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Provide visibility based rendering as part of the view api (#7241)

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* first draft

* in preview mode, just show it

* fix unit tests
This commit is contained in:
Scott Bell
2023-11-20 18:19:00 +01:00
committed by GitHub
parent b9ae461b7d
commit 7ce3ed5597
27 changed files with 130 additions and 91 deletions
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88
src/api/nice/NicelyCalled.js
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@ -1,88 +0,0 @@
/*****************************************************************************
* Open MCT, Copyright (c) 2014-2023, United States Government
* as represented by the Administrator of the National Aeronautics and Space
* Administration. All rights reserved.
*
* Open MCT is licensed under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0.
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
* Open MCT includes source code licensed under additional open source
* licenses. See the Open Source Licenses file (LICENSES.md) included with
* this source code distribution or the Licensing information page available
* at runtime from the About dialog for additional information.
*****************************************************************************/
/**
* Optimizes `requestAnimationFrame` calls to only execute when the element is visible in the viewport.
*/
export default class NicelyCalled {
#element;
#isIntersecting;
#observer;
#lastUnfiredFunc;
/**
* Constructs a NicelyCalled instance to manage visibility-based requestAnimationFrame calls.
*
* @param {HTMLElement} element - The DOM element to observe for visibility changes.
* @throws {Error} If element is not provided.
*/
constructor(element) {
if (!element) {
throw new Error(`Nice visibility must be created with an element`);
}
this.#element = element;
this.#isIntersecting = true;
this.#observer = new IntersectionObserver(this.#observerCallback);
this.#observer.observe(this.#element);
this.#lastUnfiredFunc = null;
}
#observerCallback = ([entry]) => {
if (entry.target === this.#element) {
this.#isIntersecting = entry.isIntersecting;
if (this.#isIntersecting && this.#lastUnfiredFunc) {
window.requestAnimationFrame(this.#lastUnfiredFunc);
this.#lastUnfiredFunc = null;
}
}
};
/**
* Executes a function within requestAnimationFrame if the observed element is visible.
* If the element is not visible, the function is stored and called when the element becomes visible.
* Note that if called multiple times while not visible, only the last execution is stored and executed.
*
* @param {Function} func - The function to execute.
* @returns {boolean} True if the function was executed immediately, false otherwise.
*/
execute(func) {
if (this.#isIntersecting) {
window.requestAnimationFrame(func);
return true;
} else {
this.#lastUnfiredFunc = func;
return false;
}
}
/**
* Stops observing the element for visibility changes and cleans up resources to prevent memory leaks.
*/
destroy() {
this.#observer.unobserve(this.#element);
this.#element = null;
this.#isIntersecting = null;
this.#observer = null;
this.#lastUnfiredFunc = null;
}
}