duat_core/mode/cursor/

selections.rs

use std::cell::Cell;

use gapbuf::{GapBuffer, gap_buffer};

pub use self::cursor::{Selection, VPoint};
use crate::{
    add_shifts, merging_range_by_guess_and_lazy_shift,
    text::{Change, Point, TextRange},
};

/// The list of [`Selection`]s in a [`Text`]
///
/// This list can contain any number of [`Selection`]s, and they
/// should be usable in whatever order the end user may want, without
/// breaking from, for example, modifications that should move cursors
/// backwards or ahead. If that is not the case, report it as a bug.
///
/// they are primarily meant to be interacted with from the
/// [`Handle`], with its [`edit_`] methods meant to efficiently
/// handle a large number of [`Selection`]s in an efficient manner,
/// although you can interact with them separately.
///
/// A [`Text`] will keep itself in check with regards to its
/// [`Selections`], that is, it will automatically remove and add the
/// [`MainCaret`] and [`ExtraCaret`] [tags] when the [`Selections`]
/// are altered. If it fails to do that, report it as a bug.
///
/// [`Handle`]: crate::context::Handle
/// [`edit_`]: crate::context::Handle::edit_all
/// [`Text`]: crate::text::Text
/// [`MainCaret`]: crate::text::MainCaret
/// [`ExtraCaret`]: crate::text::ExtraCaret
/// [tags]: crate::text::Tag
#[derive(Clone)]
pub struct Selections {
    buf: GapBuffer<Selection>,
    main_i: usize,
    shift_state: Cell<(usize, [i32; 3])>,
}

impl Selections {
    /// A new [`Selections`] with a set main [`Selection`]
    pub(crate) fn new(main: Selection) -> Self {
        Self {
            buf: gap_buffer![main],
            main_i: 0,
            shift_state: Cell::new((0, [0; 3])),
        }
    }

    /// Returns a new empty [`Selections`]
    pub(crate) fn new_empty() -> Self {
        Self {
            buf: GapBuffer::new(),
            main_i: 0,
            shift_state: Cell::default(),
        }
    }

    ////////// Modification functions

    /// Sets the main [`Selection`]
    pub fn set_main(&mut self, new: usize) {
        self.main_i = new.min(self.buf.len().saturating_sub(1));
    }

    /// Rotates the main [`Selection`] by an amount
    pub fn rotate_main(&mut self, amount: i32) {
        self.main_i = (self.main_i as i32 + amount).rem_euclid(self.buf.len() as i32) as usize
    }

    /// Removes all [`Selection`]s
    pub fn clear(&mut self) {
        self.buf = GapBuffer::new();
        self.shift_state.take();
    }

    /// Removes all [`Selection`]s and adds a [default `Selection`] as
    /// main
    ///
    /// [default `Selection`]: Selection::default
    pub fn reset(&mut self) {
        self.remove_extras();
        self.buf[self.main_i] = Selection::default();
    }

    /// Removes all but the main [`Selection`]
    pub fn remove_extras(&mut self) {
        if !self.is_empty() {
            let cursor = self.buf.remove(self.main_i);
            let (shift_from, shift) = self.shift_state.take();
            if shift_from <= self.main_i && shift != [0; 3] {
                cursor.shift_by(shift);
            }
            self.buf = gap_buffer![cursor];
        }
        self.main_i = 0;
    }

    ////////// Querying functions

    /// Gets the main [`Selection`], if there is one
    pub fn get_main(&self) -> Option<&Selection> {
        self.get(self.main_i)
    }

    /// Gets the `n`th [`Selection`] if there is one
    pub fn get(&self, n: usize) -> Option<&Selection> {
        if n >= self.len() {
            return None;
        }
        let (shift_from, shift) = self.shift_state.get();
        if n >= shift_from && shift != [0; 3] {
            for cursor in self.buf.range(shift_from..n + 1).iter() {
                cursor.shift_by(shift);
            }
            if n + 1 < self.buf.len() {
                self.shift_state.set((n + 1, shift));
            } else {
                self.shift_state.take();
            }
        }

        self.buf.get(n)
    }

    /// Iterates over all [`Selection`]s in order
    ///
    /// Also tells you wether the [`Selection`] is the main selection
    /// or not.
    pub fn iter(&self) -> impl Iterator<Item = (&Selection, bool)> {
        let (mut shift_from, shift) = self.shift_state.get();

        self.buf.iter().enumerate().map(move |(i, selection)| {
            if i >= shift_from && shift != [0; 3] {
                selection.shift_by(shift);
                if i + 1 < self.buf.len() {
                    self.shift_state.set((i + 1, shift));
                    shift_from = i + 1;
                } else {
                    self.shift_state.set((0, [0; 3]));
                }
            }

            (selection, i == self.main_i)
        })
    }

    /// Iterates over all [`Selection`]s in a given [`TextRange`]
    ///
    /// Also tells you the index of the [`Selection`], as well as if
    /// it is the main selection or not.
    ///
    /// This [`Iterator`] *will* include [`Selection`]s that are
    /// partially contained.
    pub fn iter_within(
        &self,
        range: impl TextRange,
    ) -> impl Iterator<Item = (usize, &Selection, bool)> {
        let (shift_from, shift) = self.shift_state.get();

        let range = if let Some(last) = self.buf.len().checked_sub(1) {
            range.to_range(self.buf[last].end_excl().byte())
        } else {
            // If there are no Selections, this value doesn't really matter.
            0..0
        };

        let m_range = merging_range_by_guess_and_lazy_shift(
            (&self.buf, self.buf.len()),
            (0, [range.start, range.end]),
            (shift_from, shift[0], 0, |byte, shift| {
                (byte as i32 + shift) as usize
            }),
            (
                |sel: &Selection| sel.start().byte(),
                |sel: &Selection| sel.end_excl().byte(),
            ),
        );

        let (s0, s1) = self.buf.range(m_range.clone()).as_slices();
        let iter = [s0, s1].into_iter().flatten().enumerate();
        iter.map(move |(i, selection)| {
            let i = i + m_range.start;
            if i >= shift_from && shift != [0; 3] {
                selection.shift_by(shift);
                if i + 1 < self.buf.len() {
                    self.shift_state.set((i + 1, shift));
                } else {
                    self.shift_state.set((0, [0; 3]));
                }
            }

            (i, selection, i == self.main_i)
        })
    }

    /// The index of the main [`Selection`]
    pub fn main_index(&self) -> usize {
        self.main_i
    }

    /// How many [`Selection`]s there are in the list
    pub fn len(&self) -> usize {
        self.buf.len()
    }

    /// Returns [`true`] when there are no [`Selection`]s
    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.len() == 0
    }

    ////////// Internal modification functions

    /// Inserts a [`Selection`] back from editing
    pub(crate) fn insert(
        &mut self,
        guess_i: usize,
        sel: Selection,
        main: bool,
    ) -> ([usize; 2], bool) {
        let (shift_from, shift) = self.shift_state.take();
        let shift_from = shift_from.min(self.len());

        // The range of cursors that will be drained
        let m_range = merging_range_by_guess_and_lazy_shift(
            (&self.buf, self.buf.len()),
            (guess_i, [sel.start(), sel.end_excl()]),
            (shift_from, shift, [0; 3], Point::shift_by),
            (Selection::start, Selection::end_excl),
        );

        // Shift all ranges that preceed the end of the cursor's range.
        if shift_from < m_range.end && shift != [0; 3] {
            for cursor in self.buf.range(shift_from..m_range.end).into_iter() {
                cursor.shift_by(shift);
            }
        }

        // Get the minimum and maximum Points in the taken range, designate
        // those as the new Selection's bounds.
        let (caret, anchor, last_cursor_overhangs) = {
            let mut c_range = m_range.clone();
            let first = c_range.next().and_then(|i| self.get(i));
            let last = c_range.last().and_then(|i| self.get(i)).or(first);
            let start = first
                .map(|first| first.lazy_v_start().min(sel.lazy_v_start()))
                .unwrap_or(sel.lazy_v_start());
            let (end, last_sel_overhangs) = if let Some(last) = last
                && last.lazy_v_end() >= sel.lazy_v_end()
            {
                (last.lazy_v_end(), true)
            } else {
                (sel.lazy_v_end(), false)
            };

            if let Some(anchor) = sel.anchor() {
                match sel.caret() < anchor {
                    true => (start, Some(end), last_sel_overhangs),
                    false => (end, Some(start), last_sel_overhangs),
                }
            } else {
                (end, (start != end).then_some(start), last_sel_overhangs)
            }
        };

        let selection = Selection::from_v(caret, anchor, sel.change_i);
        self.buf.splice(m_range.clone(), [selection]);

        if main {
            self.main_i = m_range.start;
        } else if self.main_i >= m_range.start {
            self.main_i = (self.main_i + 1 - m_range.clone().count()).max(m_range.start)
        }

        // If there are no more Selections after this, don't set the
        // shift_state.
        let cursors_taken = m_range.clone().count();
        let new_shift_from = shift_from.saturating_sub(cursors_taken).max(m_range.start) + 1;
        if new_shift_from < self.buf.len() {
            self.shift_state.set((new_shift_from, shift));
        }

        ([m_range.start, cursors_taken], last_cursor_overhangs)
    }

    /// Applies a [`Change`] to the [`Selection`]s list
    ///
    /// Returns the number of [`Selection`]s that were removed
    pub(crate) fn apply_change(&mut self, guess_i: usize, change: Change<&str>) -> usize {
        let (shift_from, shift) = self.shift_state.take();
        let shift_from = shift_from.min(self.len());

        // The range of cursors that will be drained
        let c_range = merging_range_by_guess_and_lazy_shift(
            (&self.buf, self.buf.len()),
            (guess_i, [change.start(), change.taken_end()]),
            (shift_from, shift, [0; 3], Point::shift_by),
            (Selection::start, Selection::end_excl),
        );

        // Since applied changes don't remove Selections, we need to shift all
        // Selections in the whole range. First by the original shift, in
        // order to update them to the latest shift leve, then by the
        // change.
        if c_range.end > shift_from && shift != [0; 3] {
            for cursor in self.buf.range(shift_from..c_range.end).into_iter() {
                cursor.shift_by(shift);
            }
        }
        let range = c_range.start..c_range.end.max(shift_from);
        for cursor in self.buf.range(range).into_iter() {
            cursor.shift_by_change(change);
        }

        let (cursors_taken, cursors_added) = {
            let mut cursors_taken = self.buf.splice(c_range.clone(), []);
            if let Some(first) = cursors_taken.next() {
                let last = cursors_taken.next_back().unwrap_or(first.clone());
                let (start, end) = (first.start(), last.end_excl());
                let merged = Selection::new(start, (start < end).then_some(end));
                drop(cursors_taken);
                self.buf.insert(c_range.start, merged);

                (c_range.len(), 1)
            } else {
                (0, 0)
            }
        };

        let new_shift_from =
            shift_from.saturating_sub(cursors_taken).max(c_range.start) + cursors_added;
        if new_shift_from < self.buf.len() {
            self.shift_state
                .set((new_shift_from, add_shifts(shift, change.shift())));
        }

        cursors_taken - cursors_added
    }

    /// Removes a [`Selection`], which might be brought back
    pub(crate) fn remove(&mut self, i: usize) -> Option<(Selection, bool)> {
        if i >= self.buf.len() {
            return None;
        }
        let (shift_from, shift) = self.shift_state.get();

        if i >= shift_from && shift != [0; 3] {
            for cursor in self.buf.range(shift_from..i + 1).iter() {
                cursor.shift_by(shift);
            }
            if i + 1 < self.buf.len() {
                // i here, instead of i + 1, since this Selection is about to be
                // removed.
                self.shift_state.set((i, shift));
            } else {
                self.shift_state.take();
            }
        } else if i < shift_from {
            // If I am removing before shift_from, obviously the index of the
            // first unshifted Selection is moved back.
            self.shift_state.set((shift_from - 1, shift));
        }

        let was_main = self.main_i == i;
        if self.main_i >= i {
            self.main_i = self.main_i.saturating_sub(1);
        }
        Some((self.buf.remove(i), was_main))
    }

    /// Ensures that there is at least one [`Selection`] on the list
    pub(crate) fn populate(&mut self) {
        if self.buf.is_empty() {
            self.main_i = 0;
            self.buf = gap_buffer![Selection::default()];
        }
    }
}

mod cursor {
    use std::{cell::Cell, cmp::Ordering, ops::Range};

    use bincode::{Decode, Encode};

    use crate::{
        cfg::PrintCfg,
        text::{Bytes, Change, Point, Text},
        ui::{Caret, Area},
    };

    /// A cursor in the text file. This is an editing cursor, -(not
    /// a printing cursor.
    #[derive(Default, Clone, Encode, Decode)]
    pub struct Selection {
        caret: Cell<LazyVPoint>,
        anchor: Cell<Option<LazyVPoint>>,
        pub(in crate::mode::cursor) change_i: Option<u32>,
    }

    impl Selection {
        /// Returns a new instance of [`Selection`].
        pub(crate) fn new(caret: Point, anchor: Option<Point>) -> Self {
            Self {
                caret: Cell::new(LazyVPoint::Unknown(caret)),
                anchor: Cell::new(anchor.map(LazyVPoint::Unknown)),
                change_i: None,
            }
        }

        pub(super) fn from_v(
            caret: LazyVPoint,
            anchor: Option<LazyVPoint>,
            change_i: Option<u32>,
        ) -> Self {
            Self {
                caret: Cell::new(caret),
                anchor: Cell::new(anchor),
                change_i,
            }
        }

        /// Moves to specific, pre calculated [`Point`].
        pub fn move_to(&mut self, p: Point, text: &Text) {
            if p == self.caret() {
                return;
            }
            let p = text.point_at_byte(p.byte().min(text.last_point().byte()));
            *self.caret.get_mut() = LazyVPoint::Unknown(p);
        }

        /// Internal horizontal movement function.
        ///
        /// Returns the number of distance moved through.
        pub fn move_hor(&mut self, by: i32, text: &Text) -> i32 {
            let by = by as isize;
            if by == 0 {
                return 0;
            };
            let target = self.caret.get().point().char().saturating_add_signed(by);

            let p = if target == 0 {
                Point::default()
            } else if target >= text.last_point().char() {
                text.last_point()
            } else if by.abs() < 500 {
                if by > 0 {
                    let (point, _) = text
                        .chars_fwd(self.caret()..)
                        .unwrap()
                        .take(by as usize + 1)
                        .last()
                        .unwrap();
                    point
                } else {
                    let (point, _) = text
                        .chars_rev(..self.caret())
                        .unwrap()
                        .take(by.unsigned_abs())
                        .last()
                        .unwrap();
                    point
                }
            } else {
                text.point_at_char(target)
            };

            let moved = p.char() as i32 - self.caret.get().point().char() as i32;
            *self.caret.get_mut() = LazyVPoint::Unknown(p);
            moved
        }

        /// Internal vertical movement function.
        ///
        /// Returns the distance moved in lines.
        pub fn move_ver(
            &mut self,
            by: i32,
            text: &Text,
            area: &impl Area,
            mut cfg: PrintCfg,
        ) -> i32 {
            let by = by as isize;
            if by == 0 {
                return 0;
            };

            let (vp, moved) = {
                let vp = self.caret.get().calculate(text, area, cfg);
                let line_start = {
                    let target = self.caret.get().point().line().saturating_add_signed(by);
                    text.point_at_line(target.min(text.last_point().line()))
                };

                let mut wraps = 0;
                let mut vcol = 0;

                let (wcol, p) = area
                    .print_iter(text.iter_fwd(line_start), *cfg.new_line_as('\n'))
                    .find_map(|(Caret { len, x, wrap }, item)| {
                        wraps += wrap as usize;
                        if let Some((p, char)) = item.as_real_char()
                            && (vcol + len as u16 > vp.dvcol || char == '\n')
                        {
                            return Some((x as u16, p));
                        }

                        vcol += len as u16;
                        None
                    })
                    .unwrap_or((0, text.last_point()));

                let moved = p.line() as i32 - vp.p.line() as i32;
                let vp = vp.known(p, (p.char() - line_start.char()) as u16, vcol, wcol);
                (vp, moved)
            };

            *self.caret.get_mut() = LazyVPoint::Known(vp);
            moved
        }

        /// Internal vertical movement function.
        ///
        /// Returns the distance moved in wrapped lines.
        pub fn move_ver_wrapped(
            &mut self,
            by: i32,
            text: &Text,
            area: &impl Area,
            mut cfg: PrintCfg,
        ) -> i32 {
            if by == 0 {
                return 0;
            };
            let vp = self.caret.get().calculate(text, area, cfg);

            let mut wraps = 0;

            *self.caret.get_mut() = LazyVPoint::Known(if by > 0 {
                let line_start = text.point_at_line(vp.p.line());
                let mut vcol = vp.vcol;
                let mut last = (vp.vcol, vp.wcol, vp.p);
                let mut last_valid = (vp.vcol, vp.wcol, vp.p);

                let (vcol, wcol, p) = area
                    .print_iter(text.iter_fwd(line_start), *cfg.new_line_as('\n'))
                    .skip_while(|(_, item)| item.char() <= self.char())
                    .find_map(|(Caret { x, len, wrap }, item)| {
                        wraps += wrap as i32;
                        if let Some((p, char)) = item.as_real_char() {
                            if (x..x + len).contains(&(vp.dwcol as u32))
                                || (char == '\n' && x <= vp.dwcol as u32)
                            {
                                last_valid = (vcol, x as u16, p);
                                if wraps == by {
                                    return Some((vcol, x as u16, p));
                                }
                            } else if wraps > by {
                                return Some(last);
                            }
                            last = (vcol, x as u16, p);
                        }
                        vcol += len as u16;
                        None
                    })
                    .unwrap_or(last_valid);
                vp.known(p, (p.char() - line_start.char()) as u16, vcol, wcol)
            } else {
                let end_points = text.points_after(vp.p).unwrap();
                let mut just_wrapped = false;
                let mut last_valid = (vp.wcol, vp.p);

                let mut iter = area.rev_print_iter(text.iter_rev(end_points), cfg);
                let wcol_and_p = iter.find_map(|(Caret { x, len, wrap }, item)| {
                    if let Some((p, _)) = item.as_real_char() {
                        // max(1) because it could be a '\n'
                        if (x..x + len.max(1)).contains(&(vp.dwcol as u32))
                            || (just_wrapped && x + len < vp.dwcol as u32)
                        {
                            last_valid = (x as u16, p);
                            if wraps == by {
                                return Some((x as u16, p));
                            }
                        }
                        just_wrapped = false;
                    }
                    wraps -= wrap as i32;
                    just_wrapped |= wrap;
                    None
                });

                if let Some((wcol, p)) = wcol_and_p {
                    let (ccol, vcol) = iter
                        .take_while(|(_, item)| item.as_real_char().is_none_or(|(_, c)| c != '\n'))
                        .fold((0, 0), |(ccol, vcol), (caret, item)| {
                            (ccol + item.is_real() as u16, vcol + caret.len as u16)
                        });

                    vp.known(p, ccol, vcol, wcol)
                } else {
                    let (wcol, p) = last_valid;
                    let (ccol, vcol) = area
                        .rev_print_iter(text.iter_rev(p), *cfg.new_line_as('\n'))
                        .take_while(|(_, item)| item.as_real_char().is_none_or(|(_, c)| c != '\n'))
                        .fold((0, 0), |(ccol, vcol), (caret, item)| {
                            (ccol + item.is_real() as u16, vcol + caret.len as u16)
                        });

                    vp.known(p, ccol, vcol, wcol)
                }
            });

            wraps
        }

        pub(crate) fn shift_by_change(&self, change: Change<&str>) {
            let (shift, taken) = (change.shift(), change.taken_end());
            if self.caret() >= change.start() {
                let shifted_caret = self.caret().max(taken).shift_by(shift);
                self.caret.set(LazyVPoint::Unknown(shifted_caret));
            }
            if let Some(anchor) = self.anchor.get()
                && anchor.point() >= change.start()
            {
                let shifted_anchor = anchor.point().max(taken).shift_by(shift);
                self.anchor.set(Some(LazyVPoint::Unknown(shifted_anchor)));
            }
        }

        /// Assumes tha both parts of the cursor are ahead of the
        /// shift
        pub(crate) fn shift_by(&self, shift: [i32; 3]) {
            let shifted_caret = self.caret().shift_by(shift);
            self.caret.set(LazyVPoint::Unknown(shifted_caret));
            if let Some(anchor) = self.anchor.get() {
                let shifted_anchor = anchor.point().shift_by(shift);
                self.anchor.set(Some(LazyVPoint::Unknown(shifted_anchor)));
            }
        }

        /// Sets the position of the anchor to be the same as the
        /// current cursor position in the file
        ///
        /// The `anchor` and `current` act as a range of text on the
        /// file.
        pub fn set_anchor(&mut self) {
            *self.anchor.get_mut() = Some(self.caret.get())
        }

        /// Unsets the anchor
        ///
        /// This is done so the cursor no longer has a valid
        /// selection.
        pub fn unset_anchor(&mut self) -> Option<Point> {
            self.anchor.take().map(|a| a.point())
        }

        /// Switches the position of the anchor and caret
        pub fn swap_ends(&mut self) {
            if let Some(anchor) = self.anchor.get_mut() {
                std::mem::swap(self.caret.get_mut(), anchor);
            }
        }

        /// Returns the cursor's position on the screen
        pub fn caret(&self) -> Point {
            self.caret.get().point()
        }

        /// The anchor of this [`Selection`], if it exists
        pub fn anchor(&self) -> Option<Point> {
            self.anchor.get().map(|a| a.point())
        }

        /// The byte (relative to the beginning of the file) of the
        /// caret. Indexed at 0
        pub fn byte(&self) -> usize {
            self.caret.get().point().byte()
        }

        /// The char (relative to the beginning of the file) of the
        /// caret. Indexed at 0
        pub fn char(&self) -> usize {
            self.caret.get().point().char()
        }

        /// The line of the caret. Indexed at 0.
        pub fn line(&self) -> usize {
            self.caret.get().point().line()
        }

        /// Returns the range between `caret` and `anchor`.
        ///
        /// If `anchor` isn't set, returns an empty range on `caret`.
        ///
        /// A [`Selection`]'s range will also never include the last
        /// character in a [`Text`], which must be a newline.
        ///
        /// # Warning
        ///
        /// This function will return the range that is supposed
        /// to be replaced, if `self.is_inclusive()`, this means that
        /// it will return one more byte at the end, i.e. start..=end.
        pub fn range(&self, bytes: &Bytes) -> Range<usize> {
            let [start, end] = self.point_range(bytes);
            start.byte()..end.byte()
        }

        /// The starting [`Point`] of this [`Selection`]
        pub fn start(&self) -> Point {
            if let Some(anchor) = self.anchor.get() {
                anchor.point().min(self.caret.get().point())
            } else {
                self.caret.get().point()
            }
        }

        /// The ending [`Point`] of this [`Selection`]
        pub fn end(&self, bytes: &Bytes) -> Point {
            let raw = self.end_excl();
            if raw == bytes.len() {
                panic!("equals len: {raw:?}, {bytes:#?}");
            }
            raw.fwd(bytes.char_at(raw).unwrap())
        }

        pub(super) fn end_excl(&self) -> Point {
            if let Some(anchor) = self.anchor.get() {
                anchor.point().max(self.caret.get().point())
            } else {
                self.caret.get().point()
            }
        }

        pub(crate) fn tag_points(&self, bytes: &Bytes) -> (Point, Option<[Point; 2]>) {
            let caret = self.caret();
            if let Some(anchor) = self.anchor() {
                match anchor.cmp(&caret) {
                    Ordering::Less => (caret, Some([anchor, caret])),
                    Ordering::Equal => (caret, None),
                    Ordering::Greater => {
                        let end = anchor.fwd(bytes.char_at(anchor).unwrap());
                        (caret, Some([caret, end]))
                    }
                }
            } else {
                (caret, None)
            }
        }

        /// Returns the range between `caret` and `anchor`.
        ///
        /// If `anchor` isn't set, returns a range that contains only
        /// the `caret`'s current `char`.
        pub fn point_range(&self, bytes: &Bytes) -> [Point; 2] {
            [self.start(), self.end(bytes)]
        }

        /// Returns an exclusive range between `caret` and `anchor`
        ///
        /// If `anchor` isn't set, both [`Point`]s will be the same.
        pub fn point_range_excl(&self) -> [Point; 2] {
            [self.start(), self.end_excl()]
        }

        /// Sets both the desired visual column, as well as the
        /// desired wrapped column
        pub fn set_desired_cols(&mut self, v: usize, w: usize) {
            let (v, w) = (v as u16, w as u16);
            match self.caret.get_mut() {
                LazyVPoint::Known(vp) => {
                    vp.dvcol = v;
                    vp.dwcol = w;
                }
                LazyVPoint::Unknown(p) => {
                    *self.caret.get_mut() = LazyVPoint::Desired { p: *p, dvcol: v, dwcol: w }
                }
                LazyVPoint::Desired { dvcol, dwcol, .. } => (*dvcol, *dwcol) = (v, w),
            }
        }

        /// The visual caret of this [`Selection`]
        ///
        /// [`VPoint`]s include a lot more information than regular
        /// [`Point`]s, like visual distance form the left edge, what
        /// the desired distance is, etc.
        pub fn v_caret(&self, text: &Text, area: &impl Area, cfg: PrintCfg) -> VPoint {
            let vp = self.caret.get().calculate(text, area, cfg);
            self.caret.set(LazyVPoint::Known(vp));
            vp
        }

        /// The visual anchor of this [`Selection`], if it exists
        ///
        /// [`VPoint`]s include a lot more information than regular
        /// [`Point`]s, like visual distance form the left edge, what
        /// the desired distance is, etc.
        pub fn v_anchor(&self, text: &Text, area: &impl Area, cfg: PrintCfg) -> Option<VPoint> {
            self.anchor.get().map(|anchor| {
                let vp = anchor.calculate(text, area, cfg);
                self.anchor.set(Some(LazyVPoint::Known(vp)));
                vp
            })
        }

        /// The visual range between the caret and anchor of this
        /// [`Selection`]
        ///
        /// [`VPoint`]s include a lot more information than regular
        /// [`Point`]s, like visual distance form the left edge, what
        /// the desired distance is, etc.
        pub fn v_range(&self, text: &Text, area: &impl Area, cfg: PrintCfg) -> [VPoint; 2] {
            let v_caret = self.v_caret(text, area, cfg);
            let v_anchor = self.v_anchor(text, area, cfg).unwrap_or(v_caret);
            [v_caret.min(v_anchor), v_caret.max(v_anchor)]
        }

        /// The starting [`LazyVPoint`]
        pub(super) fn lazy_v_start(&self) -> LazyVPoint {
            match self.anchor.get() {
                Some(anchor) => self.caret.get().min(anchor),
                None => self.caret.get(),
            }
        }

        /// The ending [`LazyVPoint`]
        pub(super) fn lazy_v_end(&self) -> LazyVPoint {
            match self.anchor.get() {
                Some(anchor) => self.caret.get().max(anchor),
                None => self.caret.get(),
            }
        }
    }

    /// A struct meant to minimize calculations on very large numbers
    /// of [`Selection`]s
    #[derive(Clone, Copy, Eq, Encode, Decode)]
    pub(super) enum LazyVPoint {
        Known(VPoint),
        Unknown(Point),
        Desired { p: Point, dvcol: u16, dwcol: u16 },
    }

    impl LazyVPoint {
        /// The actual [`Point`]
        fn point(self) -> Point {
            match self {
                LazyVPoint::Known(vp) => vp.p,
                LazyVPoint::Unknown(p) => p,
                LazyVPoint::Desired { p, .. } => p,
            }
        }

        /// Calculates the [`VPoint`], to be used sparingly
        fn calculate(self, text: &Text, area: &impl Area, cfg: PrintCfg) -> VPoint {
            match self {
                Self::Known(vp) => vp,
                Self::Unknown(p) => VPoint::new(p, text, area, cfg),
                Self::Desired { p, dvcol, dwcol } => {
                    let mut vp = VPoint::new(p, text, area, cfg);
                    vp.dvcol = dvcol;
                    vp.dwcol = dwcol;
                    vp
                }
            }
        }
    }

    impl Default for LazyVPoint {
        fn default() -> Self {
            Self::Desired { p: Point::default(), dvcol: 0, dwcol: 0 }
        }
    }

    #[allow(clippy::non_canonical_partial_ord_impl)]
    impl PartialOrd for LazyVPoint {
        fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
            Some(self.point().cmp(&other.point()))
        }
    }

    impl Ord for LazyVPoint {
        fn cmp(&self, other: &Self) -> Ordering {
            self.partial_cmp(other).unwrap()
        }
    }

    impl PartialEq for LazyVPoint {
        fn eq(&self, other: &Self) -> bool {
            self.point() == other.point()
        }
    }

    /// A visual [`Point`], which includes more information
    ///
    /// Alongside the byte, char, and line of the [`Point`], this
    /// struct has:
    ///
    /// - Number of [`char`]s from the left edge
    /// - Number of visual cells from the left edge
    /// - Desired number of visual cells from the left edge
    /// - Number of wrapped cells from the left edge
    /// - Desired number of wrapped cells from the left edge
    ///
    /// The difference between visual cells and wrapped cells is that
    /// visual cells are essentially "The distance a [`Point`] would
    /// be if this line were not wrapped"
    ///
    /// Desired cells are used when moving vertically, since when you
    /// move a [`Selection`] up or down to a shorter line, then to a
    /// longer one, you expect the horizontal position to hold. This
    /// is applied both in [full line] and [wrapped line] vertical
    /// movement.
    ///
    /// [full line]: crate::mode::Cursor::move_ver
    /// [wrapped line]: crate::mode::Cursor::move_ver_wrapped
    #[derive(Clone, Copy, Debug, Eq, Encode, Decode)]
    pub struct VPoint {
        p: Point,
        // No plan to support lines that are far too long
        ccol: u16,
        vcol: u16,
        dvcol: u16,
        wcol: u16,
        dwcol: u16,
    }

    impl VPoint {
        /// Returns a new [`VPoint`]
        fn new(p: Point, text: &Text, area: &impl Area, cfg: PrintCfg) -> Self {
            let [start, _] = text.points_of_line(p.line());

            let mut vcol = 0;

            let wcol = area
                .print_iter(text.iter_fwd(text.visual_line_start(start)), cfg)
                .find_map(|(caret, item)| {
                    if let Some((lhs, _)) = item.as_real_char()
                        && lhs == p
                    {
                        return Some(caret.x as u16);
                    }
                    vcol += caret.len as u16;
                    None
                })
                .unwrap_or(0);

            Self {
                p,
                ccol: (p.char() - start.char()) as u16,
                vcol,
                dvcol: vcol,
                wcol,
                dwcol: wcol,
            }
        }

        /// Returns a new [`VPoint`] from raw data
        fn known(self, p: Point, ccol: u16, vcol: u16, wcol: u16) -> Self {
            Self { p, ccol, vcol, wcol, ..self }
        }

        /// The byte index of this [`VPoint`]
        pub fn byte(&self) -> usize {
            self.p.byte()
        }

        /// The char index of this [`VPoint`]
        pub fn char(&self) -> usize {
            self.p.char()
        }

        /// The line index of this [`VPoint`]
        pub fn line(&self) -> usize {
            self.p.line()
        }

        /// Number of characters from the start of the line
        pub fn char_col(&self) -> usize {
            self.ccol as usize
        }

        /// Total space from the start of the line
        pub fn visual_col(&self) -> usize {
            self.vcol as usize
        }

        /// How much space there should be from the start of the line
        pub fn desired_visual_col(&self) -> usize {
            self.dvcol as usize
        }

        /// Total space from the left edge
        pub fn wrapped_col(&self) -> usize {
            self.wcol as usize
        }

        /// How much space there should be from the left edge
        pub fn desired_wrapped_col(&self) -> usize {
            self.dwcol as usize
        }
    }

    #[allow(clippy::non_canonical_partial_ord_impl)]
    impl PartialOrd for VPoint {
        fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
            Some(self.p.cmp(&other.p))
        }
    }

    impl Ord for VPoint {
        fn cmp(&self, other: &Self) -> Ordering {
            self.partial_cmp(other).unwrap()
        }
    }

    impl PartialEq for VPoint {
        fn eq(&self, other: &Self) -> bool {
            self.p == other.p
        }
    }

    impl std::fmt::Debug for Selection {
        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
            f.debug_struct("Selection")
                .field("caret", &self.caret.get())
                .field("anchor", &self.anchor.get())
                .field("change_i", &self.change_i)
                .finish()
        }
    }

    impl std::fmt::Debug for LazyVPoint {
        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
            match self {
                Self::Known(vp) => write!(f, "Known({:?})", vp.p),
                Self::Unknown(p) => write!(f, "Unknown({p:?}"),
                Self::Desired { p, dvcol, dwcol } => write!(f, "Desired({p:?}, {dvcol}, {dwcol})"),
            }
        }
    }
}

impl std::fmt::Debug for Selections {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        struct DebugShiftState((usize, [i32; 3]));
        impl std::fmt::Debug for DebugShiftState {
            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                write!(f, "{:?}", self.0)
            }
        }

        f.debug_struct("Selections")
            .field("buf", &self.buf)
            .field("main_i", &self.main_i)
            .field("shift_sate", &DebugShiftState(self.shift_state.get()))
            .finish()
    }
}