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

This fixes https://savannah.gnu.org/bugs/?48455.

When the user changes her mind after having pressed Esc, she cannot
unpress Esc, so do that for her by ignoring the escape code when
the subsequent keycode is outside of the normal printable range.

This restores the behavior from before nano-2.3.5 -- except that
Ctrl+Alt+key continues to report an unbound key.

This fixes https://savannah.gnu.org/bugs/?48459.

This prevents many keycode sequences from being misconstrued when a
command key plus other keystrokes accumulate in the input buffer.

This fixes https://savannah.gnu.org/bugs/?48395.

Color-pair numbers and attributes can be OR'd together -- do so,
to save an attron() call whenever the hilite is on.

To make nano save its modified buffers when it runs out of memory.

Also condense some comments, and group keys with the same result together.

Add them so that <Esc> followed by <Home> will simply do "Home" instead of
reporting an unbound key.  The same for <End>, <PageUp> and <PageDown>.

This restores the behavior from before nano-2.3.5.

It is easy to type beside the comma key and hit instead "m" or ".", so
accept also these as a separator between line and column number.  And
when being generous anyway, also accept space, slash and semicolon.

This fulfills https://savannah.gnu.org/bugs/?48305

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

When parsing a line and a column number, of course the found values
need to be passed back, otherwise it would be pointless to parse them.

And in the bargain show an error message when doing ^R unreadabledir ^T.

Precalculation of the multiline color data can be cut short when the
user is impatient and starts typing.  But this would drop the first
byte of whatever was typed -- not nice when it was just plain text,
but surprising and worse when the first keystroke was a command.

This fixes https://savannah.gnu.org/bugs/?48388.

When for a multiline syntax-coloring rule the starting regex matches at
the exact same spot as the ending regex, do a second round of resets, so
that reevaluation starts further back and gets a few more things right.

This mildly fixes https://savannah.gnu.org/bugs/?47420.

When we get a ^J as verbatim input, it is not possible to include it
into the file buffer or the prompt answer, because this would mean
adding an encoded null to the buffer or answer, and that is not what
the user intended.  One option would have been to simply ignore a ^J
in verbatim input.  But the choice has been made to act the same way
as when the ^J (0x0A) is found in the file data: start a new line.

That is the same response as to the Enter key, yes -- but the code
for the Enter key is ^M (0x0D), not ^J.  So, to be more precise,
rename the relevant variable from 'got_enter' to 'got_newline'.

When the user tab-completed a name at the Go To Directory prompt, this
name will end in a slash.  Remove this slash, so the name can be found
in the file list (where directory names don't include the final slash).

This fixes http://savannah.gnu.org/bugs/?48353

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

And order them from smallest stride to biggest stride.

So, slightly speed up the functions that check for those.

Invalid multibyte sequences get depicted with the Replacement Character,
and unassigned codepoints are shown as if they were a space.  Both have
a width of one.

Spaces and tabs and control codes never are multi-column glyphs, so
only look up the width for "normal", visible characters.

This avoids having to null-terminate every single-byte character.

Just allocate ample space up front and thus discard the delaying 'if' for
each and every character.  In most cases this will allocate far too much,
but that hardly matters: it is freed again as soon as the line is printed.

This fixes https://savannah.gnu.org/bugs/?48125.

(The fix is slightly wasteful; speeding things up will follow later.)

Use knowledge of UTF-8 instead of converting to wide characters first.

Any control character is represented by a ^ plus an ASCII character.