Struct druid::widget::Painter

pub struct Painter<T>(_);

A widget that only handles painting.

This is useful in a situation where layout is controlled elsewhere and you do not need to handle events, but you would like to customize appearance.

When is paint called?

The Painter widget will call its paint method anytime its Data is changed. If you would like it to repaint at other times (such as when hot or active state changes) you will need to call request_paint further up the tree, perhaps in a Controller widget.

Examples

Changing background color based on some part of data:

use druid::{Env, PaintCtx,Rect, RenderContext};
use druid::widget::Painter;

struct MyData { is_enabled: bool }

let my_painter = Painter::new(|ctx, data: &MyData, env| {
    let bounds = ctx.size().to_rect();
    if data.is_enabled {
        ctx.fill(bounds, &env.get(ENABLED_BG_COLOR));
    } else {

        ctx.fill(bounds, &env.get(DISABLED_BG_COLOR));
    }
});

Using painter to make a simple widget that will draw a selected color

use druid::{Color, Env, PaintCtx,Rect, RenderContext};
use druid::widget::Painter;

const CORNER_RADIUS: f64 = 4.0;
const STROKE_WIDTH: f64 = 2.0;

let colorwell: Painter<Color> = Painter::new(|ctx, data: &Color, env| {
    // Shrink the bounds a little, to ensure that our stroke remains within
    // the paint bounds.
    let bounds = ctx.size().to_rect().inset(-STROKE_WIDTH / 2.0);
    let rounded = bounds.to_rounded_rect(CORNER_RADIUS);
    ctx.fill(rounded, data);
    ctx.stroke(rounded, &env.get(druid::theme::PRIMARY_DARK), STROKE_WIDTH);
});

Implementations

impl<T> Painter<T>

pub fn new(f: impl FnMut(&mut PaintCtx<'_, '_, '_>, &T, &Env) + 'static) -> Self

Create a new Painter with the provided paint fn.

Trait Implementations

impl<T> From<Painter<T>> for BackgroundBrush<T>

pub fn from(src: Painter<T>) -> BackgroundBrush<T>

Performs the conversion.

impl<T: Data> Widget<T> for Painter<T>

pub fn event(&mut self, _: &mut EventCtx<'_, '_>, _: &Event, _: &mut T, _: &Env)

Handle an event.

pub fn lifecycle(
    &mut self,
    _: &mut LifeCycleCtx<'_, '_>,
    _: &LifeCycle,
    _: &T,
    _: &Env
)

Handle a life cycle notification.

pub fn update(&mut self, ctx: &mut UpdateCtx<'_, '_>, old: &T, new: &T, _: &Env)

Update the widget's appearance in response to a change in the app's Data or Env.

pub fn layout(
    &mut self,
    _ctx: &mut LayoutCtx<'_, '_>,
    bc: &BoxConstraints,
    _: &T,
    _: &Env
) -> Size

Compute layout.

pub fn paint(&mut self, ctx: &mut PaintCtx<'_, '_, '_>, data: &T, env: &Env)

Paint the widget appearance.