This isn't directly part of the official API, and having this class in its own file could help avoid future changes (e.g. issue 18148) affecting the size of the `src/display/api.js` file unnecessarily.
Given that this file represents the official API, it's difficult to avoid it becoming fairly large as we add new functionality. However, it also contains a couple of smaller (and internal) helpers that we can move into a new utils-file.
Also, we inline the `DEFAULT_RANGE_CHUNK_SIZE` constant since it's only used *once* and its value has never been changed in over a decade.
To make it easier to tell which PDF.js version/commit that the *built* files correspond to, they have (since many years) included `pdfjsVersion` and `pdfjsBuild` constants with that information.
As currently implemented this has a few shortcomings:
- It requires manually adding the code, with its preprocessor statements, in all relevant files.
- It requires ESLint disable statements, since it's obviously unused code.
- Being unused, this code is removed in the minified builds.
- This information would be more appropriate as comments, however Babel discards all comments during building.
- It would be helpful to have this information at the top of the *built* files, however it's being moved during building.
To address all of these issues, we'll instead utilize Webpack to insert the version/commit information as a comment placed just after the license header.
We have a fallback for the common case of Type3 fonts without a /FontDescriptor dictionary, however we also need to handle the case where it's present but lacking the required /FontName entry.
Given that Node.js has full support for the Fetch API since version 21, see the "History" data at https://nodejs.org/api/globals.html#fetch, it seems unnecessary for us to manually check for various globals before using it.
Since our primary development target is browsers in general, and Firefox in particular, being able to remove Node.js-specific compatibility code is always helpful.
Note that we still, for now, support Node.js version 20 and if the relevant globals are not available then Errors will instead be thrown from within the `PDFFetchStream` class.
This allows us to simply invoke `PDFWorker.create` unconditionally from the `getDocument` function, without having to manually check if a global `workerPort` is available first.
*This is something that occurred to me when reviewing the latest PDF.js update in mozilla-central.*
Currently we duplicate essentially the same code in both the `OutputScale.prototype.limitCanvas` and `PDFPageDetailView.prototype.update` methods, which seems unnecessary, and to avoid that we introduce a new `OutputScale.capPixels` method that is used to compute the maximum canvas pixels.
When the /OpenAction data is an Array we're currently using it as-is which could theoretically cause problems in corrupt PDF documents, hence we ensure that a "raw" destination is actually valid. (This change is covered by existing unit-tests.)
*Note:* In the Dictionary case we're using the `Catalog.parseDestDictionary` method, which already handles all of the necessary validation.
This way it helps to reduce the overall canvas dimensions and make the rendering faster.
The drawback is that when scrolling, the page can be blurry in waiting for the rendering.
The default value is 200% on desktop and will be 100% for GeckoView.
The effect is probably not even measurable, however this patch ever so slightly reduces the asynchronicity in the `fieldObjects` getter. These changes should be safe since:
- We're inside of the `PDFDocument`-class and the `annotationGlobals`-getter, which will always return a (shadowed) Promise and won't throw `MissingDataException`s, can be accessed directly without going through the `BasePdfManager`-instance.
- The `acroForm`-dictionary can be accessed through the `annotationGlobals`-data, removing the need to "manually" look it up and thus the need for using `Promise.all` here.
- We can also lookup the /Fields-data, in the `acroForm`-dictionary, synchronously since the initial `formInfo.hasFields` check guarantees that it's available.
Currently we repeat the same identical code five times in the `Page`-class when creating a `PartialEvaluator`-instance, which given the number of parameters it needs seems like unnecessary duplication.
The `ObjectLoader.prototype.load` method has a fast-path, which avoids any lookup/parsing if the entire PDF document is already loaded.
However, we still need to create an `ObjectLoader`-instance which seems unnecessary in that case.
Hence we introduce a *static* `ObjectLoader.load` method, which will help avoid creating `ObjectLoader`-instances needlessly and also (slightly) shortens the call-sites.
To ensure that the new method will be used, we extend the `no-restricted-syntax` ESLint rule to "forbid" direct usage of `new ObjectLoader()`.
Given that all the methods are already asynchronous we can just use `await` more throughout this code, rather than having to explicitly return function-calls and `undefined`.
Note also how none of the `ObjectLoader.prototype.load` call-sites use the return value.
Rather than "manually" invoking the methods from the `src/core/worker.js` file we introduce a single `PDFDocument`-method that handles this for us, and make the current methods private.
Since this code is only invoked at most *once* per document, and only for XFA documents, we can use `BasePdfManager.prototype.ensureDoc` directly rather than needing a stand-alone method.
Currently we repeat virtually the same code when calling the `PartialEvaluator.prototype.handleSetFont` method, which we can avoid by introducing an inline helper function.
Considering the name of the method, and how it's actually being used, you'd expect it to return a boolean value.
Given how it's currently being used this inconsistency doesn't cause any issues, however we should still fix this.
Rather than having a dedicated `BasePdfManager`-method for this one call-site we can instead change `PDFDocument.prototype.serializeXfaData` to a non-async method, that we invoke via `BasePdfManager.prototype.ensureDoc`.
Currently we create an intermediate `Dict` during parsing, however that seems unnecessary since (note especially the second point):
- The `NameOrNumberTree.prototype.getAll` method will already resolve any references, as needed, during parsing.
- The `Catalog.prototype.xfaImages` getter is invoked, via the `BasePdfManager`-instance, such that any `MissingDataException`s are already handled correctly.
Currently *some* of the links[1] on page three of the `issue19835.pdf` test-case aren't clickable, since the destination (of the LinkAnnotation) becomes empty.
The reason is that these destinations include the character `\x1b`, which is interpreted as the start of a Unicode escape sequence specifying the language of the string; please refer to section [7.9.2.2 Text String Type](https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf#G6.1957385) in the PDF specification.
Hence it seems that we need a way to optionally disable that behaviour, to avoid a "badly" formatted string from becoming empty (or truncated), at least for cases where we are:
- Parsing named destinations[2] and URLs.
- Handling "strings" that are actually /Name-instances.
- Building a lookup Object/Map based on some PDF data-structure.
*NOTE:* The issue that prompted this patch is obviously related to destinations, however I've gone through the `src/core/` folder and updated various other `stringToPDFString` call-sites that (directly or indirectly) fit the categories listed above.
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[1] Try clicking on anything on the line containing "Item 7A. Quantitative and Qualitative Disclosures About Market Risk 27".
[2] Unfortunately just skipping `stringToPDFString` in this case would cause other issues, such as the named destination becoming "unusable" in the viewer; see e.g. issues 14847 and 14864.
Whenever we cannot find a destination we'll fallback to checking all destinations, to account for e.g. out-of-order NameTrees, and in those cases any subsequent destination-lookups can be made a tiny bit more efficient by immediately checking the already cached destinations.
