This config setting provides the ability to disable search indexing on a
per-chapter (or sub-path) basis.
This is structured to possibly add additional settings, such as perhaps
a score multiplier or other settings.
previous implementation used `:not(.fd) + .fd` and `.fd + :not(.fd)`.
the latter selector caused many problems:
- it doesn't select footnote defs which are last children
(this can be easily triggered in a blockquote)
- it changes the margin of the next sibling, rather than the footnote def
itself, which can also *shrink* margin for elements with big margins
(this happens to headings)
- because it applies to the next sibling it is also quite hard to
override in user styles, since it may apply to any element
this commit replaces the latter selector with `:not(:has(+ .fd))`,
which fixes all of the mentioned problems.
Uses an iframe instead. The downside of iframes comes from them
not necessarily being same-origin as the main page (particularly
with `file:///` URLs), which can cause themes to fall out of sync,
but that's not a problem here since themes don't work without JS
anyway.
Before this change, the Rust `unstable-book` is 88MiB.
With this change, it becomes 15MiB. Other pages might not be
as extreme, but it's expected to help any book like this.
This change is so drastic because, if every chapter has a link to
every other chapter, the result is *O*(n<sup>2</sup>) text output.
Above mentioned function copies files (recursively) from a source to a
destination directory. For that, file/directory paths have to be created
repeatedly. This allocates as directory and file names are concatenated
into an owning path structure.
The number of allocations can be reduced by creating file/directory
paths only once and borrowing them instead of cloning/recreating them.
In bigger projects, this reduces execution time noticeably. Please note
that file system operations are dominant from performance POV.
on rust reference book this reduces total allocs from 490mb to 474mb:
==23272== Total: 490,538,699 bytes in 1,760,117 blocks
==23272== At t-gmax: 13,872,954 bytes in 4,655 blocks
==23272== At t-end: 488,516 bytes in 884 blocks
==23272== Reads: 830,509,060 bytes
==23272== Writes: 522,290,614 bytes
to
==40876== Total: 474,156,323 bytes in 1,521,025 blocks
==40876== At t-gmax: 13,872,954 bytes in 4,655 blocks
==40876== At t-end: 488,516 bytes in 884 blocks
==40876== Reads: 820,933,434 bytes
==40876== Writes: 514,838,350 bytes
