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use anyhow::Error;
use std::borrow::Cow;
use crate::Document;
use helix_core::{
graphemes::{grapheme_width, RopeGraphemes},
indent::TAB_WIDTH,
Position, RopeSlice,
};
use tui::layout::Rect;
pub const PADDING: usize = 5;
// TODO: view should be View { doc: Document(state, history,..) }
// since we can have multiple views into the same file
pub struct View {
pub doc: Document,
pub first_line: usize,
pub size: (u16, u16),
}
impl View {
pub fn new(doc: Document, size: (u16, u16)) -> Result<Self, Error> {
let view = Self {
doc,
first_line: 0,
size,
};
Ok(view)
}
pub fn ensure_cursor_in_view(&mut self) {
let cursor = self.doc.state.selection().cursor();
let line = self.doc.text().char_to_line(cursor);
let document_end = self.first_line + (self.size.1 as usize).saturating_sub(2);
// TODO: side scroll
if line > document_end.saturating_sub(PADDING) {
// scroll down
self.first_line += line - (document_end.saturating_sub(PADDING));
} else if line < self.first_line + PADDING {
// scroll up
self.first_line = line.saturating_sub(PADDING);
}
}
/// Calculates the last visible line on screen
#[inline]
pub fn last_line(&self) -> usize {
let viewport = Rect::new(6, 0, self.size.0, self.size.1 - 2); // - 2 for statusline and prompt
std::cmp::min(
self.first_line + (viewport.height as usize),
self.doc.text().len_lines() - 1,
)
}
/// Translates a document position to an absolute position in the terminal.
/// Returns a (line, col) position if the position is visible on screen.
// TODO: Could return width as well for the character width at cursor.
pub fn screen_coords_at_pos(&self, text: &RopeSlice, pos: usize) -> Option<Position> {
let line = text.char_to_line(pos);
if line < self.first_line as usize || line > self.last_line() {
// Line is not visible on screen
return None;
}
let line_start = text.line_to_char(line);
let line_slice = text.slice(line_start..pos);
let mut col = 0;
for grapheme in RopeGraphemes::new(&line_slice) {
if grapheme == "\t" {
col += TAB_WIDTH;
} else {
let grapheme = Cow::from(grapheme);
col += grapheme_width(&grapheme);
}
}
let row = line - self.first_line as usize;
Some(Position::new(row, col))
}
pub fn traverse<F>(&self, text: &RopeSlice, start: usize, end: usize, fun: F)
where
F: Fn(usize, usize),
{
let start = self.screen_coords_at_pos(text, start);
let end = self.screen_coords_at_pos(text, end);
match (start, end) {
// fully on screen
(Some(start), Some(end)) => {
// we want to calculate ends of lines for each char..
}
// from start to end of screen
(Some(start), None) => {}
// from start of screen to end
(None, Some(end)) => {}
// not on screen
(None, None) => return,
}
}
}
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