From 20529ecc4d651ae1f676ccf84384ee80584f5829 Mon Sep 17 00:00:00 2001 From: Yusuf Bera Ertan Date: Sun, 11 Oct 2020 05:58:53 +0300 Subject: [PATCH] Make scrollable programmatically scrollable for some use cases, add snap_to_bottom by default --- native/src/widget/scrollable.rs | 110 +++++++++++++++++++++++++++++--- 1 file changed, 101 insertions(+), 9 deletions(-) diff --git a/native/src/widget/scrollable.rs b/native/src/widget/scrollable.rs index 60ec2d7d2d..fbdcfe03b6 100644 --- a/native/src/widget/scrollable.rs +++ b/native/src/widget/scrollable.rs @@ -4,7 +4,7 @@ use crate::{ Hasher, Layout, Length, Point, 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. @@ -18,6 +18,8 @@ pub struct Scrollable<'a, Message, Renderer: self::Renderer> { scroller_width: u16, content: Column<'a, Message, Renderer>, style: Renderer::Style, + on_scroll: Option Message>>, + snap_to_bottom: bool, } impl<'a, Message, Renderer: self::Renderer> Scrollable<'a, Message, Renderer> { @@ -35,9 +37,36 @@ 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, } } + /// Set the [`Scrollable`] to snap to bottom when the user + /// scrolls to bottom. 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) -> Self { + self.snap_to_bottom = true; + 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(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 @@ -191,6 +220,9 @@ where let content = layout.children().next().unwrap(); let content_bounds = content.bounds(); + self.state.prev_offset = self.state.offset(bounds, content_bounds); + let mut did_scroll = false; + // TODO: Event capture. Nested scrollables should capture scroll events. if is_mouse_over { match event { @@ -204,6 +236,7 @@ where self.state.scroll(y, bounds, content_bounds); } } + did_scroll = true; } _ => {} } @@ -232,7 +265,7 @@ where } Event::Mouse(mouse::Event::CursorMoved { .. }) => { if let (Some(scrollbar), Some(scroller_grabbed_at)) = - (scrollbar, self.state.scroller_grabbed_at) + (&scrollbar, self.state.scroller_grabbed_at) { self.state.scroll_to( scrollbar.scroll_percentage( @@ -242,6 +275,7 @@ where bounds, content_bounds, ); + did_scroll = true; } } _ => {} @@ -251,7 +285,7 @@ where Event::Mouse(mouse::Event::ButtonPressed( mouse::Button::Left, )) => { - if let Some(scrollbar) = scrollbar { + if let Some(scrollbar) = &scrollbar { if let Some(scroller_grabbed_at) = scrollbar.grab_scroller(cursor_position) { @@ -264,6 +298,8 @@ where content_bounds, ); + did_scroll = true; + self.state.scroller_grabbed_at = Some(scroller_grabbed_at); } @@ -273,6 +309,32 @@ where } } + if did_scroll { + 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), + )); + } + } + let cursor_position = if is_mouse_over && !is_mouse_over_scrollbar { Point::new( cursor_position.x, @@ -308,6 +370,15 @@ 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, @@ -389,10 +460,13 @@ 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, - offset: f32, + prev_offset: u32, + snap_to_bottom: bool, + offset: RefCell, + scroll_to: RefCell>, } impl State { @@ -418,7 +492,8 @@ 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); } @@ -432,15 +507,32 @@ 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. /// @@ -450,7 +542,7 @@ 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.