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Improve the StructTreeLayerBuilder.render method

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In hindsight it occurred to me that there's a couple of smaller issues with this method after it's made asynchronous (in PR 18658).

 - If the `render`-method is invoked back-to-back the existing caching doesn't guarantee that re-parsing won't occur, which we can address by introducing a new (private) promise.

 - If there's any errors fetching and/or parsing the structTree-data, we'd attempt to parse it again on re-rendering despite that being pointless.
This commit is contained in:
Jonas Jenwald 2024-09-04 11:08:56 +02:00
parent d3698223a8
commit 4b8628637a
1 changed files with 18 additions and 6 deletions
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24
web/struct_tree_layer_builder.js
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@ -76,7 +76,9 @@ const HEADING_PATTERN = /^H(\d+)$/;
class StructTreeLayerBuilder { class StructTreeLayerBuilder {
#promise; #promise;
#treeDom = undefined; #treeDom = null;
#treePromise;
#elementAttributes = new Map(); #elementAttributes = new Map();
@ -85,13 +87,23 @@ class StructTreeLayerBuilder {
} }
async render() { async render() {
if (this.#treeDom !== undefined) { if (this.#treePromise) {
return this.#treeDom; return this.#treePromise;
}
const { promise, resolve, reject } = Promise.withResolvers();
this.#treePromise = promise;
try {
this.#treeDom = this.#walk(await this.#promise);
} catch (ex) {
reject(ex);
} }
const treeDom = (this.#treeDom = this.#walk(await this.#promise));
this.#promise = null; this.#promise = null;
treeDom?.classList.add("structTree");
return treeDom; this.#treeDom?.classList.add("structTree");
resolve(this.#treeDom);
return promise;
} }
async getAriaAttributes(annotationId) { async getAriaAttributes(annotationId) {