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use {
crate::crossterm::terminal,
std::convert::{
TryFrom,
TryInto,
},
};
/// A default width which is used when we failed measuring the real terminal width
const DEFAULT_TERMINAL_WIDTH: u16 = 50;
/// A default height which is used when we failed measuring the real terminal width
const DEFAULT_TERMINAL_HEIGHT: u16 = 20;
/// A rectangular part of the screen
#[derive(Debug, PartialEq, Eq, Clone)]
pub struct Area {
pub left: u16,
pub top: u16,
pub width: u16,
pub height: u16,
}
impl Default for Area {
fn default() -> Self {
Self::uninitialized()
}
}
impl Area {
/// build a new area. You'll need to set the position and size
/// before you can use it
pub const fn uninitialized() -> Area {
Area {
left: 0,
top: 0,
height: 1,
width: 5,
}
}
/// build a new area.
pub const fn new(left: u16, top: u16, width: u16, height: u16) -> Area {
Area {
left,
top,
width,
height,
}
}
/// build an area covering the whole terminal
pub fn full_screen() -> Area {
let (width, height) = terminal_size();
Area {
left: 0,
top: 0,
width,
height,
}
}
pub const fn right(&self) -> u16 {
self.left + self.width
}
pub const fn bottom(&self) -> u16 {
self.top + self.height
}
/// tell whether the char at (x,y) is in the area
pub const fn contains(&self, x: u16, y: u16) -> bool {
x >= self.left && x < self.left + self.width && y >= self.top && y < self.top + self.height
}
/// shrink the area
pub fn pad(&mut self, dx: u16, dy: u16) {
// this will crash if padding is too big. feature?
self.left += dx;
self.top += dy;
self.width -= 2 * dx;
self.height -= 2 * dy;
}
/// symmetrically shrink the area if its width is bigger than `max_width`
pub fn pad_for_max_width(&mut self, max_width: u16) {
if max_width >= self.width {
return;
}
let pw = self.width - max_width;
self.left += pw / 2;
self.width -= pw;
}
/// Return an option which when filled contains
/// a tupple with the top and bottom of the vertical
/// scrollbar. Return none when the content fits
/// the available space.
pub fn scrollbar<U>(
&self,
scroll: U, // number of lines hidden on top
content_height: U,
) -> Option<(u16, u16)>
where
U: Into<usize>,
{
compute_scrollbar(scroll, content_height, self.height, self.top)
}
}
/// Compute the min and max y (from the top of the terminal, both inclusive)
/// for the thumb part of the scrollbar which would represent the scrolled
/// content in the available height.
///
/// If you represent some data in an Area, you should directly use the
/// scrollbar method of Area.
pub fn compute_scrollbar<U1, U2, U3>(
scroll: U1, // 0 for no scroll, positive if scrolled
content_height: U1, // number of lines of the content
available_height: U3, // for an area it's usually its height
top: U2, // distance from the top of the screen
) -> Option<(U2, U2)>
where
U1: Into<usize>, // the type in which you store your content length and content scroll
U2: Into<usize> + TryFrom<usize>, // the drawing type (u16 for an area)
<U2 as TryFrom<usize>>::Error: std::fmt::Debug,
U3: Into<usize> + TryFrom<usize>, // the type used for available height
<U3 as TryFrom<usize>>::Error: std::fmt::Debug,
{
let scroll: usize = scroll.into();
let content_height: usize = content_height.into();
let available_height: usize = available_height.into();
let top: usize = top.into();
if content_height <= available_height {
return None;
}
let mut track_before = scroll * available_height / content_height;
if track_before == 0 && scroll > 0 {
track_before = 1;
}
let thumb_height = available_height * available_height / content_height;
let scrollbar_top = top + track_before;
let mut scrollbar_bottom = scrollbar_top + thumb_height;
if scroll + available_height < content_height && available_height > 3 {
scrollbar_bottom = scrollbar_bottom
.min(top + available_height - 2)
.max(scrollbar_top);
}
// by construction those two conversions are OK
// (or it's a bug, which, well, is possible...)
let scrollbar_top = scrollbar_top.try_into().unwrap();
let scrollbar_bottom = scrollbar_bottom.try_into().unwrap();
Some((scrollbar_top, scrollbar_bottom))
}
/// Return a (width, height) with the dimensions of the available
/// terminal in characters.
#[must_use]
pub fn terminal_size() -> (u16, u16) {
let size = terminal::size();
size.unwrap_or((DEFAULT_TERMINAL_WIDTH, DEFAULT_TERMINAL_HEIGHT))
}