+ <B>o</B> Control characters are displayed in the <B>^</B><I>X</I> notation.
+
+ <B>o</B> DEL (character 127) is displayed as <B>^?</B>.
+
+ <B>o</B> Values above 128 are either meta characters (if the screen has not
+ been initialized, or if <B><A HREF="curs_inopts.3X.html">meta(3X)</A></B> has been called with a <B>TRUE</B> param-
+ eter), shown in the <B>M-</B><I>X</I> notation, or are displayed as themselves.
+ In the latter case, the values may not be printable; this follows
+ the X/Open specification.
+
+ <B>o</B> Values above 256 may be the names of the names of function keys.
+
+ <B>o</B> Otherwise (if there is no corresponding name) the function returns
+ null, to denote an error. X/Open also lists an "UNKNOWN KEY" re-
+ turn value, which some implementations return rather than null.
+
+ The corresponding <B>key_name</B> returns a character string corresponding to
+ the wide-character value <I>w</I>. The two functions do not return the same
+ set of strings; the latter returns null where the former would display
+ a meta character.
+
+
+</PRE><H3><a name="h3-filter_nofilter">filter/nofilter</a></H3><PRE>
+ The <B>filter</B> routine, if used, must be called before <B>initscr</B> or <B>newterm</B>
+ are called. Calling <B>filter</B> causes these changes in initialization:
+
+ <B>o</B> <B>LINES</B> is set to 1;
+
+ <B>o</B> the capabilities <B>clear</B>, <B>cud1</B>, <B>cud</B>, <B>cup</B>, <B>cuu1</B>, <B>cuu</B>, <B>vpa</B> are dis-
+ abled;
+
+ <B>o</B> the capability <B>ed</B> is disabled if <B>bce</B> is set;
+
+ <B>o</B> and the <B>home</B> string is set to the value of <B>cr</B>.
+
+ The <B>nofilter</B> routine cancels the effect of a preceding <B>filter</B> call.
+ That allows the caller to initialize a screen on a different device,
+ using a different value of <B>$TERM</B>. The limitation arises because the
+ <B>filter</B> routine modifies the in-memory copy of the terminal information.
+
+
+</PRE><H3><a name="h3-use_env">use_env</a></H3><PRE>
+ The <B>use_env</B> routine, if used, should be called before <B>initscr</B> or
+ <B>newterm</B> are called (because those compute the screen size). It modi-
+ fies the way <B>ncurses</B> treats environment variables when determining the
+ screen size.
+
+ <B>o</B> Normally <B>ncurses</B> looks first at the terminal database for the
+ screen size.
+
+ If <B>use_env</B> was called with <B>FALSE</B> for parameter, it stops here un-
+ less <B>use_tioctl</B> was also called with <B>TRUE</B> for parameter.
+
+ <B>o</B> Then it asks for the screen size via operating system calls. If
+ successful, it overrides the values from the terminal database.
+
+ <B>o</B> Finally (unless <B>use_env</B> was called with <B>FALSE</B> parameter), <B>ncurses</B>
+ examines the <B>LINES</B> or <B>COLUMNS</B> environment variables, using a value
+ in those to override the results from the operating system or ter-
+ minal database.
+
+ <B>Ncurses</B> also updates the screen size in response to <B>SIGWINCH</B>, un-
+ less overridden by the <B>LINES</B> or <B>COLUMNS</B> environment variables,
+
+
+</PRE><H3><a name="h3-use_tioctl">use_tioctl</a></H3><PRE>
+ The <B>use_tioctl</B> routine, if used, should be called before <B>initscr</B> or
+ <B>newterm</B> are called (because those compute the screen size). After
+ <B>use_tioctl</B> is called with <B>TRUE</B> as an argument, <B>ncurses</B> modifies the
+ last step in its computation of screen size as follows:
+
+ <B>o</B> checks if the <B>LINES</B> and <B>COLUMNS</B> environment variables are set to a
+ number greater than zero.
+
+ <B>o</B> for each, <B>ncurses</B> updates the corresponding environment variable
+ with the value that it has obtained via operating system call or
+ from the terminal database.
+
+ <B>o</B> <B>ncurses</B> re-fetches the value of the environment variables so that
+ it is still the environment variables which set the screen size.
+
+ The <B>use_env</B> and <B>use_tioctl</B> routines combine as summarized here:
+
+ <I>use</I><B>_</B><I>env</I> <I>use</I><B>_</B><I>tioctl</I> <I>Summary</I>
+ ----------------------------------------------------------------
+ TRUE FALSE This is the default behavior. <B>ncurses</B>
+ uses operating system calls unless over-
+ ridden by $LINES or $COLUMNS environment
+ variables.
+
+ TRUE TRUE <B>ncurses</B> updates $LINES and $COLUMNS
+ based on operating system calls.
+ FALSE TRUE <B>ncurses</B> ignores $LINES and $COLUMNS, us-
+ es operating system calls to obtain
+ size.
+ FALSE FALSE <B>ncurses</B> relies on the terminal database
+ to determine size.
+
+
+</PRE><H3><a name="h3-putwin_getwin">putwin/getwin</a></H3><PRE>
+ The <B>putwin</B> routine writes all data associated with window (or pad) <I>win</I>
+ into the file to which <I>filep</I> points. This information can be later re-
+ trieved using the <B>getwin</B> function.
+
+ The <B>getwin</B> routine reads window related data stored in the file by
+ <B>putwin</B>. The routine then creates and initializes a new window using
+ that data. It returns a pointer to the new window. There are a few
+ caveats:
+
+ <B>o</B> the data written is a copy of the <B>WINDOW</B> structure, and its associ-
+ ated character cells. The format differs between the wide-charac-
+ ter (<B>ncursesw</B>) and non-wide (<B>ncurses</B>) libraries. You can transfer
+ data between the two, however.
+
+ <B>o</B> the retrieved window is always created as a top-level window (or
+ pad), rather than a subwindow.
+
+ <B>o</B> the window's character cells contain the color pair <I>value</I>, but not
+ the actual color <I>numbers</I>. If cells in the retrieved window use
+ color pairs which have not been created in the application using
+ <B>init_pair</B>, they will not be colored when the window is refreshed.
+
+
+</PRE><H3><a name="h3-delay_output">delay_output</a></H3><PRE>
+ The <B>delay_output</B> routine inserts an <I>ms</I> millisecond pause in output.
+ This routine should not be used extensively because padding characters
+ are used rather than a CPU pause. If no padding character is speci-
+ fied, this uses <B>napms</B> to perform the delay.
+
+
+</PRE><H3><a name="h3-flushinp">flushinp</a></H3><PRE>
+ The <B>flushinp</B> routine throws away any typeahead that has been typed by
+ the user and has not yet been read by the program.
+
+
+</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
+ Except for <B>flushinp</B>, routines that return an integer return <B>ERR</B> upon
+ failure and <B>OK</B> (SVr4 specifies only "an integer value other than <B>ERR</B>")
+ upon successful completion.
+
+ Routines that return pointers return <B>NULL</B> on error.
+
+ X/Open does not define any error conditions. In this implementation
+
+ <B>flushinp</B>
+ returns an error if the terminal was not initialized.
+
+ <B>putwin</B>
+ returns an error if the associated <B>fwrite</B> calls return an er-
+ ror.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+
+</PRE><H3><a name="h3-filter">filter</a></H3><PRE>
+ The SVr4 documentation describes the action of <B>filter</B> only in the
+ vaguest terms. The description here is adapted from the XSI Curses
+ standard (which erroneously fails to describe the disabling of <B>cuu</B>).
+
+
+</PRE><H3><a name="h3-keyname">keyname</a></H3><PRE>
+ The <B>keyname</B> function may return the names of user-defined string capa-
+ bilities which are defined in the terminfo entry via the <B>-x</B> option of
+ <B>tic</B>. This implementation automatically assigns at run-time keycodes to
+ user-defined strings which begin with "k". The keycodes start at
+ KEY_MAX, but are not guaranteed to be the same value for different runs
+ because user-defined codes are merged from all terminal descriptions
+ which have been loaded. The <B><A HREF="curs_extend.3X.html">use_extended_names(3X)</A></B> function controls
+ whether this data is loaded when the terminal description is read by
+ the library.
+
+
+</PRE><H3><a name="h3-nofilter_use_tioctl">nofilter/use_tioctl</a></H3><PRE>
+ The <B>nofilter</B> and <B>use_tioctl</B> routines are specific to <B>ncurses</B>. They
+ were not supported on Version 7, BSD or System V implementations. It
+ is recommended that any code depending on <B>ncurses</B> extensions be condi-
+ tioned using NCURSES_VERSION.
+
+
+</PRE><H3><a name="h3-putwin_getwin">putwin/getwin</a></H3><PRE>
+ The <B>putwin</B> and <B>getwin</B> functions have several issues with portability:
+
+ <B>o</B> The files written and read by these functions use an implementa-
+ tion-specific format. Although the format is an obvious target for
+ standardization, it has been overlooked.
+
+ Interestingly enough, according to the copyright dates in Solaris
+ source, the functions (along with <B>scr_init</B>, etc.) originated with
+ the University of California, Berkeley (in 1982) and were later (in
+ 1988) incorporated into SVr4. Oddly, there are no such functions
+ in the 4.3BSD curses sources.
+
+ <B>o</B> Most implementations simply dump the binary <B>WINDOW</B> structure to the
+ file. These include SVr4 curses, NetBSD and PDCurses, as well as
+ older <B>ncurses</B> versions. This implementation (as well as the X/Open
+ variant of Solaris curses, dated 1995) uses textual dumps.
+
+ The implementations which use binary dumps use block-I/O (the
+ <B>fwrite</B> and <B>fread</B> functions). Those that use textual dumps use
+ buffered-I/O. A few applications may happen to write extra data in
+ the file using these functions. Doing that can run into problems
+ mixing block- and buffered-I/O. This implementation reduces the
+ problem on writes by flushing the output. However, reading from a
+ file written using mixed schemes may not be successful.
+
+
+</PRE><H3><a name="h3-unctrl_wunctrl">unctrl/wunctrl</a></H3><PRE>
+ The XSI Curses standard, Issue 4 describes these functions. It states
+ that <B>unctrl</B> and <B>wunctrl</B> will return a null pointer if unsuccessful, but
+ does not define any error conditions. This implementation checks for
+ three cases:
+
+ <B>o</B> the parameter is a 7-bit US-ASCII code. This is the case that
+ X/Open Curses documented.
+
+ <B>o</B> the parameter is in the range 128-159, i.e., a C1 control code. If
+ <B><A HREF="legacy_coding.3X.html">use_legacy_coding(3X)</A></B> has been called with a <B>2</B> parameter, <B>unctrl</B>
+ returns the parameter, i.e., a one-character string with the param-
+ eter as the first character. Otherwise, it returns "~@", "~A",
+ etc., analogous to "^@", "^A", C0 controls.
+
+ X/Open Curses does not document whether <B>unctrl</B> can be called before
+ initializing curses. This implementation permits that, and returns
+ the "~@", etc., values in that case.
+
+ <B>o</B> parameter values outside the 0 to 255 range. <B>unctrl</B> returns a null
+ pointer.
+
+ The strings returned by <B>unctrl</B> in this implementation are determined at
+ compile time, showing C1 controls from the upper-128 codes with a "~"
+ prefix rather than "^". Other implementations have different conven-
+ tions. For example, they may show both sets of control characters with
+ "^", and strip the parameter to 7 bits. Or they may ignore C1 controls
+ and treat all of the upper-128 codes as printable. This implementation
+ uses 8 bits but does not modify the string to reflect locale. The
+ <B><A HREF="legacy_coding.3X.html">use_legacy_coding(3X)</A></B> function allows the caller to change the output
+ of <B>unctrl</B>.
+
+ Likewise, the <B><A HREF="curs_inopts.3X.html">meta(3X)</A></B> function allows the caller to change the output
+ of <B>keyname</B>, i.e., it determines whether to use the "M-" prefix for
+ "meta" keys (codes in the range 128 to 255). Both <B>use_legacy_cod-</B>
+ <B><A HREF="use_legacy_coding.3X.html">ing(3X)</A></B> and <B><A HREF="curs_inopts.3X.html">meta(3X)</A></B> succeed only after curses is initialized. X/Open
+ Curses does not document the treatment of codes 128 to 159. When
+ treating them as "meta" keys (or if <B>keyname</B> is called before initializ-
+ ing curses), this implementation returns strings "M-^@", "M-^A", etc.