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//! Logic related to the positioning of the cursor within text.
use crate::geom::{Range, Rect};
use crate::text::{self, FontSize, Point, Scalar};
/// An index representing the position of a cursor within some text.
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Index {
/// The byte index of the line upon which the cursor is situated.
pub line: usize,
/// The index within all possible cursor positions for the line.
///
/// For example, for the line `foo`, a `char` of `1` would indicate the cursor's position
/// as `f|oo` where `|` is the cursor.
pub char: usize,
}
/// Every possible cursor position within each line of text yielded by the given iterator.
///
/// Yields `(xs, y_range)`, where `y_range` is the `Range` occupied by the line across the *y*
/// axis and `xs` is every possible cursor position along the *x* axis
#[derive(Clone)]
pub struct XysPerLine<'a, I> {
lines_with_rects: I,
font: &'a text::Font,
text: &'a str,
font_size: FontSize,
}
/// Similarly to `XysPerLine`, yields every possible cursor position within each line of text
/// yielded by the given iterator.
///
/// Rather than taking an iterator type yielding lines and positioning data, this method
/// constructs its own iterator to do so internally, saving some boilerplate involved in common
/// `XysPerLine` use cases.
///
/// Yields `(xs, y_range)`, where `y_range` is the `Range` occupied by the line across the *y*
/// axis and `xs` is every possible cursor position along the *x* axis.
#[derive(Clone)]
pub struct XysPerLineFromText<'a> {
xys_per_line: XysPerLine<
'a,
std::iter::Zip<
std::iter::Cloned<std::slice::Iter<'a, text::line::Info>>,
text::line::Rects<std::iter::Cloned<std::slice::Iter<'a, text::line::Info>>>,
>,
>,
}
/// Each possible cursor position along the *x* axis within a line of text.
///
/// `Xs` iterators are produced by the `XysPerLine` iterator.
pub struct Xs<'a, 'b> {
next_x: Option<Scalar>,
layout: text::LayoutIter<'a, 'b>,
}
impl Index {
/// The cursor index of the beginning of the word (block of non-whitespace) before `self`.
///
/// If `self` is at the beginning of the line, call previous, which returns the last
/// index position of the previous line, or None if it's the first line
///
/// If `self` points to whitespace, skip past that whitespace, then return the index of
/// the start of the word that precedes the whitespace
///
/// If `self` is in the middle or end of a word, return the index of the start of that word
pub fn previous_word_start<I>(self, text: &str, mut line_infos: I) -> Option<Self>
where
I: Iterator<Item = text::line::Info>,
{
let Index { line, char } = self;
if char > 0 {
line_infos.nth(line).and_then(|line_info| {
let line_count = line_info.char_range().count();
let mut chars_rev = (&text[line_info.byte_range()]).chars().rev();
if char != line_count {
chars_rev.nth(line_count - char - 1);
}
let mut new_char = 0;
let mut hit_non_whitespace = false;
for (i, char_) in chars_rev.enumerate() {
// loop until word starts, then continue until the word ends
if !char_.is_whitespace() {
hit_non_whitespace = true;
}
if char_.is_whitespace() && hit_non_whitespace {
new_char = char - i;
break;
}
}
Some(Index {
line: line,
char: new_char,
})
})
} else {
self.previous(line_infos)
}
}
/// The cursor index of the end of the first word (block of non-whitespace) after `self`.
///
/// If `self` is at the end of the text, this returns `None`.
///
/// If `self` is at the end of a line other than the last, this returns the first index of
/// the next line.
///
/// If `self` points to whitespace, skip past that whitespace, then return the index of
/// the end of the word after the whitespace
///
/// If `self` is in the middle or start of a word, return the index of the end of that word
pub fn next_word_end<I>(self, text: &str, mut line_infos: I) -> Option<Self>
where
I: Iterator<Item = text::line::Info>,
{
let Index { line, char } = self;
line_infos.nth(line).and_then(|line_info| {
let line_count = line_info.char_range().count();
if char < line_count {
let mut chars = (&text[line_info.byte_range()]).chars();
let mut new_char = line_count;
let mut hit_non_whitespace = false;
if char != 0 {
chars.nth(char - 1);
}
for (i, char_) in chars.enumerate() {
// loop until word starts, then continue until the word ends
if !char_.is_whitespace() {
hit_non_whitespace = true;
}
if char_.is_whitespace() && hit_non_whitespace {
new_char = char + i;
break;
}
}
Some(Index {
line: line,
char: new_char,
})
} else {
line_infos.next().map(|_| Index {
line: line + 1,
char: 0,
})
}
})
}
/// The cursor index that comes before `self`.
///
/// If `self` is at the beginning of the text, this returns `None`.
///
/// If `self` is at the beginning of a line other than the first, this returns the last
/// index position of the previous line.
///
/// If `self` is a position other than the start of a line, it will return the position
/// that is immediately to the left.
pub fn previous<I>(self, mut line_infos: I) -> Option<Self>
where
I: Iterator<Item = text::line::Info>,
{
let Index { line, char } = self;
if char > 0 {
let new_char = char - 1;
line_infos.nth(line).and_then(|info| {
if new_char <= info.char_range().count() {
Some(Index {
line: line,
char: new_char,
})
} else {
None
}
})
} else if line > 0 {
let new_line = line - 1;
line_infos.nth(new_line).map(|info| {
let new_char = info.end_char() - info.start_char;
Index {
line: new_line,
char: new_char,
}
})
} else {
None
}
}
/// The cursor index that follows `self`.
///
/// If `self` is at the end of the text, this returns `None`.
///
/// If `self` is at the end of a line other than the last, this returns the first index of
/// the next line.
///
/// If `self` is a position other than the end of a line, it will return the position that
/// is immediately to the right.
pub fn next<I>(self, mut line_infos: I) -> Option<Self>
where
I: Iterator<Item = text::line::Info>,
{
let Index { line, char } = self;
line_infos.nth(line).and_then(|info| {
if char >= info.char_range().count() {
line_infos.next().map(|_| Index {
line: line + 1,
char: 0,
})
} else {
Some(Index {
line: line,
char: char + 1,
})
}
})
}
/// Clamps `self` to the given lines.
///
/// If `self` would lie after the end of the last line, return the index at the end of the
/// last line.
///
/// If `line_infos` is empty, returns cursor at line=0 char=0.
pub fn clamp_to_lines<I>(self, line_infos: I) -> Self
where
I: Iterator<Item = text::line::Info>,
{
let mut last = None;
for (i, info) in line_infos.enumerate() {
if i == self.line {
let num_chars = info.char_range().len();
let char = std::cmp::min(self.char, num_chars);
return Index {
line: i,
char: char,
};
}
last = Some((i, info));
}
match last {
Some((i, info)) => Index {
line: i,
char: info.char_range().len(),
},
None => Index { line: 0, char: 0 },
}
}
}
/// Every possible cursor position within each line of text yielded by the given iterator.
///
/// Yields `(xs, y_range)`, where `y_range` is the `Range` occupied by the line across the *y*
/// axis and `xs` is every possible cursor position along the *x* axis
pub fn xys_per_line<'a, I>(
lines_with_rects: I,
font: &'a text::Font,
text: &'a str,
font_size: FontSize,
) -> XysPerLine<'a, I> {
XysPerLine {
lines_with_rects: lines_with_rects,
font: font,
text: text,
font_size: font_size,
}
}
/// Similarly to `xys_per_line`, this produces an iterator yielding every possible cursor
/// position within each line of text yielded by the given iterator.
///
/// Rather than taking an iterator yielding lines and their positioning data, this method
/// constructs its own iterator to do so internally, saving some boilerplate involved in common
/// `xys_per_line` use cases.
///
/// Yields `(xs, y_range)`, where `y_range` is the `Range` occupied by the line across the *y*
/// axis and `xs` is every possible cursor position along the *x* axis.
pub fn xys_per_line_from_text<'a>(
text: &'a str,
line_infos: &'a [text::line::Info],
font: &'a text::Font,
font_size: FontSize,
max_width: Scalar,
x_align: text::Justify,
line_spacing: Scalar,
) -> XysPerLineFromText<'a> {
let line_infos = line_infos.iter().cloned();
let line_rects = text::line::rects(
line_infos.clone(),
font_size,
max_width,
x_align,
line_spacing,
);
let lines = line_infos.clone();
let lines_with_rects = lines.zip(line_rects.clone());
XysPerLineFromText {
xys_per_line: text::cursor::xys_per_line(lines_with_rects, font, text, font_size),
}
}
/// Convert the given character index into a cursor `Index`.
pub fn index_before_char<I>(line_infos: I, char_index: usize) -> Option<Index>
where
I: Iterator<Item = text::line::Info>,
{
for (i, line_info) in line_infos.enumerate() {
let start_char = line_info.start_char;
let end_char = line_info.end_char();
if start_char <= char_index && char_index <= end_char {
return Some(Index {
line: i,
char: char_index - start_char,
});
}
}
None
}
/// Determine the *xy* location of the cursor at the given cursor `Index`.
pub fn xy_at<'a, I>(xys_per_line: I, idx: Index) -> Option<(Scalar, Range)>
where
I: Iterator<Item = (Xs<'a, 'a>, Range)>,
{
for (i, (xs, y)) in xys_per_line.enumerate() {
if i == idx.line {
for (j, x) in xs.enumerate() {
if j == idx.char {
return Some((x, y));
}
}
}
}
None
}
/// Find the closest line for the given `y` position, and return the line index, Xs iterator, and y-range of that line
///
/// Returns `None` if there are no lines
pub fn closest_line<'a, I>(y_pos: Scalar, xys_per_line: I) -> Option<(usize, Xs<'a, 'a>, Range)>
where
I: Iterator<Item = (Xs<'a, 'a>, Range)>,
{
let mut xys_per_line_enumerated = xys_per_line.enumerate();
xys_per_line_enumerated
.next()
.and_then(|(first_line_idx, (first_line_xs, first_line_y))| {
let mut closest_line = (first_line_idx, first_line_xs, first_line_y);
let mut closest_diff = (y_pos - first_line_y.middle()).abs();
for (line_idx, (line_xs, line_y)) in xys_per_line_enumerated {
if line_y.contains(y_pos) {
closest_line = (line_idx, line_xs, line_y);
break;
} else {
let diff = (y_pos - line_y.middle()).abs();
if diff < closest_diff {
closest_line = (line_idx, line_xs, line_y);
closest_diff = diff;
} else {
break;
}
}
}
Some(closest_line)
})
}
/// Find the closest cursor index to the given `xy` position, and the center `Point` of that
/// cursor.
///
/// Returns `None` if the given `text` is empty.
pub fn closest_cursor_index_and_xy<'a, I>(xy: Point, xys_per_line: I) -> Option<(Index, Point)>
where
I: Iterator<Item = (Xs<'a, 'a>, Range)>,
{
closest_line(xy[1], xys_per_line).and_then(
|(closest_line_idx, closest_line_xs, closest_line_y)| {
let (closest_char_idx, closest_x) =
closest_cursor_index_on_line(xy[0], closest_line_xs);
let index = Index {
line: closest_line_idx,
char: closest_char_idx,
};
let point = [closest_x, closest_line_y.middle()].into();
Some((index, point))
},
)
}
/// Find the closest cursor index to the given `x` position on the given line along with the
/// `x` position of that cursor.
pub fn closest_cursor_index_on_line<'a>(x_pos: Scalar, line_xs: Xs<'a, 'a>) -> (usize, Scalar) {
let mut xs_enumerated = line_xs.enumerate();
// `xs` always yields at least one `x` (the start of the line).
let (first_idx, first_x) = xs_enumerated.next().unwrap();
let first_diff = (x_pos - first_x).abs();
let mut closest = (first_idx, first_x);
let mut closest_diff = first_diff;
for (i, x) in xs_enumerated {
let diff = (x_pos - x).abs();
if diff < closest_diff {
closest = (i, x);
closest_diff = diff;
} else {
break;
}
}
closest
}
impl<'a, I> Iterator for XysPerLine<'a, I>
where
I: Iterator<Item = (text::line::Info, Rect)>,
{
// The `Range` occupied by the line across the *y* axis, along with an iterator yielding
// each possible cursor position along the *x* axis.
type Item = (Xs<'a, 'a>, Range);
fn next(&mut self) -> Option<Self::Item> {
let XysPerLine {
ref mut lines_with_rects,
font,
text,
font_size,
} = *self;
let scale = text::pt_to_scale(font_size);
lines_with_rects.next().map(|(line_info, line_rect)| {
let line = &text[line_info.byte_range()];
let (x, y) = (line_rect.left() as f32, line_rect.top() as f32);
let point = text::rt::Point { x: x, y: y };
let y = line_rect.y;
let layout = font.layout(line, scale, point);
let xs = Xs {
next_x: Some(line_rect.x.start),
layout: layout,
};
(xs, y)
})
}
}
impl<'a> Iterator for XysPerLineFromText<'a> {
type Item = (Xs<'a, 'a>, Range);
fn next(&mut self) -> Option<Self::Item> {
self.xys_per_line.next()
}
}
impl<'a, 'b> Iterator for Xs<'a, 'b> {
// Each possible cursor position along the *x* axis.
type Item = Scalar;
fn next(&mut self) -> Option<Self::Item> {
self.next_x.map(|x| {
self.next_x = self.layout.next().map(|g| {
g.pixel_bounding_box()
.map(|r| r.max.x as Scalar)
.unwrap_or_else(|| x + g.unpositioned().h_metrics().advance_width as Scalar)
});
x
})
}
}