<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML ><HEAD ><TITLE >Colors</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE=" NCURSES Programming HOWTO " HREF="index.html"><LINK REL="PREVIOUS" TITLE="Windows" HREF="windows.html"><LINK REL="NEXT" TITLE="Interfacing with the key board" HREF="keys.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >NCURSES Programming HOWTO</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="windows.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="keys.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="COLOR" ></A >10. Colors</H1 ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="COLORBASICS" ></A >10.1. The basics</H2 ><P >Life seems dull with no colors. Curses has a nice mechanism to handle colors. Let's get into the thick of the things with a small program.</P ><DIV CLASS="EXAMPLE" ><A NAME="BSICO" ></A ><P ><B >Example 9. A Simple Color example </B ></P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="PROGRAMLISTING" ><SPAN CLASS="INLINEMEDIAOBJECT" >#include <ncurses.h> void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string); int main(int argc, char *argv[]) { initscr(); /* Start curses mode */ if(has_colors() == FALSE) { endwin(); printf("Your terminal does not support color\n"); exit(1); } start_color(); /* Start color */ init_pair(1, COLOR_RED, COLOR_BLACK); attron(COLOR_PAIR(1)); print_in_middle(stdscr, LINES / 2, 0, 0, "Viola !!! In color ..."); attroff(COLOR_PAIR(1)); getch(); endwin(); } void print_in_middle(WINDOW *win, int starty, int startx, int width, char *string) { int length, x, y; float temp; if(win == NULL) win = stdscr; getyx(win, y, x); if(startx != 0) x = startx; if(starty != 0) y = starty; if(width == 0) width = 80; length = strlen(string); temp = (width - length)/ 2; x = startx + (int)temp; mvwprintw(win, y, x, "%s", string); refresh(); } </SPAN ></PRE ></FONT ></TD ></TR ></TABLE ></DIV ><P >As you can see, to start using color, you should first call the function <TT CLASS="LITERAL" > start_color()</TT >. After that, you can use color capabilities of your terminals using various functions. To find out whether a terminal has color capabilities or not, you can use <TT CLASS="LITERAL" >has_colors()</TT > function, which returns FALSE if the terminal does not support color. </P ><P >Curses initializes all the colors supported by terminal when start_color() is called. These can be accessed by the define constants like <TT CLASS="LITERAL" >COLOR_BLACK </TT > etc. Now to actually start using colors, you have to define pairs. Colors are always used in pairs. That means you have to use the function <TT CLASS="LITERAL" >init_pair() </TT > to define the foreground and background for the pair number you give. After that that pair number can be used as a normal attribute with <TT CLASS="LITERAL" >COLOR_PAIR()</TT >function. This may seem to be cumbersome at first. But this elegant solution allows us to manage color pairs very easily. To appreciate it, you have to look into the the source code of "dialog", a utility for displaying dialog boxes from shell scripts. The developers have defined foreground and background combinations for all the colors they might need and initialized at the beginning. This makes it very easy to set attributes just by accessing a pair which we already have defined as a constant.</P ><P >The following colors are defined in <TT CLASS="LITERAL" >curses.h</TT >. You can use these as parameters for various color functions. <TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="PROGRAMLISTING" > COLOR_BLACK 0 COLOR_RED 1 COLOR_GREEN 2 COLOR_YELLOW 3 COLOR_BLUE 4 COLOR_MAGENTA 5 COLOR_CYAN 6 COLOR_WHITE 7</PRE ></FONT ></TD ></TR ></TABLE ></P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="CHANGECOLORDEFS" ></A >10.2. Changing Color Definitions</H2 ><P >The function <TT CLASS="LITERAL" >init_color()</TT >can be used to change the rgb values for the colors defined by curses initially. Say you wanted to lighten the intensity of red color by a minuscule. Then you can use this function as</P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="PROGRAMLISTING" > init_color(COLOR_RED, 700, 0, 0); /* param 1 : color name * param 2, 3, 4 : rgb content min = 0, max = 1000 */</PRE ></FONT ></TD ></TR ></TABLE ><P >If your terminal cannot change the color definitions, the function returns ERR. The function <TT CLASS="LITERAL" >can_change_color()</TT > can be used to find out whether the terminal has the capability of changing color content or not. The rgb content is scaled from 0 to 1000. Initially RED color is defined with content 1000(r), 0(g), 0(b). </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="COLORCONTENT" ></A >10.3. Color Content</H2 ><P >The functions <TT CLASS="LITERAL" >color_content()</TT > and <TT CLASS="LITERAL" >pair_content()</TT > can be used to find the color content and foreground, background combination for the pair. </P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="windows.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="keys.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Windows</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Interfacing with the key board</TD ></TR ></TABLE ></DIV ></BODY ></HTML >