- Update the `LinkAnnotationElement._bindJSAction` call-site to actually agree with the JSDocs, by passing in the `data`.
- Prevent the links created by `LinkAnnotationElement._bindJSAction` from being displayed with empty hashes; compare with e.g. `LinkAnnotationElement. _bindNamedAction`.
- The overall indentation-level in `WidgetAnnotationElement._setEventListener` can be reduced slightly by using early returns, which improves the overall readability of this method a bit. (We're also able to avoid unnecessary `in` usage here.)
- The code can also be made *slightly* more efficient overall, by moving the `this.data.actions` check into `WidgetAnnotationElement._setEventListeners` instead. This way we can avoid useless `this._setEventListener`-calls when there are no actions present.
- Actually remove the `isDown` property when destroying the scripting-instance.
- Mark all `mouseState` usage as "private" in the various classes.
- Ensure that the `AnnotationLayer` actually treats the parameter as properly *optional*, the same way that the viewer components do.
- For now remove the `mouseState` parameter from the `PDFPageView` class, and keep it only on the `BaseViewer`, since it's questionable if all of the scripting-functionality will work all that well without e.g. a full `BaseViewer`.
- Append the `mouseState` to the JSDoc for the `AnnotationElement` class, and just move its definition into the base-`AnnotationElement` class.
* the goal is to execute actions like Open or OpenAction
* can be tested with issue6106.pdf (auto-print)
* once #12701 is merged, we can add page actions
Similar to other markers that we currently skip, by ignoring the Coding style component (COC) marker we'll at least prevent outright errors (although some JPEG 2000 images may look slightly wrong).
* move set/clear|Timeout/Interval and crackURL code in pdf.js
* remove the "backdoor" in the proxy (used to dispatch event) and so return the dispatch function in the initializer
* remove listeners if an error occured during sandbox initialization
* add support for alert and prompt in the sandbox
* add a function to eval in the global scope
There doesn't seem to be anything definitive about this in
the spec, but from experimenting, it seems acrobat lets
PDFs override the widths of the standard fonts.
I completely missed this previously, but we obviously should remove the scriptElement as well to *really* clean-up everything properly.
Given that there's multiple existing usages of `loadScript` in the code-base, the safest/quickest solution seemed to be to have call-sites opt-in to remove the scriptElement using a new parameter.
This simplifies not just this code, but the unit-tests as well, and should be sufficient as far as I can tell.
Note also that currently, in the *built* `pdf.sandbox.js` file, there's even a line reading `testMode = testMode && false;` because of an accidentally flipped pre-processor statement.
Finally, in the `scripting_spec.js` unit-test, defines `sandboxBundleSrc` at the top of the file to make it easier to find and/or change it when necessary.
Each quadrilateral needs to have its own link element, so the first
quadrilateral can use the already created element, but the next
quadrilaterals need to clone that element.
Not only does this reduce boilerplate since the documentation is the
same for all annotation classes, it also wasn't correct for the
annotation types that support quadpoints since they return an array of
section elements instead of a single one.
There's no good reason, as far as I can tell, to use search-and-replace to include the *stringified* `pdf.scripting.js` file in the built `pdf.sandbox.js` file. Instead we could, and even should, utilize the existing `PDFJSDev.eval(...)`-functionality, which is not only simpler but will also be more efficient as well (no need for a regular expression).
The current location feels somewhat strange, and also inconsistent with the existing way that bundling is done.
Finally, add the version/build numbers at the top of the *built* `pdf.sandbox.js` files, since all other built files include that information given that it's often helpful to be able to easily determine the *exact* version.
*This is a recent regression, which I stumbled upon while working on cleaning-up the gulpfile related to `pdf.sandbox.js` building.*
By placing the `ColorConverters` functionality in the `src/display/display_utils.js` file, you end up including a *significant* chunk of the `pdf.js` file in the built `pdf.scripting.js`/`pdf.sandbox.js` files.
Given that I cannot imagine that this was actually intended, since it inflates the built files with unnecessary/unused code, this moves `ColorConverters` to a new file instead (thus breaking the dependencies).
To hopefully reduce the risk future bugs, along these lines, a big comment is also placed at the top of the new file.
Finally, the `ColorConverters` is converted to a class with static methods, since this felt slightly cleaner overall.
In addition to the existing /Root and /Pages validation, also check that the /Pages-entry actually is a dictionary and that it has a valid /Count-entry.
This way we can avoid picking a trailer candidate which e.g. the `Catalog.numPages` getter will just end up rejecting, thus breaking PDF document loading completely.
Given that we already include the "Content-Disposition"-header filename, when it exists, it shouldn't hurt to also include the information from the "Content-Length"-header.
For PDF documents opened via a URL, which should be a very common way for the PDF.js library to be used, this will[1] thus provide a way of getting the PDF filesize without having to wait for the `getDownloadInfo`-promise to resolve[2].
With these API improvements, we can also simplify the filesize handling in the `PDFDocumentProperties` class.
---
[1] Assuming that the server is correctly configured, of course.
[2] Since that's not *guaranteed* to happen in general, with e.g. `disableAutoFetch = true` set.
* quickjs-eval.js has been generated using https://github.com/mozilla/pdf.js.quickjs/
* lazy load of sandbox code
* Rewrite tests to use the sandbox
* Add a task `watch-sandbox` which update bundle pdf.sandbox.js on change in the sandbox code
- Add support for logical assignment operators, i.e. `&&=`, `||=`, and `??=`, with a Babel-plugin. Given that these required incrementing the ECMAScript version in the ESLint and Acorn configurations, and that platform/browser support is still fairly limited, always transpiling them seems appropriate for now.
- Cache the `hasJSActions` promise in the API, similar to the existing `getAnnotations` caching. With this implemented, the lookup should now be cheap enough that it can be called unconditionally in the viewer.
- Slightly improve cleanup of resources when destroying the `WorkerTransport`.
- Remove the `annotationStorage`-property from the `PDFPageView` constructor, since it's not necessary and also brings it more inline with the `BaseViewer`.
- Update the `BaseViewer.createAnnotationLayerBuilder` method to actaually agree with the `IPDFAnnotationLayerFactory` interface.[1]
- Slightly tweak a couple of JSDoc comments.
---
[1] We probably ought to re-factor both the `IPDFTextLayerFactory` and `IPDFAnnotationLayerFactory` interfaces to take parameter objects instead, since especially the `IPDFAnnotationLayerFactory` one is becoming quite unwieldy. Given that that would likely be a breaking change for any custom viewer-components implementation, this probably requires careful deprecation.
* remove 1st param of _createPopup (almost useless for a method)
* prepend popup div to avoid to have them on top of some highlights (and so "disable" partially mouse events)
* add a ref test for issue #12504
* in some pdf, there are actions with "event.source.hidden = ..."
* in order to handle visibility when printing, annotationStorage is extended to store multiple properties (value, hidden, editable, ...)
* When no actions then set it to null instead of empty object
* Even if a field has no actions, it needs to listen to events from the sandbox in order to be updated if an action changes something in it.
By using optional chaining, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining, it's possible to reduce unnecessary code-repetition in many cases.
Note that these changes also reduce the size of the *built* `pdf.js` file, when `SKIP_BABEL == true` is set, and for the `MOZCENTRAL` build-target that result in a `0.1%` filesize reduction from a simple and mostly mechanical code change.
Note that a number of these cases are covered by existing unit-tests, and a few others only matter for the development/build scripts.
Furthermore, I've also tried to the best of my ability to test each case *manually* to hopefully further reduce the likelihood of this patch introducing any bugs.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-useless-escape
The vast majority of the time, unless a Pattern is active, the `strokeColor`-property contains a "simple" colour value represented by a String. Hence it seems somewhat ridiculous to do a `hasOwnProperty` check on a String, and it's should thus be possible to improve things a tiny bit here.
Unfortunately using a simple `instanceof` check would only work for `TilingPattern`s, but not for the `ShadingIRs` given how they are implemented; see `src/display/pattern_helper.js`. (While that file could probably do with some clean-up, given the age of some of its code, that probably shouldn't happen here.)
Finally, the `this.type = "Pattern"`-property of the various Shadings/TilingPatterns were removed, since I cannot see why it's necessary when we can simply check for a `getPattern` method instead. Note that part of this code even pre-dates the main/worker-thread split, which probably in part explains why it looks the way it does.
The `PartialEvaluator.hasBlendModes` method is necessary to determine if there's any blend modes on a page, which unfortunately requires *synchronous* parsing of the /Resources of each page before its rendering can start (see the "StartRenderPage"-message).
In practice it's not uncommon for certain /Resources-entries to be found on more than one page (referenced via the XRef-table), which thus leads to unnecessary re-fetching/re-parsing of data in `PartialEvaluator.hasBlendModes`.
To improve performance, especially in pathological cases, we can cache /Resources-entries when it's absolutely clear that they do not contain *any* blend modes at all[1]. This way, subsequent `PartialEvaluator.hasBlendModes` calls can be made significantly more efficient.
This patch was tested using the PDF file from issue 6961, i.e. https://github.com/mozilla/pdf.js/files/121712/test.pdf:
```
[
{ "id": "issue6961",
"file": "../web/pdfs/issue6961.pdf",
"md5": "a80e4357a8fda758d96c2c76f2980b03",
"rounds": 100,
"type": "eq"
}
]
```
which gave the following results when comparing this patch against the `master` branch:
```
-- Grouped By browser, page, stat --
browser | page | stat | Count | Baseline(ms) | Current(ms) | +/- | % | Result(P<.05)
------- | ---- | ------------ | ----- | ------------ | ----------- | ---- | ------ | -------------
firefox | 0 | Overall | 100 | 1034 | 555 | -480 | -46.39 | faster
firefox | 0 | Page Request | 100 | 489 | 7 | -482 | -98.67 | faster
firefox | 0 | Rendering | 100 | 545 | 548 | 2 | 0.45 |
firefox | 1 | Overall | 100 | 912 | 428 | -484 | -53.06 | faster
firefox | 1 | Page Request | 100 | 487 | 1 | -486 | -99.77 | faster
firefox | 1 | Rendering | 100 | 425 | 427 | 2 | 0.51 |
```
---
[1] In the case where blend modes *are* found, it becomes a lot more difficult to know if it's generally safe to skip /Resources-entries. Hence we don't cache anything in that case, however note that most document/pages do not utilize blend modes anyway.
* it's faster to generate the color code in using a table for components
* it's very likely a way faster to parse (when setting the color in the canvas)
This fixes only those warnings, as reported by https://lgtm.com/projects/g/mozilla/pdf.js?mode=list, that make sense (as far as I'm concerned).
Hence this patch leaves the following things unaddressed:
- The "recommendation"-category, since it only complains about unused variables. However, note that all of those cases are purposely included and that there's thus ESLint-disable comments added to explictly allow them.
- The "warning"-category, which still contains two complaints. However, as far as I can tell, they are both false positives.
Given first of all the false positives of the LGTM static analyzer, and secondly that we'd need to add (essentially duplicated) disable-comments for the unused variable cases, it's not entirely clear to me if we actually want to work towards including LGTM in the PDF.js project (e.g. running alongside Travis) or if we should just close issue 11965.
Given that the `Map`-pattern apparently has undesirable performance characteristics, change this getter back to using an Object instead and check its size before returning it.
Rather than returning an *empty* Object[1] we should be returning `null` instead, since that's consistent with existing API-functionality.
To avoid having to *manually* track if the Object is empty, this patch also introduces a small helper function to check its size.
As can be seen in `src/core/fonts.js`, this method only accepts *one* parameter, hence it's somewhat difficult to understand what the Annotation-code is actually attempting to do here.
The only possible explanation that I can imagine, is that the intention was initially to call `Font.charToGlyph` *directly* instead. However, note that that'd would not actually have been correct, since that'd ignore one level of font-caching (see `this.charsCache`). Hence the unused arguments are removed, in `src/core/annotation.js`, and the `Font.charToGlyph` method is now marked as "private" as intended.
This patch removes unnecessary escape-sequence in (mostly) strings, as a first step, since the ones in regular expressions probably requires more careful testing (just in case).
The only exception is a regular expression in `src/core/annotation.js`, since we should have both unit- and reference-tests for this code *and* given [this information on MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Character_Classes#Types):
> Inside a character set, the dot loses its special meaning and matches a literal dot.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-useless-escape
Given that `Object.fromEntries` doesn't seem to *guarantee* that a `null` prototype is used, we thus hack around that by using `Object.assign` with `Object.create(null)`.
This provides a work-around to avoid having to conditionally try to initialize the `openAction`-object in multiple places.
Given that `Object.fromEntries` doesn't seem to *guarantee* that a `null` prototype is used, we thus hack around that by using `Object.assign` with `Object.create(null)`.
Different fonts incorrectly end up with *identical* hashes, despite having different /ToUnicode data.
The issue, and it's very interesting that we've apparently not seen it before, appears to be caused by the fact that different /ToUnicode entries share the *same* underlying `ArrayBuffer`, which thus becomes problematic at the `const dataUint32 = new Uint32Array(data.buffer, 0, blockCounts);` line. The simplest solution thus seem to be to just *copy* the input, when it's an `ArrayBuffer`, rather than using it as-is. (Note that if we'd stringified the input, when calling `MurmurHash3_64.update`, the issue would also have been fixed. In this case, we're already creating an unique TypedArray.)
Given that this code is used on the worker-thread, where SystemJS is still used during development, we need to (for now) handle this folder the same way as the `src/core/` one.
Since we no longer use SystemJS to load the unit-tests, there's now nothing that prevents us from using optional chaining and nullish coalescing in the `src/display/` directory.
*Please note:* Once https://bugzilla.mozilla.org/show_bug.cgi?id=1247687 is implemented, and we've removed SystemJS completely, this entire patch can (and even should) be reverted.
This is similar to the existing `getLookupTableFactory` helper function, but is implemented as outlined in issue 6774.
The re-formatting of the tables were done automatically, by using find-and-replace with regular expressions.
For reasons that I don't even pretend to understand, using this particular structure for these *very* long lookup tables allow SystemJS to process the files correctly/quickly and the development viewer thus works as intended.
While the *built* `pdf.worker.js` file still works correctly with these changes, despite these two files being excluded by Babel[1], the development viewer does not because of issues with SystemJS[2] and/or its Babel-plugin (both of which are old).
Furthermore, note also that excluding these two files from Babel-processing isn't *generally* necessary since e.g. the `gulp mozcentral` command works anyway. The explanation is rather that it's actually the source-map generation which fails for these huge sequences when building the `pdf.worker.js` file.
However, not using standard `import`/`export` statements in all files means we also need to use SystemJS when e.e. running the unit-tests. This is very unfortunate, since SystemJS (or its old Babel-version) doesn't support modern ECMAScript features such as e.g. optional chaining and nullish coalescing.
Unfortunately it also seems that https://bugzilla.mozilla.org/show_bug.cgi?id=1247687, which tracks the implementation of worker-modules in Firefox, has stalled since there hasn't been any updates for six months now.
To hopefully address all of the above, this patch is the first in a series that attempts to further reduce our reliance on SystemJS.
---
[1] The only difference being how the dependencies are handled, in the Webpack-bundled file.
[2] Parsing takes way too long and consumes too much memory, thus rendering the development viewer essentially unusable.
This brings the new `pdf.scripting.js` bundling more in-line with the pre-existing handling for the `pdf.js`/`pdf.worker.js` files:
- Add a new `src/pdf.scripting.js` file as the entry-point for the build scripts.
- Add the version/build numbers at the top of the *built* `pdf.scripting.js` files, since all other built files include that information given that it's often helpful to be able to easily determine the *exact* version.
- Tweak the `createScriptingBundle` in the gulp-file, since it looks like a little bit too much copy-and-paste in the variable names.
- Handle the arguments correctly in `PartialEvaluator.handleColorN`.
For TilingPatterns with a base-ColorSpace, we're currently using the `args` when computing the color. However, as can be seen we're passing the Array as-is to the `ColorSpace.getRgb` method, which means that the `Name` is included as well.[1]
Thankfully this hasn't, as far as I know, caused any actual bugs, but that may be more luck than anything else given how the `ColorSpace` code is implemented. This can be easily fixed though, simply by popping the `Name`-object off of the `args` Array.
- Cache TilingPatterns using the `Name`-string, rather than the object directly.
This is not only consistent with other caches in `PartialEvaluator`, but importantly it also ensures that the cache lookup always works correctly. Note that since `Name`-objects, similar to other primitives, uses a cache themselves a *manually* triggered `cleanup`-call could thus (theoretically) cause the `LocalTilingPatternCache` to not find an existing entry. While the likelihood of this happening is *extremely* small, it's still something that we should fix.
---
[1] The `args` Array can e.g. look like this: `[0.043, 0.09, 0.188, 0.004, /P1]`, which means that we're passing in the `Name`-object to the `ColorSpace` method.
Ensure that these tooltip-only Annotations are handled as "internalLink"s, to ensure that they behave as expected in PresentationMode (e.g. they should still use a `pointer`-cursor).
Ensure that `PDFLinkService.getDestinationHash` won't create links with empty hashes, since those don't really make a lot of sense in general (this improves things for tooltip-only Annotations).
This PDF file can be used for testing: http://mirrors.ctan.org/macros/latex/contrib/pdfcomment/doc/pdfcomment.pdf#page=14
For an invalid Annotation, there's one code-path where `undefined` is returned from `AnnotationFactory._create`. That'd currently, incorrectly, trigger an error during the `PDFDocument._collectFieldObjects` parsing which thus seem good to avoid.
Along these lines, the filtering in `PDFDocument.fieldObjects` is also updated to handle both `null` and `undefined` the same way.
Some pdf softwares don't remove highlight annotations but make the QuadPoints array empty.
And the Rect for the annotation can be [-32768, -32768, 32768, 32768] so it leads to have a giant div which catches all the mouse events and make the pdf unusable when there are some forms elements.
This modernizes and improves the code, by using `async`/`await` and by extracting the helper function to its own method.
To hopefully avoid confusion, given the next patch, the method is also re-named to `goToDestination` to make is slightly clearer what it actually does.
Given that *all* fonts are, ever since PR 7347, now cached in the "normal" `fontCache` there's actually no reason for the special `font.translated` construction. (Given how Objects in JavaScript are references, rather than raw values, the old code shouldn't have caused any significant memory overhead.)
Instead we can simply store the `cacheKey`, which is a simple string, on only the Font `Dict`s where it's needed and thus look-up all fonts using the `fontCache` instead.
If this method is ever passed invalid/unexpected data, or if during the course of parsing (since it's used recursively) such data is found, it will fail in a non-graceful way.
Hence this patch, which ensures that we don't attempt to access non-existent properties and also that errors such as the one fixed in PR 12479 wouldn't have occured.
*This patch is based on a couple of smaller things that I noticed when working on PR 12479.*
- Don't store the /Fields on the `formInfo` getter, since that feels like overloading it with unintended (and too complex) data, and utilize a `hasFields` boolean instead.
This functionality was originally added in PR 12271, to help determine what kind of form data a PDF document contains, and I think that we should ensure that the return value of `formInfo` only consists of "simple" data.
With these changes the `fieldObjects` getter instead has to look-up the /Fields manually, however that shouldn't be a problem since the access is guarded by a `formInfo.hasFields` check which ensures that the data both exists and is valid. Furthermore, most documents doesn't even have any /AcroForm data anyway.
- Determine the `hasFields` property *first*, to ensure that it's always correct even if there's errors when checking e.g. the /XFA or /SigFlags entires, since the `fieldObjects` getter depends on it.
- Simplify a loop in `fieldObjects`, since the object being accessed is a `Map` and those have built-in iteration support.
- Use a higher logging level for errors in the `formInfo` getter, and include the actual error message, since that'd have helped with fixing PR 12479 a lot quicker.
- Update the JSDoc comment in `src/display/api.js` to list the return values correctly, and also slightly extend/improve the description.
This allows us to make a slight simplification in `PartialEvaluator.loadFont`, which thus removes an old TODO-comment from the method.
Furthermore, in `PartialEvaluator.translateFont`, the CMap-handling is now limited to only *composite* fonts to avoid having to wait for a "dummy"-Promise for most fonts.
- Actually register/unregister the `WorkerTask`s, used when saving each page, correctly.
To prevent issues when terminating the Worker, we purposely wait for all running `WorkerTask`s to complete first. Hence we need to actually handle `WorkerTask`s the same way in "SaveDocument" as in the rest of this file, see e.g. "GetOperatorList" and "GetTextContent".
- Access `PDFDocument` properties in a generally safe/consistent way.
While the current code works fine, given how the PDF document is being loaded, it still seems like a very good idea to be *consistent* in how we access these kind of properties (since in general you need to avoid `MissingDataException` everywhere in this file).
- Change a variable name, since there's essentially no precedent in the code-base for *local* variable names to start with an underscore.
Support for the `scope` parameter, in `MessageHandler.on`, was removed in PR 11110 however this particular case was unused/unnecessary for years prior to that change. (From a quick look through the history, I'm not even sure if it was actually needed in the first place.)
In practice it's not uncommon for PDF documents to re-use the same TilingPatterns more than once, and parsing them is essentially equal to parsing of a (small) page since a `getOperatorList` call is required.
By caching the internal TilingPattern representation we can thus avoid having to re-parse the same data over and over, and there's also *less* asynchronous parsing required for repeated TilingPatterns.
Initially I had intended to include (standard) benchmark results with this patch, however it's not entirely clear that this is actually necessary here given the preliminary results.
When testing this manually in the development viewer, using `pdfBug=Stats`, the following (approximate) reduction in rendering times were observed when comparing `master` against this patch:
- http://pubs.usgs.gov/sim/3067/pdf/sim3067sheet-2.pdf (from issue 2765): `6800 ms` -> `4100 ms`.
- https://github.com/mozilla/pdf.js/files/1046131/stepped.pdf (from issue 8473): `54000 ms` -> `13000 ms`
- https://github.com/mozilla/pdf.js/files/1046130/proof.pdf (from issue 8473): `5900 ms` -> `2500 ms`
As always, whenever you're dealing with documents which are "slow", there's usually a certain level of subjectivity involved with regards to what's deemed acceptable performance.
Hence it's not clear to me that we want to regard any of the referenced issues as fixed, however the improvements are significant enough to warrant caching of TilingPatterns in my opinion.
This simplifies/consolidates the ESLint configuration slightly in the `src/` folder, and prevents the addition of any new files where `var` is being used.[1]
Hence we no longer need to manually add `/* eslint no-var: error */` in files, which is easy to forget, and can instead disable the rule in the `src/core/` files where `var` is still in use.
---
[1] Obviously the `no-var` rule can, in the same way as every other rule, be disabled on a case-by-case basis where actually necessary.
Previously this rule has been enabled in the `web/` folder, and in select files in the `src/` sub-folders.
In this case, enabling of this rule didn't actually require any further code changes.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-var
Previously this rule has been enabled in the `web/` folder, and in select files in the `src/` sub-folders.
Note that a number of the files in the `src/display/` folder were already enforcing the `no-var` rule, and thanks to Prettier the necessary re-writing will be (mostly) handled automatically.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/no-var
This changes the `transformOrigin` calculations in `AnnotationElement._createContainer` and `PopupAnnotationElement.render`, to ensure that e.g. the clickable area of annotations and/or popups are both positioned correctly.
The problem occurs for *negative* values, since they're not negated correctly because of how the `transformOrigin` strings were build; see issue 12406 for a more in-depth explanation. Previously, for negative values, the `transformOrigin` strings would thus be ignored since they're not valid.
- Check that the "Info"-entry, in the XRef-trailer, is actually a dictionary before accessing it. This is similar to the `PDFDocument.documentInfo` method and follows the general principal of validating data carefully before accessing it, given how often PDF-software may create corrupt PDF files.
- Slightly simplify the "XFA"-lookup, since there's no point in trying to fetch something from the empty dictionary.
Currently there's nothing that prevents modification of the `Dict.empty` primitive, which obviously needs to be *truly* empty to prevent any future (hard to find) bugs.
This patch contains a possible approach for fixing issue 12294, which compared to other PRs is purposely limited to the affected `WidgetAnnotation` code.
As mentioned elsewhere, considering that we're (at least for now) trying to fix *one specific* case, I think that we should avoid modifying the `Dict` primitive[1] and/or avoid a solution that (indirectly) modifies an existing `Dict`-instance[2].
This patch simply fixes the issue at hand, since that seems easiest for now, and I'd suggest that we worry about a more general approach if/when that actually becomes necessary.
Hence the solution implemented here, for `WidgetAnnotation`, is to simply use a combination of the local *and* AcroForm /DR resources during OperatorList-parsing to ensure that things work correctly regardless of where a particular /Font resource is found.
For saving of form-data, on the other hand, we want to avoid increasing the file-size unnecessarily and need to be smarter than just merging all of the available resources. To achive this, a new `WidgetAnnotation._getSaveFieldResources` method will when necessary produce a combined resources `Dict` with only the minimum amount of data from the AcroForm /DR resources included.
---
[1] You want to avoid anything that could cause the general `Dict` implementation to become slower, or more complex, just for handling an edge-case in my opinion.
[2] If an existing `Dict`-instance is modified unexpectedly, that could very easily lead to problems elsewhere since e.g. `Dict`-instances created during parsing are not expected to be changed.
