These routines set options that change the style of output within curses. All options are initially FALSE, unless otherwise stated. It is not necessary to turn these options off before calling endwin.
If clearok is called with TRUE as argument, the next call to wrefresh with this window will clear the screen completely and redraw the entire screen from scratch. This is useful when the contents of the screen are uncertain, or in some cases for a more pleasing visual effect. If the win argument to clearok is the global variable curscr, the next call to wrefresh with any window causes the screen to be cleared and repainted from scratch.
If idlok is called with TRUE as second argument, curses considers using the hardware insert/delete line feature of terminals so equipped. Calling idlok with FALSE as second argument disables use of line insertion and deletion. This option should be enabled only if the application needs insert/delete line, for example, for a screen editor. It is disabled by default because insert/delete line tends to be visually annoying when used in applications where it isnt really needed. If insert/delete line cannot be used, curses redraws the changed portions of all lines.
If idcok is called with FALSE as second argument, curses no longer considers using the hardware insert/delete character feature of terminals so equipped. Use of character insert/delete is enabled by default. Calling idcok with TRUE as second argument re-enables use of character insertion and deletion.
If immedok is called with TRUE as argument, any change in the window image, such as the ones caused by waddch, wclrtobot, wscrl, etc., automatically cause a call to wrefresh. However, it may degrade performance considerably, due to repeated calls to wrefresh. It is disabled by default.
Normally, the hardware cursor is left at the location of the window cursor being refreshed. The leaveok option allows the cursor to be left wherever the update happens to leave it. It is useful for applications where the cursor is not used, since it reduces the need for cursor motions.
The setscrreg and wsetscrreg routines allow the application programmer to set a software scrolling region in a window. top and bot are the line numbers of the top and bottom margin of the scrolling region. (Line 0 is the top line of the window.) If this option and scrollok are enabled, an attempt to move off the bottom margin line causes all lines in the scrolling region to scroll one line in the direction of the first line. Only the text of the window is scrolled. (Note that this has nothing to do with the use of a physical scrolling region capability in the terminal, like that in the VT100. If idlok is enabled and the terminal has either a scrolling region or insert/delete line capability, they will probably be used by the output routines.)
The scrollok option controls what happens when the cursor of a window is moved off the edge of the window or scrolling region, either as a result of a newline action on the bottom line, or typing the last character of the last line. If disabled, (bf is FALSE), the cursor is left on the bottom line. If enabled, (bf is TRUE), the window is scrolled up one line (Note that to get the physical scrolling effect on the terminal, it is also necessary to call idlok).
The nl and nonl routines control whether the underlying display device translates the return key into newline on input, and whether it translates newline into return and line-feed on output (in either case, the call addch(\n) does the equivalent of return and line feed on the virtual screen). Initially, these translations do occur. If you disable them using nonl, curses will be able to make better use of the line-feed capability, resulting in faster cursor motion. Also, curses will then be able to detect the return key.
The functions setscrreg and wsetscrreg return OK upon success and ERR upon failure. All other routines that return an integer always return OK.
These functions are described in the XSI Curses standard, Issue 4.
The XSI Curses standard is ambiguous on the question of whether raw() should disable the CRLF translations controlled by nl() and nonl(). BSD curses did turn off these translations; AT&T curses (at least as late as SVr1) did not. We choose to do so, on the theory that a programmer requesting raw input wants a clean (ideally 8-bit clean) connection that the operating system does not mess with.
Some historic curses implementations had, as an undocumented feature, the ability to do the equivalent of clearok(..., 1) by saying touchwin(stdscr) or clear(stdscr). This will not work under ncurses.
Earlier System V curses implementations specified that with scrollok enabled, any window modification triggering a scroll also forced a physical refresh. XSI Curses does not require this, and ncurses avoids doing it to perform better vertical-motion optimization at wrefresh time.
The XSI Curses standard does not mention that the cursor should be made invisible as a side-effect of leaveok. SVr4 curses documentation does this, but the code does not. Use curs_set to make the cursor invisible.
Note that clearok, leaveok, scrollok, idcok, nl, nonl and setscrreg may be macros.
The immedok routine is useful for windows that are used as terminal emulators.
curses(3), curs_addch(3), curs_clear(3), curs_initscr(3), curs_scroll(3), curs_refresh(3)