Introduction
============

The only specification I could find describing mouse input escape sequences
was the /usr/share/doc/xterm/ctlseqs.txt.gz file installed on my Ubuntu
machine.

Here are the relevant escape sequences:

 * [ON] CSI '?' M 'h'                   Enable mouse input mode M
 * [OFF] CSI '?' M 'l'                  Disable mouse input mode M
 * [EVT] CSI 'M' F X Y                  Mouse event (default or mode 1005)
 * [EVT6] CSI '<' F ';' X ';' Y 'M'     Mouse event with mode 1006
 * [EVT6] CSI '<' F ';' X ';' Y 'm'     Mouse event with mode 1006 (up)
 * [EVT15] CSI F ';' X ';' Y 'M'        Mouse event with mode 1015

The first batch of modes affect what events are reported:

 * 9: Presses only (not as well-supported as the other modes)
 * 1000: Presses and releases
 * 1002: Presses, releases, and moves-while-pressed
 * 1003: Presses, releases, and all moves

The next batch of modes affect the encoding of the mouse events:

 * 1005: The X and Y coordinates are UTF-8 codepoints rather than bytes.
 * 1006: Use the EVT6 sequences instead of EVT
 * 1015: Use the EVT15 sequence instead of EVT (aka URVXT-mode)

Support for modes in existing terminals
=======================================

                                 |  9   1000 1002 1003 | 1004 | overflow     | defhi | 1005 1006 1015
---------------------------------+---------------------+------+--------------+-------+----------------
Eclipse TM Terminal (Neon)       |  _    _    _    _   |  _   | n/a          | n/a   |  _    _    _
gnome-terminal 3.6.2             |  X    X    X    X   |  _   | suppressed*b | 0x07  |  _    X    X
iTerm2 2.1.4                     |  _    X    X    X   |  OI  | wrap*z       | n/a   |  X    X    X
jediterm/IntelliJ                |  _    X    X    X   |  _   | ch='?'       | 0xff  |  X    X    X
Konsole 2.13.2                   |  _    X    X    *a  |  _   | suppressed   | 0xff  |  X    X    X
mintty 2.2.2                     |  X    X    X    X   |  OI  | ch='\0'      | 0xff  |  X    X    X
putty 0.66                       |  _    X    X    _   |  _   | suppressed   | 0xff  |  _    X    X
rxvt 2.7.10                      |  X    X    _    _   |  _   | wrap*z       | n/a   |  _    _    _
screen(under xterm)              |  X    X    X    X   |  _   | suppressed   | 0xff  |  _    _    _
urxvt 9.21                       |  X    X    X    X   |  _   | wrap*z       | n/a   |  X    _    X
xfce4-terminal 0.6.3 (GTK2 VTE)  |  X    X    X    X   |  _   | wrap         | n/a   |  _    _    _
xterm                            |  X    X    X    X   |  OI  | ch='\0'      | 0xff  |  X    X    X

*a: Mode 1003 is handled the same way as 1002.
*b: The coordinate wraps from 0xff to 0x00, then maxs out at 0x07.  I'm
    guessing this behavior is a bug?  I'm using the Xubuntu 14.04
    gnome-terminal.
*z: These terminals have a bug where column 224 (and row 224, presumably)
    yields a truncated escape sequence.  224 + 32 is 0, so it would normally
    yield `CSI 'M' F '\0' Y`, but the '\0' is interpreted as a NUL-terminator.

Problem 1: How do these flags work?
===================================

Terminals accept the OFF sequence with any of the input modes.  This makes
little sense--there are two multi-value settings, not seven independent flags!

All the terminals handle Granularity the same way.  ON-Granularity sets
Granularity to the specified value, and OFF-Granularity sets Granularity to
OFF.

Terminals vary in how they handle the Encoding modes.  For example:

 * xterm.  ON-Encoding sets Encoding.  OFF-Encoding with a non-active Encoding
   has no effect.  OFF-Encoding otherwise resets Encoding to Default.

 * mintty (tested 2.2.2), iTerm2 2.1.4, and jediterm.  ON-Encoding sets
   Encoding.  OFF-Encoding resets Encoding to Default.

 * Konsole (tested 2.13.2) seems to configure each encoding method
   independently.  The effective Encoding is the first enabled encoding in this
   list:
    - Mode 1006
    - Mode 1015
    - Mode 1005
    - Default

 * gnome-terminal (tested 3.6.2) also configures each encoding method
   independently.  The effective Encoding is the first enabled encoding in
   this list:
    - Mode 1006
    - Mode 1015
    - Default
   Mode 1005 is not supported.

 * xfce4 terminal 0.6.3 (GTK2 VTE) always outputs the default encoding method.