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Restore the MAX_TEXT_DIVS_TO_RENDER limit in the textLayer

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This limit is currently completely non-functional, since the check happens *after* the entire textLayer has been parsed and appended to the DOM. It seems that this has been *accidentally* broken ever since the introduction of `ReadableStream` support.
The reason that this hasn't caused noticeable textLayer-related performance issues in practice is probably because we nowadays manage to coalesce the textLayer into fewer overall DOM elements, whereas years ago many PDF documents ended up with one DOM element *per* glyph.

By moving this check, and thus restoring the functionality, we're also able to remove the `render` helper function and simplify the code.
This commit is contained in:
Jonas Jenwald 2024-05-07 11:37:07 +02:00
parent 30840e411e
commit 8d86e18a32
1 changed files with 16 additions and 27 deletions
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43
src/display/text_layer.js
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@ -16,7 +16,7 @@
/** @typedef {import("./display_utils").PageViewport} PageViewport */
/** @typedef {import("./api").TextContent} TextContent */
import { AbortException, Util } from "../shared/util.js";
import { AbortException, Util, warn } from "../shared/util.js";
import { setLayerDimensions } from "./display_utils.js";
/**
@ -282,23 +282,6 @@ function layout(params) {
}
}
function render(task) {
if (task._canceled) {
return;
}
const textDivs = task._textDivs;
const capability = task._capability;
const textDivsLength = textDivs.length;
// No point in rendering many divs as it would make the browser
// unusable even after the divs are rendered.
if (textDivsLength > MAX_TEXT_DIVS_TO_RENDER) {
capability.resolve();
return;
}
capability.resolve();
}
class TextLayerRenderTask {
#reader = null;
@ -389,7 +372,19 @@ class TextLayerRenderTask {
* @private
*/
_processItems(items) {
const textDivs = this._textDivs,
textContentItemsStr = this._textContentItemsStr;
for (const item of items) {
// No point in rendering many divs as it would make the browser
// unusable even after the divs are rendered.
if (textDivs.length > MAX_TEXT_DIVS_TO_RENDER) {
warn("Ignoring additional textDivs for performance reasons.");
this._processItems = () => {}; // Avoid multiple warnings for one page.
return;
}
if (item.str === undefined) {
if (
item.type === "beginMarkedContentProps" ||
@ -407,7 +402,7 @@ class TextLayerRenderTask {
}
continue;
}
this._textContentItemsStr.push(item.str);
textContentItemsStr.push(item.str);
appendText(this, item);
}
}
@ -435,28 +430,22 @@ class TextLayerRenderTask {
* @private
*/
_render() {
const { promise, resolve, reject } = Promise.withResolvers();
const styleCache = this._styleCache;
const pump = () => {
this.#reader.read().then(({ value, done }) => {
if (done) {
resolve();
this._capability.resolve();
return;
}
Object.assign(styleCache, value.styles);
this._processItems(value.items);
pump();
}, reject);
}, this._capability.reject);
};
this.#reader = this.#textContentSource.getReader();
pump();
promise.then(() => {
render(this);
}, this._capability.reject);
}
}