By using the `signal` option when invoking `addEventListener`, see [MDN](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#signal), we're able to remove an arbitrary number of event listeners with (effectively) a single line of code.
Besides getting rid of a bunch of `removeEventListener`-calls, which means shorter code, we no longer need to manually keep track of event-handling functions.
By using the `signal` option when invoking `addEventListener`, see [MDN](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener#signal), we're able to remove an arbitrary number of event listeners with (effectively) a single line of code.
Besides getting rid of a bunch of `removeEventListener`-calls, which means shorter code, we no longer need to manually keep track of event-handling functions.
This patch updates the minimum supported browsers as follows:
- Safari 16.4, which was released on 2023-03-27; see https://developer.apple.com/documentation/safari-release-notes/safari-16_4-release-notes
Nowadays we usually we try, where feasible and possible, to support browsers/environments that are about two years old. The reasons for limiting support to a slightly more recent Safari version include:
- Safari has always been slower, compared to other browsers, at implementing e.g. new JavaScript features.
- Trying to provide support for Safari is often difficult, and over the years we have seen *a lot* of bugs that are specific to Safari.
- Safari is, and has been for many years, only listed as "mostly" supported in the FAQ.
- This allows us to remove feature-testing, only relevant to Safari, from the main code-base.
By limiting support to only "recent" browsers we reduce the risk of holding back improvements of the built-in Firefox PDF Viewer, and also (significantly) reduce the maintenance/support burden for the PDF.js core contributors.
*Please note:* As always, the minimum supported browser version assumes that a `legacy`-build of the PDF.js library is being used; see https://github.com/mozilla/pdf.js/wiki/Frequently-Asked-Questions#faq-support
This allows us to get rid of the `@private` JSDoc comments, which were
used to convey intent back when proper private methods could not be used
yet in JavaScript. This improves code readability/maintenance and enables
better usage validation by tooling such as ESlint.
These CSS rules were imported straight from mozilla-central, and contains a property that causes the RTL-rule to be skipped everywhere else (even when using the development viewer in Firefox).
This allows us to get rid of the `@private` JSDoc comments, which were
used to convey intent back when proper private methods could not be used
yet in JavaScript. This improves code readability/maintenance and enables
better usage validation by tooling such as ESlint.
This replaces our custom `PromiseCapability`-class with the new native `Promise.withResolvers()` functionality, which does *almost* the same thing[1]; please see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/withResolvers
The only difference is that `PromiseCapability` also had a `settled`-getter, which was however not widely used and the call-sites can either be removed or re-factored to avoid it. In particular:
- In `src/display/api.js` we can tweak the `PDFObjects`-class to use a "special" initial data-value and just compare against that, in order to replace the `settled`-state.
- In `web/app.js` we change the only case to manually track the `settled`-state, which should hopefully be OK given how this is being used.
- In `web/pdf_outline_viewer.js` we can remove the `settled`-checks, since the code should work just fine without it. The only thing that could potentially happen is that we try to `resolve` a Promise multiple times, which is however *not* a problem since the value of a Promise cannot be changed once fulfilled or rejected.
- In `web/pdf_viewer.js` we can remove the `settled`-checks, since the code should work fine without them:
- For the `_onePageRenderedCapability` case the `settled`-check is used in a `EventBus`-listener which is *removed* on its first (valid) invocation.
- For the `_pagesCapability` case the `settled`-check is used in a print-related helper that works just fine with "only" the other checks.
- In `test/unit/api_spec.js` we can change the few relevant cases to manually track the `settled`-state, since this is both simple and *test-only* code.
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[1] In browsers/environments that lack native support, note [the compatibility data](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/withResolvers#browser_compatibility), it'll be polyfilled via the `core-js` library (but only in `legacy` builds).
With recent improvements to the `AppOptions`, e.g. with better validation and testing, one remaining "annoyance" is the `compatibilityParams` handling. Especially since there's only *a single* parameter left, limited to GENERIC builds.
To further reduce the amount of unnecessary code in e.g. the Firefox PDF Viewer, we can move the `compatibilityParams` handling into the user-options instead since that keeps the previous precedence order between default/user-options.
- Use slightly shorter variable names when initializing the preferences.
- Correctly copy the "old" preference-values before writing to storage, since Objects are passed by reference in JavaScript. (Only applies to the GENERIC viewer.)
- Use `await` fully when writing new preference-values to storage. (Only applies to the GENERIC viewer.)
- Stub the `get`-method in the Firefox PDF Viewer, since it's unused there nowadays.
This old method is essentially just adding, a small amount of, unnecessary indirection and we can easily invoke `PDFViewerApplication.open` directly from the extension-specific code instead.
The following are some highlights of this patch:
- In the Worker we only extract a *subset* of the potential contents of the `Usage` dictionary, to avoid having to implement/test a bunch of code that'd be completely unused in the viewer.
- In order to still allow the user to *manually* override the default visible layers in the viewer, the viewable/printable state is purposely *not* enforced during initialization in the `OptionalContentConfig` constructor.
- Printing will now always use the *default* visible layers, rather than using the same state as the viewer (as was the case previously).
This ensures that the printing-output will correctly take the `Usage` dictionary into account, and in practice toggling of visible layers rarely seem to be necessary except in the viewer itself (if at all).[1]
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[1] In the unlikely case that it'd ever be deemed necessary to support fine-grained control of optional content visibility during printing, some new (additional) UI would likely be needed to support that case.
