.\"***************************************************************************
-.\" Copyright (c) 1998-2013,2014 Free Software Foundation, Inc. *
+.\" Copyright (c) 1998-2014,2015 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_initscr.3x,v 1.20 2014/03/01 22:31:22 tom Exp $
+.\" $Id: curs_initscr.3x,v 1.24 2015/07/21 23:01:38 tom Exp $
.TH curs_initscr 3X ""
.de bP
.IP \(bu 4
.br
\fBbool isendwin(void);\fR
.br
-\fBSCREEN *newterm(char *type, FILE *outfd, FILE *infd);\fR
+\fBSCREEN *newterm(char *\fP\fItype\fP\fB, FILE *\fP\fIoutfd\fP\fB, FILE *\fP\fIinfd\fP\fB);\fR
.br
-\fBSCREEN *set_term(SCREEN *new);\fR
+\fBSCREEN *set_term(SCREEN *\fP\fInew\fP\fB);\fR
.br
-\fBvoid delscreen(SCREEN* sp);\fR
+\fBvoid delscreen(SCREEN* \fP\fIsp\fP\fB);\fR
.br
.SH DESCRIPTION
+.SS initscr
\fBinitscr\fR is normally the first \fBcurses\fR routine to call when
initializing a program.
A few special routines sometimes need to be called before it;
If errors occur, \fBinitscr\fR writes an appropriate error
message to standard error and exits;
otherwise, a pointer is returned to \fBstdscr\fR.
+.SS newterm
.PP
A program that outputs to more than one terminal should use the \fBnewterm\fR
routine for each terminal instead of \fBinitscr\fR.
another file pointer for input from the terminal
.PP
If the \fItype\fR parameter is \fBNULL\fR, \fB$TERM\fR will be used.
+.SS endwin
.PP
The program must also call
\fBendwin\fR for each terminal being used before exiting from \fBcurses\fR.
.PP
Calling \fBrefresh\fR or \fBdoupdate\fR after a
temporary escape causes the program to resume visual mode.
+.SS isendwin
.PP
The \fBisendwin\fR routine returns \fBTRUE\fR if \fBendwin\fR has been
called without any subsequent calls to \fBwrefresh\fR,
and \fBFALSE\fR otherwise.
+.SS set_term
.PP
The \fBset_term\fR routine is used to switch between different terminals.
The screen reference \fBnew\fR becomes the new current terminal.
The previous terminal is returned by the routine.
This is the only routine which manipulates \fBSCREEN\fR pointers;
all other routines affect only the current terminal.
+.SS delscreen
.PP
The \fBdelscreen\fR routine frees storage associated with the
\fBSCREEN\fR data structure.
.SH NOTES
Note that \fBinitscr\fR and \fBnewterm\fR may be macros.
.SH PORTABILITY
-These functions are described in the XSI Curses standard, Issue 4.
-It specifies that portable applications must not
-call \fBinitscr\fR more than once.
+These functions were described in the XSI Curses standard, Issue 4.
+As of 2015, the current document is X/Open Curses, Issue 7.
+.SS Differences
+X/Open specifies that portable applications must not
+call \fBinitscr\fR more than once:
+.bP
+The portable way to use \fBinitscr\fP is once only,
+using \fBrefresh\fP (see curs_refresh(3X)) to restore the screen after \fBendwin\fP.
+.bP
+This implementation allows using \fBinitscr\fP after \fBendwin\fP.
.PP
Old versions of curses, e.g., BSD 4.4, may have returned a null pointer
from \fBinitscr\fR when an error is detected, rather than exiting.
It is safe but redundant to check the return value of \fBinitscr\fR
in XSI Curses.
+.SS Unset TERM Variable
.PP
If the TERM variable is missing or empty, \fBinitscr\fP uses the
value \*(``unknown\*('',
which normally corresponds to a terminal entry with the \fIgeneric\fP
(\fIgn\fP) capability.
-Generic entries are detected by \fBsetupterm\fP(3X) and cannot be
+Generic entries are detected by \fBsetupterm\fP (see curs_terminfo(3X)) and cannot be
used for full-screen operation.
Other implementations may handle a missing/empty TERM variable differently.
+.SS Signal Handlers
+.PP
+Quoting from X/Open Curses, section 3.1.1:
+.RS 5
+.PP
+\fICurses implementations may provide for special handling of the SIGINT,
+SIGQUIT and SIGTSTP signals if their disposition is SIG_DFL at the time
+\fBinitscr()\fP is called \fP...
+.PP
+\fIAny special handling for these signals may remain in effect for the
+life of the process or until the process changes the disposition of
+the signal.\fP
+.PP
+\fINone of the Curses functions are required to be safe with respect to signals \fP...
+.RE
+.PP
+This implementation establishes signal handlers during initialization,
+e.g., \fBinitscr\fP or \fBnewterm\fP.
+Applications which must handle these signals should set up the corresponding
+handlers \fIafter\fP initializing the library:
+.TP 5
+.B SIGINT
+The handler \fIattempts\fP to cleanup the screen on exit.
+Although it \fIusually\fP works as expected, there are limitations:
+.RS 5
+.bP
+Walking the \fBSCREEN\fP list is unsafe, since all list management
+is done without any signal blocking.
+.bP
+On systems which have \fBREENTRANT\fP turned on, \fBset_term\fP uses
+functions which could deadlock or misbehave in other ways.
+.bP
+\fBendwin\fP calls other functions, many of which use stdio or
+other library functions which are clearly unsafe.
+.RE
+.TP 5
+.B SIGTERM
+This uses the same handler as \fBSIGINT\fP, with the same limitations.
+It is not mentioned in X/Open Curses, but is more suitable for this
+purpose than \fBSIGQUIT\fP (which is used in debugging).
+.TP 5
+.B SIGTSTP
+This handles the \fIstop\fP signal, used in job control.
+When resuming the process, this implementation discards pending
+input with \fBflushinput\fP (see curs_util(3X)), and repaints the screen
+assuming that it has been completely altered.
+It also updates the saved terminal modes with \fBdef_shell_mode\fP (see curs_kernel(3X)).
+.TP 5
+.B SIGWINCH
+This handles the window-size changes which were initially ignored in
+the standardization efforts.
+The handler sets a (signal-safe) variable
+which is later tested in \fBwgetch\fP (see curs_getch(3X)).
+If \fBkeypad\fP has been enabled for the corresponding window,
+\fBwgetch\fP returns the key symbol \fBKEY_RESIZE\fP.
+At the same time, \fBwgetch\fP calls \fBresizeterm\fP to adjust the
+standard screen \fBstdscr\fP,
+and update other data such as \fBLINES\fP and \fBCOLS\fP.
.SH SEE ALSO
\fBcurses\fR(3X),
\fBcurs_kernel\fR(3X),
projects / ncurses.git / blobdiff