Add FixedLayout

cursive-core/src/direction.rs

@@ -154,6 +154,14 @@ impl Direction {
         }
     }
 
+    /// Returns the direction opposite `self`.
+    pub fn opposite(self) -> Self {
+        match self {
+            Direction::Abs(abs) => Direction::Abs(abs.opposite()),
+            Direction::Rel(rel) => Direction::Rel(rel.swap()),
+        }
+    }
+
     /// Shortcut to create `Direction::Rel(Relative::Back)`
     pub fn back() -> Self {
         Direction::Rel(Relative::Back)
@@ -191,7 +199,7 @@ impl Direction {
 }
 
 /// Direction relative to an orientation.
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Relative {
     // TODO: handle right-to-left? (Arabic, ...)
     /// Front relative direction.
@@ -217,6 +225,39 @@ impl Relative {
             (Orientation::Vertical, Relative::Back) => Absolute::Down,
         }
     }
+
+    /// Picks one of the two values in a tuple.
+    ///
+    /// First one is `self` is `Front`, second one if `self` is `Back`.
+    pub fn pick<T>(self, (front, back): (T, T)) -> T {
+        match self {
+            Relative::Front => front,
+            Relative::Back => back,
+        }
+    }
+
+    /// Returns the other relative direction.
+    pub fn swap(self) -> Self {
+        match self {
+            Relative::Front => Relative::Back,
+            Relative::Back => Relative::Front,
+        }
+    }
+
+    /// Returns the relative position of `a` to `b`.
+    ///
+    /// If `a < b`, it would be `Front`.
+    /// If `a > b`, it would be `Back`.
+    /// If `a == b`, returns `None`.
+    pub fn a_to_b(a: usize, b: usize) -> Option<Self> {
+        use std::cmp::Ordering;
+
+        match a.cmp(&b) {
+            Ordering::Less => Some(Relative::Front),
+            Ordering::Greater => Some(Relative::Back),
+            Ordering::Equal => None,
+        }
+    }
 }
 
 /// Absolute direction (up, down, left, right).
@@ -251,4 +292,29 @@ impl Absolute {
             _ => None,
         }
     }
+
+    /// Returns the direction opposite `self`.
+    pub fn opposite(self) -> Self {
+        match self {
+            Absolute::Left => Absolute::Right,
+            Absolute::Right => Absolute::Left,
+            Absolute::Up => Absolute::Down,
+            Absolute::Down => Absolute::Up,
+            Absolute::None => Absolute::None,
+        }
+    }
+
+    /// Splits this absolute direction into an orientation and relative direction.
+    ///
+    /// For example, `Right` will give `(Horizontal, Back)`.
+    pub fn split(self) -> (Orientation, Relative) {
+        match self {
+            Absolute::Left => (Orientation::Horizontal, Relative::Front),
+            Absolute::Right => (Orientation::Horizontal, Relative::Back),
+            Absolute::Up => (Orientation::Vertical, Relative::Front),
+            Absolute::Down => (Orientation::Vertical, Relative::Back),
+            // TODO: Remove `Absolute::None`
+            Absolute::None => panic!("None direction not supported here"),
+        }
+    }
 }

cursive-core/src/event.rs

@@ -522,6 +522,8 @@ pub enum Event {
 
     // Having a doc-hidden event prevents people from having exhaustive
     // matches, allowing us to add events in the future.
+    //
+    // In addition we may not want people to listen to the exit event?
     #[doc(hidden)]
     /// The application is about to exit.
     Exit,

cursive-core/src/printer.rs

@@ -2,12 +2,14 @@
 
 use crate::backend::Backend;
 use crate::direction::Orientation;
+use crate::rect::Rect;
 use crate::theme::{
     BorderStyle, ColorStyle, Effect, PaletteColor, Style, Theme,
 };
 use crate::utils::lines::simple::{prefix, suffix};
 use crate::with::With;
 use crate::Vec2;
+
 use enumset::EnumSet;
 use std::cmp::min;
 use unicode_segmentation::UnicodeSegmentation;
@@ -541,6 +543,13 @@ impl<'a, 'b> Printer<'a, 'b> {
         self.clone().with(|s| s.enabled &= enabled)
     }
 
+    /// Returns a new sub-printer for the given viewport.
+    ///
+    /// This is a combination of offset + cropped.
+    pub fn windowed(&self, viewport: Rect) -> Self {
+        self.offset(viewport.top_left()).cropped(viewport.size())
+    }
+
     /// Returns a new sub-printer with a cropped area.
     ///
     /// The new printer size will be the minimum of `size` and its current size.
@@ -601,6 +610,9 @@ impl<'a, 'b> Printer<'a, 'b> {
     }
 
     /// Returns a new sub-printer with a content offset.
+    ///
+    /// This is useful for parent views that only show a subset of their
+    /// child, like `ScrollView`.
     pub fn content_offset<S>(&self, offset: S) -> Self
     where
         S: Into<Vec2>,

cursive-core/src/rect.rs

@@ -1,5 +1,7 @@
 //! Rectangles on the 2D character grid.
+use crate::direction::{Absolute, Orientation};
 use crate::Vec2;
+
 use std::ops::Add;
 
 /// A non-empty rectangle on the 2D grid.
@@ -7,6 +9,7 @@ use std::ops::Add;
 pub struct Rect {
     /// Top-left corner, inclusive
     top_left: Vec2,
+
     /// Bottom-right corner, inclusive
     bottom_right: Vec2,
 }
@@ -90,6 +93,30 @@ impl Rect {
         self
     }
 
+    /// Returns the start and end coordinate of one side of this rectangle.
+    ///
+    /// Both start and end are inclusive.
+    pub fn side(self, orientation: Orientation) -> (usize, usize) {
+        match orientation {
+            Orientation::Vertical => (self.top(), self.bottom()),
+            Orientation::Horizontal => (self.left(), self.right()),
+        }
+    }
+
+    /// Returns the coordinate of the given edge.
+    ///
+    /// All edges are inclusive.
+    pub fn edge(self, side: Absolute) -> usize {
+        match side {
+            Absolute::Left => self.left(),
+            Absolute::Right => self.right(),
+            Absolute::Up => self.top(),
+            Absolute::Down => self.bottom(),
+            // TODO: Remove `None` from `Absolute` enum
+            Absolute::None => panic!("None is not a valid edge."),
+        }
+    }
+
     /// Adds the given offset to this rectangle.
     pub fn offset<V>(&mut self, offset: V)
     where

cursive-core/src/vec.rs

@@ -87,6 +87,21 @@ impl XY<usize> {
         })
     }
 
+    /// Checked addition with a signed vec.
+    ///
+    /// Will return `None` if any coordinates exceeds bounds.
+    pub fn checked_add<O: Into<XY<isize>>>(&self, other: O) -> Option<Self> {
+        let other = other.into();
+        self.zip_map(other, |s, o| {
+            if o > 0 {
+                s.checked_add(o as usize)
+            } else {
+                s.checked_sub((-o) as usize)
+            }
+        })
+        .both()
+    }
+
     /// Term-by-term integer division that rounds up.
     ///
     /// # Examples

cursive-core/src/view/view_trait.rs

@@ -83,9 +83,7 @@ pub trait View: Any + AnyView {
     /// View groups should implement this to forward the call to each children.
     ///
     /// Default implementation is a no-op.
-    fn call_on_any<'a>(&mut self, _: &Selector<'_>, _: AnyCb<'a>) {
+    fn call_on_any<'a>(&mut self, _: &Selector<'_>, _: AnyCb<'a>) {}
-        // TODO: FnMut -> FnOnce once it works
-    }
 
     /// Moves the focus to the view identified by the given selector.
     ///
@@ -99,12 +97,10 @@ pub trait View: Any + AnyView {
     /// This view is offered focus. Will it take it?
     ///
     /// `source` indicates where the focus comes from.
-    /// When the source is unclear, `Front` is usually used.
+    /// When the source is unclear (for example mouse events),
+    /// `Direction::none()` can be used.
     ///
     /// Default implementation always return `false`.
-    ///
-    /// If the source is `Direction::Abs(Absolute::None)`, it is _recommended_
-    /// not to change the current focus selection.
     fn take_focus(&mut self, source: Direction) -> bool {
         let _ = source;
         false
@@ -125,6 +121,8 @@ pub trait View: Any + AnyView {
     /// Returns the type of this view.
     ///
     /// Useful when you have a `&dyn View`.
+    ///
+    /// View implementation don't usually have to override this.
     fn type_name(&self) -> &'static str {
         std::any::type_name::<Self>()
     }

cursive-core/src/views/fixed_layout.rs

@@ -0,0 +1,269 @@
+use crate::direction::{Absolute, Direction, Relative};
+use crate::event::{Event, EventResult, Key};
+use crate::rect::Rect;
+use crate::view::IntoBoxedView;
+use crate::{Printer, Vec2, View, With};
+
+/// Arranges its children in a fixed layout.
+///
+/// Usually meant to use an external layout engine.
+pub struct FixedLayout {
+    children: Vec<Child>,
+    focus: usize,
+}
+
+struct Child {
+    view: Box<dyn View>,
+    position: Rect,
+}
+
+new_default!(FixedLayout);
+
+impl FixedLayout {
+    /// Returns a new, empty `FixedLayout`.
+    pub fn new() -> Self {
+        FixedLayout {
+            children: Vec::new(),
+            focus: 0,
+        }
+    }
+
+    /// Adds a child. Chainable variant.
+    pub fn child<V: IntoBoxedView>(self, position: Rect, view: V) -> Self {
+        self.with(|s| s.add_child(position, view))
+    }
+
+    /// Adds a child.
+    pub fn add_child<V: IntoBoxedView>(&mut self, position: Rect, view: V) {
+        self.children.push(Child {
+            view: view.as_boxed_view(),
+            position,
+        });
+    }
+
+    /// Returns index of focused inner view
+    pub fn get_focus_index(&self) -> usize {
+        self.focus
+    }
+
+    /// Attemps to set the focus on the given child.
+    ///
+    /// Returns `Err(())` if `index >= self.len()`, or if the view at the
+    /// given index does not accept focus.
+    pub fn set_focus_index(&mut self, index: usize) -> Result<(), ()> {
+        if self
+            .children
+            .get_mut(index)
+            .map(|child| child.view.take_focus(Direction::none()))
+            .unwrap_or(false)
+        {
+            self.focus = index;
+            Ok(())
+        } else {
+            Err(())
+        }
+    }
+
+    /// How many children are in this view.
+    pub fn len(&self) -> usize {
+        self.children.len()
+    }
+
+    /// Returns `true` if this view has no children.
+    pub fn is_empty(&self) -> bool {
+        self.children.is_empty()
+    }
+
+    /// Returns a reference to a child.
+    pub fn get_child(&self, i: usize) -> Option<&dyn View> {
+        self.children.get(i).map(|c| &*c.view)
+    }
+
+    /// Returns a mutable reference to a child.
+    pub fn get_child_mut(&mut self, i: usize) -> Option<&mut dyn View> {
+        self.children.get_mut(i).map(|c| &mut *c.view)
+    }
+
+    /// Sets the position for the given child.
+    pub fn set_child_position(&mut self, i: usize, position: Rect) {
+        self.children[i].position = position;
+    }
+
+    /// Removes a child.
+    ///
+    /// If `i` is within bounds, the removed child will be returned.
+    pub fn remove_child(&mut self, i: usize) -> Option<Box<dyn View>> {
+        if i >= self.len() {
+            return None;
+        }
+
+        if self.focus > i
+            || (self.focus != 0 && self.focus == self.children.len() - 1)
+        {
+            self.focus -= 1;
+        }
+
+        Some(self.children.remove(i).view)
+    }
+
+    fn iter_mut<'a>(
+        source: Direction,
+        children: &'a mut [Child],
+    ) -> Box<dyn Iterator<Item = (usize, &mut Child)> + 'a> {
+        let children = children.iter_mut().enumerate();
+        match source {
+            Direction::Rel(Relative::Front) => Box::new(children),
+            Direction::Rel(Relative::Back) => Box::new(children.rev()),
+            Direction::Abs(abs) => {
+                // Sort children by the given direction
+                let mut children: Vec<_> = children.collect();
+                children.sort_by_key(|(_, c)| c.position.edge(abs));
+                Box::new(children.into_iter())
+            }
+        }
+    }
+
+    fn move_focus(&mut self, target: Absolute) -> EventResult {
+        let source = Direction::Abs(target.opposite());
+        let (orientation, rel) = target.split();
+
+        fn intersects(a: (usize, usize), b: (usize, usize)) -> bool {
+            a.1 >= b.0 && a.0 <= b.1
+        }
+
+        let current_position = self.children[self.focus].position;
+        let current_side = current_position.side(orientation.swap());
+        let current_edge = current_position.edge(target);
+
+        let children =
+            Self::iter_mut(source, &mut self.children).filter(|(_, c)| {
+                // Only select children actually aligned with us
+                Some(rel)
+                    == Relative::a_to_b(current_edge, c.position.edge(target))
+                    && intersects(
+                        c.position.side(orientation.swap()),
+                        current_side,
+                    )
+            });
+
+        for (i, c) in children {
+            if c.view.take_focus(source) {
+                self.focus = i;
+                return EventResult::Consumed(None);
+            }
+        }
+
+        EventResult::Ignored
+    }
+
+    fn check_focus_grab(&mut self, event: &Event) {
+        if let Event::Mouse {
+            offset,
+            position,
+            event,
+        } = *event
+        {
+            if !event.grabs_focus() {
+                return;
+            }
+
+            let position = match position.checked_sub(offset) {
+                None => return,
+                Some(pos) => pos,
+            };
+
+            for (i, child) in self.children.iter_mut().enumerate() {
+                if child.position.contains(position)
+                    && child.view.take_focus(Direction::none())
+                {
+                    self.focus = i;
+                }
+            }
+        }
+    }
+}
+
+impl View for FixedLayout {
+    fn draw(&self, printer: &Printer) {
+        for child in &self.children {
+            child.view.draw(&printer.windowed(child.position));
+        }
+    }
+
+    fn layout(&mut self, _size: Vec2) {
+        // TODO: re-compute children positions?
+        for child in &mut self.children {
+            child.view.layout(child.position.size());
+        }
+    }
+
+    fn on_event(&mut self, event: Event) -> EventResult {
+        if self.is_empty() {
+            return EventResult::Ignored;
+        }
+
+        self.check_focus_grab(&event);
+
+        let child = &mut self.children[self.focus];
+
+        let result = child
+            .view
+            .on_event(event.relativized(child.position.top_left()));
+
+        match result {
+            EventResult::Ignored => match event {
+                Event::Key(Key::Tab) => unimplemented!(),
+                Event::Key(Key::Left) => self.move_focus(Absolute::Left),
+                Event::Key(Key::Right) => self.move_focus(Absolute::Right),
+                Event::Key(Key::Up) => self.move_focus(Absolute::Up),
+                Event::Key(Key::Down) => self.move_focus(Absolute::Down),
+                _ => EventResult::Ignored,
+            },
+            res => res,
+        }
+    }
+
+    fn important_area(&self, size: Vec2) -> Rect {
+        if self.is_empty() {
+            return Rect::from_size((0, 0), size);
+        }
+
+        let child = &self.children[self.focus];
+
+        child.view.important_area(child.position.size())
+            + child.position.top_left()
+    }
+
+    fn required_size(&mut self, _constraint: Vec2) -> Vec2 {
+        self.children
+            .iter()
+            .map(|c| c.position.bottom_left() + (1, 1))
+            .fold(Vec2::zero(), Vec2::max)
+    }
+
+    fn take_focus(&mut self, source: Direction) -> bool {
+        // TODO: what if source = None?
+        match source {
+            Direction::Abs(Absolute::None) => {
+                // For now, take focus if any view is focusable.
+                for child in &mut self.children {
+                    if child.view.take_focus(source) {
+                        return true;
+                    }
+                }
+
+                false
+            }
+            source => {
+                for (i, c) in Self::iter_mut(source, &mut self.children) {
+                    if c.view.take_focus(source) {
+                        self.focus = i;
+                        return true;
+                    }
+                }
+
+                false
+            }
+        }
+    }
+}

cursive-core/src/views/linear_layout.rs

@@ -319,7 +319,7 @@ impl LinearLayout {
             .any(View::needs_relayout)
     }
 
-    /// Returns a cyclic mutable iterator starting with the child in focus
+    /// Returns a mutable iterator starting with the child in focus
     fn iter_mut<'a>(
         &'a mut self,
         from_focus: bool,

cursive-core/src/views/mod.rs

@@ -69,6 +69,7 @@ mod dialog;
 mod dummy;
 mod edit_view;
 mod enableable_view;
+mod fixed_layout;
 mod hideable_view;
 mod last_size_view;
 mod layer;
@@ -103,6 +104,7 @@ pub use self::dialog::{Dialog, DialogFocus};
 pub use self::dummy::DummyView;
 pub use self::edit_view::EditView;
 pub use self::enableable_view::EnableableView;
+pub use self::fixed_layout::FixedLayout;
 pub use self::hideable_view::HideableView;
 pub use self::last_size_view::LastSizeView;
 pub use self::layer::Layer;

cursive-core/src/xy.rs

@@ -437,6 +437,25 @@ impl<T> XY<Option<T>> {
     pub fn unwrap_or(self, other: XY<T>) -> XY<T> {
         self.zip_map(other, Option::unwrap_or)
     }
+
+    /// Returns a new `XY` if both components are present in `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use cursive_core::XY;
+    /// assert_eq!(XY::new(Some(1), None).both(), None);
+    /// assert_eq!(XY::new(Some(1), Some(2)).both(), Some(XY::new(1, 2)));
+    /// ```
+    pub fn both(self) -> Option<XY<T>> {
+        match self {
+            XY {
+                x: Some(x),
+                y: Some(y),
+            } => Some(XY::new(x, y)),
+            _ => None,
+        }
+    }
 }
 
 impl XY<bool> {

examples/src/bin/fixed_layout.rs

@@ -0,0 +1,15 @@
+fn main() {
+    let mut siv = cursive::default();
+
+    siv.add_layer(
+        cursive::views::Dialog::around(
+            cursive::views::FixedLayout::new().child(
+                cursive::Rect::from_size((0, 0), (10, 1)),
+                cursive::views::TextView::new("abc"),
+            ),
+        )
+        .button("Quit", |s| s.quit()),
+    );
+
+    siv.run();
+}