githubmirror/lapce

lapce-ui/src/scroll.rs
1 109 строк36 KB
Dongdong Zhou
fix alpha depth issue in painting
19 июл 2022, 22:23
19 июл 2022, 22:2369e6b83
use std::time::Duration;
use std::time::Instant;

use druid::Cursor;
use druid::{
    kurbo::{Affine, Point, Rect, Size, Vec2},
    Insets, WidgetId,
};
use druid::{
    theme, BoxConstraints, Data, Env, Event, EventCtx, LayoutCtx, LifeCycle,
    LifeCycleCtx, PaintCtx, RenderContext, TimerToken, UpdateCtx, Widget, WidgetPod,
};

use lapce_data::{
    command::{LapceUICommand, LAPCE_UI_COMMAND},
    config::{Config, GetConfig, LapceTheme},
};

/// Minimum length for any scrollbar to be when measured on that
/// scrollbar's primary axis.
pub const SCROLLBAR_MIN_SIZE: f64 = 45.0;

/// Denotes which scrollbar, if any, is currently being hovered over
/// by the mouse.
#[derive(Debug, Copy, Clone)]
enum BarHoveredState {
    /// Neither scrollbar is being hovered by the mouse.
    None,
    /// The vertical scrollbar is being hovered by the mouse.
    Vertical,
    /// The horizontal scrollbar is being hovered by the mouse.
    Horizontal,
}

/// Denotes which scrollbar, if any, is currently being dragged.
#[derive(Debug, Copy, Clone)]
enum BarHeldState {
    /// Neither scrollbar is being dragged.
    None,
    /// Vertical scrollbar is being dragged. Contains an `f64` with
    /// the initial y-offset of the dragging input.
    Vertical(f64, Vec2),
    /// Horizontal scrollbar is being dragged. Contains an `f64` with
    /// the initial x-offset of the dragging input.
    Horizontal(f64, Vec2),
}

#[derive(Clone, Copy, Default, Debug, PartialEq)]
struct Viewport {
    /// The size of the area that we have a viewport into.
    pub content_size: Size,
    /// The view rectangle.
    pub rect: Rect,
}

impl Viewport {
    /// Tries to find a position for the view rectangle that is contained in the content rectangle.
    ///
    /// If the supplied origin is good, returns it; if it isn't, we try to return the nearest
    /// origin that would make the view rectangle contained in the content rectangle. (This will
    /// fail if the content is smaller than the view, and we return `0.0` in each dimension where
    /// the content is smaller.)
    pub fn clamp_view_origin(&self, origin: Point) -> Point {
        let x = origin
            .x
            .min(self.content_size.width - self.rect.width())
            .max(0.0);
        let y = origin
            .y
            .min(self.content_size.height - self.rect.height())
            .max(0.0);
        Point::new(x, y)
    }

    /// Changes the viewport offset by `delta`, while trying to keep the view rectangle inside the
    /// content rectangle.
    ///
    /// Returns true if the offset actually changed. Even if `delta` is non-zero, the offset might
    /// not change. For example, if you try to move the viewport down but it is already at the
    /// bottom of the child widget, then the offset will not change and this function will return
    /// false.
    pub fn pan_by(&mut self, delta: Vec2) -> bool {
        self.pan_to(self.rect.origin() + delta)
    }

    /// Sets the viewport origin to `pos`, while trying to keep the view rectangle inside the
    /// content rectangle.
    ///
    /// Returns true if the position changed. Note that the valid values for the viewport origin
    /// are constrained by the size of the child, and so the origin might not get set to exactly
    /// `pos`.
    pub fn pan_to(&mut self, origin: Point) -> bool {
        let new_origin = self.clamp_view_origin(origin);
        if (new_origin - self.rect.origin()).hypot2() > 1e-12 {
            self.rect = self.rect.with_origin(new_origin);
            true
        } else {
            false
        }
    }

    pub fn force_pan_to(&mut self, origin: Point) {
        self.rect = self.rect.with_origin(origin);
    }

    /// Pan the smallest distance that makes the target [`Rect`] visible.
    ///
    /// If the target rect is larger than viewport size, we will prioritize
    /// the region of the target closest to its origin.
    pub fn pan_to_visible(&mut self, rect: Rect) -> bool {
        /// Given a position and the min and max edges of an axis,
        /// return a delta by which to adjust that axis such that the value
        /// falls between its edges.
        ///
        /// if the value already falls between the two edges, return 0.0.
        fn closest_on_axis(val: f64, min: f64, max: f64) -> f64 {
            assert!(min <= max);
            if val > min && val < max {
                0.0
            } else if val <= min {
                val - min
            } else {
                val - max
            }
        }

        // clamp the target region size to our own size.
        // this means we will show the portion of the target region that
        // includes the origin.
        let target_size = Size::new(
            rect.width().min(self.rect.width()),
            rect.height().min(self.rect.height()),
        );
        let rect = rect.with_size(target_size);

        let x0 = closest_on_axis(rect.min_x(), self.rect.min_x(), self.rect.max_x());
        let x1 = closest_on_axis(rect.max_x(), self.rect.min_x(), self.rect.max_x());
        let y0 = closest_on_axis(rect.min_y(), self.rect.min_y(), self.rect.max_y());
        let y1 = closest_on_axis(rect.max_y(), self.rect.min_y(), self.rect.max_y());

        let delta_x = if x0.abs() > x1.abs() { x0 } else { x1 };
        let delta_y = if y0.abs() > y1.abs() { y0 } else { y1 };
        let new_origin = self.rect.origin() + Vec2::new(delta_x, delta_y);
        self.pan_to(new_origin)
    }
}

struct ClipBox<T, W> {
    child: WidgetPod<T, W>,
    port: Viewport,
    constrain_horizontal: bool,
    constrain_vertical: bool,
}

impl<T, W: Widget<T>> ClipBox<T, W> {
    /// Creates a new `ClipBox` wrapping `child`.
    pub fn new(child: W) -> Self {
        Self {
            child: WidgetPod::new(child),
            port: Default::default(),
            constrain_horizontal: false,
            constrain_vertical: false,
        }
    }

    /// Returns a reference to the child widget.
    pub fn child(&self) -> &W {
        self.child.widget()
    }

    /// Returns a mutable reference to the child widget.
    pub fn child_mut(&mut self) -> &mut W {
        self.child.widget_mut()
    }

    /// Returns a the viewport describing this `ClipBox`'s position.
    pub fn viewport(&self) -> Viewport {
        self.port
    }

    /// Returns the size of the rectangular viewport into the child widget.
    /// To get the position of the viewport, see [`viewport_origin`].
    ///
    /// [`viewport_origin`]: struct.ClipBox.html#method.viewport_origin
    pub fn viewport_size(&self) -> Size {
        self.port.rect.size()
    }

    /// Returns the size of the child widget.
    pub fn content_size(&self) -> Size {
        self.port.content_size
    }

    /// Builder-style method for deciding whether to constrain the child horizontally. The default
    /// is `false`. See [`constrain_vertical`] for more details.
    ///
    /// [`constrain_vertical`]: struct.ClipBox.html#constrain_vertical
    pub fn constrain_horizontal(mut self, constrain: bool) -> Self {
        self.set_constrain_horizontal(constrain);
        self
    }

    /// Determine whether to constrain the child horizontally.
    ///
    /// See [`constrain_vertical`] for more details.
    ///
    /// [`constrain_vertical`]: struct.ClipBox.html#constrain_vertical
    pub fn set_constrain_horizontal(&mut self, constrain: bool) {
        self.constrain_horizontal = constrain;
    }

    /// Builder-style method for deciding whether to constrain the child vertically. The default
    /// is `false`.
    ///
    /// This setting affects how a `ClipBox` lays out its child.
    ///
    /// - When it is `false` (the default), the child does receive any upper bound on its height:
    ///   the idea is that the child can be as tall as it wants, and the viewport will somehow get
    ///   moved around to see all of it.
    /// - When it is `true`, the viewport's maximum height will be passed down as an upper bound on
    ///   the height of the child, and the viewport will set its own height to be the same as its
    ///   child's height.
    pub fn constrain_vertical(mut self, constrain: bool) -> Self {
        self.set_constrain_vertical(constrain);
        self
    }

    /// Determine whether to constrain the child vertically.
    ///
    /// See [`constrain_vertical`] for more details.
    ///
    /// [`constrain_vertical`]: struct.ClipBox.html#constrain_vertical
    pub fn set_constrain_vertical(&mut self, constrain: bool) {
        self.constrain_vertical = constrain;
    }

    /// Changes the viewport offset by `delta`.
    ///
    /// Returns true if the offset actually changed. Even if `delta` is non-zero, the offset might
    /// not change. For example, if you try to move the viewport down but it is already at the
    /// bottom of the child widget, then the offset will not change and this function will return
    /// false.
    pub fn pan_by(&mut self, delta: Vec2) -> bool {
        self.pan_to(self.viewport_origin() + delta)
    }

    /// Sets the viewport origin to `pos`.
    ///
    /// Returns true if the position changed. Note that the valid values for the viewport origin
    /// are constrained by the size of the child, and so the origin might not get set to exactly
    /// `pos`.
    pub fn pan_to(&mut self, origin: Point) -> bool {
        if self.port.pan_to(origin) {
            self.child
                .set_viewport_offset(self.viewport_origin().to_vec2());
            true
        } else {
            false
        }
    }

    pub fn force_pan_to(&mut self, origin: Point) {
        self.port.force_pan_to(origin);
        self.child
            .set_viewport_offset(self.viewport_origin().to_vec2());
    }

    /// Adjust the viewport to display as much of the target region as is possible.
    ///
    /// Returns `true` if the viewport changes.
    ///
    /// This will move the viewport the smallest distance that fully shows
    /// the target region. If the target region is larger than the viewport,
    /// we will display the portion that fits, prioritizing the portion closest
    /// to the origin.
    pub fn pan_to_visible(&mut self, region: Rect) -> bool {
        if self.port.pan_to_visible(region) {
            self.child
                .set_viewport_offset(self.viewport_origin().to_vec2());
            true
        } else {
            false
        }
    }

    /// Returns the origin of the viewport rectangle.
    pub fn viewport_origin(&self) -> Point {
        self.port.rect.origin()
    }

    /// Allows this `ClipBox`'s viewport rectangle to be modified. The provided callback function
    /// can modify its argument, and when it is done then this `ClipBox` will be modified to have
    /// the new viewport rectangle.
    pub fn with_port<F: FnOnce(&mut Viewport)>(&mut self, f: F) {
        f(&mut self.port);
        self.child
            .set_viewport_offset(self.viewport_origin().to_vec2());
    }
}

impl<T: Data, W: Widget<T>> Widget<T> for ClipBox<T, W> {
    fn event(&mut self, ctx: &mut EventCtx, ev: &Event, data: &mut T, env: &Env) {
        let viewport = ctx.size().to_rect();
        let force_event = self.child.is_hot() || self.child.has_active();
        if let Some(child_event) = ev.transform_scroll(
            self.viewport_origin().to_vec2(),
            viewport,
            force_event,
        ) {
            self.child.event(ctx, &child_event, data, env);
        }
    }

    fn lifecycle(
        &mut self,
        ctx: &mut LifeCycleCtx,
        ev: &LifeCycle,
        data: &T,
        env: &Env,
    ) {
        self.child.lifecycle(ctx, ev, data, env);
    }

    fn update(&mut self, ctx: &mut UpdateCtx, _old_data: &T, data: &T, env: &Env) {
        self.child.update(ctx, data, env);
    }

    fn layout(
        &mut self,
        ctx: &mut LayoutCtx,
        bc: &BoxConstraints,
        data: &T,
        env: &Env,
    ) -> Size {
        bc.debug_check("ClipBox");

        let content_size = self.child.layout(ctx, bc, data, env);
        self.port.content_size = content_size;
        self.child.set_origin(ctx, data, env, Point::ORIGIN);

        self.port.rect = self.port.rect.with_size(bc.constrain(content_size));
        let new_offset = self.port.clamp_view_origin(self.viewport_origin());
        self.pan_to(new_offset);
        self.viewport_size()
    }

    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
        let viewport = ctx.size().to_rect();
        let offset = self.viewport_origin().to_vec2();
        ctx.with_save(|ctx| {
            ctx.clip(viewport.inflate(1.0, 0.0));
            ctx.transform(Affine::translate(-offset));

            let mut visible = ctx.region().clone();
            visible += offset;
            ctx.with_child_ctx(visible, |ctx| self.child.paint_raw(ctx, data, env));
        });
    }
}

#[derive(Debug, Copy, Clone)]
struct ScrollComponent {
    /// Current opacity for both scrollbars
    pub opacity: f64,
    /// ID for the timer which schedules scrollbar fade out
    pub timer_id: TimerToken,
    /// Which if any scrollbar is currently hovered by the mouse
    pub hovered: BarHoveredState,
    /// Which if any scrollbar is currently being dragged by the mouse
    pub held: BarHeldState,
    pub fade_start: Option<Instant>,
    pub vertical_scroll_for_horizontal: bool,
}

impl Default for ScrollComponent {
    fn default() -> Self {
        Self {
            opacity: 0.0,
            timer_id: TimerToken::INVALID,
            hovered: BarHoveredState::None,
            held: BarHeldState::None,
            fade_start: None,
            vertical_scroll_for_horizontal: false,
        }
    }
}

impl ScrollComponent {
    /// Constructs a new [`ScrollComponent`](struct.ScrollComponent.html) for use.
    pub fn new() -> ScrollComponent {
        Default::default()
    }

    /// true if either scrollbar is currently held down/being dragged
    pub fn are_bars_held(&self) -> bool {
        !matches!(self.held, BarHeldState::None)
    }

    /// Makes the scrollbars visible, and resets the fade timer.
    pub fn reset_scrollbar_fade<F>(&mut self, request_timer: F, env: &Env)
    where
        F: FnOnce(Duration) -> TimerToken,
    {
        self.opacity = env.get(theme::SCROLLBAR_MAX_OPACITY);
        self.fade_start = None;
        let fade_delay = 500;
        let deadline = Duration::from_millis(fade_delay);
        self.timer_id = request_timer(deadline);
    }

    /// Calculates the paint rect of the vertical scrollbar, or `None` if the vertical scrollbar is
    /// not visible.
    pub fn calc_vertical_bar_bounds(
        &self,
        port: &Viewport,
        config: &Config,
        env: &Env,
    ) -> Option<Rect> {
        let viewport_size = port.rect.size();
        let content_size = port.content_size;
        let scroll_offset = port.rect.origin().to_vec2();

        if viewport_size.height >= content_size.height {
            return None;
        }

        let bar_width = config.ui.scroll_width() as f64;
        let bar_pad = env.get(theme::SCROLLBAR_PAD);

        let percent_visible = viewport_size.height / content_size.height;
        let percent_scrolled =
            scroll_offset.y / (content_size.height - viewport_size.height);

        let length = (percent_visible * viewport_size.height).ceil();
        let length = length.max(SCROLLBAR_MIN_SIZE);

        let top_y_offset =
            ((viewport_size.height - length) * percent_scrolled).ceil();
        let bottom_y_offset = top_y_offset + length;

        let x0 = scroll_offset.x + viewport_size.width - bar_width - bar_pad;
        let y0 = scroll_offset.y + top_y_offset;

        let x1 = scroll_offset.x + viewport_size.width - bar_pad;
        let y1 = scroll_offset.y + bottom_y_offset;

        Some(Rect::new(x0, y0, x1, y1))
    }

    /// Calculates the paint rect of the horizontal scrollbar, or `None` if the horizontal
    /// scrollbar is not visible.
    pub fn calc_horizontal_bar_bounds(
        &self,
        port: &Viewport,
        config: &Config,
        env: &Env,
    ) -> Option<Rect> {
        let viewport_size = port.rect.size();
        let content_size = port.content_size;
        let scroll_offset = port.rect.origin().to_vec2();

        if viewport_size.width >= content_size.width {
            return None;
        }

        let bar_width = if viewport_size.height < 40.0 {
            5.0
        } else {
            config.ui.scroll_width() as f64
        };
        let bar_pad = env.get(theme::SCROLLBAR_PAD);

        let percent_visible = viewport_size.width / content_size.width;
        let percent_scrolled =
            scroll_offset.x / (content_size.width - viewport_size.width);

        let length = (percent_visible * viewport_size.width).ceil();
        let length = length.max(SCROLLBAR_MIN_SIZE);

        let horizontal_padding = if viewport_size.height >= content_size.height {
            0.0
        } else {
            bar_pad + bar_pad + bar_width
        };

        let left_x_offset = ((viewport_size.width - length - horizontal_padding)
            * percent_scrolled)
            .ceil();
        let right_x_offset = left_x_offset + length;

        let x0 = scroll_offset.x + left_x_offset;
        let y0 = scroll_offset.y + viewport_size.height - bar_width - bar_pad;

        let x1 = scroll_offset.x + right_x_offset;
        let y1 = scroll_offset.y + viewport_size.height - bar_pad;

        Some(Rect::new(x0, y0, x1, y1))
    }

    /// Draw scroll bars.
    pub fn draw_bars(
        &self,
        ctx: &mut PaintCtx,
        port: &Viewport,
        env: &Env,
        config: &Config,
    ) {
        let scroll_offset = port.rect.origin().to_vec2();
        if self.opacity <= 0.0 {
            return;
        }

        let brush = ctx.render_ctx.solid_brush(
            config
                .get_color_unchecked(LapceTheme::LAPCE_SCROLL_BAR)
                .clone()
                .with_alpha(self.opacity),
        );
        let border_brush = ctx.render_ctx.solid_brush(
            config
                .get_color_unchecked(LapceTheme::LAPCE_SCROLL_BAR)
                .clone()
                .with_alpha(self.opacity),
        );

        let _radius = env.get(theme::SCROLLBAR_RADIUS);
        let edge_width = env.get(theme::SCROLLBAR_EDGE_WIDTH);

        ctx.with_save(|ctx| {
            ctx.incr_alpha_depth();
            // Vertical bar
            if let Some(bounds) = self.calc_vertical_bar_bounds(port, config, env) {
                let rect = (bounds - scroll_offset).inset(-edge_width / 2.0);
                ctx.render_ctx.fill(rect, &brush);
                ctx.render_ctx.stroke(rect, &border_brush, edge_width);
            }

            // Horizontal bar
            if let Some(bounds) = self.calc_horizontal_bar_bounds(port, config, env)
            {
                let rect = (bounds - scroll_offset).inset(-edge_width / 2.0);
                ctx.render_ctx.fill(rect, &brush);
                ctx.render_ctx.stroke(rect, &border_brush, edge_width);
            }
        })
    }

    /// Tests if the specified point overlaps the vertical scrollbar
    ///
    /// Returns false if the vertical scrollbar is not visible
    pub fn point_hits_vertical_bar(
        &self,
        port: &Viewport,
        pos: Point,
        config: &Config,
        env: &Env,
    ) -> bool {
        let viewport_size = port.rect.size();
        let scroll_offset = port.rect.origin().to_vec2();

        if let Some(mut bounds) = self.calc_vertical_bar_bounds(port, config, env) {
            // Stretch hitbox to edge of widget
            bounds.x1 = scroll_offset.x + viewport_size.width;
            bounds.contains(pos)
        } else {
            false
        }
    }

    /// Tests if the specified point overlaps the horizontal scrollbar
    ///
    /// Returns false if the horizontal scrollbar is not visible
    pub fn point_hits_horizontal_bar(
        &self,
        port: &Viewport,
        pos: Point,
        config: &Config,
        env: &Env,
    ) -> bool {
        let viewport_size = port.rect.size();
        let scroll_offset = port.rect.origin().to_vec2();

        if let Some(mut bounds) = self.calc_horizontal_bar_bounds(port, config, env)
        {
            // Stretch hitbox to edge of widget
            bounds.y1 = scroll_offset.y + viewport_size.height;
            bounds.contains(pos)
        } else {
            false
        }
    }

    /// Checks if the event applies to the scroll behavior, uses it, and marks it handled
    ///
    /// Make sure to call on every event
    pub fn event(
        &mut self,
        port: &mut Viewport,
        ctx: &mut EventCtx,
        event: &Event,
        config: &Config,
        env: &Env,
    ) {
        let viewport_size = port.rect.size();
        let content_size = port.content_size;
        let scroll_offset = port.rect.origin().to_vec2();

        let scrollbar_is_hovered = match event {
            Event::MouseMove(e) | Event::MouseUp(e) | Event::MouseDown(e) => {
                let offset_pos = e.pos + scroll_offset;
                self.point_hits_vertical_bar(port, offset_pos, config, env)
                    || self.point_hits_horizontal_bar(port, offset_pos, config, env)
            }
            _ => false,
        };

        if scrollbar_is_hovered || ctx.is_active() {
            ctx.set_cursor(&Cursor::Arrow);
        }

        if self.are_bars_held() {
            // if we're dragging a scrollbar
            match event {
                Event::MouseMove(event) => {
                    match self.held {
                        BarHeldState::Vertical(offset, initial_scroll_offset) => {
                            let scale_y = viewport_size.height / content_size.height;
                            let y = initial_scroll_offset.y
                                + (event.pos.y - offset) / scale_y;
                            port.pan_to(Point::new(initial_scroll_offset.x, y));
                            ctx.set_handled();
                        }
                        BarHeldState::Horizontal(offset, initial_scroll_offset) => {
                            let scale_x = viewport_size.width / content_size.width;
                            let x = initial_scroll_offset.x
                                + (event.pos.x - offset) / scale_x;
                            port.pan_to(Point::new(x, initial_scroll_offset.y));
                            ctx.set_handled();
                        }
                        _ => (),
                    }
                    ctx.request_paint();
                }
                Event::MouseUp(_) => {
                    self.held = BarHeldState::None;
                    ctx.set_active(false);

                    if !scrollbar_is_hovered {
                        self.hovered = BarHoveredState::None;
                        self.reset_scrollbar_fade(
                            |d| ctx.request_timer(d, None),
                            env,
                        );
                    }

                    ctx.set_handled();
                }
                _ => (), // other events are a noop
            }
        } else if scrollbar_is_hovered {
            // if we're over a scrollbar but not dragging
            match event {
                Event::MouseMove(event) => {
                    let offset_pos = event.pos + scroll_offset;
                    if self.point_hits_vertical_bar(port, offset_pos, config, env) {
                        self.hovered = BarHoveredState::Vertical;
                    } else if self
                        .point_hits_horizontal_bar(port, offset_pos, config, env)
                    {
                        self.hovered = BarHoveredState::Horizontal;
                    } else {
                    }

                    self.opacity = env.get(theme::SCROLLBAR_MAX_OPACITY);
                    self.timer_id = TimerToken::INVALID; // Cancel any fade out in progress
                    ctx.request_paint();
                    ctx.set_handled();
                }
                Event::MouseDown(event) => {
                    let pos = event.pos + scroll_offset;

                    if self.point_hits_vertical_bar(port, pos, config, env) {
                        ctx.set_active(true);
                        self.held = BarHeldState::Vertical(
                            // The bounds must be non-empty, because the point hits the scrollbar.
                            event.pos.y,
                            scroll_offset,
                        );
                    } else if self.point_hits_horizontal_bar(port, pos, config, env)
                    {
                        ctx.set_active(true);
                        self.held = BarHeldState::Horizontal(
                            // The bounds must be non-empty, because the point hits the scrollbar.
                            event.pos.x,
                            scroll_offset,
                        );
                    } else {
                    }

                    ctx.set_handled();
                }
                // if the mouse was downed elsewhere, moved over a scroll bar and released: noop.
                Event::MouseUp(_) => (),
                _ => (),
            }
        } else if !ctx.is_hot() {
            match event {
                // Event::MouseMove(_) => {
                //     // if we have just stopped hovering
                //     if self.hovered.is_hovered() && !scrollbar_is_hovered {
                //         self.hovered = BarHoveredState::None;
                //         self.reset_scrollbar_fade(|d| ctx.request_timer(d), env);
                //     }
                // }
                Event::AnimFrame(_) => {
                    if let Some(start) = self.fade_start {
                        let _elapsed = start.elapsed().subsec_millis();
                        let diff = 0.02;
                        self.opacity = env.get(theme::SCROLLBAR_MAX_OPACITY)
                            - diff * (start.elapsed().subsec_millis() as f64 / 20.0);
                        if self.opacity > 0.0 {
                            ctx.request_anim_frame();
                        } else {
                            self.fade_start = None;
                        }
                        ctx.request_paint();
                    }
                }
                Event::Timer(id) if *id == self.timer_id => {
                    // Schedule scroll bars animation
                    self.timer_id = TimerToken::INVALID;
                    self.fade_start = Some(Instant::now());
                    ctx.request_anim_frame();
                    ctx.request_paint();
                    ctx.set_handled();
                }
                _ => (),
            }
        }
    }

    /// Applies mousewheel scrolling if the event has not already been handled
    pub fn handle_scroll(
        &mut self,
        port: &mut Viewport,
        ctx: &mut EventCtx,
        event: &Event,
        env: &Env,
    ) {
        if !ctx.is_handled() {
            if let Event::Wheel(mouse) = event {
                let mut delta = mouse.wheel_delta.round();
                if self.vertical_scroll_for_horizontal {
                    delta.x = delta.y;
                }
                if port.pan_by(delta) {}
                ctx.request_paint();
                self.reset_scrollbar_fade(|d| ctx.request_timer(d, None), env);
                ctx.set_handled();
            }
        }
    }

    /// Perform any necessary action prompted by a lifecycle event
    ///
    /// Make sure to call on every lifecycle event
    pub fn lifecycle(
        &mut self,
        ctx: &mut LifeCycleCtx,
        event: &LifeCycle,
        env: &Env,
    ) {
        match event {
            LifeCycle::HotChanged(_) => {
                self.reset_scrollbar_fade(|d| ctx.request_timer(d, None), env);
            }
            LifeCycle::Size(_) => {
                // Show the scrollbars any time our size changes
                ctx.request_paint();
                self.reset_scrollbar_fade(|d| ctx.request_timer(d, None), env);
            }
            _ => (),
        }
    }
}

pub struct LapceScroll<T, W> {
    clip: ClipBox<T, W>,
    scroll_component: ScrollComponent,
    hide_bar: bool,
}

impl<T, W: Widget<T>> LapceScroll<T, W> {
    /// Create a new scroll container.
    ///
    /// This method will allow scrolling in all directions if child's bounds
    /// are larger than the viewport. Use [vertical](#method.vertical) and
    /// [horizontal](#method.horizontal) methods to limit scrolling to a specific axis.
    pub fn new(child: W) -> LapceScroll<T, W> {
        Self {
            clip: ClipBox::new(child),
            scroll_component: ScrollComponent::new(),
            hide_bar: false,
        }
    }

    /// Restrict scrolling to the vertical axis while locking child width.
    pub fn vertical(mut self) -> Self {
        self.clip = self
            .clip
            .constrain_vertical(false)
            .constrain_horizontal(true);

        self
    }

    /// Restrict scrolling to the horizontal axis while locking child height.
    pub fn horizontal(mut self) -> Self {
        self.clip = self
            .clip
            .constrain_vertical(true)
            .constrain_horizontal(false);

        self
    }

    pub fn hide_bar(mut self) -> Self {
        self.hide_bar = true;
        self
    }

    pub fn vertical_scroll_for_horizontal(mut self) -> Self {
        self.scroll_component.vertical_scroll_for_horizontal = true;
        self
    }

    /// Returns a reference to the child widget.
    pub fn child(&self) -> &W {
        self.clip.child()
    }

    /// Returns a mutable reference to the child widget.
    pub fn child_mut(&mut self) -> &mut W {
        self.clip.child_mut()
    }

    /// Returns the size of the child widget.
    pub fn child_size(&self) -> Size {
        self.clip.content_size()
    }

    pub fn set_child_size(&mut self, size: Size) {
        self.clip.port.content_size = size;
    }

    /// Returns the current scroll offset.
    pub fn offset(&self) -> Vec2 {
        self.clip.viewport_origin().to_vec2()
    }

    /// Scroll `delta` units.
    ///
    /// Returns `true` if the scroll offset has changed.
    pub fn scroll_by(&mut self, delta: Vec2) -> bool {
        self.clip.pan_by(delta)
    }

    pub fn force_scroll_to(&mut self, point: Point) {
        self.clip.force_pan_to(point)
    }

    pub fn scroll_to(&mut self, point: Point) -> bool {
        self.clip.pan_to(point)
    }

    /// Scroll the minimal distance to show the target rect.
    ///
    /// If the target region is larger than the viewport, we will display the
    /// portion that fits, prioritizing the portion closest to the origin.
    pub fn scroll_to_visible(&mut self, region: Rect, _env: &Env) -> bool {
        self.clip.pan_to_visible(region)
    }

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

impl<T: Data + GetConfig, W: Widget<T>> Widget<T> for LapceScroll<T, W> {
    fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
        let scroll_component = &mut self.scroll_component;
        self.clip.with_port(|port| {
            scroll_component.event(port, ctx, event, data.get_config(), env);
        });
        if !ctx.is_handled() {
            self.clip.event(ctx, event, data, env);
        }

        self.clip.with_port(|port| {
            scroll_component.handle_scroll(port, ctx, event, env);
        });

        match event {
            Event::Command(cmd) if cmd.is(LAPCE_UI_COMMAND) => {
                let command = cmd.get_unchecked(LAPCE_UI_COMMAND);
                if let LapceUICommand::ResetFade = command {
                    scroll_component
                        .reset_scrollbar_fade(|d| ctx.request_timer(d, None), env);
                }
            }
            _ => (),
        }
    }

    fn lifecycle(
        &mut self,
        ctx: &mut LifeCycleCtx,
        event: &LifeCycle,
        data: &T,
        env: &Env,
    ) {
        self.scroll_component.lifecycle(ctx, event, env);
        self.clip.lifecycle(ctx, event, data, env);
    }

    fn update(&mut self, ctx: &mut UpdateCtx, old_data: &T, data: &T, env: &Env) {
        self.clip.update(ctx, old_data, data, env);
    }

    fn layout(
        &mut self,
        ctx: &mut LayoutCtx,
        bc: &BoxConstraints,
        data: &T,
        env: &Env,
    ) -> Size {
        bc.debug_check("Scroll");

        let old_viewport = self.clip.port;
        let child_size = self.clip.layout(ctx, bc, data, env);

        let self_size = bc.constrain(child_size);
        // The new size might have made the current scroll offset invalid. This makes it valid
        // again.
        let _ = self.scroll_by(Vec2::ZERO);
        if old_viewport != self.clip.port {
            self.scroll_component
                .reset_scrollbar_fade(|d| ctx.request_timer(d, None), env);
        }

        self_size
    }

    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
        self.clip.paint(ctx, data, env);
        if !self.hide_bar {
            self.scroll_component.draw_bars(
                ctx,
                &self.clip.viewport(),
                env,
                data.get_config(),
            );
        }
    }
}

pub struct LapcePadding<T, W> {
    left: f64,
    right: f64,
    top: f64,
    bottom: f64,

    child: WidgetPod<T, W>,
}

impl<T, W: Widget<T>> LapcePadding<T, W> {
    pub fn new(insets: impl Into<Insets>, child: W) -> Self {
        let insets = insets.into();
        Self {
            left: insets.x0,
            right: insets.x1,
            top: insets.y0,
            bottom: insets.y1,
            child: WidgetPod::new(child),
        }
    }

    pub fn child_size(&self) -> Size {
        self.child.layout_rect().size()
    }

    pub fn child(&self) -> &W {
        self.child.widget()
    }

    /// Returns a mutable reference to the child widget.
    pub fn child_mut(&mut self) -> &mut W {
        self.child.widget_mut()
    }
}

impl<T: Data, W: Widget<T>> Widget<T> for LapcePadding<T, W> {
    fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
        self.child.event(ctx, event, data, env)
    }

    fn lifecycle(
        &mut self,
        ctx: &mut LifeCycleCtx,
        event: &LifeCycle,
        data: &T,
        env: &Env,
    ) {
        self.child.lifecycle(ctx, event, data, env)
    }

    fn update(&mut self, ctx: &mut UpdateCtx, _old_data: &T, data: &T, env: &Env) {
        self.child.update(ctx, data, env);
    }

    fn layout(
        &mut self,
        ctx: &mut LayoutCtx,
        bc: &BoxConstraints,
        data: &T,
        env: &Env,
    ) -> Size {
        bc.debug_check("Padding");

        let hpad = self.left + self.right;
        let vpad = self.top + self.bottom;

        let child_bc = bc.shrink((hpad, vpad));
        let size = self.child.layout(ctx, &child_bc, data, env);
        let origin = Point::new(self.left, self.top);
        self.child.set_origin(ctx, data, env, origin);

        let my_size = Size::new(size.width + hpad, size.height + vpad);
        let my_insets = self.child.compute_parent_paint_insets(my_size);
        ctx.set_paint_insets(my_insets);
        my_size
    }

    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
        self.child.paint(ctx, data, env);
    }
}

pub struct LapceIdentityWrapper<W> {
    id: WidgetId,
    inner: W,
}

impl<W> LapceIdentityWrapper<W> {
    /// Assign an identity to a widget.
    pub fn wrap(inner: W, id: WidgetId) -> LapceIdentityWrapper<W> {
        Self { id, inner }
    }

    pub fn inner(&self) -> &W {
        &self.inner
    }

    pub fn inner_mut(&mut self) -> &mut W {
        &mut self.inner
    }
}

impl<T: Data, W: Widget<T>> Widget<T> for LapceIdentityWrapper<W> {
    fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
        self.inner.event(ctx, event, data, env);
    }

    fn lifecycle(
        &mut self,
        ctx: &mut LifeCycleCtx,
        event: &LifeCycle,
        data: &T,
        env: &Env,
    ) {
        self.inner.lifecycle(ctx, event, data, env)
    }

    fn update(&mut self, ctx: &mut UpdateCtx, old_data: &T, data: &T, env: &Env) {
        self.inner.update(ctx, old_data, data, env);
    }

    fn layout(
        &mut self,
        ctx: &mut LayoutCtx,
        bc: &BoxConstraints,
        data: &T,
        env: &Env,
    ) -> Size {
        self.inner.layout(ctx, bc, data, env)
    }

    fn paint(&mut self, ctx: &mut PaintCtx, data: &T, env: &Env) {
        self.inner.paint(ctx, data, env);
    }

    fn id(&self) -> Option<WidgetId> {
        Some(self.id)
    }
}