for SelectView<T> {
     }
 
     fn layout(&mut self, size: Vec2) {
+        self.last_size = size;
+
         if !self.popup {
             self.scrollbase.set_heights(size.y, self.items.len());
         }

src/view/stack_view.rs

@@ -12,6 +12,7 @@ use theme::ColorStyle;
 /// Only the top-most view is active and can receive input.
 pub struct StackView {
     layers: Vec<Layer>,
+    last_size: Vec2,
 }
 
 struct Layer {
@@ -27,7 +28,10 @@ new_default!(StackView);
 impl StackView {
     /// Creates a new empty StackView
     pub fn new() -> Self {
-        StackView { layers: Vec::new() }
+        StackView {
+            layers: Vec::new(),
+            last_size: Vec2::zero(),
+        }
     }
 
     /// Adds new view on top of the stack in the center of the screen.
@@ -54,6 +58,17 @@ impl StackView {
         self.layers.pop();
         ::B::clear();
     }
+
+    /// Computes the offset of the current top view.
+    pub fn offset(&self) -> Vec2 {
+        let mut previous = Vec2::zero();
+        for layer in &self.layers {
+            let offset = layer.position
+                .compute_offset(layer.size, self.last_size, previous);
+            previous = offset;
+        }
+        previous
+    }
 }
 
 impl View for StackView {
@@ -82,6 +97,8 @@ impl View for StackView {
     }
 
     fn layout(&mut self, size: Vec2) {
+        self.last_size = size;
+
         // The call has been made, we can't ask for more space anymore.
         // Let's make do with what we have.