Currently the alternate screen get messed up on resize if it has
different colors or mode.

Before this patch executing
	printf '\e[10000000000I'
or
	printf '\e[10000000000Z'
resulted in long delay.

sel.alt is only changed by
	sel.alt = IS_SET(MODE_ALTSCREEN);

Thanks to Yuri Karaban for suggesting this!

These changes make -g correspond to <cols>x<rows> and honor it so non-tiling
window managers can work with the size hints afterwards. It also adds a -i
flag to force the window size. This is needed so -g keeps being useful in dwm.

The large and repeated expression used in memmove to indirect
the line can be simplified using a pointer, that makes more
clear where begins and where ends the movement.

Current CSI parsing code uses strtol to parse arguments and allows them
to be negative. Negative argument is not properly handled in tdeletechar
and tinsertblank and results in memory corruption in memmove.

Reproduce with printf '\e[-500@'

Patch also removes special handling for corner case and simplifies
the code.

Removed
	term.dirty[term.c.y] = 1
because tclearregion sets dirty flag.

tscrollup and tscrolldown do not use tsetdirt, but their code is
equivalent to

        tsetdirt(orig, term.bot-n);
        tsetdirt(orig+n, term.bot);

tclearregion also marks cleared lines as dirty.
In tscrolldown it sets lines from term.bot-n+1 to term.bot dirty, and in
tscrollup it sets lines from orig to orig+n-1 dirty.

In both functions all lines from orig to term.bot are effectively set
dirty, but in tscrolldown lines from orig+n to term.bot are set dirty
twice, and in tscrollup lines from orig to term.bot-n are set dirty
twice.

These patches make it clear which lines are set dirty and sets them
dirty once in each funciton.

techo compares signed char to '\x20'. Any character with code less then
'\x20' is treated as control character.  This way characters with MSB
set to 1 are considered control characters too.

Also this patch makes techo display DEL character as ^?.

To reprocuce the bug, enable echo mode using printf '\e[12l',
then type DEL character or any non-ASCII character.

Patch moves MODBIT to macros section and uses it in tselcs.

I found the SERRNO Macro slightly confusing, since you have to look
it up, if you don't know it already. A web search showed it does
not seem to be any kind of standard. Also there was no reason in
the commit log when it was introduced in 2009. As you can see it
also leads to new patches, which don't use this macro (probably the
author did not know about it).

Remove special case for \e because it is handled well by "control code"
case.

Replaced #defines with typedefs where possible, patch attached.

I don't like this alt screen thing, but when
allowaltscreen == 0, the cursor is still saved
and restored after calling 'less' (or 'man').

This patch makes allowaltscreen == 0 usable.

This patch cleans up a style inconsistency.

Backspace key must generate the backspace character (\010) and
Delete key must generate the delete character (\0177). In
some systems the kernel configuration for erasing previous character
is \0177, so some programs (for example cat, ed, mail, ...), can not
understand the correct meaning of backspace. In this cases it is only
needed this command:

	stty erase 

This patch replaces current utf decoder with a new one, which is ~50
lines shorter and should be easier to understand. Parsing 5 and 6
sequences, if necessary, requires trivial modification of UTF_SIZ
constant and utfbyte, utfmask, utfmin, utfmax arrays.

These capabilities inform to programs how print in local printer
of the terminal.

This is very usefull in order to can select what is sent
to the plumber.

These new combinations generate the same behaviour (basically) of
vt102. It is a good way of communicating st with other programs.

[0] http://www.vt100.net/docs/vt102-ug/chapter2.html

This sequence is very useful because allows comunicate the content
of the terminal to another program.

This sequence print the current line. It is different to the
'printer on' sequence, where all the characters that arrive to the
terminal are printer. Here only the ascii characters are printed.

Add some note about the main reason why st is still that big.

This sequence control when the printer is enabled or disabled. This
sequence control the behaviour of the -o option.

Since we are using xmalloc, xrealloc ..., then it is not logical
call directly to strdup.

Signed-off-by: Roberto E. Vargas Caballero <k0ga@shike2.com>

The patch to add w3img support destroys our way to handle fps and so stop
wasting resources on fast scrolling. Due to w3img being a hack to display
images in an ugly way, is there no need to support this. Use some real way to
display images.

It is not defined when lateral effects of expressions are
calculated, so an expression as:

	--last >= gp && !(selected(last - gp, y)

is non portable.

The error condition was duplicated in two different switches.
This new version centralized the error handling in only one place.