View::focus_view: replace () with zero-sized ViewNotFound

cursive-core/src/cursive.rs

@@ -12,7 +12,7 @@ use crate::{
     event::{Event, EventResult},
     printer::Printer,
     theme,
-    view::{self, Finder, IntoBoxedView, Position, View},
+    view::{self, Finder, IntoBoxedView, Position, View, ViewNotFound},
     views::{self, LayerPosition},
     Dump, Vec2,
 };
@@ -616,18 +616,21 @@ impl Cursive {
     /// Moves the focus to the view identified by `name`.
     ///
     /// Convenient method to call `focus` with a [`view::Selector::Name`].
-    pub fn focus_name(&mut self, name: &str) -> Result<(), ()> {
+    pub fn focus_name(&mut self, name: &str) -> Result<(), ViewNotFound> {
         self.focus(&view::Selector::Name(name))
     }
 
     /// Same as [`focus_name`](Cursive::focus_name).
     #[deprecated(note = "`focus_id` is being renamed to `focus_name`")]
-    pub fn focus_id(&mut self, id: &str) -> Result<(), ()> {
+    pub fn focus_id(&mut self, id: &str) -> Result<(), ViewNotFound> {
         self.focus(&view::Selector::Name(id))
     }
 
     /// Moves the focus to the view identified by `sel`.
-    pub fn focus(&mut self, sel: &view::Selector<'_>) -> Result<(), ()> {
+    pub fn focus(
+        &mut self,
+        sel: &view::Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         self.root.focus_view(sel)
     }
 

cursive-core/src/view/mod.rs

@@ -117,7 +117,7 @@ pub use self::scrollable::Scrollable;
 pub use self::size_cache::SizeCache;
 pub use self::size_constraint::SizeConstraint;
 pub use self::view_path::ViewPath;
-pub use self::view_trait::View;
+pub use self::view_trait::{View, ViewNotFound};
 pub use self::view_wrapper::ViewWrapper;
 
 #[deprecated(note = "`Boxable` is being renamed to `Resizable`")]

cursive-core/src/view/scroll/core.rs

@@ -6,7 +6,7 @@ use crate::{
     printer::Printer,
     rect::Rect,
     theme::ColorStyle,
-    view::{ScrollStrategy, Selector, SizeCache},
+    view::{ScrollStrategy, Selector, SizeCache, ViewNotFound},
     with::With,
     Vec2, XY,
 };
@@ -282,9 +282,9 @@ impl Core {
         &mut self,
         selector: &Selector<'_>,
         inner_focus_view: F,
-    ) -> Result<(), ()>
+    ) -> Result<(), ViewNotFound>
     where
-        F: FnOnce(&Selector) -> Result<(), ()>,
+        F: FnOnce(&Selector) -> Result<(), ViewNotFound>,
     {
         inner_focus_view(selector)
     }

cursive-core/src/view/view_trait.rs

@@ -6,6 +6,18 @@ use crate::Printer;
 use crate::Vec2;
 use std::any::Any;
 
+/// Error indicating a view was not found.
+#[derive(Debug)]
+pub struct ViewNotFound;
+
+impl std::fmt::Display for ViewNotFound {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "View could not be found")
+    }
+}
+
+impl std::error::Error for ViewNotFound {}
+
 /// Main trait defining a view behaviour.
 ///
 /// This is what you should implement to define a custom View.
@@ -90,8 +102,8 @@ pub trait View: Any + AnyView {
     /// Returns `Ok(())` if the view was found and selected.
     ///
     /// Default implementation simply returns `Err(())`.
-    fn focus_view(&mut self, _: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(&mut self, _: &Selector<'_>) -> Result<(), ViewNotFound> {
-        Err(())
+        Err(ViewNotFound)
     }
 
     /// This view is offered focus. Will it take it?

cursive-core/src/view/view_wrapper.rs

@@ -1,9 +1,10 @@
-use crate::direction::Direction;
+use crate::{
-use crate::event::{AnyCb, Event, EventResult};
+    direction::Direction,
-use crate::rect::Rect;
+    event::{AnyCb, Event, EventResult},
-use crate::view::{Selector, View};
+    rect::Rect,
-use crate::Printer;
+    view::{Selector, View, ViewNotFound},
-use crate::Vec2;
+    Printer, Vec2,
+};
 
 /// Generic wrapper around a view.
 ///
@@ -84,9 +85,12 @@ pub trait ViewWrapper: 'static {
     }
 
     /// Wraps the `focus_view` method.
-    fn wrap_focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn wrap_focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         self.with_view_mut(|v| v.focus_view(selector))
-            .unwrap_or(Err(()))
+            .unwrap_or(Err(ViewNotFound))
     }
 
     /// Wraps the `needs_relayout` method.
@@ -135,7 +139,10 @@ impl<T: ViewWrapper> View for T {
         self.wrap_needs_relayout()
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         self.wrap_focus_view(selector)
     }
 

cursive-core/src/views/canvas.rs

@@ -1,10 +1,10 @@
-use crate::direction::Direction;
+use crate::{
-use crate::event::{AnyCb, Event, EventResult};
+    direction::Direction,
-use crate::rect::Rect;
+    event::{AnyCb, Event, EventResult},
-use crate::view::{Selector, View};
+    rect::Rect,
-use crate::Printer;
+    view::{Selector, View, ViewNotFound},
-use crate::Vec2;
+    Printer, Vec2, With,
-use crate::With;
+};
 
 // Define this type separately to appease the Clippy god
 type CallOnAny<T> = Box<dyn for<'a> FnMut(&mut T, &Selector, AnyCb<'a>)>;
@@ -51,7 +51,7 @@ pub struct Canvas<T> {
     layout: Box<dyn FnMut(&mut T, Vec2)>,
     take_focus: Box<dyn FnMut(&mut T, Direction) -> bool>,
     needs_relayout: Box<dyn Fn(&T) -> bool>,
-    focus_view: Box<dyn FnMut(&mut T, &Selector) -> Result<(), ()>>,
+    focus_view: Box<dyn FnMut(&mut T, &Selector) -> Result<(), ViewNotFound>>,
     call_on_any: CallOnAny<T>,
     important_area: Box<dyn Fn(&T, Vec2) -> Rect>,
 }
@@ -85,7 +85,7 @@ impl<T> Canvas<T> {
             layout: Box::new(|_, _| ()),
             take_focus: Box::new(|_, _| false),
             needs_relayout: Box::new(|_| true),
-            focus_view: Box::new(|_, _| Err(())),
+            focus_view: Box::new(|_, _| Err(ViewNotFound)),
             call_on_any: Box::new(|_, _, _| ()),
             important_area: Box::new(|_, size| {
                 Rect::from_corners((0, 0), size)
@@ -245,7 +245,7 @@ impl<T> Canvas<T> {
     /// Sets the closure for `focus_view()`.
     pub fn set_focus_view<F>(&mut self, f: F)
     where
-        F: 'static + FnMut(&mut T, &Selector<'_>) -> Result<(), ()>,
+        F: 'static + FnMut(&mut T, &Selector<'_>) -> Result<(), ViewNotFound>,
     {
         self.focus_view = Box::new(f);
     }
@@ -255,7 +255,7 @@ impl<T> Canvas<T> {
     /// Chainable variant.
     pub fn with_focus_view<F>(self, f: F) -> Self
     where
-        F: 'static + FnMut(&mut T, &Selector<'_>) -> Result<(), ()>,
+        F: 'static + FnMut(&mut T, &Selector<'_>) -> Result<(), ViewNotFound>,
     {
         self.with(|s| s.set_focus_view(f))
     }
@@ -286,7 +286,10 @@ impl<T: 'static> View for Canvas<T> {
         (self.needs_relayout)(&self.state)
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         (self.focus_view)(&mut self.state, selector)
     }
 

cursive-core/src/views/dialog.rs

@@ -1,14 +1,14 @@
-use crate::align::*;
+use crate::{
-use crate::direction::{Absolute, Direction, Relative};
+    align::*,
-use crate::event::{AnyCb, Event, EventResult, Key};
+    direction::{Absolute, Direction, Relative},
-use crate::rect::Rect;
+    event::{AnyCb, Event, EventResult, Key},
-use crate::theme::ColorStyle;
+    rect::Rect,
-use crate::view::{IntoBoxedView, Margins, Selector, View};
+    theme::ColorStyle,
-use crate::views::{BoxedView, Button, DummyView, LastSizeView, TextView};
+    utils::markup::StyledString,
-use crate::Cursive;
+    view::{IntoBoxedView, Margins, Selector, View, ViewNotFound},
-use crate::Printer;
+    views::{BoxedView, Button, DummyView, LastSizeView, TextView},
-use crate::Vec2;
+    Cursive, Printer, Vec2, With,
-use crate::{utils::markup::StyledString, With};
+};
 use std::cell::Cell;
 use std::cmp::max;
 use unicode_width::UnicodeWidthStr;
@@ -764,7 +764,10 @@ impl View for Dialog {
         self.content.call_on_any(selector, callback);
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         self.content.focus_view(selector)
     }
 

cursive-core/src/views/fixed_layout.rs

@@ -2,7 +2,7 @@ use crate::{
     direction::{Absolute, Direction, Relative},
     event::{AnyCb, Event, EventResult, Key},
     rect::Rect,
-    view::{IntoBoxedView, Selector},
+    view::{IntoBoxedView, Selector, ViewNotFound},
     {Printer, Vec2, View, With},
 };
 
@@ -72,7 +72,10 @@ impl FixedLayout {
     ///
     /// 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<(), ()> {
+    pub fn set_focus_index(
+        &mut self,
+        index: usize,
+    ) -> Result<(), ViewNotFound> {
         if self
             .children
             .get_mut(index)
@@ -82,7 +85,7 @@ impl FixedLayout {
             self.focus = index;
             Ok(())
         } else {
-            Err(())
+            Err(ViewNotFound)
         }
     }
 
@@ -352,7 +355,10 @@ impl View for FixedLayout {
         }
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         for (i, child) in self.children.iter_mut().enumerate() {
             if child.view.focus_view(selector).is_ok() {
                 self.focus = i;
@@ -360,6 +366,6 @@ impl View for FixedLayout {
             }
         }
 
-        Err(())
+        Err(ViewNotFound)
     }
 }

cursive-core/src/views/linear_layout.rs

@@ -1,11 +1,10 @@
-use crate::direction;
+use crate::{
-use crate::event::{AnyCb, Event, EventResult, Key};
+    direction,
-use crate::rect::Rect;
+    event::{AnyCb, Event, EventResult, Key},
-use crate::view::{IntoBoxedView, Selector, SizeCache, View};
+    rect::Rect,
-use crate::Printer;
+    view::{IntoBoxedView, Selector, SizeCache, View, ViewNotFound},
-use crate::Vec2;
+    Printer, Vec2, With, XY,
-use crate::With;
+};
-use crate::XY;
 use log::debug;
 use std::cmp::min;
 use std::ops::Deref;
@@ -228,7 +227,10 @@ impl LinearLayout {
     ///
     /// 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<(), ()> {
+    pub fn set_focus_index(
+        &mut self,
+        index: usize,
+    ) -> Result<(), ViewNotFound> {
         if self
             .children
             .get_mut(index)
@@ -238,7 +240,7 @@ impl LinearLayout {
             self.focus = index;
             Ok(())
         } else {
-            Err(())
+            Err(ViewNotFound)
         }
     }
 
@@ -713,7 +715,10 @@ impl View for LinearLayout {
         }
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         for (i, child) in self.children.iter_mut().enumerate() {
             if child.view.focus_view(selector).is_ok() {
                 self.focus = i;
@@ -721,7 +726,7 @@ impl View for LinearLayout {
             }
         }
 
-        Err(())
+        Err(ViewNotFound)
     }
 
     fn important_area(&self, _: Vec2) -> Rect {

cursive-core/src/views/list_view.rs

@@ -1,11 +1,10 @@
-use crate::direction;
+use crate::{
-use crate::event::{AnyCb, Callback, Event, EventResult, Key};
+    direction,
-use crate::rect::Rect;
+    event::{AnyCb, Callback, Event, EventResult, Key},
-use crate::view::{IntoBoxedView, Selector, View};
+    rect::Rect,
-use crate::Cursive;
+    view::{IntoBoxedView, Selector, View, ViewNotFound},
-use crate::Printer;
+    Cursive, Printer, Vec2, With,
-use crate::Vec2;
+};
-use crate::With;
 use log::debug;
 use std::rc::Rc;
 use unicode_width::UnicodeWidthStr;
@@ -435,7 +434,10 @@ impl View for ListView {
         }
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         if let Some(i) = self
             .children
             .iter_mut()
@@ -447,7 +449,7 @@ impl View for ListView {
             self.focus = i;
             Ok(())
         } else {
-            Err(())
+            Err(ViewNotFound)
         }
     }
 

cursive-core/src/views/named_view.rs

@@ -1,5 +1,7 @@
-use crate::event::AnyCb;
+use crate::{
-use crate::view::{Selector, View, ViewWrapper};
+    event::AnyCb,
+    view::{Selector, View, ViewNotFound, ViewWrapper},
+};
 use owning_ref::{OwningHandle, RcRef};
 use std::cell::{RefCell, RefMut};
 use std::ops::DerefMut;
@@ -106,7 +108,10 @@ impl<T: View + 'static> ViewWrapper for NamedView<T> {
         }
     }
 
-    fn wrap_focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn wrap_focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         match selector {
             #[allow(deprecated)]
             &Selector::Name(name) | &Selector::Id(name)
@@ -117,7 +122,7 @@ impl<T: View + 'static> ViewWrapper for NamedView<T> {
             s => self
                 .view
                 .try_borrow_mut()
-                .map_err(|_| ())
+                .map_err(|_| ViewNotFound)
                 .and_then(|mut v| v.deref_mut().focus_view(s)),
         }
     }

cursive-core/src/views/screens_view.rs

@@ -1,7 +1,8 @@
-use crate::event::AnyCb;
+use crate::{
-use crate::view::Selector;
+    event::AnyCb,
-use crate::views::BoxedView;
+    view::{Selector, View, ViewNotFound},
-use crate::View;
+    views::BoxedView,
+};
 
 /// Identifies a screen in the cursive root.
 pub type ScreenId = usize;
@@ -129,7 +130,10 @@ where
         }
     }
 
-    fn wrap_focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn wrap_focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         for (i, child) in self.screens.iter_mut().enumerate() {
             if child.focus_view(selector).is_ok() {
                 self.active_screen = i;
@@ -137,6 +141,6 @@ where
             }
         }
 
-        Err(())
+        Err(ViewNotFound)
     }
 }

cursive-core/src/views/scroll_view.rs

@@ -1,7 +1,7 @@
 use crate::{
     direction::Direction,
     event::{AnyCb, Event, EventResult},
-    view::{scroll, ScrollStrategy, Selector, View},
+    view::{scroll, ScrollStrategy, Selector, View, ViewNotFound},
     Cursive, Printer, Rect, Vec2, With,
 };
 
@@ -361,7 +361,10 @@ where
         self.inner.call_on_any(selector, cb)
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         self.inner.focus_view(selector).map(|()| {
             self.scroll_to_important_area();
         })

cursive-core/src/views/stack_view.rs

@@ -1,13 +1,14 @@
-use crate::direction::Direction;
+use crate::{
-use crate::event::{AnyCb, Event, EventResult};
+    direction::Direction,
-use crate::theme::ColorStyle;
+    event::{AnyCb, Event, EventResult},
-use crate::view::{
+    theme::ColorStyle,
-    IntoBoxedView, Offset, Position, Selector, View, ViewWrapper,
+    view::{
+        IntoBoxedView, Offset, Position, Selector, View, ViewNotFound,
+        ViewWrapper,
+    },
+    views::{BoxedView, CircularFocus, Layer, ShadowView},
+    Printer, Vec2, With,
 };
-use crate::views::{BoxedView, CircularFocus, Layer, ShadowView};
-use crate::Printer;
-use crate::Vec2;
-use crate::With;
 use std::cell;
 use std::ops::Deref;
 
@@ -189,7 +190,10 @@ impl<T: View> View for ChildWrapper<T> {
         }
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         match *self {
             ChildWrapper::Shadow(ref mut v) => v.focus_view(selector),
             ChildWrapper::Backfilled(ref mut v) => v.focus_view(selector),
@@ -680,14 +684,17 @@ impl View for StackView {
         }
     }
 
-    fn focus_view(&mut self, selector: &Selector<'_>) -> Result<(), ()> {
+    fn focus_view(
+        &mut self,
+        selector: &Selector<'_>,
+    ) -> Result<(), ViewNotFound> {
         for layer in &mut self.layers {
             if layer.view.focus_view(selector).is_ok() {
                 return Ok(());
             }
         }
 
-        Err(())
+        Err(ViewNotFound)
     }
 }
 

cursive/src/backends/curses/n.rs

@@ -203,7 +203,7 @@ impl Backend {
         }
 
         // Is it a UTF-8 starting point?
-        let event = if 32 <= ch && ch <= 255 && ch != 127 {
+        let event = if (32..=255).contains(&ch) && ch != 127 {
             utf8::read_char(ch as u8, || Some(ncurses::getch() as u8))
                 .map(Event::Char)
                 .unwrap_or_else(|e| {