Check-in [294a0c172c]

option will not be defined on serial channels.

# Echo and Cooking Control

Terminals have a number of modes of operation.  Two of the most useful
things that can be set relate to echoing and cooking.

Echoing is fairly simple to understand.  If a terminal has echoing
turned on, every character read is written to the terminal
automatically without any action from the program reading from the
terminal.  Most of the time this is a good thing as people want to
see what they have typed, but sometimes it is not so good.  Examples
include where someone is typing in a password \(when they also want
their lines cooked\) and where an application is being controlled by
single key-presses \(which is a case where neither echoing or cooking
are desirable, with echoing being a problem because the key press is
causing a different set of visible changes in the program's output.\)

Cooking is also fairly simple.  A terminal is producing cooked input
when it is working in simply-editable line-at-a-time mode.  When the
terminal isn't in cooked mode, it delivers raw input directly and
immediately to the program.  Cooked input is the default and is useful
for a lot of purposes, but sometimes \(when the application wants to
use single key-presses to control it\) raw input is definitely
preferable.  Example uses of raw input include text editors \(such as
vi or emacs\) or terminal-based menu systems.

I propose supporting these operation modes within Tcl through a single
new option to the **fconfigure** command \(to definitely be implemented
on Unix serial channels - because that is the type of stdin in a
normal interactive session - and suitably on other platforms if
possible\): **-inputmode**.  This will have three legal values:

 **normal**: This will turn on both echoing and cooking of input, and can
 be considered to be the default configuration for all terminals.

 **password**: This will turn off echoing but leave cooking turned on.

 **raw**: This will turn off both echoing and line-cooking.

I'm not aware off-hand of any use-cases for echoed raw mode.  While
there is theoretically a problem due to cross-talk between channels
\(similar to that which was observed with the rationale for the
**-closemode** option\), it is practically unlikely to be one since
applications that take parsed input from several serial lines are very
rare.

option will not be defined on serial channels.

# Echo and Cooking Control

Terminals have a number of modes of operation.  Two of the most useful
things that can be set relate to echoing and cooking.

_Echoing_ is fairly simple to understand.  If a terminal has echoing
turned on, every character read is written to the terminal
automatically without any action from the program reading from the
terminal.  Most of the time this is a good thing as people want to
see what they have typed, but sometimes it is not so good.  Examples
include where someone is typing in a password \(when they also want
their lines cooked\) and where an application is being controlled by
single key-presses \(which is a case where neither echoing or cooking
are desirable, with echoing being a problem because the key press is
causing a different set of visible changes in the program's output.\)

_Cooking_ is also fairly simple.  A terminal is producing cooked input
when it is working in simply-editable line-at-a-time mode.  When the
terminal isn't in cooked mode, it delivers raw input directly and
immediately to the program.  Cooked input is the default and is useful
for a lot of purposes, but sometimes \(when the application wants to
use single key-presses to control it\) raw input is definitely
preferable.  Example uses of raw input include text editors \(such as
vi or emacs\) or terminal-based menu systems.

I propose supporting these operation modes within Tcl through a single
new option to the **fconfigure** command \(to definitely be implemented
on Unix serial channels — because that is the type of stdin in a
normal interactive session — and suitably on other platforms if
possible\): **-inputmode**.  This will have three legal values:

 * **normal**: This will turn on both echoing and cooking of input, and can
 be considered to be the default configuration for all terminals.

 * **password**: This will turn off echoing but leave cooking turned on.

 * **raw**: This will turn off both echoing and line-cooking.

I'm not aware off-hand of any use-cases for echoed raw mode.  While
there is theoretically a problem due to cross-talk between channels
\(similar to that which was observed with the rationale for the
**-closemode** option\), it is practically unlikely to be one since
applications that take parsed input from several serial lines are very
rare.