- The <STRONG>use_env</STRONG> routine, if used, is called before <STRONG>initscr</STRONG> or
- <STRONG>newterm</STRONG> are called. When called with <STRONG>FALSE</STRONG> as an argu-
- ment, the values of <STRONG>lines</STRONG> and <STRONG>columns</STRONG> specified in the
- <EM>terminfo</EM> database will be used, even if environment vari-
- ables <STRONG>LINES</STRONG> and <STRONG>COLUMNS</STRONG> (used by default) are set, or if
- <STRONG>curses</STRONG> is running in a window (in which case default be-
- havior would be to use the window size if <STRONG>LINES</STRONG> and
- <STRONG>COLUMNS</STRONG> are not set). Note that setting <STRONG>LINES</STRONG> or <STRONG>COLUMNS</STRONG>
- overrides the corresponding size which may be obtained
- from the operating system.
+ The <STRONG>use_env</STRONG> routine, if used, should be called before
+ <STRONG>initscr</STRONG> or <STRONG>newterm</STRONG> are called (because those compute the
+ screen size). It modifies the way <STRONG>ncurses</STRONG> treats environ-
+ ment variables when determining the screen size.
+
+ <STRONG>o</STRONG> Normally ncurses looks first at the terminal database
+ for the screen size.
+
+ If <STRONG>use_env</STRONG> was called with <STRONG>FALSE</STRONG> for parameter, it
+ stops here unless If <STRONG>use_tioctl</STRONG> was also called with
+ <STRONG>TRUE</STRONG> for parameter.
+
+ <STRONG>o</STRONG> Then it asks for the screen size via operating system
+ calls. If successful, it overrides the values from
+ the terminal database.
+
+ <STRONG>o</STRONG> Finally (unless <STRONG>use_env</STRONG> was called with <STRONG>FALSE</STRONG> parame-
+ ter), ncurses examines the <STRONG>LINES</STRONG> or <STRONG>COLUMNS</STRONG> environ-
+ ment variables, using a value in those to override the
+ results from the operating system or terminal data-
+ base.
+
+ Ncurses also updates the screen size in response to
+ SIGWINCH, unless overridden by the <STRONG>LINES</STRONG> or <STRONG>COLUMNS</STRONG>
+ environment variables,
+
+ The <STRONG>use_tioctl</STRONG> routine, if used, should be called before
+ <STRONG>initscr</STRONG> or <STRONG>newterm</STRONG> are called (because those compute the
+ screen size). After <STRONG>use_tioctl</STRONG> is called with <STRONG>TRUE</STRONG> as an
+ argument, ncurses modifies the last step in its computa-
+ tion of screen size as follows:
+
+ <STRONG>o</STRONG> checks if the <STRONG>LINES</STRONG> and <STRONG>COLUMNS</STRONG> environment variables
+ are set to a number greater than zero.
+
+ <STRONG>o</STRONG> for each, ncurses updates the corresponding environ-
+ ment variable with the value that it has obtained via
+ operating system call or from the terminal database.
+
+ <STRONG>o</STRONG> ncurses re-fetches the value of the environment vari-
+ ables so that it is still the environment variables
+ which set the screen size.
+
+ The <STRONG>use_env</STRONG> and <STRONG>use_tioctl</STRONG> routines combine as summarized
+ here:
+
+ <EM>use</EM><STRONG>_</STRONG><EM>env</EM> <EM>use</EM><STRONG>_</STRONG><EM>tioctl</EM> <EM>Summary</EM>
+ ----------------------------------------------------------------
+ TRUE FALSE This is the default behavior. ncurses
+ uses operating system calls unless over-
+ ridden by $LINES or $COLUMNS environment
+ variables.
+ TRUE TRUE ncurses updates $LINES and $COLUMNS
+ based on operating system calls.
+
+ FALSE TRUE ncurses ignores $LINES and $COLUMNS, us-
+ es operating system calls to obtain
+ size.
+ FALSE FALSE ncurses relies on the terminal database
+ to determine size.