Feature request: ScrollService

[jplatte]

Hey! I think similar to ResizeService it would be good to have a ScrollService in yew. I'm not sure whether it could easily be parameterized over either listening to scroll events on window or an individual element (a 'scroll' event listener on document.documentElement or document.body never fires if the whole page is scrollable, so that's not the solution). Here's my current solution for detecting whole-page scrolling:

use std::fmt;

use stdweb::{js, Value};
use yew::callback::Callback;

/// A service that fires events when the browser window scrolls.
#[derive(Debug)]
pub struct ScrollService;

/// A handle to the event listener for scroll events.
#[must_use]
pub struct ScrollTask(Option<Value>);

impl fmt::Debug for ScrollTask {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("ScrollTask")
    }
}

impl ScrollService {
    /// Creates a new ScrollService.
    pub fn new() -> ScrollService {
        ScrollService
    }

    /// Register a callback that will be called when the browser window resizes.
    pub fn register(&mut self, callback: Callback<()>) -> ScrollTask {
        let callback = move || callback.emit(());
        let handle = js! {
            var callback = @{callback};
            var handle = function() {
                callback();
            };
            window.addEventListener("scroll", handle);
            return handle;
        };
        ScrollTask(Some(handle))
    }
}

impl Drop for ScrollTask {
    fn drop(&mut self) {
        let handle = self.0.take().expect("Scroll task already empty.");
        js! {
            @(no_return)
            window.removeEventListener("scroll", @{handle});
        }
    }
}

[mc1098]

#1842 removes services so this feature request no longer applies.
Seems a shame to close this, I'm not sure if this can be moved to discussions so we don't lose this?

[jplatte]

I've taken a quick look and ported my code to not use this abstraction anymore, though the one above was outdated anyways. This can trivially be implemented using gloo::events::EventListener. Here's how I got rid of it: jplatte/caniuse.rs@8b19841