*Please note:* While I don't have a document that this patches fixes, the current code is however not entirely correct as far as I can tell.
Looking at how the `Widths` array is parsed in `PartialEvaluator.extractWidths`, it's clear that the implementation in `PartialEvaluator.preEvaluateFont` is a bit too simplistic. In particular, by only wrapping the data into a TypedArray, there's no attempt to handle *indirect* objects which could potentially lead to colliding `hash`es being computed.
To hopefully help prevent any future bugs, make sure that composite/non-composite fonts cannot accidentally get matching `hash`es. Given the differences between those font types, that's very unlikely to be useful or even correct in general.
Without this some *composite* fonts may incorrectly end up with matching `hash`es, thus breaking rendering since we'll not actually try to load/parse some of the fonts.
*Please note:* Given that the document, in the referenced issue, doesn't embed *any* of its fonts there's no guarantee that it renders correctly in all configurations even with this patch.
With modern JavaScript modules, where you explicitly list the properties that should be exported, it's no longer necessary to wrap *all* of the code within one file into a top-level closure.[1]
This patch reduces the size, of even the *built* `pdf.worker.js` file, since there's now a lot less unnecessary whitespace.
---
[1] For files which contain *different* functionality, some closures may however still make sense in order to separate the code.
It might be possible to remove some of those cases later, e.g. once private class fields becomes generally available/usable in browsers.
With modern JavaScript modules, where you explicitly list the properties that should be exported, it's no longer necessary to wrap all of the code in a closure.[1]
This patch also tries to clean-up/improve a couple of the existing JSDoc-comments.
---
[1] This reduces the size, even of the *built* `pdf.js` file, since there's now a lot less unnecessary whitespace.
*My apologies for breaking this; thankfully PR 13303 hasn't reach mozilla-central yet.*
It's (obviously) necessary to initialize a `PredictorStream`-instance fully, since otherwise breakage may occur if there's errors during the actual stream parsing.
To reproduce this issue, try opening the PDF document from issue 13051 locally and observe the following message in the console:
```
Warning: Invalid stream: "ReferenceError: this hasn't been initialised - super() hasn't been called"
```
- app.alert and few other function can use an object as parameter ({cMsg: ...});
- support app.alert with a question and a yes/no answer;
- update field siblings when one is changed in an action;
- stop calculation if calculate is set to false in the middle of calculations;
- get a boolean for checkboxes when they've been set through annotationStorage instead of a string.
Also, removes a couple of unnecessary local variables in the `Stepper.breakIt` method.
Finally, this patch also disables the ESLint `no-var` rule, in preparation for the next patch, for a couple of data-structures that need to remain globally available.
It shouldn't be possible for the `getBytes`-call to throw a `MissingDataException`, since all resources are loaded *before* e.g. font-parsing ever starts; see f0817015bd/src/core/object_loader.js (L111-L126)
Furthermore, even if we'd *somehow* re-throw a `MissingDataException` here that still won't help considering where the `Type1Font`-instance is created. Note how in the `Font`-constructor we simply catch any errors and fallback to a standard font, which means that a `MissingDataException` would just lead to rendering errors anyway; see f0817015bd/src/core/fonts.js (L648-L691)
All-in-all, it's not possible for a `MissingDataException` to be thrown in `getHeaderBlock` and this code-path can thus be removed.
Obviously the `Font`-class is still *very* large, given particularly how TrueType fonts are handled, however this patch-series at least improves things by moving a number of functions/classes into their own files.
As a follow-up it might make sense to try and re-factor/extract the TrueType parsing into its own file, since all of this code is quite old, however that's probably best left for another time.
For e.g. `gulp mozcentral`, the *built* `pdf.worker.js` files decreases from `1 620 332` to `1 617 466` bytes with this patch-series.
These changes were made automatically, using `gulp lint --fix`.
Given the large size of this patch, the manual fixes are done separately in the next commit.
