Struct druid::scroll_component::ScrollComponent

pub struct ScrollComponent {
    pub opacity: f64,
    pub timer_id: TimerToken,
    pub hovered: BarHoveredState,
    pub held: BarHeldState,
}

Embeddable component exposing reusable scroll handling logic.

In most situations composing Scroll is a better idea for general UI construction. However some cases are not covered by composing those widgets, such as when a widget needs fine grained control over its scrolling state or doesn't make sense to exist alone without scrolling behavior.

ScrollComponent contains the input-handling and scrollbar-positioning logic used by Scroll. It can be used to add this logic to a custom widget when the need arises.

It can be used like this:

• Store an instance of ScrollComponent in your widget's struct, and wrap the child widget to be scrolled in a ClipBox.
• Call event and lifecycle with all event and lifecycle events before propagating them to children.
• Call handle_scroll with all events after handling / propagating them.
• Call draw_bars to draw the scrollbars.

Taking a look at the Scroll source code can be helpful. You can also do scrolling without wrapping a child in a ClipBox, but you will need to do certain event and paint transformations yourself; see the ClipBox source code for an example.

Fields

opacity: f64

Current opacity for both scrollbars

timer_id: TimerToken

ID for the timer which schedules scrollbar fade out

hovered: BarHoveredState

Which if any scrollbar is currently hovered by the mouse

held: BarHeldState

Which if any scrollbar is currently being dragged by the mouse

Implementations

impl ScrollComponent

pub fn new() -> ScrollComponent

Constructs a new ScrollComponent for use.

pub fn are_bars_held(&self) -> bool

true if either scrollbar is currently held down/being dragged

pub fn reset_scrollbar_fade<F>(&mut self, request_timer: F, env: &Env) where
    F: FnOnce(Duration) -> TimerToken, 

Makes the scrollbars visible, and resets the fade timer.

pub fn calc_vertical_bar_bounds(
    &self,
    port: &Viewport,
    env: &Env
) -> Option<Rect>

Calculates the paint rect of the vertical scrollbar, or None if the vertical scrollbar is not visible.

pub fn calc_horizontal_bar_bounds(
    &self,
    port: &Viewport,
    env: &Env
) -> Option<Rect>

Calculates the paint rect of the horizontal scrollbar, or None if the horizontal scrollbar is not visible.

pub fn draw_bars(
    &self,
    ctx: &mut PaintCtx<'_, '_, '_>,
    port: &Viewport,
    env: &Env
)

Draw scroll bars.

pub fn point_hits_vertical_bar(
    &self,
    port: &Viewport,
    pos: Point,
    env: &Env
) -> bool

Tests if the specified point overlaps the vertical scrollbar

Returns false if the vertical scrollbar is not visible

pub fn point_hits_horizontal_bar(
    &self,
    port: &Viewport,
    pos: Point,
    env: &Env
) -> bool

Tests if the specified point overlaps the horizontal scrollbar

Returns false if the horizontal scrollbar is not visible

pub fn event(
    &mut self,
    port: &mut Viewport,
    ctx: &mut EventCtx<'_, '_>,
    event: &Event,
    env: &Env
)

Checks if the event applies to the scroll behavior, uses it, and marks it handled

Make sure to call on every event

pub fn handle_scroll(
    &mut self,
    port: &mut Viewport,
    ctx: &mut EventCtx<'_, '_>,
    event: &Event,
    env: &Env
)

Applies mousewheel scrolling if the event has not already been handled

pub fn lifecycle(
    &mut self,
    ctx: &mut LifeCycleCtx<'_, '_>,
    event: &LifeCycle,
    env: &Env
)

Perform any necessary action prompted by a lifecycle event

Make sure to call on every lifecycle event

Trait Implementations

impl Clone for ScrollComponent

pub fn clone(&self) -> ScrollComponent

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for ScrollComponent

impl Debug for ScrollComponent

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

Formats the value using the given formatter.

impl Default for ScrollComponent

pub fn default() -> Self

Returns the "default value" for a type.