+ curses supports color attributes on terminals with that
+ capability. To use these routines start_color must be
called, usually right after initscr. Colors are always
used in pairs (referred to as color-pairs). A color-pair
consists of a foreground color (for characters) and a
@@ -91,18 +93,89 @@
The routine pair_content allows a programmer to find out
how a given color-pair is currently defined.
- RoutineDescriptions
+
+
+ The curses library combines these inputs to produce the
+ actual foreground and background colors shown on the
+ screen:
+
+ o per-character video attributes (e.g., via waddch),
+
+ o the window attribute (e.g., by wattrset), and
+
+ o the background character (e.g., wbkgdset).
+
+ Per-character and window attributes are usually set by a
+ parameter containing video attributes including a COL-
+ OR_PAIR value. Some functions such as wattr_set use a
+ separate parameter which is the color pair number.
+
+ The background character is a special case: it includes a
+ character value, just as if it were passed to waddch.
+
+ The curses library does the actual work of combining these
+ color pairs in an internal function called from waddch:
+
+ o If the parameter passed to waddch is blank, and it us-
+ es the special color pair 0,
+
+ ocurses next checks the window attribute.
+
+ o If the window attribute does not use color pair 0,
+ curses uses the color pair from the window at-
+ tribute.
+
+ o Otherwise, curses uses the background character.
+
+ o If the parameter passed to waddch is notblank, or it
+ does not use the special color pair 0, curses prefers
+ the color pair from the parameter, if it is nonzero.
+ Otherwise, it tries the window attribute next, and fi-
+ nally the background character.
+
+ Some curses functions such as wprintw call waddch. Those
+ do not combine its parameter with a color pair. Conse-
+ quently those calls use only the window attribute or the
+ background character.
+
+
+
The start_color routine requires no arguments. It must be
- called if the programmer wants to use colors, and before
- any other color manipulation routine is called. It is
- good practice to call this routine right after initscr.
- start_color initializes eight basic colors (black, red,
- green, yellow, blue, magenta, cyan, and white), and two
- global variables, COLORS and COLOR_PAIRS (respectively
- defining the maximum number of colors and color-pairs the
- terminal can support). It also restores the colors on the
- terminal to the values they had when the terminal was just
- turned on.
+ called if the programmer wants to use colors, and before
+ any other color manipulation routine is called. It is
+ good practice to call this routine right after initscr.
+ start_color does this:
+
+ o It initializes two global variables, COLORS and COL-
+ OR_PAIRS (respectively defining the maximum number of
+ colors and color-pairs the terminal can support).
+
+ o It initializes the special color pair 0 to the default
+ foreground and background colors. No other color
+ pairs are initialized.
+
+ o It restores the colors on the terminal to the values
+ they had when the terminal was just turned on.
+
+ o If the terminal supports the initc (initialize_color)
+ capability, start_color initializes its internal table
+ representing the red, green and blue components of the
+ color palette.
+
+ The components depend on whether the terminal uses CGA
+ (aka "ANSI") or HLS (i.e., the hls (hue_lightness_sat-
+ uration) capability is set). The table is initialized
+ first for eight basic colors (black, red, green, yel-
+ low, blue, magenta, cyan, and white), and after that
+ (if the terminal supports more than eight colors) the
+ components are initialized to 1000.
+
+ start_color does not attempt to set the terminal's
+ color palette to match its built-in table. An appli-
+ cation may use init_color to alter the internal table
+ along with the terminal's color.
These limits apply to color values and color pairs. Val-
ues outside these limits are not legal, and may result in
@@ -200,7 +273,9 @@
to by the second and third arguments are in the range 0
through COLORS, inclusive.
- Colors
+
+
In <curses.h> the following macros are defined. These are
the default colors. curses also assumes that COLOR_BLACK
is the default background color for all terminals.
@@ -216,7 +291,7 @@
In the ncurses implementation, there is a separate color
activation flag, color palette, color pairs table, and as-
sociated COLORS and COLOR_PAIRS counts for each screen;
@@ -277,7 +352,7 @@