Add the keycodes and routines to allow the user to forego setting the
mark explicitly (with M-A / ^6) and instead quickly select a few words
or lines by holding down Shift together with the movement keys.
(Some combinations with Shift are swallowed by some terminal emulators.
To work around some of those, the combinations Shift+Alt+Left/Right work
as Shift+Home/End and Shift+Alt+Up/Down work as Shift+PageUp/PageDown.)
This also prevents the message from spilling into the help lines
when the terminal is less than four columns wide. (Not that one
can read anything then, but it looks better.)
Even when the edit window consists of just one or two lines, the PageUp
and PageDown functions (^Y and ^V) should continue to move the window.
This fixes https://savannah.gnu.org/bugs/?48805.
When using the default speller or the formatter, the placewewant is
remembered. So it should be remembered too when the user specifies
a different speller.
(This behavior was inadvertently lost last year, in commit 82d737e.)
It is quicker to do a handful of superfluous compares at the end of
each line than it is to compute and keep track of and compare the
remaining line length the whole time.
The typical line is some sixty characters long, the typical search
string ten characters -- with a shorter search string the speedup is
even higher: some fifteen percent. Only when the string is longer
than half the average line length does searching become slower with
this new method.
All this for a UTF-8 locale. For a C locale it makes no difference.
Now that mbstrncasecmp() does the right thing, there is no need any
more to verify that only a valid multibyte sequence was matched.
(See https://savannah.gnu.org/bugs/?45579 for a test case.)
Also, this will make it possible to search for invalid sequences.
(Currently it isn't possible to enter a search string with invalid
characters, but... a user might edit the search history file. And
if pasting at the prompt is implemented, it will be trivial to enter
invalid sequences if you have a file that contains them.)
Persisting might lead to count 'n' reaching zero, which would mean that
the needle has matched, which is wrong when one of the strings contains
an invalid or incomplete multibyte sequence.
That is: don't run towlower() on the two differing bytes when having
reached the end of one of the strings.
This fixes https://savannah.gnu.org/bugs/?48700.
In the bargain, don't do the conversion to lowercase twice.
Furthermore, persist when encountering invalid byte sequences --
until finding bytes that differ.
The needle is never part of the hay -- it is always a separate string.
(And even if needle and haystack were identical, the routine works fine,
the case does not need special treatment.)
Benno Schulenberg