- These functions are an extension to the curses library.
- They permit an application to dynamically allocate a color
- pair using the foreground/background colors rather than
- assign a fixed color pair number, and return an unused
- pair to the pool.
-
- The number of colors may be related to the number of pos-
- sible color pairs for a given terminal, or it may not:
-
- o While almost all terminals allow setting the color
- attributes independently, it is unlikely that your
- terminal allows you to modify the attributes of a
- given character cell without rewriting it. That is,
- the foreground and background colors are applied as a
+ These functions are an extension to the curses library. They permit an
+ application to dynamically allocate a color pair using the
+ foreground/background colors rather than assign a fixed color pair
+ number, and return an unused pair to the pool.
+
+ The number of colors may be related to the number of possible color
+ pairs for a given terminal, or it may not:
+
+ o While almost all terminals allow setting the color attributes
+ independently, it is unlikely that your terminal allows you to
+ modify the attributes of a given character cell without rewriting
+ it. That is, the foreground and background colors are applied as a
pair.
- o Color pairs are the curses library's way of managing a
- color palette on a terminal. If the library does not
- keep track of the combinations of colors which are
- displayed, it will be inefficient.
+ o Color pairs are the curses library's way of managing a color
+ palette on a terminal. If the library does not keep track of the
+ combinations of colors which are displayed, it will be inefficient.
- o For simple terminal emulators with only a few dozen
- color combinations, it is convenient to use the maxi-
- mum number of combinations as the limit on color
- pairs:
+ o For simple terminal emulators with only a few dozen color
+ combinations, it is convenient to use the maximum number of
+ combinations as the limit on color pairs:
- COLORS*COLORS
+ COLORS*COLORS
- o Terminals which support defaultcolors distinct from
- "ANSI colors" add to the possible combinations, pro-
- ducing this total:
+ o Terminals which support defaultcolors distinct from "ANSI colors"
+ add to the possible combinations, producing this total:
- (COLORS+1)*(COLORS+1)
+ (COLORS+1)*(COLORS+1)
- o An application might use up to a few dozen color pairs
- to implement a predefined color scheme.
+ o An application might use up to a few dozen color pairs to implement
+ a predefined color scheme.
- Beyond that lies in the realm of programs using the
- foreground and background colors for "ASCII art" (or
- some other non-textual application).
+ Beyond that lies in the realm of programs using the foreground and
+ background colors for "ASCII art" (or some other non-textual
+ application).
- Also beyond those few dozen pairs, the required size
- for a table to represent the combinations grows
- rapidly with an increasing number of colors.
+ Also beyond those few dozen pairs, the required size for a table to
+ represent the combinations grows rapidly with an increasing number
+ of colors.
- These functions allow a developer to let the screen
- library manage color pairs.
+ These functions allow a developer to let the screen library manage
+ color pairs.
- The alloc_pair function accepts parameters for foreground
- and background color, and checks if that color combination
- is already associated with a color pair.
+ The alloc_pair function accepts parameters for foreground and
+ background color, and checks if that color combination is already
+ associated with a color pair.
- o If the combination already exists, alloc_pair returns
- the existing pair.
+ o If the combination already exists, alloc_pair returns the existing
+ pair.
- o If the combination does not exist, alloc_pair allo-
- cates a new color pair and returns that.
+ o If the combination does not exist, alloc_pair allocates a new color
+ pair and returns that.
- o If the table fills up, alloc_pair discards the least-
- recently allocated entry using free_pair and allocates
- a new color pair.
+ o If the table fills up, alloc_pair discards the least-recently
+ allocated entry using free_pair and allocates a new color pair.
- All of the color pairs are allocated from a table of pos-
- sible color pairs. The size of the table is determined by
- the terminfo pairs capability. The table is shared with
- init_pair; in fact alloc_pair calls init_pair after updat-
- ing the ncurses library's fast index to the colors versus
- color pairs.
+ All of the color pairs are allocated from a table of possible color
+ pairs. The size of the table is determined by the terminfo pairs
+ capability. The table is shared with init_pair; in fact alloc_pair
+ calls init_pair after updating the ncurses library's fast index to the
+ colors versus color pairs.
- The find_pair function accepts parameters for foreground
- and background color, and checks if that color combination
- is already associated with a color pair, returning the
- pair number if it has been allocated. Otherwise it
- returns -1.
+ The find_pair function accepts parameters for foreground and background
+ color, and checks if that color combination is already associated with
+ a color pair, returning the pair number if it has been allocated.
+ Otherwise it returns -1.
- The alloc_pair function returns a color pair number in the
- range 1 through COLOR_PAIRS-1, unless it encounters an
- error updating its fast index to the color pair values,
- preventing it from allocating a color pair. In that case,
- it returns -1.
+ The alloc_pair function returns a color pair number in the range 1
+ through COLOR_PAIRS-1, unless it encounters an error updating its fast
+ index to the color pair values, preventing it from allocating a color
+ pair. In that case, it returns -1.
- The find_pair function returns a color pair number if the
- given color combination has been associated with a color
- pair, or -1 if not.
+ The find_pair function returns a color pair number if the given color
+ combination has been associated with a color pair, or -1 if not.
- Likewise, free_pair returns OK unless it encounters an
- error updating the fast index or if no such color pair is
- in use.
+ Likewise, free_pair returns OK unless it encounters an error updating
+ the fast index or if no such color pair is in use.
- These routines are specific to ncurses. They were not
- supported on Version 7, BSD or System V implementations.
- It is recommended that any code depending on them be con-
- ditioned using NCURSES_VERSION.
+ These routines are specific to ncurses. They were not supported on
+ Version 7, BSD or System V implementations. It is recommended that any
+ code depending on them be conditioned using NCURSES_VERSION.