In implementing caret browsing mode in pdf.js, I didn't notice that selectstart isn't always triggered.
So this patch removes the use of selectstart and rely only on selectionchange.
In order to simplify the selection management, the selection code is moved in the AnnotationUIManager:
- it simplifies the code;
- it allows to have only one listener for selectionchange instead of having one by visible page
for selectstart.
I had to add a delay in the integration tests for highlighting (there's a comment with an explanation),
it isn't really nice, but it's the only way I found and in real life there always is a delay between
press and release.
The function caretPositionFromPoint return the position within the last visible element
and sometimes there are some elements on top of the ones in the text layer.
So the idea is to hide the visible elements which aren't in the text layer in order
to get the right caret position.
*Please note:* This is a micro optimization, hence I fully understand if the patch is rejected.
Currently we create two temporary Arrays and have to iterate twice in total when building the final `hexNumbers` Array.
With this patch there's only one temporary Array and a single iteration required to build the final `hexNumbers` Array.
When highlighting, the annotation editor layer is disabled to get pointer events
from the text layer, but the annotation layer must be then disabled either in
order to avoid bad interactions.
Previously we'd simply export this directly from `web/app_options.js`, which meant that it'd be technically possible to *accidentally* modify the `compatibilityParams` Object when accessing it.
To avoid this we instead introduce a new `AppOptions`-method that is used to lookup data in `compatibilityParams`, which means that we no longer need to export this Object.
Based on these changes, it's now possible to simplify some existing code in `AppOptions` by taking full advantage of the nullish coalescing (`??`) operator.
Given that the "PREFERENCE" kind is used e.g. to generate the preference-list for the Firefox PDF Viewer, those options need to be carefully validated.
With this patch we'll now check this unconditionally in development mode, during testing, and when creating the preferences in the gulpfile.
Over time, as we've started relying more and more on import maps, the number of aliases have increased a lot. This is now affecting the size and readability of `createWebpackConfig`, which was already fairly large and complex, hence moving the aliases to their own function should help improve things a little bit.
As part of the changes in PR 17686 we "accidentally" enabled source-maps for the *minified* builds, which seems unnecessary since those have never been included in the `pdfjs-dist` output.
Locally this patch reduces the run-time of `gulp minified` by ~15 percent.
Rather than first building the library and then use Terser "manually" to minify the files, we can utilize a Webpack plugin to combine these steps which helps to simplify the gulpfile.
