perspective 2.0.0

A data visualization and analytics component, especially well-suited for large and/or streaming datasets.
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////////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2018, the Perspective Authors.
//
// This file is part of the Perspective library, distributed under the terms
// of the Apache License 2.0.  The full license can be found in the LICENSE
// file.

use std::future::Future;

use wasm_bindgen::JsCast;
use web_sys::*;

use crate::js::plugin::JsPerspectiveViewerPlugin;
use crate::utils::ApiResult;

/// Given an async `task` which draws `plugin`, activates the plugin in stages
/// to prevent screen shearing.  First, and plugin is appended ot the DOM with
/// opacity 0, then rendered.  After rendering, the previous plugin is removed
/// and the opacity is set back to 1.
///
/// # Arguments
/// - `viewer` the root `<perspective-viewer>` element.
/// - `plugin` the plugin custom element.
/// - `task` an async task which renders the plugin.
pub async fn activate_plugin<T>(
    viewer: &HtmlElement,
    plugin: &JsPerspectiveViewerPlugin,
    task: impl Future<Output = ApiResult<T>>,
) -> ApiResult<T> {
    let html_plugin = plugin.unchecked_ref::<HtmlElement>();
    if html_plugin.parent_node().is_none() {
        html_plugin.style().set_property("opacity", "0")?;
        viewer.append_child(html_plugin)?;
    }

    let result = task.await;
    let first_child = viewer.children().item(0).unwrap();
    if first_child != *plugin.unchecked_ref::<Element>() {
        viewer.remove_child(&first_child)?;
    }

    html_plugin.style().set_property("opacity", "1")?;
    result
}