== The shift-selection trick in X terminal programs

Seeing [[this http://twitter.com/zaitcev/status/2880884065]] today
reminded me of a relatively obscure feature and counter-feature in
_xterm_ and similar imitators like gnome-terminal and konsole.

First, the feature (sometimes 'feature'): in order to let text mode
programs still have clickable objects, _xterm_ lets programs steal left
mouse (button-1) clicks; instead of selecting text, the program gets
escape sequences that tell it about the click and it can do whatever it
wants with them. The most obvious application is text-mode web browsers
like _links_, which uses it to let you click on links.

(The [[Xterm Control Sequences
http://invisible-island.net/xterm/ctlseqs/ctlseqs.html]] documentation
calls this 'mouse tracking'.)

This spawned an immediate demand for a counter-feature, and so in
_xterm_ and its imitators ~~shift plus left mouse button always selects
text~~, even if a program has put _xterm_ in this special mouse tracking
mode. In _xterm_, all of the usual double and triple click selection
tricks work when shifted; your mileage may vary in gnome-terminal et al.

This doesn't seem to be documented in the _xterm_ manpage, so I'm
not sure where I learned it; it may have been ambient X knowledge
at some point back in the days, and I just picked it up. It's
fortunate that it seems to have been well enough known to be
copied by the people writing gnome-terminal, _konsole_, and so on.

(_xterm_ has a great deal of [[peculiar features
../sysadmin/XtermZiconbeep]] that are at best half-known these days, or
that usually take careful study of the manpage to spot.)