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Make scrollable programmatically scrollable for some use cases, add s…
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…nap_to_bottom by default
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@yusdacra
yusdacra committed Nov 14, 2020
1 parent 62295f5 commit 98fe127
Showing 1 changed file with 156 additions and 65 deletions.
221 changes: 156 additions & 65 deletions native/src/widget/scrollable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ use crate::{
Rectangle, Size, Vector, Widget,
};

use std::{f32, hash::Hash, u32};
use std::{cell::RefCell, f32, hash::Hash, u32};

/// A widget that can vertically display an infinite amount of content with a
/// scrollbar.
Expand All @@ -23,6 +23,8 @@ pub struct Scrollable<'a, Message, Renderer: self::Renderer> {
scroller_width: u16,
content: Column<'a, Message, Renderer>,
style: Renderer::Style,
on_scroll: Option<Box<dyn Fn(f32, f32) -> Message>>,
snap_to_bottom: bool,
}

impl<'a, Message, Renderer: self::Renderer> Scrollable<'a, Message, Renderer> {
Expand All @@ -40,9 +42,36 @@ impl<'a, Message, Renderer: self::Renderer> Scrollable<'a, Message, Renderer> {
scroller_width: 10,
content: Column::new(),
style: Renderer::Style::default(),
on_scroll: None,
snap_to_bottom: false,
}
}

/// Whether to set the [`Scrollable`] to snap to bottom when the user
/// scrolls to bottom or not. This will keep the scrollable at the bottom
/// even if new content is added to the scrollable.
///
/// [`Scrollable`]: struct.Scrollable.html
pub fn snap_to_bottom(mut self, snap: bool) -> Self {
self.snap_to_bottom = snap;
self
}

/// Sets a function to call when the [`Scrollable`] is scrolled.
///
/// The function takes two `f32` as arguments. First is the percentage of
/// where the scrollable is at right now. Second is the percentage of where
/// the scrollable was *before*. `0.0` means top and `1.0` means bottom.
///
/// [`Scrollable`]: struct.Scrollable.html
pub fn on_scroll<F>(mut self, message_constructor: F) -> Self
where
F: 'static + Fn(f32, f32) -> Message,
{
self.on_scroll = Some(Box::new(message_constructor));
self
}

/// Sets the vertical spacing _between_ elements.
///
/// Custom margins per element do not exist in Iced. You should use this
Expand Down Expand Up @@ -210,7 +239,7 @@ where
.map(|scrollbar| scrollbar.is_mouse_over(cursor_position))
.unwrap_or(false);

let event_status = {
let mut event_status = {
let cursor_position = if is_mouse_over && !is_mouse_over_scrollbar {
Point::new(
cursor_position.x,
Expand All @@ -235,64 +264,44 @@ where
)
};

if let event::Status::Captured = event_status {
return event::Status::Captured;
}

if is_mouse_over {
match event {
Event::Mouse(mouse::Event::WheelScrolled { delta }) => {
match delta {
mouse::ScrollDelta::Lines { y, .. } => {
// TODO: Configurable speed (?)
self.state.scroll(y * 60.0, bounds, content_bounds);
if let event::Status::Ignored = event_status {
self.state.prev_offset = self.state.offset(bounds, content_bounds);

if is_mouse_over {
match event {
Event::Mouse(mouse::Event::WheelScrolled { delta }) => {
match delta {
mouse::ScrollDelta::Lines { y, .. } => {
// TODO: Configurable speed (?)
self.state.scroll(
y * 60.0,
bounds,
content_bounds,
);
}
mouse::ScrollDelta::Pixels { y, .. } => {
self.state.scroll(y, bounds, content_bounds);
}
}
mouse::ScrollDelta::Pixels { y, .. } => {
self.state.scroll(y, bounds, content_bounds);
}
}

return event::Status::Captured;
event_status = event::Status::Captured;
}
_ => {}
}
_ => {}
}
}

if self.state.is_scroller_grabbed() {
match event {
Event::Mouse(mouse::Event::ButtonReleased(
mouse::Button::Left,
)) => {
self.state.scroller_grabbed_at = None;
if self.state.is_scroller_grabbed() {
match event {
Event::Mouse(mouse::Event::ButtonReleased(
mouse::Button::Left,
)) => {
self.state.scroller_grabbed_at = None;

return event::Status::Captured;
}
Event::Mouse(mouse::Event::CursorMoved { .. }) => {
if let (Some(scrollbar), Some(scroller_grabbed_at)) =
(scrollbar, self.state.scroller_grabbed_at)
{
self.state.scroll_to(
scrollbar.scroll_percentage(
scroller_grabbed_at,
cursor_position,
),
bounds,
content_bounds,
);

return event::Status::Captured;
event_status = event::Status::Captured;
}
}
_ => {}
}
} else if is_mouse_over_scrollbar {
match event {
Event::Mouse(mouse::Event::ButtonPressed(
mouse::Button::Left,
)) => {
if let Some(scrollbar) = scrollbar {
if let Some(scroller_grabbed_at) =
scrollbar.grab_scroller(cursor_position)
Event::Mouse(mouse::Event::CursorMoved { .. }) => {
if let (Some(scrollbar), Some(scroller_grabbed_at)) =
(&scrollbar, self.state.scroller_grabbed_at)
{
self.state.scroll_to(
scrollbar.scroll_percentage(
Expand All @@ -303,18 +312,70 @@ where
content_bounds,
);

self.state.scroller_grabbed_at =
Some(scroller_grabbed_at);

return event::Status::Captured;
event_status = event::Status::Captured;
}
}
_ => {}
}
} else if is_mouse_over_scrollbar {
match event {
Event::Mouse(mouse::Event::ButtonPressed(
mouse::Button::Left,
)) => {
if let Some(scrollbar) = &scrollbar {
if let Some(scroller_grabbed_at) =
scrollbar.grab_scroller(cursor_position)
{
self.state.scroll_to(
scrollbar.scroll_percentage(
scroller_grabbed_at,
cursor_position,
),
bounds,
content_bounds,
);

self.state.scroller_grabbed_at =
Some(scroller_grabbed_at);

event_status = event::Status::Captured;
}
}
}
_ => {}
}
_ => {}
}
}

event::Status::Ignored
if let event::Status::Captured = event_status {
if self.snap_to_bottom {
let new_offset = self.state.offset(bounds, content_bounds);

if new_offset < self.state.prev_offset {
self.state.snap_to_bottom = false;
} else {
let scroll_perc = new_offset as f32
/ (content_bounds.height - bounds.height);

if scroll_perc >= 1.0 - f32::EPSILON {
self.state.snap_to_bottom = true;
}
}
}

if let Some(on_scroll) = &self.on_scroll {
messages.push(on_scroll(
self.state.offset(bounds, content_bounds) as f32
/ (content_bounds.height - bounds.height),
self.state.prev_offset as f32
/ (content_bounds.height - bounds.height),
));
}

event::Status::Captured
} else {
event::Status::Ignored
}
}

fn draw(
Expand All @@ -328,6 +389,15 @@ where
let bounds = layout.bounds();
let content_layout = layout.children().next().unwrap();
let content_bounds = content_layout.bounds();

if self.state.snap_to_bottom {
self.state.scroll_to(1.0, bounds, content_bounds);
}

if let Some(scroll_to) = self.state.scroll_to.borrow_mut().take() {
self.state.scroll_to(scroll_to, bounds, content_bounds);
}

let offset = self.state.offset(bounds, content_bounds);
let scrollbar = renderer.scrollbar(
bounds,
Expand Down Expand Up @@ -409,10 +479,13 @@ where
/// The local state of a [`Scrollable`].
///
/// [`Scrollable`]: struct.Scrollable.html
#[derive(Debug, Clone, Copy, Default)]
#[derive(Debug, Default, Clone)]
pub struct State {
scroller_grabbed_at: Option<f32>,
offset: f32,
prev_offset: u32,
snap_to_bottom: bool,
offset: RefCell<f32>,
scroll_to: RefCell<Option<f32>>,
}

impl State {
Expand All @@ -438,7 +511,8 @@ impl State {
return;
}

self.offset = (self.offset - delta_y)
let offset_val = *self.offset.borrow();
*self.offset.borrow_mut() = (offset_val - delta_y)
.max(0.0)
.min((content_bounds.height - bounds.height) as f32);
}
Expand All @@ -452,15 +526,32 @@ impl State {
/// [`Scrollable`]: struct.Scrollable.html
/// [`State`]: struct.State.html
pub fn scroll_to(
&mut self,
&self,
percentage: f32,
bounds: Rectangle,
content_bounds: Rectangle,
) {
self.offset =
*self.offset.borrow_mut() =
((content_bounds.height - bounds.height) * percentage).max(0.0);
}

/// Marks the scrollable to scroll to `perc` percentage (between 0.0 and 1.0)
/// in the next `draw` call.
///
/// [`Scrollable`]: struct.Scrollable.html
/// [`State`]: struct.State.html
pub fn scroll_to_percentage(&mut self, perc: f32) {
*self.scroll_to.borrow_mut() = Some(perc.max(0.0).min(1.0));
}

/// Marks the scrollable to scroll to bottom in the next `draw` call.
///
/// [`Scrollable`]: struct.Scrollable.html
/// [`State`]: struct.State.html
pub fn scroll_to_bottom(&mut self) {
self.scroll_to_percentage(1.0);
}

/// Returns the current scrolling offset of the [`State`], given the bounds
/// of the [`Scrollable`] and its contents.
///
Expand All @@ -470,7 +561,7 @@ impl State {
let hidden_content =
(content_bounds.height - bounds.height).max(0.0).round() as u32;

self.offset.min(hidden_content as f32) as u32
self.offset.borrow().min(hidden_content as f32) as u32
}

/// Returns whether the scroller is currently grabbed or not.
Expand Down

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