In order to eventually get rid of SystemJS and start using native `import`s instead, we'll need to provide "complete" file identifiers since otherwise there'll be MIME type errors when attempting to use `import`.
Please find additional details about the ESLint rule at https://eslint.org/docs/rules/prefer-const
Note that this patch is generated automatically, by using the ESLint `--fix` argument, and will thus require some additional clean-up (which is done separately).
Note that Prettier, purposely, has only limited [configuration options](https://prettier.io/docs/en/options.html). The configuration file is based on [the one in `mozilla central`](https://searchfox.org/mozilla-central/source/.prettierrc) with just a few additions (to avoid future breakage if the defaults ever changes).
Prettier is being used for a couple of reasons:
- To be consistent with `mozilla-central`, where Prettier is already in use across the tree.
- To ensure a *consistent* coding style everywhere, which is automatically enforced during linting (since Prettier is used as an ESLint plugin). This thus ends "all" formatting disussions once and for all, removing the need for review comments on most stylistic matters.
Many ESLint options are now redundant, and I've tried my best to remove all the now unnecessary options (but I may have missed some).
Note also that since Prettier considers the `printWidth` option as a guide, rather than a hard rule, this patch resorts to a small hack in the ESLint config to ensure that *comments* won't become too long.
*Please note:* This patch is generated automatically, by appending the `--fix` argument to the ESLint call used in the `gulp lint` task. It will thus require some additional clean-up, which will be done in a *separate* commit.
(On a more personal note, I'll readily admit that some of the changes Prettier makes are *extremely* ugly. However, in the name of consistency we'll probably have to live with that.)
This attempts to provide more "default" methods in the base class, in order to reduce unnecessary duplication and to improve self-documentation of the `BaseViewer` class slightly.
The following changes are made (in no particular order):
- Have `BaseViewer` implement the `_scrollIntoView` method, and *extend* it as necessary in `PDFViewer`/`PDFSinglePageViewer`.
- Simply inline the `BaseViewer._resizeBuffer` method, in `BaseViewer.update`, since there's only one call-site at this point.
- Provide a default implementation of `_isScrollModeHorizontal` in `BaseViewer`, and have `PDFSinglePageViewer` override it.
- Provide a default implementation of `_getVisiblePages`, and have `PDFViewer` extend it and `PDFSinglePageViewer` override it.
Since most of the important rendering code is already (almost) identical between `PDFViewer.update` and `PDFSinglePageViewer.update`, it's possible to further reduce duplication by moving the code into `BaseViewer.update` instead.
This is relevant for e.g. `PDFSinglePageViewer`, and `PDFViewer` with Presentation Mode active.
By moving this code to a helper method in `BaseViewer`, it's thus possible to reduce the amount of duplicate code that currently needed in `PDFViewer` and `PDFSinglePageViewer`.
Note how in `BaseViewer.forceRendering` the Scroll mode is used to determine how pre-rendering will work. Currently this is broken in Presentation Mode, if horizontal scrolling was enabled prior to entering fullscreen.
Furthermore, there's a few additional cases where the `this.scrollMode === ScrollMode.HORIZONTAL` check is pointless either in Presentation Mode or when a `PDFSinglePageViewer` instance is used.
The new `PDFSinglePageViewer` class extends the previously created abstract `BaseViewer` class.
There's *a lot* of existing functionality in `PDFViewer` that depends on all the pages being loaded and synchronously available, once the `setDocument` method has been called.
Given that initializing `PDFPageView` instances requires passing a DOM element to which the page is attached, the simplest solution I could come up with is to append all pages to a (hidden) document fragment and just swap them (one at a time) into the viewer when page switching occurs.
