This is a quickfix for the problem observed with external link blocking
during certain history navigation actions (when the cached iframe content is
loaded/restored before the viewer setup is completed).
Since external link blocking doesn't depend on the translations (that
are asynchronously loaded during the viewer setup) it can be performed
unconditionally. However, the current dependence of `on_content_load()`
on viewer setup has to be addressed too.
Before this fix clicking an external link in the viewer iframe had no
effect (other than an error being reported in the browser dev tools
console) because the attempt to navigate the top browser context was
suppressed due to sandboxing - the click handling code changed the
target of the link but navigating to that target was blocked. Now the
click handler works as follows:
1. Changes the target of the link to the catch page only if the
link is going to be opened in a new tab or window (in this case
sandboxing restrictions do not apply).
2. Otherwise directly navigates the viewer window to external URL
or the catch page.
An unhandled scenario is opening an external link in a new tab/window
via a middle click or context menu - such events cannot be intercepted
and therefore there is no way of blocking external links accessed in
the said way.
In firefox, when PDF content is displayed in the viewer, changing the
viewer URL in the address bar had no effect. The most prominent
manifestation of this bug was the broken book home button but the same
issue was present even if the fragment component of the viewer URL was
edited manually. The bug was a result of
1. an optimization preventing any actions if the new content URL is the
same as the old content URL (this was needed to break the infinite loop
of mutual updates of the top-window and content window/iframe URLs when
any one of them changes).
2. sandboxing of the iframe and inability to access the content URL in
iframe because of cross-origin restrictions when the content is a PDF
displayed by the builtin viewer.
Now that issue is fixed. A slight remaining defect is that the
addressbar URL is still not updated when a PDF file is loaded/displayed
in the viewer.
The previous "fix" (merged PR #924) was buggy. It not only didn't work
in Chromium v90, but in more recent versions too.
I verified that this fix works in Firefox (v111) and Chromium (v90):
- Attempts by the ZIM content to break out of the viewer iframe are
blocked.
- PDFs are displayed in the viewer.
Added a <noscript> elements which hides everything on the welcome page if javascript is not enabled.
It displays a text to tell the user to navigate to /nojs endpoint
Added cursor type and hints to the UI language selection button. The
hints are always in English since seeing a hint in an unfamiliar language
doesn't help and English is the current lingua franca.
This prevents scripts running inside an iframe from inadvertently
manipulating the top browsing context. However a malicious script could
still remove the sandboxing imposed on it (because the combination of
"allow-same-origin" and "allow-scripts" is vulnerable).
Since kiwixNav is sticky for larger screens now, the tiles area on mobile devices is incredibly low.
This change hides kiwixNav if the screen is scrolled.
If a translation JSON file doesn't contain the 'name' (self-name)
attribute of the translation language then that language is not included
in the list of languages available in the UI language selector.
The language selector on the welcome page has been replaced with
a smaller button that opens a modal language selector. Though the
code for introducing such a modal language selector has been added
in i18n.js, its appearance relies on styles defined in index.css.
Once this new UI for changing the UI language is approved, it must be
used in the ZIM viewer too.
Known issues:
- selecting the language with arrow keys (using the keyboard only,
without pressing space first, so that the full list of languages is
shown) doesn't work because as soon as the current language is changed
the modal language selector disappears.
If the userlang query param is present in the URL it is used to set the
UI language and then is removed from the URL.
Unlike the ZIM viewer, changing the UI language on the welcome page
isn't recorded in the navigation history (and probably it should work
the same way in the ZIM viewer where the appearance of the web page is
affected by the UI language changes to a significantly smaller extent).
This translation has to deal with handling of plural forms which is a
tricky part of internationalization, but we are not going to complicate
things in our code and will offload the headache to translators (they
will have to invent a single message for all numbers).
Veloman Yunkan
translatewiki.net
Nikhil Tanwar