Changes `PDFOutlineView`/`PDFAttachmentView` to be initialized once, since we're always creating them, and refactor their `render` methods to instead pass in the `outline`/`attachments`.
For consistency with other "classes", the `PDFOutlineView`/`PDFAttachmentView` are renamed to `PDFOutlineViewer`/`PDFAttachmentViewer`.
Also, make sure that the outline/attachments are reset when the document is closed. Currently we keep the old ones around until the `getOutline`/`getAttachments` API calls are resolved for a new document.
To reduce code duplication, the initialization code now uses the `reset` method.
Also, this patch moves `charactersToNormalize` out of `PDFFindController`, since it seemed better suited to be a "constant".
Open http://www.puolustusvoimat.fi/wcm/61ba4180411e702ea19ee9e364705c96/luonnonmuonaohjelmalumo1985.pdf?MOD=AJPERES#pagemode=bookmarks.
Note how the outline looks entirely empty, but hovering over it you'll see that there are entries present. There's two separate issues here, first of all the fact that you cannot visually make out the outline items, and secondly that the lack of text means that the clickable area becomes too small.
In Adobe Reader this issue is somewhat mitigated, since they use an icon for every item. For PDF.js, the easist way to address this seems to be making use of a default title.
This issue should be *very* rare in practice, but given the simplicity of the solution I think that we should fix this.
The `hasImage` property is a left-over from older thumbnail code, and has been made obsolete by `renderingState`.
Having two different properties tracking (basically) the same state is asking for trouble, since it's very easy to forget to update one of them, with annoying bugs as the result.
This is required to be able to use it in the annotation display code,
where we now apply it to sanitize the filename of the FileAttachment
annotation. The PDF file from https://bugzilla.mozilla.org/show_bug.cgi?id=1230933 has shown that some PDF generators include the path of the file rather than the filename, which causes filenames with weird initial characters. PDF viewers handle this differently (for example Foxit Reader just replaces forward slashes with spaces), but we think it's better to only show the filename as intended.
Additionally we add unit tests for the `getFilenameFromUrl` helper
function.
The Chrome extension enforces that local files cannot be embedded in
non-local web pages. The previous check was too strict (because the
origin of a file:-URL is "null"), and prevented local PDF from being
viewed in local files).
This patch fixes that problem, by querying the actual tab URL via the
background page.
Steps to verify:
1. Create a HTML file: `<iframe src=test.pdf width=100% height=100%>`
2. Build and load the extension.
3. Allow file access to the extension at `chrome://extensions`
4. Open the HTML file from a file:// URL.
5. VERIFY: The extension should attempt to load the PDF file.
6. Now open the following (replace ID with the extension ID, which you
can find at `chrome://extensions`):
`data:text/html,<iframe src="chrome-extension://ID/file:///test.pdf">`
7. VERIFY: The next error should be displayed:
"Refused to load a local file in a non-local page for security reasons."
Fixes 6898.
Note that this doesn't prevent the warning for PDF files that *do* ask for a password, e.g. http://async5.org/moz/passwordOU.pdf, but it's not clear to me if/how we could avoid that.
Re: issue 5089.
(Note that since there are other outline features that we currently don't support, e.g. bold/italic text and custom colours, I thus think we can keep the referenced issue open.)
Apparently some PDF files can have annotations with `URI` entries ending with `null` characters, thus breaking the links.
To handle this edge-case of bad PDFs, this patch moves the already existing utility function from `ui_utils.js` into `util.js`, in order to fix those URLs.
Fixes 6832.
Most code for Popup annotations is already present for Text annotations.
This patch extracts the popup creation logic from the Text annotation
code so it can be reused for Popup annotations.
Not only does this add support for Popup annotations, the Text
annotation code is also considerably easier. If a `Popup` entry is
available for a Text annotation, it will not be more than an image. The
popup will be handled by the Popup annotation. However, it is also
possible for Text annotations to not have a separate Popup annotation,
in which case the Text annotation handles the popup creation itself.
This patch makes the naming consistent with the `TextLayerBuilder`, and also the new `AnnotationLayer`, and should thus help reduce possible confusion when working with the code.
Please note that the files were renamed using `git mv`, in order to preserve blame.
Additionally simplify the div creation logic (it needs to happen only
once, so it should not be in the for-loop) and remove/rename variables
for shorter code.
This patch goes a bit further than issue 6612 requires, and replaces all kinds of whitespace with standard spaces.
When testing this locally, it actually seemed to slightly improve two existing test-cases (`tracemonkey-text` and `taro-text`).
Fixes 6612.
Currently `getAnnotations` will *only* fetch annotations that are either `viewable` or `printable`. This is "hidden" inside the `core.js` file, meaning that API consumers might be confused as to why they are not recieving *all* the annotations present for a page.
I thus think that the API should, by default, return *all* available annotations unless specifically told otherwise. In e.g. the default viewer, we obviously only want to display annotations that are `viewable`, hence this patch adds an `intent` parameter to `getAnnotations` that makes it possible to decide if only `viewable` or `printable` annotations should be fetched.
In my opinion, this event shouldn't be dispatched in `PDFPageView.cssTransform`, since that would cause *two* events to be fired when "normal" zooming is used (once in `PDFPageView.cssTransform`, and once in `PDFPageView.draw`).
Fixes 6463.
For documents with different page sizes, ensure that the correct page becomes visible on load when e.g. the 'page' hash parameter was provided (bug 1191279, issue 6393)
This is a quick fix to get `scrollIntoView` working again for search results, but we really ought to re-write that function since it seems way too brittle.
Fixes 6596.
This patch contains an alternative solution (see the referenced PRs in 4718), in order for the indeterminate loading bar to have a consistent speed regardless of width.
Fixes 4718.
Currently this constant is present in `viewer.js`, but it is not used there at all. Instead, it is used in `view_history.js` where we have a global for it. We might as well move the constant to `view_history.js` as that is the only place where it is used, thereby removing a global and an unused constant from `viewer.js`.
If your Internet Explorer 11 default compatibility settings are set to "I.E 7 Compatibility", the PDF plugin will not load. This fix is the same one used by AngularJS to force the browser to use HTML5 mode.
*This regressed in PR 5356.*
Rather than just backing out the offending code, this patch restores scrolling in PresentationMode by making the `overflow: hidden;` check optional and letting the callers that need it (e.g. `PDFFindController`) opt-in to use it.
When the user edits the URL and changes the reference fragment (hash),
PDF.js intercepts this action, and saves the then-current history state
in the previous history entry. This is implemented by navigating back,
editing the history and navigating forward again.
The current logic has a flaw: It assumes that calling history.back() and
history.forward() immediately updates the history state. This is however
not guaranteed by the web standards, which states that calling e.g.
history.back "must traverse the history by a delta -1", which means that
the browser must QUEUE a task to traverse the session history, per spec:
http://w3.org/TR/2011/WD-html5-20110113/history.html#dom-history-backhttps://html.spec.whatwg.org/multipage/browsers.html#dom-history-back
Firefox and Internet Explorer deviate from the standards by immediately
changing the history state instead of queuing the navigation.
WebKit derived browsers (Chrome, Opera, Safari) and Opera presto do not.
The user-visible consequence of strictly adhering to the standards in
PDF.js can be shown as follows:
1. Edit the URL.
2. Append #page=2 for example.
3. Press Enter.
-> Presto and WebKit: PDF.js reverts to the previous URL.
-> Gecko and Trident: PDF.js keeps the new URL, as expected.
To fix the issue, modification of the previous history item happens in
a few asynchronous steps, guided by the popstate event to detect when
the history navigation request has been committed.
--
Some more implementation notes:
I have removed the preventDefault and stopPropagation calls, because
popstate is not cancelable, and window is already the last target of the
event propagation.
The previous allowHashChange logic was hard to follow, because it did
not explain that hashchange will be called twice; once during the
popstate handler for history.back() (which will reset allowHashChange),
and again for history.forward() (where allowHashChange will be false).
The purpose of allowHashChange is now more explicit, by incorporating
the logic in the replacePreviousHistoryState helper function.
*This regressed in PR 4920.*
The main motivation for PR 4920 was to quickly get rid of old canvases when pages are evicted from the `PDFPageViewBuffer` cache. However it inadvertently broke the use-case where the `canvas` is used as a preview, on scale or rotation changes, until the re-rendering is finished.
Fixes 6467.
In PR 5552, specifically commit 9f384bbb41, the meaning of `this.annotationLayer` changed in `PDFPageView`. Previously it referred directly to a DOM element, but now it's instead an instance of `AnnotationsLayerBuilder`.
This patch tweaks things so that we won't try to hide a non-existent `annotationLayer` div in `PDFPageView_reset`, and also so that we don't attempt to insert empty (`null`) DOM elements in `PDFPageView_draw`.
*Follow-up to PR 6299.*
This patch reduces unnecessary code duplication for the `canvas` to `image` conversion. It also does a bit of re-ordering (and adds new lines) in `_getPageDrawContext`, since that function currently is a bit hard to read.
Since some browsers render `null` characters, and others don't, this patch adds a way to remove them to prevent display issues in the viewer UI.
Given that documents may contain very long outlines, I've added a utility function to avoid creating a lot of unnecessary `RegExp` objects.
To avoid any future issues, this utility function is used for both the outline and the attachments.
Fixes 6416.
Prior to PR 6242, the width of all outline items was set such that their right (or left, in RTL locales) edges lined up vertically. In my opinion that looked more consistent, therefore this patch adjusts the CSS to make sure that this will be the case again.
The patch also makes the `border-radius` values of outline items a bit more consistent.
This issue is actually, in a sense, "caused" by the fact that the API/viewer supports partial loading/rendering. Previously when the *entire* document was always fetched before rendering begun, we knew all page sizes in advance and this issue didn't exist.
Now we use the size of *one* page in order to set the initial size of every page, until we've fetched the pages and thus know their correct sizes.
This means that during loading the size of the pages can change, which may cause the initial position to become scrolled out of view.
The most naive solution to this problem would perhaps be to delay setting the initial position on load for all documents, until all pages are fetched. However I think that would be a *really* bad idea, since doing so would make the initial rendering slower and make it feel sluggish for most documents.
Since there is generally no way of knowing if a document has different sized pages prior to loading it, we can only check once the pages are available.
Hence this patch, which treats documents with different sized pages as a special case, by re-applying the initial position when all pages have become available.
It appears to me that the `expanded/collapsed` part of the names got switched around, since I'd expect the following convention:
- `v` == expanded
- `>` == collapsed
- This commit adds a '>' before every outline item that has subitems.
- Click on the '>' to collapse all subitems under that item (which turns
the '>' in a 'v').
- Shift + click expands/collapses all descendant items under that tree.
- Double-clicking on the "Show Document Outline" button in the toolbar
expands/collapses all outline items.
The JSON file is generated as follows.
1. Go to the src/chrome/app/resources directory of Chromium's source.
2. Find the translation ID of the "Allow access to file URLs" string:
grep 'Allow access to file URLs' generated_resources_en-GB.xtb
3. With the ID that you've found, locate the other translations.
grep 3341703758641437857 generated_resources_*.xtb
4. If the result looks OK, serialize the result as JSON and save it.
> path/to/pdf.js/web/chrome-i18n-allow-access-to-file-urls.json \
python -c "import json;print(json.dumps({ \
$(grep 3341703758641437857 generated_resources_*.xtb | \
sed "s@generated_resources_\([^.]\+\)\.xtb:<translation[^>]\+>\(.\+\)</translation>@'\1':'''\2''',@" \
)}, sort_keys=True, indent=2))"
(Strings are taken from Chromium 45.0.2448.0 (ccrev.com/337313).
Currently in `switchSidebarView` there is code that attempts to handle the `outline` or `attachments` being disabled. However, given the placement of it, that code does not actually accomplish anything. Even more strange is the fact that the way that the buttons are disabled, that code won't ever be hit.
(Looking back with `git blame`, it seems that it has never worked as you'd expect.)
Hence this patch, which correctly disables switching to the `outline` or `attachments` views when they are disabled.
Once PR 6314 restores the 'pagemode' hash parameter, this patch thus makes it impossible to switch to a disabled sidebar view by modifying the 'pagemode' hash of an already loaded document.
This regressed in 0ef6212b64.
Since the 'pagemode' hash parameter requires certain viewer functionality (e.g. thumbnails and an outline) in order to work, it seemed reasonable to move the functionality from `pdf_link_service.js` into `viewer.js`.
Similar to `namedaction`, this patch makes use of an event to forward the 'pagemode' parameter.
Built-in DOM properties are slower than plain JS properties.
A few lines before, textContent is assigned as follows:
textDiv.textContent = geom.str;
So replacing textDiv.textContent.length with geom.str.length slightly
improves performance without side effects.
Since the zoom value should be in percent, using `PDFViewer.currentScale` will be wrong by a factor of 100, potentially causing the zoom level of the document to become wrong on load.
*This fixes a regression from PR 6192.*
Under some circumstances, the `resize` event handler in `viewer.js` is fired before the scale has been set. This can lead to PDF documents being rendered at the wrong zoom level when they are opened.
It seems that a way to reliably trigger this is to, using the Firefox addon, open a PDF file that triggers the `fallback` bar, in a new background tab (i.e. middle clicking on a link, or use the context menu).
Prior to PR 6192, we checked the selected option in the `scaleSelect` dropdown instead. Since `pageAutoOption` is selected by default in `viewer.html`, this should explain why the issue wasn't visible previously.
Fixes#6106
To avoid future regressions, two new unit tests were added:
1. A new PDF based on the report from #6106, which contains an
OpenAction of type JavaScript and a string "this.print({...}".
2. An existing PDF from https://bugzil.la/1001080 (from #4698).
Although it does not matter, since we don't execute the JavaScript code,
I have also changed "print(true)" to "print({})" since the print method
takes an object (not a boolean). See "Printing PDF documents", page 62:
http://adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/js_developer_guide.pdf
The special handling of the 'custom' scale value is only relevant for the `scaleSelect` dropdown in the standard viewer, hence I think that it should be placed in `viewer.js` instead.
Ordinarily, local files cannot be embedded in a non-local website. Until
this commit, the extension allowed websites to embed local PDF files on
non-local (e.g. http(s)) websites. This unintended feature is now
disabled, to align better with Chrome's existing security policies
(=local file:-URLs cannot be loaded in a tab unless expicitly allowed).
After the creation of `PDFViewer`, its `_resetView` method takes care of resetting, among other things, the page number property. Hence we don't need to set `pdfViewer.currentPageNumber = 1;` here any more, and the comment is no longer accurate either.
*With this patch we're getting very close to fixing 6158.*
The only use-case for `PDFViewerApplication.updateScaleControls` is to try and avoid calling `selectScaleOption` from the `scalechange` event handler in viewer.js.
This will *only* happen when the user has manually changed the scale by using the `<select>` dropdown, which means that in reality this is just a micro optimization. Furthermore, `selectScaleOption` is only skipped for the "named" scale values (e.g. `auto`, `page-actual`, `page-fit`, `page-width`), thus further reducing the value of this code.
Also, since we're updating the scale `<select>` dropdown from an event handler, we're currently depending on the event being dispatched (and handled) completely before the next `scalechange` event. Relying on the execution order of the code in this way, even though it currently works, seems unfortunate since it *could* potentially cause the internal scale value and the UI from getting out of sync.
*This is the next step towards fixing 6158.*
This patch removes the dependency on the state of the scale `<select>` dropdown from the `resize` event handler, and instead uses the (in `PDFViewer`) stored `currentScaleValue`.
I believe that the way this code is currently written is purely for historical reasons, since originally *only* the numerical scale was stored internally (hence there was no other way to access the scale value).
However, since we now store the scale value, we should use it instead of quering the DOM. This helps ensure that the internally stored scale value is always accurately displayed in the UI (which should be good since, after the creation of `PDFViewer`, the `<select>` DOM element is now updated by an event handler).
*The next step towards fixing issue 6158.*
We can just as well access `pdfViewer.currentScaleValue` directly in `PDFViewerApplication`, instead of having a helper function which just acts as a wrapper for it.
Currently if the zoom level is reset multiple times in a row, i.e. by pressing <kbd>Ctrl</kbd>+<kbd>0</kbd>, the pages can be re-rendered each time even though their size shouldn't change. Whether this happens can depend on the size of the viewer, but documents with pages in landscape mode seem to be very susceptible to this. (An example is: https://wiki.mozilla.org/images/5/55/MobileOpportunity.pdf.)
This can also effect documents with pages in portrait mode, when they are displayed in Presentation Mode.
The reason for this unnecessary re-rendering is that due to limited numerical precision, the new scale value may change in *only* the last decimal place.
This is similar to the already existing, separate, CSS file used for the `textLayer`, and it's necessary in order for the `pageviewer` components example to actually show annotations correctly.
Considering that most methods of `SimpleLinkService` are complete stubs, or practically "useless" considering what they return, we can actually simplify it even more.
*Note:* This depends on the previous patch, that did a small amount of refactoring of `PDFViewer_scrollPageIntoView`, since `PDFViewer.linkService.page` is no longer accessed.
----------
Currently the `pageviewer` components example doesn't work correctly (an error is printed in the console), since no `linkService` is present when the `AnnotationsLayerBuilder` is created.
*Note:* Given that this uses the `SimpleLinkService`, clicking on e.g. internal links won't actually do anything. However, given that internal links (and similar features) are pretty much useless when only *one* page is loaded the `pageviewer` example, I don't think that really matters.
Also, using the complete `PDFLinkService` would require a `PDFViewer` instance. That would significantly complicate the example, thus making it both less clear and less self contained.
Currently in `PDFViewer_scrollPageIntoView`, we're accessing a number of properties in an indirect and overly complicated way. In particular, using `this.linkService.page` is a *very* roundabout way to access `this.currentPageNumber`.
The reason for this appears to be entirely historical, since prior to PR 5361 the code was placed in `PDFPageView` (or `PageView` as it was called at the time).
This patch is the the first step towards to addressing issue 6158, which will be done by refactoring the code for setting/getting the current scale in `viewer.js`.
Before this patch, zooming in/out via the scroll wheel caused the page
to be zoomed relative to the upper-left corner of the page, i.e. the
upper-left corner of the page stays at a fixed position.
After this patch, the page is zoomed relative to the cursor position,
i.e. after zooming in/out, the part under the cursor 'has not moved'.
This only applies when the page does not fit in the viewport, because
pages smaller than the viewpoer are always centered.
In `viewer.js` we have code that ensures that the document is re-rendered on zooming and rotation. However, for `components` based viewers this might not work correctly, since there's currently no code which handles that.
Note that there is a good chance that this "just works" in many `components` viewers already, thanks to the `watchScroll` function.
The explanation is that zooming or rotation, most of the time, causes the viewer to change its (scrollable) size, thus triggering `PDFViewer_update` through `PDFViewer_scrollUpdate`.
However, in general there's no guarantee that this will actually work (since zooming and rotation doesn't necessarily change the size of the viewer for all documents), and requiring every viewer `components` implementer to provide methods for this doesn't seem like a great idea.
The reason that this code can be moved is that the `if (this.loading && page === 1)` check, in the `pagechange` event handler in viewer.js, is never satisfied since `this.loading` is not defined in that scope.
This *could* be considered a regression from PR 5295, since prior to that `this.loading` was using the `PDFViewerApplication` scope (or `PDFView` as it were).
However, I don't think that we need to fix that since we've been shipping this code in no less than *three* Firefox releases (uplifted in https://bugzilla.mozilla.org/show_bug.cgi?id=1084158), without breaking the world.
An explanation of why the `pagechange` code works, despite `this.loading === undefined`, is that `set currentPageNumber` (in `PDFViewer`) returns early whenever `this.pdfDocument` isn't set. This check is, for all intents and purposes, functionally equivalent to checking `PDFViewerApplication.loading`.
Hence we can move the page switching code into `PDFViewer`, and also remove `PDFViewerApplication.loading` since it's not used any more.
(The `this.loading` property was added in PR 686, which was before the current viewer even existed.)
*Note:* The changes in this patch should also be beneficial to the viewer `components`, since requiring every implementer to provide their own `pagechange` event handler just to get `PDFViewer.currentPageNumber` to actually work seems like an unnecessary complication.
Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1170063.
The bug only mentions the <kbd>Meta</kbd> key, but given that a similar situation can occur for <kbd>Ctrl</kbd>, it seemed reasonable to also handle that case in the same patch.
The only possible caveat with the patch is that because of the use of `shadow`, things won't work perfectly if either of the prefs are changed *while* the viewer is active. In this case a reload is required in order for it to work correctly, but given that the issue this patch fixes should be quite rare anyway, that seems OK.
Currently `PDFLinkService` requires access to a `PDFHistory` instance in order for it to work correctly (and to avoid errors). If we want `PDFLinkService` to be more useful in custom viewers, I don't think that we actually want to force it to have a `PDFHistory` instance.
Hence this patch, which contains a very simply approach to make `PDFHistory` optional.
Reuse the existing getOutputScale() machinery to render and/or rescale
thumbnail images to the native display resolution. Fixes blurry thumbnails on
HiDPI displays making it a lot easier to make out the content.
During A/B testing we found a significant preference (increased engagement
time, reduced downloads of original PDF for local viewing) for the version that
doesn't animate loading thumbnails.
Profiling shows that the transition effects hit at a pessimal time when the
compositor is busy rendering the main PDF page view, and rendering thumbnail
previews, causing the main scroll view to stutter. With the transition removed
scrolling is perceptibly smoother in Chrome and Firefox. We also hypothesize
that the transition effects added to a perception of slowness but presumably
the aforementioned stutter is the primary issue here.
Having recently spent some time staring at the PasswordPrompt, while fixing issue 6010, I felt that the current border style does not really give a good visual indication that the input field actually has focus.
The current appearance was first introduced in PR 3527; but I don't know if having a different border style in Overlay dialogs was intentional, or if it just "happened".
However, given the colour palette used in the viewer UI, I think that using the same border style for all .toolbarFields makes sense.
*This patch addresses an issue I stumbled upon while working on rewriting the history implementation.*
Currently the `updateviewarea` UI event doesn't include the `location`, and in the event handler in viewer.js we instead reach into `PDFViewer` to retrieve it. Not only does this seem conceptually wrong, it also makes the `updateviewarea` event less useful in general since it's currently only possible to access the `location` if you have a reference to the `PDFViewer`.
To me, this simply appears to be an oversight in the implementation, hence this patch which adds `location` to the `updateviewarea` event. It also changes `location` to be a "private" property of `PDFViewer`.
*This is a follow-up to PR 5966.*
Now that https://bugzilla.mozilla.org/show_bug.cgi?id=1151931 has landed, we're unfortunately in a situation where Firefox warns about `unreachable code after return statement` multiple times when using the PDF.js code in `node make server` mode.
I'm really sorry about the churn in this code!
However I don't think it's a good idea to let Firefox continue to printing these warnings in the console, since it increases the risk of missing actual errors.
This patch:
- Simplifies the way fields are passed to the document properties overlay
- Simplifies the way fields are filled internally in the document properties overlay
- Avoids passing a document properties reference to the secondary toolbar
- This patch uncomments a large portion of the Firefox specific code in viewer.js, by using a preprocessor "trick", to enable linting. Doing this actually uncovered some issues, e.g. variables defined multiple times.
- This patch also fixes a spelling error, `adobe pdfwritter` -> `abobe pdfwriter`, in the `KNOWN_GENERATORS` list used when reporting telemetry data in Firefox.
*Please note:* there's still some Firefox specific code that is commented out, but it's usually just one (or two) lines of code. Hence the risk that errors creep in should be much lower, compared to entire code-blocks.
This patch:
- Puts public methods at the top of the file
- Puts private methods below the public methods and marks them with an underscore
- Adds JSDoc comments to the class
- Adds setDocumentAndUrl to avoid having to handle that in `viewer.js`
This patch:
- Passes in a reference to the current PDFThumbnailViewer, which is used to ensure that the current thumbnail becomes visible when exiting PresentationMode.
- Changes the way that the event listeners for the contextmenu items are defined, to avoid passing in a reference to the SecondaryToolbar.
- Ensures that |supportsFullscreen| always returns a boolean.
Currently `supportsFullscreen` will, when the browser supports the fullscreen API, return e.g. `function mozRequestFullScreen()` instead of `true`.
- Simplifies the |click| handler code when PresentationMode is active.
This code has been obsolete ever since PR 2919 landed.
- Removes hack used to workaround a bug in WebKit browsers, which caused |mousemove| events to be fired when the cursor changed.
This was fixed close to a year ago, see http://code.google.com/p/chromium/issues/detail?id=103041.
This patch:
- Adds a couple of utility methods to `PDFViewer` to enable checking `presentationModeState` without cumbersome comparisons.
- Disentangles `PresentationMode` from `PDFHistory` and `HandTool`, by adding event listeners for `presentationmodechanged` to both of them.
- Adds a utility function to `PDFViewerApplication` for requesting PresentationMode.
- Prevents initialization of `PresentationMode` if the browser does not support the fullscreen API.
The line that this patch removes has been commented out since 2012 (!), see commit c8a6a9ba00.
Also, since the patch is trivial, I'm fixing the formatting of a comment to stop [GitHub from marking it with a red color](https://github.com/mozilla/pdf.js/blob/master/web/viewer.html#L394) (and IE from complaining).
After the refactoring in PR 5678, the B2G viewer now prints the following in the console:
```
ReferenceError: DownloadManager is not defined
```
This will obviously not matter once the B2G viewer is replaced with the new components-based one. But until that happens, I think it makes sense to just stub the class to suppress the error.
