Function createOrUpdateImage

libs/echarts/echarts.simple.js:7522–7564

* Caution: User should cache loaded images, but not just count on LRU. * Consider if required images more than LRU size, will dead loop occur? * * @param {string|HTMLImageElement|HTMLCanvasElement|Canvas} newImageOrSrc * @param {HTMLImageElement|HTMLCanvasElement|Canvas} image Existent image. *

(newImageOrSrc, image, hostEl, cb, cbPayload)

 * @return {HTMLImageElement|HTMLCanvasElement|Canvas} image
 */
function createOrUpdateImage(newImageOrSrc, image, hostEl, cb, cbPayload) {
    if (!newImageOrSrc) {
        return image;
    }
    else if (typeof newImageOrSrc === 'string') {

        // Image should not be loaded repeatly.
        if ((image && image.__zrImageSrc === newImageOrSrc) || !hostEl) {
            return image;
        }

        // Only when there is no existent image or existent image src
        // is different, this method is responsible for load.
        var cachedImgObj = globalImageCache.get(newImageOrSrc);

        var pendingWrap = {hostEl: hostEl, cb: cb, cbPayload: cbPayload};

        if (cachedImgObj) {
            image = cachedImgObj.image;
            !isImageReady(image) && cachedImgObj.pending.push(pendingWrap);
        }
        else {
            image = new Image();
            image.onload = image.onerror = imageOnLoad;

            globalImageCache.put(
                newImageOrSrc,
                image.__cachedImgObj = {
                    image: image,
                    pending: [pendingWrap]
                }
            );

            image.src = image.__zrImageSrc = newImageOrSrc;
        }

        return image;
    }
    // newImageOrSrc is an HTMLImageElement or HTMLCanvasElement or Canvas
    else {
        return newImageOrSrc;
    }
}

function imageOnLoad() {
    var cachedImgObj = this.__cachedImgObj;