Struct ScrollState 

pub struct ScrollState {
    pub area: Rect,
    pub orientation: ScrollbarOrientation,
    pub offset: usize,
    pub page_len: usize,
    pub max_offset: usize,
    pub scroll_by: Option<usize>,
    pub overscroll_by: Option<usize>,
    pub mouse: MouseFlags,
    pub non_exhaustive: NonExhaustive,
}

Scroll state.

The current visible page is represented as the pair (offset, page_len).

The limit for scrolling is given as max_offset, which is the maximum offset where a full page can still be displayed.

Note

that the total length of the widgets data is NOT max_offset + page_len. The page_len can be different for every offset selected. Only if the offset is set to max_offset and after the next round of rendering len == max_offset + page_len will hold true.

Note

In terms of ScrollbarState,

• offset is position,
• page_len is viewport_content_length and
• max_offset is content_length.

Fields

area: Rect

Area of the Scrollbar. readonly. renewed for each render.

orientation: ScrollbarOrientation

Vertical/Horizontal scroll? readonly. renewed for each render.

offset: usize

Current offset. read+write

page_len: usize

Length of the current displayed page. This value can be used for page-up/page-down handling. read+write

max_offset: usize

Maximum offset that is accessible with scrolling.

This offset is calculated as item_count - last_page_items. Both are abstract values and can denote items or columns/rows as the widget sees fit. read+write

scroll_by: Option<usize>

How many items are scrolled per scroll event. When not set it defaults to 1/10 of the page_len, which gives a decent median between scroll speed and disorientation. read+write

overscroll_by: Option<usize>

By how much can the max_offset be exceeded. This allows displaying some empty space at the end of the content, which can be more intuitive for some widgets. read+write

mouse: MouseFlags

Mouse support. read+write

non_exhaustive: NonExhaustive

Implementations

impl ScrollState

pub fn new() -> Self

pub fn set_orientation(&mut self, orientation: ScrollbarOrientation)

pub fn is_vertical(&self) -> bool

Vertical scroll?

pub fn is_horizontal(&self) -> bool

Horizontal scroll?

pub fn clear(&mut self)

Resets the offset to 0.

pub fn offset(&self) -> usize

Current vertical offset.

pub fn set_offset(&mut self, offset: usize) -> bool

Change the offset. There is no limitation to the value set here. It’s therefore possible that this is an invalid offset for the widget. The widget must deal with this situation.

pub fn scroll_to_pos(&mut self, pos: usize) -> bool

Scroll to make the given pos visible. Adjusts the offset just enough to make this happen. Does nothing if the position is already visible.

pub fn scroll_to_range(&mut self, range: Range<usize>) -> bool

Scroll to make the given range visible.Adjusts the offset just enough to make this happen. Does nothing if the range is already visible.

pub fn scroll_up(&mut self, n: usize) -> bool

Scroll up by n.

pub fn scroll_down(&mut self, n: usize) -> bool

Scroll down by n.

pub fn scroll_left(&mut self, n: usize) -> bool

Scroll left by n.

pub fn scroll_right(&mut self, n: usize) -> bool

Scroll right by n.

pub fn limited_offset(&self, offset: usize) -> usize

Calculate the offset limited to max_offset+overscroll_by.

pub fn max_offset(&self) -> usize

Maximum offset that is accessible with scrolling.

This is shorter than the length of the content by whatever fills the last page. This is the base for the scrollbar content_length.

pub fn set_max_offset(&mut self, max: usize)

Maximum offset that is accessible with scrolling.

This is shorter than the length of the content by whatever fills the last page. This is the base for the scrollbar content_length.

pub fn page_len(&self) -> usize

Page-size at the current offset.

pub fn set_page_len(&mut self, page: usize)

Page-size at the current offset.

pub fn scroll_by(&self) -> usize

Suggested scroll per scroll-event. Defaults to 1/10 of the page

pub fn set_scroll_by(&mut self, scroll: Option<usize>)

Suggested scroll per scroll-event. Defaults to 1/10 of the page

pub fn overscroll_by(&self) -> usize

Allowed overscroll

pub fn set_overscroll_by(&mut self, overscroll_by: Option<usize>)

Allowed overscroll

pub fn items_added(&mut self, pos: usize, n: usize)

Update the state to match adding items.

pub fn items_removed(&mut self, pos: usize, n: usize)

Update the state to match removing items.

impl ScrollState

pub fn map_position_index(&self, pos: u16, base: u16, length: u16) -> usize

Maps a screen-position to an offset. pos - row/column clicked base - x/y of the range length - width/height of the range.

Trait Implementations

impl Clone for ScrollState

fn clone(&self) -> ScrollState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ScrollState

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ScrollState

fn default() -> Self

Returns the “default value” for a type.

impl HandleEvent<Event, MouseOnly, ScrollOutcome> for ScrollState

fn handle(&mut self, event: &Event, _qualifier: MouseOnly) -> ScrollOutcome

Handle an event.

impl PartialEq for ScrollState

fn eq(&self, other: &ScrollState) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl RelocatableState for ScrollState

fn relocate(&mut self, shift: (i16, i16), clip: Rect)

Relocate the areas in this widgets state.

impl Eq for ScrollState

impl StructuralPartialEq for ScrollState