Also, avoid an unused-variable warning when configured with
--enable-tiny --enable-help --enable-multibuffer.

Searching for an empty string should be impossible, it should never
happen, but it is bit too hard to verify this at the moment.

If the length of the haystack is smaller than the length of the needle,
this means that also the length of the tail will be smaller -- because
pointer will be bigger than or equal to haystack -- so the pointer gets
readjusted to be a needle length before the end of the haystack, which
means that it ends up /before/ the haystack: thus the while loop will
never run.

On average, this saves some 200 nanoseconds per line.

Because it is slightly faster.

It is not an index, it is not an offset from anything,
it is a direct pointer.

And because I think it looks slightly better.

This avoids https://savannah.gnu.org/bugs/?49912 while at the same time
avoiding to draw the edit window twice in a row -- the first drawing
would use a wrong margin, which results in a visible and irritating
shift left or right of the content upon the second drawing.

This fixes https://savannah.gnu.org/bugs/?50877.

We should measure the length of each /translated/ shortcut description,
not of the original English one.

This fixes https://savannah.gnu.org/bugs/?50899.

This addresses https://savannah.gnu.org/bugs/?50897

.
Reported-by: Hannu Nyman <hannu.nyman@iki.fi>

This elides a counter and a comparison from the central loop,
and thus makes the search a tiny bit faster.

And one-letter variables I cannot "see" -- they are too small.

An iterator should not be called "start_col", because it is only the
starting column at the very beginning.

Also, start_col (after the rename) can never be /larger/ than column.

The mbwidth() function itself checks whether UTF-8 is being used
and does the right thing.

Backspace is a more logical counterpart of Space than minus.

Also, harmonize some configure-option descriptions,
add a slash after a subdir, and fix a typo.

Also, add two missing configure options, and frob some other things.

It complained of "Unbound key" until now.

That is: nest the conditions consistently.
And in the bargain rename the variable.

Also, mention that help texts can now be searched through, update
a copyright notice, and update and simplify a copyright year.

And in the process transform the token DISABLE_HELP to ENABLE_HELP.

This avoids applying the default syntax, or the syntax specified
with --syntax, to a ^G help text.

And allow 'N' for searching the next occurrence.  Add the
same keystrokes to the file browser too, for consistency.

Since the help text is searchable, an <End> would go to the end of the
text but would leave a blank line above the statusbar -- a blank line
that wasn't there before, and that is not reached when simply holding
down <Down> all the way from the top.

So that the shortcut explanations get properly aligned.

When nano has multiple files open, closing a help buffer should
not switch to the next buffer in the ring but to the preceding one,
because it was from there that the help screen was invoked.

Also, save and restore all the flags in a single swoop.

There is no need to restore NOREAD_MODE after unsetting it, because
any files mentioned on the command line have already been /not/ read.

However, prefer moving the starting point of the text backwards over
moving it forward, so that of the same paragraph more text is shown
instead of less.  But scroll an empty line out of view -- no text is
"lost" then.

The top-left corner changing is far more conspicuous than the top right.

Allow the user to search in a help text with ^W and M-W.

Achieve this by not writing the help text directly to the screen
but first writing it to a temporary file and then opening this file
in a new buffer, and treating it specially: the normal file-reading
feedback is suppressed, the titlebar shows the headline of the text,
the cursor is hidden, and the menu is limited to just the up and down
movements and searching.

This fulfills https://savannah.gnu.org/bugs/?28994

.
Signed-off-by: Rishabh Dave <rishabhddave@gmail.com>

This fixes https://savannah.gnu.org/bugs/?50872.

The go_back_chunks() function will do this clipping.

This fixes https://savannah.gnu.org/bugs/?50866.

And make the strings after "start=" and  "end=" more readable.