Struct ScrollComponent

pub struct ScrollComponent { /* private fields */ }

Logic for a scroll region

This struct handles some scroll logic. It does not provide scroll bars.

Implementations

impl ScrollComponent

pub fn is_gliding(&self) -> bool

True if momentum scrolling is active

pub fn max_offset(&self) -> Offset

Get the maximum offset

Note: the minimum offset is always zero.

pub fn offset(&self) -> Offset

Get the current offset

To translate a coordinate from the outer region to a coordinate of the scrolled region, add this offset.

pub fn set_sizes(&mut self, window_size: Size, content_size: Size) -> Action

Set sizes:

• window_size: size of scroll region on the outside
• content_size: size of scroll region on the inside (usually larger)

Like Self::set_offset this generates a Action due to potential change in offset. In practice the caller will likely be performing all required updates regardless and the return value can be safely ignored.

pub fn set_offset(&mut self, offset: Offset) -> Action

Set the scroll offset

The offset is clamped to the available scroll range. Returns Action::empty() if the offset is identical to the old offset, or Action::REGION_MOVED if the offset changes.

Also cancels any momentum scrolling, but only if offset is not equal to the current offset.

pub fn focus_rect( &mut self, cx: &mut EventCx<'_>, rect: Rect, window_rect: Rect, ) -> Action

Scroll to make the given rect visible

Inputs:

• rect: the rect to focus in child’s coordinate space
• window_rect: the rect of the scroll window

Sets Scroll::Rect to ensure correct scrolling of parents.

Returns Action::REGION_MOVED when the scroll offset changes.

pub fn scroll( &mut self, cx: &mut EventCx<'_>, window_rect: Rect, scroll: Scroll, ) -> Action

Handle a Scroll action

pub fn scroll_by_event( &mut self, cx: &mut EventCx<'_>, event: Event, id: Id, window_rect: Rect, ) -> (bool, IsUsed)

Use an event to scroll, if possible

Consumes the following events: Command, Scroll, PressStart, PressMove, PressEnd, Timer(pl) where pl == (1<<60) + 1. May request timer updates.

Implements scroll by Home/End, Page Up/Down and arrow keys, by mouse wheel and touchpad.

PressStart is consumed only if the maximum scroll offset is non-zero and event configuration enables panning for this press source (may depend on modifiers), and if so grabs press events from this source. PressMove is used to scroll by the motion delta and to track speed; PressEnd initiates momentum-scrolling if the speed is high enough.

Returns (moved, is_used) where moved means this component scrolled (scrolling of a parent is possible even if !moved).

Trait Implementations

impl Clone for ScrollComponent

fn clone(&self) -> ScrollComponent

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ScrollComponent

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

Formats the value using the given formatter.

impl Default for ScrollComponent

fn default() -> ScrollComponent

Returns the “default value” for a type.