Based on a number of opened issues, it seems that the "Is an extension" field might be causing some confusion as to its meaning. Without providing too much detail, I'm still thinking that we could attempt to clarify that it's referring to either of the *browser* extensions.
Since we're already using core-js elsewhere in `compatibility.js`, we can reduce the amount of code we need to maintain ourselves.
https://github.com/zloirock/core-js#weakmap
Some PDF files contain JavaScript actions that consist of nothing more that one, or possibly several, empty string(s). At least to me, printing a warning/showing the fallback seems completely unnecessary in that case.
Furthermore, this patch also makes use of an early `return`, so that we no longer will attempt to check for printing instructions when no JavaScript is present in the PDF file.
*Note:* It would perhaps make sense to change the API/core code, such that we ignore empty entries there instead. However, that would probably be considered a breaking changing with respect to backwards compatibility, hence this simple viewer only solution.
Fixes 5767.
I don't know if this is a regression, but I noticed earlier today that depending on the initial scale *and* sidebar state, the `annotationLayer` of the first rendered page may end up duplicated; please see screen-shot below.
[screen-shot]
I can reproduce this reliable with e.g. https://arxiv.org/pdf/1112.0542v1.pdf#zoom=page-width&pagemode=bookmarks.
When the document loads, rendering of the first page begins immediately. When the sidebar is then opened, that forces re-rendering which thus aborts rendering of the first page.
Note that calling `PDFPageView.draw()` will always, provided an `AnnotationLayerFactory` instance exists, call `AnnotationLayerBuilder.render()`. Hence the events described above will result in *two* such calls, where the actual annotation rendering/updating happens asynchronously.
For reasons that I don't (at all) understand, when multiple `pdfPage.getAnnotations()` promises are handled back-to-back (in `AnnotationLayerBuilder.render()`), the `this.div` property seems to not update in time for the subsequent calls.
This thus, at least in Firefox, result in double rendering of all annotations on the first page.
Obviously it'd be good to find out why it breaks, since it *really* shouldn't, but this patch at least provides a (hopefully) acceptable work-around by ignoring `getAnnotations()` calls for `AnnotationLayerBuilder` instances that we're destroying (in `PDFPageView.reset()`).
*It appears that this accidentally broken in PR 8775.*
Note that `PDFHistory.forward` is only used with certain named actions, and these aren't that commonly used, which ought to explain why this error managed to sneak in.
Steps to reproduce the issue (and verify the fix):
1. Navigate to e.g. http://mirrors.ctan.org/info/lshort/english/lshort.pdf
2. Click on a couple of links, or outline items, such that the history is populated with a few entries.
3. In the console, execute `PDFViewerApplication.pdfHistory.back()` one or more times, thus navigating back to a previous viewer position.
4. In the console, execute `PDFViewerApplication.pdfHistory.forward() one or more times.
At the last step above, no (forward) navigation happens with the current `master`; now compare with this patch.
