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#[allow(clippy::module_name_repetitions)]
#[derive(Debug, Clone)]
pub struct ListState {
/// The selected item. If `None`, no item is currently selected.
pub selected: Option<usize>,
/// The total number of elements in the list. This is necessary to correctly
/// handle item selection.
pub(crate) num_elements: usize,
/// Indicates if the selection is circular. If true, calling `next` on the last
/// element returns the first, and calling `previous` on the first returns the last.
///
/// True by default.
pub(crate) infinite_scrolling: bool,
/// The state for the viewport. Keeps track which item to show
/// first and how much it is truncated.
pub(crate) view_state: ViewState,
}
#[derive(Debug, Clone, Default, Eq, PartialEq)]
pub(crate) struct ViewState {
/// The index of the first item displayed on the screen.
pub(crate) offset: usize,
/// The truncation in rows/columns of the first item displayed on the screen.
pub(crate) first_truncated: u16,
}
impl Default for ListState {
fn default() -> Self {
Self {
selected: None,
num_elements: 0,
infinite_scrolling: true,
view_state: ViewState::default(),
}
}
}
impl ListState {
pub(crate) fn set_infinite_scrolling(&mut self, infinite_scrolling: bool) {
self.infinite_scrolling = infinite_scrolling;
}
/// Returns the index of the currently selected item, if any.
#[must_use]
#[deprecated(since = "0.9.0", note = "Use ListState's selected field instead.")]
pub fn selected(&self) -> Option<usize> {
self.selected
}
/// Selects an item by its index.
pub fn select(&mut self, index: Option<usize>) {
self.selected = index;
if index.is_none() {
self.view_state.offset = 0;
}
}
/// Selects the next element of the list. If circular is true,
/// calling next on the last element selects the first.
///
/// # Example
///
/// ```rust
/// use tui_widget_list::ListState;
///
/// let mut list_state = ListState::default();
/// list_state.next();
/// ```
pub fn next(&mut self) {
if self.num_elements == 0 {
return;
}
let i = match self.selected {
Some(i) => {
if i >= self.num_elements - 1 {
if self.infinite_scrolling {
0
} else {
i
}
} else {
i + 1
}
}
None => 0,
};
self.select(Some(i));
}
/// Selects the previous element of the list. If circular is true,
/// calling previous on the first element selects the last.
///
/// # Example
///
/// ```rust
/// use tui_widget_list::ListState;
///
/// let mut list_state = ListState::default();
/// list_state.previous();
/// ```
pub fn previous(&mut self) {
if self.num_elements == 0 {
return;
}
let i = match self.selected {
Some(i) => {
if i == 0 {
if self.infinite_scrolling {
self.num_elements - 1
} else {
i
}
} else {
i - 1
}
}
None => 0,
};
self.select(Some(i));
}
/// Updates the number of elements that are present in the list.
pub(crate) fn set_num_elements(&mut self, num_elements: usize) {
self.num_elements = num_elements;
}
/// Returns the index of the first item currently displayed on the screen.
#[must_use]
pub fn scroll_offset_index(&self) -> usize {
self.view_state.offset
}
}