The intention with preferences such as `sidebarViewOnLoad`/`scrollModeOnLoad`/`spreadModeOnLoad` were always that they should be able to *unconditionally* override their view history counterparts.
Due to the way that these preferences were initially implemented[1], trying to e.g. force the sidebar to remain hidden on load cannot be guaranteed[2]. The reason for this is the use of "enumeration values" containing zero, which in hindsight was an unfortunate choice on my part.
At this point it's also not as simple as just re-numbering the affected structures, since that would wreak havoc on existing (modified) preferences. The only reasonable solution that I was able to come up with was to change the *default* values of the preferences themselves, but not their actual values or the meaning thereof.
As part of the refactoring, the `disablePageMode` preference was combined with the *adjusted* `sidebarViewOnLoad` one, to hopefully reduce confusion by not tracking related state separately.
Additionally, the `showPreviousViewOnLoad` and `disableOpenActionDestination` preferences were combined into a *new* `viewOnLoad` enumeration preference, to further avoid tracking related state separately.
This is *really* the best that we can do here, since other proposed solutions would interfere with (and break) the painstakingly implemented browsing history that's present in the default viewer.
I'm still not convinced that this is a good idea in general, but this patch implements it in a way where it is possible to toggle[1] for users that wish to have this feature. In particular, there's a couple of reasons why I'm not finding this feature necessary/great:
- It's already possible to easily obtain the current hash, by simply clicking on the `viewBookmark` button at any time.
- Hash changes requires a bit of special handling[2], i.e. extra code, to prevent issues when the browser history is traversed (see `PDFHistory._popState`). Currently this is only necessary when the user has manually changed the hash, with this patch it will always be the case (assuming the feature is active).
- It's not always possible to change the URL when updating the browser history. For example: In the Firefox built-in viewer, the URL cannot be modified for local files (i.e. those using the `file://` protocol).
This leads to inconsistent behaviour, and may in some cases even result in errors being thrown and the history thus not updating, if the browser prevents changes to the URL during `pushState`/`replaceState` calls.
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[1] Using the `historyUpdateUrl` viewer preference.
[2] This depends, to a great extent, on browsers always firing `popstate` events *before* `hashchange` events, which may or may not actually be guaranteed.
Given that it's really not clear to me if this is actually desired functionality in the default viewer, and considering that it doesn't fit in *great* with the way that `PDFHistory` is initialized, this feature is currently off by default[1].
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[1] It's controlled with the `disableOpenActionDestination` Preference/AppOption.
Rather than having a (somewhat) randomly choosen list of Preferences which `AppOptions` are allowed to override, it makes much more sense to simply add an AppOption to allow custom implementations to ignore Preferences altogether (it's also inline with the AppOption that allows the `ViewHistory` to be bypassed on load).
This patch is the first step to be able to eventually get rid of the `attachDOMEventsToEventBus` function, by allowing `EventBus` instances to simply re-dispatch most[1] events to the DOM.
Note that the re-dispatching is purposely implemented to occur *after* all registered `EventBus` listeners have been serviced, to prevent the ordering issues that necessitated the duplicated page/scale-change events.
The DOM events are currently necessary for the `mozilla-central` tests, see https://hg.mozilla.org/mozilla-central/file/tip/browser/extensions/pdfjs/test, and perhaps also for custom deployments of the PDF.js default viewer.
Once this have landed, and been successfully uplifted to `mozilla-central`, I intent to submit a patch to update the test-code to utilize the new preference. This will thus, eventually, make it possible to remove the `attachDOMEventsToEventBus` functionality.
*Please note:* I've successfully ran all `mozilla-central` tests locally, with these patches applied.
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[1] The exception being events that originated on the `window` or `document`, since those are already globally available anyway.
For some reason, these weren't added to `AppOptions` despite actually being set and read from `web/app.js`. Not adding them creates inconsistencies, since all other options *are* present in `web/app_options.js`.
It appears that Microsoft silently fixed the problem that required disabling of fullscreen mode, in e.g. `iframe`s, in IE 11; please see issue 4711 and PR 5525 for historical context.
Unfortunately my Google-fu isn't strong enough to find any *official* information regarding the fixing of the browser bug in IE. However testing of the default viewer in IE 11, with this patch applied, it now appears that Presentation Mode is working correctly even in an `iframe` in IE 11.
Further anecdotal evidence that the bug is in fact fixed, is for example that jQuery previously contained a work-around for the IE bug. However, that's removed over two years ago now; see ff1a0822f7 and the issues referenced there.
Given that the default viewer isn't intended to be used as-is anyway (in custom deployments), it didn't seem necessary to keep the `disableFullscreen` option around since it was *only* ever added for compatibility purposes.
Fixes 9585.
One additional complication with removing this option from the global `PDFJS` object, is that the viewer currently needs to check `disableAutoFetch` in a couple of places. To address this I'm thus proposing adding a getter in `PDFDocumentProxy`, to allow checking the *actually* used values for a particular `getDocument` invocation.
The `appConfig` contains (mostly) references to various DOM elements, used when initializing the viewer components.
Hence `defaultUrl` seem like a slightly better fit for the new `AppOptions` abstraction, not to mention that it should thus be easier to set/modify it for custom deployments of the default viewer.
The way that various options are handled in the default viewer is currently a bit of a mess (to say the least). Some viewer options reside in the global `PDFJS` object, while others reside in `Preferences`. To make matters worse, some options even exist in both of the two.
Since the goal, with PDF.js version `2.0`, is to reduce our usage of the global `PDFJS` object, we'll instead want pass in the options when initializing the viewer components and when calling API methods (such as `getDocument`).
However given the current state of things in the default viewer, this wouldn't be exactly easy to implement. Hence this patch, which attempts to consolidate the way that viewer (and later API) options are handled by introducing a `AppOptions` singleton that provides *one* centralized way of interacting with the various options in the default viewer.
