There's no good reason for calling this helper function without a `url` parameter, and this way we can prevent that from happening.
Note how the `PDFOutlineViewer` call-site was already doing the right thing here, and only the `LinkAnnotationElement` call-site needed a small adjustment to make it work.
This includes the information in the core and display layers. The
date parsing logic from the document properties is rewritten according
to the specification and now includes unit tests.
Moreover, missing unit tests for the color of a popup annotation have
been added.
Finally the styling of the popup is changed slightly to make the text a
bit smaller (it's currently quite large in comparison to other viewers)
and to make the drop shadow a bit more subtle. The former is done to be
able to easily include the modification date in the popup similar to how
other viewers do this.
This will further help reduce the amount of image data that's currently being held alive, by explicitly removing the `src` attribute.
Please note that this is mostly relevant for browsers which do not support `URL.createObjectURL`, or where `disableCreateObjectURL` was manually set by the user, since `blob:` URLs will be revoked (see the previous patch).
However, using `about:memory` (in Firefox) it does seem that this may also be generally helpful, given that calling `URL.revokeObjectURL` won't invalidate the image data itself (as far as I can tell).
Natively supported JPEG images are sent as-is, using a `blob:` or possibly a `data` URL, to the main-thread for loading/decoding.
However there's currently no attempt at releasing these resources, which are held alive by `blob:` URLs, which seems unfortunately given that images can be arbitrarily large.
As mentioned in https://developer.mozilla.org/en-US/docs/Web/API/URL/createObjectURL the lifetime of these URLs are tied to the document, hence they are not being removed when a page is cleaned-up/destroyed (e.g. when being removed from the `PDFPageViewBuffer` in the viewer).
This is easy to test with the help of `about:memory` (in Firefox), which clearly shows the number of `blob:` URLs becomming arbitrarily large *without* this patch. With this patch however the `blob:` URLs are immediately release upon clean-up as expected, and the memory consumption should thus be considerably reduced for long documents with (simple) JPEG images.
Given that the function is (purposely) independent of the verbosity level and that its message is worded to only apply on the main-thread, there's no reason to duplicate this across the built `pdf.js`/`pdf.worker.js` files.
This file (currently) contains not only DOM-specific helper functions/classes, but is used generally for various helper code relevant for main-thread functionality.
