+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
+(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 \fBSIGINT\fP,
+\fBSIGQUIT\fP and \fBSIGTSTP\fP signals
+if their disposition is \fBSIG_DFL\fP 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 \fBcurs_kernel\fR(3X)).
+.TP 5
+.B SIGWINCH
+This handles the window-size changes which were 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.
projects / ncurses.git / blobdiff