The PDF.js API has only ever supported accessing the original file ID, however the second one that (should) exist in *modified* documents have thus far been completely inaccessible through the API.
That seems like a simple oversight, caused e.g. by the viewer not needing it, since it really shouldn't hurt to provide API-users with the ability to check if a PDF document has been modified since its creation.[1]
Please refer to https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/PDF32000_2008.pdf#G13.2261661 for additional information.
For an example of how to update existing code to use the new API, please see the changes in the `web/app.js` file included in this patch.
*Please note:* While I'm not sure if we'll ever be able to remove the old `PDFDocumentProxy.fingerprint` getter, given that it's existed since "forever", that probably isn't a big deal given that it's now limited to only `GENERIC`-builds.
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[1] Although this obviously depends on the PDF software following the specification, by updating the second file ID as intended.
Please refer to https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm
Based on that information, and manually testing our code, the implementation in `cloneValue` has the following shortcomings:
- Attempting to clone `function`s is only prevented when they're part of an Object, but is currently allowed when they occur standalone.
- Cloning of `Symbol`s is currently not prevented, which it should be since the native structured clone algorithm throws.
- Any disallowed types should be checked first, to reduce the risk of future changes accidentally allowing something that shouldn't be supported.
Using `instanceof Object` is generally problematic, since it's not guaranteed to always do the right thing for all Objects.
(I stumbled upon this while working on another patch, when I noticed that the `outlineView` was broken with workers disabled.)
- it aims to fix#13583;
- fix the switch to breakBefore target;
- force the layout of an unsplittable element on an empty page;
- don't fail when there is horizontal overflow (except in lr-tb);
- handle correctly overflow in the same content area (bug 1717805, bug 1717668);
- fix a typo in radial gradient first argument.
- some pdf use some fonts which are not embedded or they don't have any width array or don't have any css info (e.g. for standard fonts or Arial).
- so add widths arrays for Liberation fonts in order to compute the ones for other fonts in using scale factors array.
- the break element has been deprecated in XFA 2.4 but some old documents can use it, so replace it with one (or more) of its possible substitutions:
- breakBefore;
- breakAfter;
- overflow.
- when binding (after parsing) we get a map between some template nodes and some data nodes;
- so set user data in input handlers in using data node uids in the annotation storage;
- to save the form, just put the value we have in the storage in the correct data nodes, serialize the xml as a string and then write the string at the end of the pdf using src/core/writer.js;
- fix few bugs around data bindings:
- the "Off" issue in Bug 1716980.
According to a comment in `readCmapTable`, we're assuming that the cmap tables (when more than one exist) are sorted in ascending order. If that's not the case, keep checking the following cmap tables in order to fix the referenced issue.
- when the CSS line-height property is set to 'normal' then the value depends of the user agent. So use a line height based on the font itself and if for any reasons this value is not available use 1.2 as default.
- it's a partial fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1717681.
This patch provides an overall simpler *and* more consistent way of handling the `viewport` parameter during printing of XFA forms, since it's now again guaranteed to always be an instance of `PageViewport`.
Furthermore, for anyone attempting to e.g. implement custom printing of XFA forms this probably cannot hurt either.
Apparently some really bad PDF software can create documents with *empty* `Name`-entries, which we thus need to somehow deal with.
While I don't know if this patch is necessarily the best solution, it should at least ensure that the *empty* `Name`-instance cannot accidentally match a proper `Name`-instance (and it doesn't require changes to a lot of existing code).[1]
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[1] I briefly considered using a `Symbol` rather than an Object, but quickly decided against that since the former one [is not clonable](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm#supported_types) and `Name`-instances may be sent to the API.
- it aims to fix https://bugzilla.mozilla.org/show_bug.cgi?id=1716838.
- some fonts in the pdf in the bug where bold when they shouldn't so write the font properties in the html to avoid to use some wrong inherited ones.
- partial fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1716980;
- some pdf can contain an invalid font family (e.g. 'Windings 3') so in this case remove the space;
- the font family in typeface attribute doesn't always match the one defined in the FontDescriptor dictionary.
Given that we're not imposing any font-type restrictions[1] in the non-/FontDescriptor case, it's not really clear to me why we'd actually need to do that in the general case.
Please note that there's some *expected* movement, all of which should be improvements, in the `fips197.pdf` file with this patch.
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[1] With the exception of Type3-fonts, of course.
