- it'll help to be able to move popups on screen to let the user read the text
- popups won't inherit some properties from their parent:
- the popup can be misrendered if for example the parent has a clip-path property.
- add an outline to the popup when the parent is focused.
- hide a popup when it's clicked.
Fix handling of /Filter-entries, since the current implementation could potentially corrupt the data if there's multiple filters present.
Please note that filters are applied *sequentially* during decoding, starting from the first one in the Array, hence the first Array-entry needs to be /FlateDecode in order for things to actually work correctly.
To prevent a future bug, if we want to save more "complex" data such as images, also ensure that we include any existing /DecodeParms-entries when updating the /Filter-entry.
The existing unit-test doesn't work as intended, since the page never actually renders. Note how `cleanup` is *not* allowed to run when parsing and/or rendering is ongoing, however an (old) incorrect condition could prevent rendering from ever starting.
This is very old code, which has been slightly re-factored a couple of times (many years ago), however this doesn't appear to affect e.g. the default viewer since the incorrect behaviour seem highly dependent on "unlucky" timing.
Note also how at the start of the `PDFPageProxy.prototype.render`-method we purposely cancel any pending `cleanup`-call, to prevent unnecessary re-parsing for multiple sequential `render`-calls.
Finally, avoid running `cleanup` when document/page destruction has already started since it's pointless in that case.
After PR 16226 the deprecated SVG back-end is now unused in development mode, with the exception of unit-tests, hence we can re-factor how it's exposed in the API to avoid including a useless webpack-closure in e.g. the *built-in* Firefox PDF Viewer.
Given that this API method isn't used anywhere within the PDF.js library itself, except for the unit-tests, we can avoid including what's effectively dead code in e.g. the *built-in* Firefox PDF Viewer.
- Don't attempt to lookup an "SM" entry, since we're only using "SMask" in the `PDFImage` code and I also cannot find any mention in the PDF specification about that being a valid abbreviation for a Soft Mask entry. (There's only a `SM = Smoothness Tolerance` Graphics State parameter, which is obviously something completely different.)
- Don't lookup the /SMask and /Mask entries unless it's actually an inline image, since it's pointless otherwise.
- Last, but most importantly, only check for the *existence* of /SMask and /Mask entries but don't actually fetch the data. Note that if either one exists it'll contain a Stream, and those cannot be cached on the `XRef`-instance, which leads to unnecessary parsing/allocations and in this case we're not using the actual data for anything.
