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> NCURSES Programming HOWTO </TITLE
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><DIV
CLASS="ARTICLE"
><DIV
CLASS="TITLEPAGE"
><H1
CLASS="TITLE"
><A
NAME="AEN2"
>NCURSES Programming HOWTO</A
></H1
><H3
CLASS="AUTHOR"
><A
NAME="AEN4"
> Pradeep Padala </A
></H3
><DIV
CLASS="AFFILIATION"
><DIV
CLASS="ADDRESS"
><P
CLASS="ADDRESS"
><CODE
CLASS="EMAIL"
>&#60;<A
HREF="mailto:ppadala@gmail.com"
>ppadala@gmail.com</A
>&#62;</CODE
></P
></DIV
></DIV
><P
CLASS="PUBDATE"
>v1.9, 2005-06-20<BR></P
><DIV
CLASS="REVHISTORY"
><TABLE
WIDTH="100%"
BORDER="0"
><TR
><TH
ALIGN="LEFT"
VALIGN="TOP"
COLSPAN="3"
><B
>Revision History</B
></TH
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.9</TD
><TD
ALIGN="LEFT"
>2005-06-20</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>The license has been changed to the MIT-style license used
by NCURSES. Note that the programs are also re-licensed under this.</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.8</TD
><TD
ALIGN="LEFT"
>2005-06-17</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Lots of updates. Added references and perl examples.
Changes to examples. Many grammatical and stylistic changes to the
content. Changes to NCURSES history.</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.7.1</TD
><TD
ALIGN="LEFT"
>2002-06-25</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Added a README file for building and instructions
for building from source.</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.7</TD
><TD
ALIGN="LEFT"
>2002-06-25</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Added "Other formats" section and made a lot of fancy
changes to the programs. Inlining of programs is gone.</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.6.1</TD
><TD
ALIGN="LEFT"
>2002-02-24</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Removed the old Changelog section, cleaned the makefiles</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.6</TD
><TD
ALIGN="LEFT"
>2002-02-16</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Corrected a lot of spelling mistakes, added ACS variables
section</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.5</TD
><TD
ALIGN="LEFT"
>2002-01-05</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Changed structure to present proper TOC</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.3.1</TD
><TD
ALIGN="LEFT"
>2001-07-26</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Corrected maintainers paragraph, Corrected stable release number</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.3</TD
><TD
ALIGN="LEFT"
>2001-07-24</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Added copyright notices to main document (LDP license)
and programs (GPL), Corrected
printw_example.</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.2</TD
><TD
ALIGN="LEFT"
>2001-06-05</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Incorporated ravi's changes. Mainly to introduction, menu,
form, justforfun sections</TD
></TR
><TR
><TD
ALIGN="LEFT"
>Revision 1.1</TD
><TD
ALIGN="LEFT"
>2001-05-22</TD
><TD
ALIGN="LEFT"
>Revised by: ppadala</TD
></TR
><TR
><TD
ALIGN="LEFT"
COLSPAN="3"
>Added "a word about window" section, Added scanw_example.</TD
></TR
></TABLE
></DIV
><DIV
><DIV
CLASS="ABSTRACT"
><P
></P
><A
NAME="AEN67"
></A
><P
> <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>This document is intended to be an "All in One" guide for programming with
ncurses and its sister libraries. We graduate from a simple "Hello World"
program to more complex form manipulation. No prior experience in ncurses is
assumed. Send comments to <A
HREF="mailto:ppadala@gmail.com"
TARGET="_top"
>this address</A
>
</I
></SPAN
>
</P
><P
></P
></DIV
></DIV
><HR></DIV
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
>1. <A
HREF="#INTRO"
>Introduction</A
></DT
><DD
><DL
><DT
>1.1. <A
HREF="#WHATIS"
>What is NCURSES?</A
></DT
><DT
>1.2. <A
HREF="#WHATCANWEDO"
>What we can do with NCURSES</A
></DT
><DT
>1.3. <A
HREF="#WHERETOGETIT"
>Where to get it</A
></DT
><DT
>1.4. <A
HREF="#PURPOSE"
>Purpose/Scope of the document</A
></DT
><DT
>1.5. <A
HREF="#ABOUTPROGRAMS"
>About the Programs</A
></DT
><DT
>1.6. <A
HREF="#OTHERFORMATS"
>Other Formats of the document</A
></DT
><DD
><DL
><DT
>1.6.1. <A
HREF="#LISTFORMATS"
>Readily available formats from tldp.org</A
></DT
><DT
>1.6.2. <A
HREF="#BUILDSOURCE"
>Building from source</A
></DT
></DL
></DD
><DT
>1.7. <A
HREF="#CREDITS"
>Credits</A
></DT
><DT
>1.8. <A
HREF="#WISHLIST"
>Wish List</A
></DT
><DT
>1.9. <A
HREF="#COPYRIGHT"
>Copyright</A
></DT
></DL
></DD
><DT
>2. <A
HREF="#HELLOWORLD"
>Hello World !!!</A
></DT
><DD
><DL
><DT
>2.1. <A
HREF="#COMPILECURSES"
>Compiling With the NCURSES Library</A
></DT
><DT
>2.2. <A
HREF="#DISSECTION"
>Dissection</A
></DT
><DD
><DL
><DT
>2.2.1. <A
HREF="#ABOUT-INITSCR"
>About initscr()</A
></DT
><DT
>2.2.2. <A
HREF="#MYST-REFRESH"
>The mysterious refresh()</A
></DT
><DT
>2.2.3. <A
HREF="#ABOUT-ENDWIN"
>About endwin()</A
></DT
></DL
></DD
></DL
></DD
><DT
>3. <A
HREF="#GORY"
>The Gory Details</A
></DT
><DT
>4. <A
HREF="#INIT"
>Initialization</A
></DT
><DD
><DL
><DT
>4.1. <A
HREF="#ABOUTINIT"
>Initialization functions</A
></DT
><DT
>4.2. <A
HREF="#RAWCBREAK"
>raw() and cbreak()</A
></DT
><DT
>4.3. <A
HREF="#ECHONOECHO"
>echo() and noecho()</A
></DT
><DT
>4.4. <A
HREF="#KEYPAD"
>keypad()</A
></DT
><DT
>4.5. <A
HREF="#HALFDELAY"
>halfdelay()</A
></DT
><DT
>4.6. <A
HREF="#MISCINIT"
>Miscellaneous Initialization functions</A
></DT
><DT
>4.7. <A
HREF="#INITEX"
>An Example</A
></DT
></DL
></DD
><DT
>5. <A
HREF="#AWORDWINDOWS"
>A Word about Windows</A
></DT
><DT
>6. <A
HREF="#PRINTW"
>Output functions</A
></DT
><DD
><DL
><DT
>6.1. <A
HREF="#ADDCHCLASS"
>addch() class of functions</A
></DT
><DT
>6.2. <A
HREF="#AEN298"
>mvaddch(), waddch() and mvwaddch()</A
></DT
><DT
>6.3. <A
HREF="#PRINTWCLASS"
>printw() class of functions</A
></DT
><DD
><DL
><DT
>6.3.1. <A
HREF="#PRINTWMVPRINTW"
>printw() and mvprintw</A
></DT
><DT
>6.3.2. <A
HREF="#WPRINTWMVWPRINTW"
>wprintw() and mvwprintw</A
></DT
><DT
>6.3.3. <A
HREF="#VWPRINTW"
>vwprintw()</A
></DT
><DT
>6.3.4. <A
HREF="#SIMPLEPRINTWEX"
>A Simple printw example</A
></DT
></DL
></DD
><DT
>6.4. <A
HREF="#ADDSTRCLASS"
>addstr() class of functions</A
></DT
><DT
>6.5. <A
HREF="#ACAUTION"
>A word of caution</A
></DT
></DL
></DD
><DT
>7. <A
HREF="#SCANW"
>Input functions</A
></DT
><DD
><DL
><DT
>7.1. <A
HREF="#GETCHCLASS"
>getch() class of functions</A
></DT
><DT
>7.2. <A
HREF="#SCANWCLASS"
>scanw() class of functions</A
></DT
><DD
><DL
><DT
>7.2.1. <A
HREF="#SCANWMVSCANW"
>scanw() and mvscanw</A
></DT
><DT
>7.2.2. <A
HREF="#WSCANWMVWSCANW"
>wscanw() and mvwscanw()</A
></DT
><DT
>7.2.3. <A
HREF="#VWSCANW"
>vwscanw()</A
></DT
></DL
></DD
><DT
>7.3. <A
HREF="#GETSTRCLASS"
>getstr() class of functions</A
></DT
><DT
>7.4. <A
HREF="#GETSTREX"
>Some examples</A
></DT
></DL
></DD
><DT
>8. <A
HREF="#ATTRIB"
>Attributes</A
></DT
><DD
><DL
><DT
>8.1. <A
HREF="#ATTRIBDETAILS"
>The details</A
></DT
><DT
>8.2. <A
HREF="#ATTRONVSATTRSET"
>attron() vs attrset()</A
></DT
><DT
>8.3. <A
HREF="#ATTR_GET"
>attr_get()</A
></DT
><DT
>8.4. <A
HREF="#ATTR_FUNCS"
>attr_ functions</A
></DT
><DT
>8.5. <A
HREF="#WATTRFUNCS"
>wattr functions</A
></DT
><DT
>8.6. <A
HREF="#CHGAT"
>chgat() functions</A
></DT
></DL
></DD
><DT
>9. <A
HREF="#WINDOWS"
>Windows</A
></DT
><DD
><DL
><DT
>9.1. <A
HREF="#WINDOWBASICS"
>The basics</A
></DT
><DT
>9.2. <A
HREF="#LETBEWINDOW"
>Let there be a Window !!!</A
></DT
><DT
>9.3. <A
HREF="#BORDEREXEXPL"
>Explanation</A
></DT
><DT
>9.4. <A
HREF="#OTHERSTUFF"
>The other stuff in the example</A
></DT
><DT
>9.5. <A
HREF="#OTHERBORDERFUNCS"
>Other Border functions</A
></DT
></DL
></DD
><DT
>10. <A
HREF="#COLOR"
>Colors</A
></DT
><DD
><DL
><DT
>10.1. <A
HREF="#COLORBASICS"
>The basics</A
></DT
><DT
>10.2. <A
HREF="#CHANGECOLORDEFS"
>Changing Color Definitions</A
></DT
><DT
>10.3. <A
HREF="#COLORCONTENT"
>Color Content</A
></DT
></DL
></DD
><DT
>11. <A
HREF="#KEYS"
>Interfacing with the key board</A
></DT
><DD
><DL
><DT
>11.1. <A
HREF="#KEYSBASICS"
>The Basics</A
></DT
><DT
>11.2. <A
HREF="#SIMPLEKEYEX"
>A Simple Key Usage example</A
></DT
></DL
></DD
><DT
>12. <A
HREF="#MOUSE"
>Interfacing with the mouse</A
></DT
><DD
><DL
><DT
>12.1. <A
HREF="#MOUSEBASICS"
>The Basics</A
></DT
><DT
>12.2. <A
HREF="#GETTINGEVENTS"
>Getting the events</A
></DT
><DT
>12.3. <A
HREF="#MOUSETOGETHER"
>Putting it all Together</A
></DT
><DT
>12.4. <A
HREF="#MISCMOUSEFUNCS"
>Miscellaneous Functions</A
></DT
></DL
></DD
><DT
>13. <A
HREF="#SCREEN"
>Screen Manipulation</A
></DT
><DD
><DL
><DT
>13.1. <A
HREF="#GETYX"
>getyx() functions</A
></DT
><DT
>13.2. <A
HREF="#SCREENDUMP"
>Screen Dumping</A
></DT
><DT
>13.3. <A
HREF="#WINDOWDUMP"
>Window Dumping</A
></DT
></DL
></DD
><DT
>14. <A
HREF="#MISC"
>Miscellaneous features</A
></DT
><DD
><DL
><DT
>14.1. <A
HREF="#CURSSET"
>curs_set()</A
></DT
><DT
>14.2. <A
HREF="#TEMPLEAVE"
>Temporarily Leaving Curses mode</A
></DT
><DT
>14.3. <A
HREF="#ACSVARS"
>ACS_ variables</A
></DT
></DL
></DD
><DT
>15. <A
HREF="#OTHERLIB"
>Other libraries</A
></DT
><DT
>16. <A
HREF="#PANELS"
>Panel Library</A
></DT
><DD
><DL
><DT
>16.1. <A
HREF="#PANELBASICS"
>The Basics</A
></DT
><DT
>16.2. <A
HREF="#COMPILEPANELS"
>Compiling With the Panels Library</A
></DT
><DT
>16.3. <A
HREF="#PANELBROWSING"
>Panel Window Browsing</A
></DT
><DT
>16.4. <A
HREF="#USERPTRUSING"
>Using User Pointers</A
></DT
><DT
>16.5. <A
HREF="#PANELMOVERESIZE"
>Moving and Resizing Panels</A
></DT
><DT
>16.6. <A
HREF="#PANELSHOWHIDE"
>Hiding and Showing Panels</A
></DT
><DT
>16.7. <A
HREF="#PANELABOVE"
>panel_above() and panel_below() Functions</A
></DT
></DL
></DD
><DT
>17. <A
HREF="#MENUS"
>Menus Library</A
></DT
><DD
><DL
><DT
>17.1. <A
HREF="#MENUBASICS"
>The Basics</A
></DT
><DT
>17.2. <A
HREF="#COMPILEMENUS"
>Compiling With the Menu Library</A
></DT
><DT
>17.3. <A
HREF="#MENUDRIVER"
>Menu Driver: The work horse of the menu system</A
></DT
><DT
>17.4. <A
HREF="#MENUWINDOWS"
>Menu Windows</A
></DT
><DT
>17.5. <A
HREF="#SCROLLMENUS"
>Scrolling Menus</A
></DT
><DT
>17.6. <A
HREF="#MULTICOLUMN"
>Multi Columnar Menus</A
></DT
><DT
>17.7. <A
HREF="#MULTIVALUEMENUS"
>Multi Valued Menus</A
></DT
><DT
>17.8. <A
HREF="#MENUOPT"
>Menu Options</A
></DT
><DT
>17.9. <A
HREF="#MENUUSERPTR"
>The useful User Pointer</A
></DT
></DL
></DD
><DT
>18. <A
HREF="#FORMS"
>Forms Library</A
></DT
><DD
><DL
><DT
>18.1. <A
HREF="#FORMBASICS"
>The Basics</A
></DT
><DT
>18.2. <A
HREF="#COMPILEFORMS"
>Compiling With the Forms Library</A
></DT
><DT
>18.3. <A
HREF="#PLAYFIELDS"
>Playing with Fields</A
></DT
><DD
><DL
><DT
>18.3.1. <A
HREF="#FETCHINFO"
>Fetching Size and Location of Field</A
></DT
><DT
>18.3.2. <A
HREF="#MOVEFIELD"
>Moving the field</A
></DT
><DT
>18.3.3. <A
HREF="#JUSTIFYFIELD"
>Field Justification</A
></DT
><DT
>18.3.4. <A
HREF="#FIELDDISPATTRIB"
>Field Display Attributes</A
></DT
><DT
>18.3.5. <A
HREF="#FIELDOPTIONBITS"
>Field Option Bits</A
></DT
><DT
>18.3.6. <A
HREF="#FIELDSTATUS"
>Field Status</A
></DT
><DT
>18.3.7. <A
HREF="#FIELDUSERPTR"
>Field User Pointer</A
></DT
><DT
>18.3.8. <A
HREF="#VARIABLESIZEFIELDS"
>Variable-Sized Fields</A
></DT
></DL
></DD
><DT
>18.4. <A
HREF="#FORMWINDOWS"
>Form Windows</A
></DT
><DT
>18.5. <A
HREF="#FILEDVALIDATE"
>Field Validation</A
></DT
><DT
>18.6. <A
HREF="#FORMDRIVER"
>Form Driver: The work horse of the forms system</A
></DT
><DD
><DL
><DT
>18.6.1. <A
HREF="#PAGENAVREQ"
>Page Navigation Requests</A
></DT
><DT
>18.6.2. <A
HREF="#INTERFIELDNAVREQ"
>Inter-Field Navigation Requests</A
></DT
><DT
>18.6.3. <A
HREF="#INTRAFIELDNAVREQ"
>Intra-Field Navigation Requests</A
></DT
><DT
>18.6.4. <A
HREF="#SCROLLREQ"
>Scrolling Requests</A
></DT
><DT
>18.6.5. <A
HREF="#EDITREQ"
>Editing Requests</A
></DT
><DT
>18.6.6. <A
HREF="#ORDERREQ"
>Order Requests</A
></DT
><DT
>18.6.7. <A
HREF="#APPLICCOMMANDS"
>Application Commands</A
></DT
></DL
></DD
></DL
></DD
><DT
>19. <A
HREF="#TOOLS"
>Tools and Widget Libraries</A
></DT
><DD
><DL
><DT
>19.1. <A
HREF="#CDK"
>CDK (Curses Development Kit)</A
></DT
><DD
><DL
><DT
>19.1.1. <A
HREF="#WIDGETLIST"
>Widget List</A
></DT
><DT
>19.1.2. <A
HREF="#CDKATTRACT"
>Some Attractive Features</A
></DT
><DT
>19.1.3. <A
HREF="#CDKCONCLUSION"
>Conclusion</A
></DT
></DL
></DD
><DT
>19.2. <A
HREF="#DIALOG"
>The dialog</A
></DT
><DT
>19.3. <A
HREF="#PERLCURSES"
>Perl Curses Modules CURSES::FORM and CURSES::WIDGETS</A
></DT
></DL
></DD
><DT
>20. <A
HREF="#JUSTFORFUN"
>Just For Fun !!!</A
></DT
><DD
><DL
><DT
>20.1. <A
HREF="#GAMEOFLIFE"
>The Game of Life</A
></DT
><DT
>20.2. <A
HREF="#MAGIC"
>Magic Square</A
></DT
><DT
>20.3. <A
HREF="#HANOI"
>Towers of Hanoi</A
></DT
><DT
>20.4. <A
HREF="#QUEENS"
>Queens Puzzle</A
></DT
><DT
>20.5. <A
HREF="#SHUFFLE"
>Shuffle</A
></DT
><DT
>20.6. <A
HREF="#TT"
>Typing Tutor</A
></DT
></DL
></DD
><DT
>21. <A
HREF="#REF"
>References</A
></DT
></DL
></DIV
><DIV
CLASS="SECT1"
><H2
CLASS="SECT1"
><A
NAME="INTRO"
>1. Introduction</A
></H2
><P
>In the olden days of teletype terminals, terminals were away from computers and
were connected to them through serial cables. The terminals could be configured
by sending a series of bytes. All the capabilities (such as
moving the cursor to a new location, erasing part of the screen, scrolling the
screen, changing modes etc.) of terminals could be accessed through these
series of bytes. These control seeuqnces are usually called escape sequences,
because they start
with an escape(0x1B) character. Even today, with proper emulation, we can send
escape sequences to the emulator and achieve the same effect on a terminal
window.</P
><P
>Suppose you wanted to print a line in color. Try typing this on your console.</P
><PRE
CLASS="PROGRAMLISTING"
>echo "^[[0;31;40mIn Color"</PRE
><P
>The first character is an escape character, which looks like two characters ^
and [. To be able to print it, you have to press CTRL+V and then the ESC key.
All the others are normal printable characters. You should be able to see the
string "In Color" in red. It stays that way and to revert back to the original
mode type this.</P
><PRE
CLASS="PROGRAMLISTING"
>echo "^[[0;37;40m"</PRE
><P
>Now, what do these magic characters mean? Difficult to comprehend? They might
even be different for different terminals. So the designers of UNIX invented a
mechanism named <TT
CLASS="LITERAL"
>termcap</TT
>. It is a file that
lists all the capabilities of a particular terminal, along with the escape
sequences needed to achieve a particular effect. In the later years, this was
replaced by <TT
CLASS="LITERAL"
>terminfo</TT
>. Without delving too
much into details, this mechanism allows application
programs to query the terminfo database and obtain the control characters to be
sent to a terminal or terminal emulator.</P
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="WHATIS"
>1.1. What is NCURSES?</A
></H3
><P
>
You might be wondering, what the import of all this technical gibberish is. In
the above scenario, every application program is supposed to query the terminfo
and perform the necessary stuff (sending control characters etc.). It soon became
difficult to manage this complexity and this gave birth to 'CURSES'. Curses is
a pun on the name "cursor optimization". The Curses library forms a wrapper
over working with raw terminal codes, and provides highly flexible and
efficient API (Application Programming Interface). It provides functions to
move the cursor, create windows, produce colors, play with mouse etc. The
application programs need not worry about the underlying terminal capabilities.</P
><P
>So what is NCURSES? NCURSES is a clone of the original System V Release 4.0
(SVr4) curses. It is a freely distributable library, fully compatible with
older version of curses. In short, it is a library of functions that manages
an application's display on character-cell terminals. In the remainder of the
document, the terms curses and ncurses are used interchangeably. </P
><P
>A detailed history of NCURSES can be found in the NEWS file from the source
distribution. The current package is maintained by
<A
HREF="mailto:dickey@his.com"
TARGET="_top"
>Thomas Dickey</A
>.
You can contact the maintainers at <A
HREF="mailto:bug-ncurses@gnu.org"
TARGET="_top"
>bug-ncurses@gnu.org</A
>.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="WHATCANWEDO"
>1.2. What we can do with NCURSES</A
></H3
><P
>NCURSES not only creates a wrapper over terminal capabilities, but also gives a
robust framework to create nice looking UI (User Interface)s in text mode. It
provides functions to create windows etc. Its sister libraries panel, menu and
form provide an extension to the basic curses library. These libraries usually
come along with curses. One can create applications that contain multiple
windows, menus, panels and forms. Windows can be managed independently, can
provide 'scrollability' and even can be hidden.</P
><P
>
Menus provide the user with an easy command selection option. Forms allow the
creation of easy-to-use data entry and display windows. Panels extend the
capabilities of ncurses to deal with overlapping and stacked windows.</P
><P
>These are just some of the basic things we can do with ncurses. As we move
along, We will see all the capabilities of these libraries. </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="WHERETOGETIT"
>1.3. Where to get it</A
></H3
><P
>All right, now that you know what you can do with ncurses, you must be rearing
to get started. NCURSES is usually shipped with your installation. In case
you don't have the library or want to compile it on your own, read on.</P
><P
><SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Compiling the package</I
></SPAN
> </P
><P
>NCURSES can be obtained from <A
HREF="ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz"
TARGET="_top"
>ftp://ftp.gnu.org/pub/gnu/ncurses/ncurses.tar.gz</A
> or any of the ftp
sites mentioned in <A
HREF="http://www.gnu.org/order/ftp.html"
TARGET="_top"
>http://www.gnu.org/order/ftp.html</A
>. </P
><P
>Read the README and INSTALL files for details on to how to install it. It
usually involves the following operations.</P
><PRE
CLASS="PROGRAMLISTING"
> tar zxvf ncurses&lt;version&gt;.tar.gz # unzip and untar the archive
cd ncurses&lt;version&gt; # cd to the directory
./configure # configure the build according to your
# environment
make # make it
su root # become root
make install # install it</PRE
><P
><SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Using the RPM </I
></SPAN
></P
><P
>NCURSES RPM can be found and downloaded from <A
HREF="http://rpmfind.net"
TARGET="_top"
>http://rpmfind.net </A
>. The RPM can be installed with the following
command after becoming root.</P
><PRE
CLASS="PROGRAMLISTING"
> rpm -i &lt;downloaded rpm&gt;</PRE
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="PURPOSE"
>1.4. Purpose/Scope of the document</A
></H3
><P
>This document is intended to be a "All in One" guide for programming with
ncurses and its sister libraries. We graduate from a simple "Hello World"
program to more complex form manipulation. No prior experience in ncurses is
assumed. The writing is informal, but a lot of detail is provided for
each of the examples.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ABOUTPROGRAMS"
>1.5. About the Programs</A
></H3
><P
>All the programs in the document are available in zipped form
<A
HREF="http://www.tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs.tar.gz"
TARGET="_top"
>here</A
>. Unzip and untar it. The directory structure looks like this.</P
><PRE
CLASS="PROGRAMLISTING"
>ncurses
|
|----&gt; JustForFun -- just for fun programs
|----&gt; basics -- basic programs
|----&gt; demo -- output files go into this directory after make
| |
| |----&gt; exe -- exe files of all example programs
|----&gt; forms -- programs related to form library
|----&gt; menus -- programs related to menus library
|----&gt; panels -- programs related to panels library
|----&gt; perl -- perl equivalents of the examples (contributed
| by Anuradha Ratnaweera)
|----&gt; Makefile -- the top level Makefile
|----&gt; README -- the top level README file. contains instructions
|----&gt; COPYING -- copyright notice</PRE
><P
>The individual directories contain the following files.</P
><PRE
CLASS="PROGRAMLISTING"
>Description of files in each directory
--------------------------------------
JustForFun
|
|----&gt; hanoi.c -- The Towers of Hanoi Solver
|----&gt; life.c -- The Game of Life demo
|----&gt; magic.c -- An Odd Order Magic Square builder
|----&gt; queens.c -- The famous N-Queens Solver
|----&gt; shuffle.c -- A fun game, if you have time to kill
|----&gt; tt.c -- A very trivial typing tutor
basics
|
|----&gt; acs_vars.c -- ACS_ variables example
|----&gt; hello_world.c -- Simple "Hello World" Program
|----&gt; init_func_example.c -- Initialization functions example
|----&gt; key_code.c -- Shows the scan code of the key pressed
|----&gt; mouse_menu.c -- A menu accessible by mouse
|----&gt; other_border.c -- Shows usage of other border functions apa
| -- rt from box()
|----&gt; printw_example.c -- A very simple printw() example
|----&gt; scanw_example.c -- A very simple getstr() example
|----&gt; simple_attr.c -- A program that can print a c file with
| -- comments in attribute
|----&gt; simple_color.c -- A simple example demonstrating colors
|----&gt; simple_key.c -- A menu accessible with keyboard UP, DOWN
| -- arrows
|----&gt; temp_leave.c -- Demonstrates temporarily leaving curses mode
|----&gt; win_border.c -- Shows Creation of windows and borders
|----&gt; with_chgat.c -- chgat() usage example
forms
|
|----&gt; form_attrib.c -- Usage of field attributes
|----&gt; form_options.c -- Usage of field options
|----&gt; form_simple.c -- A simple form example
|----&gt; form_win.c -- Demo of windows associated with forms
menus
|
|----&gt; menu_attrib.c -- Usage of menu attributes
|----&gt; menu_item_data.c -- Usage of item_name() etc.. functions
|----&gt; menu_multi_column.c -- Creates multi columnar menus
|----&gt; menu_scroll.c -- Demonstrates scrolling capability of menus
|----&gt; menu_simple.c -- A simple menu accessed by arrow keys
|----&gt; menu_toggle.c -- Creates multi valued menus and explains
| -- REQ_TOGGLE_ITEM
|----&gt; menu_userptr.c -- Usage of user pointer
|----&gt; menu_win.c -- Demo of windows associated with menus
panels
|
|----&gt; panel_browse.c -- Panel browsing through tab. Usage of user
| -- pointer
|----&gt; panel_hide.c -- Hiding and Un hiding of panels
|----&gt; panel_resize.c -- Moving and resizing of panels
|----&gt; panel_simple.c -- A simple panel example
perl
|----&gt; 01-10.pl -- Perl equivalents of first ten example programs</PRE
><P
>There is a top level Makefile included in the main directory. It builds all the
files and puts the ready-to-use exes in demo/exe directory. You can also
do selective make by going into the corresponding directory. Each directory
contains a README file explaining the purpose of each c file in the directory.</P
><P
>For every example, I have included path name for the file relative to the
examples directory. </P
><P
> If you prefer browsing individual programs, point your browser to
<A
HREF="http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/"
TARGET="_top"
>http://tldp.org/HOWTO/NCURSES-Programming-HOWTO/ncurses_programs/</A
></P
><P
>All the programs are released under the same license that is used by ncurses
(MIT-style). This gives you the ability to do pretty much anything other than
claiming them as yours. Feel free to use them in your programs as appropriate.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="OTHERFORMATS"
>1.6. Other Formats of the document</A
></H3
><P
>This howto is also availabe in various other formats on the tldp.org site.
Here are the links to other formats of this document.</P
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="LISTFORMATS"
>1.6.1. Readily available formats from tldp.org</A
></H4
><P
></P
><UL
><LI
><P
><A
HREF="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/pdf/NCURSES-Programming-HOWTO.pdf"
TARGET="_top"
>Acrobat PDF Format</A
></P
></LI
><LI
><P
><A
HREF="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/ps/NCURSES-Programming-HOWTO.ps.gz"
TARGET="_top"
>PostScript Format</A
></P
></LI
><LI
><P
><A
HREF="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html/NCURSES-Programming-HOWTO-html.tar.gz"
TARGET="_top"
>In Multiple HTML pages</A
></P
></LI
><LI
><P
><A
HREF="http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/NCURSES-Programming-HOWTO.html"
TARGET="_top"
>In One big HTML format</A
></P
></LI
></UL
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="BUILDSOURCE"
>1.6.2. Building from source</A
></H4
><P
>If above links are broken or if you want to experiment with sgml read on.
<PRE
CLASS="PROGRAMLISTING"
>&#13; Get both the source and the tar,gzipped programs, available at
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/NCURSES-Programming-HOWTO.sgml
http://cvsview.tldp.org/index.cgi/LDP/howto/docbook/
NCURSES-HOWTO/ncurses_programs.tar.gz
Unzip ncurses_programs.tar.gz with
tar zxvf ncurses_programs.tar.gz
Use jade to create various formats. For example if you just want to create
the multiple html files, you would use
jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt;
NCURSES-Programming-HOWTO.sgml
to get pdf, first create a single html file of the HOWTO with
jade -t sgml -i html -d &lt;path to docbook html stylesheet&gt; -V nochunks
NCURSES-Programming-HOWTO.sgml &gt; NCURSES-ONE-BIG-FILE.html
then use htmldoc to get pdf file with
htmldoc --size universal -t pdf --firstpage p1 -f &lt;output file name.pdf&gt;
NCURSES-ONE-BIG-FILE.html
for ps, you would use
htmldoc --size universal -t ps --firstpage p1 -f &lt;output file name.ps&gt;
NCURSES-ONE-BIG-FILE.html</PRE
></P
><P
>See <A
HREF="http://www.tldp.org/LDP/LDP-Author-Guide/"
TARGET="_top"
>LDP Author guide</A
> for more details. If all else failes, mail me at
<A
HREF="ppadala@gmail.com"
TARGET="_top"
>ppadala@gmail.com</A
></P
></DIV
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="CREDITS"
>1.7. Credits</A
></H3
><P
>I thank <A
HREF="mailto:sharath_1@usa.net"
TARGET="_top"
>Sharath</A
> and Emre Akbas for
helping me with few sections. The introduction was initially written by sharath.
I rewrote it with few excerpts taken from his initial work. Emre helped in
writing printw and scanw sections.</P
><P
>Perl equivalents of the example programs are contributed by <A
HREF="mailto:Aratnaweera@virtusa.com"
TARGET="_top"
>Anuradha Ratnaweera</A
>. </P
><P
>Then comes <A
HREF="mailto:parimi@ece.arizona.edu"
TARGET="_top"
>Ravi Parimi</A
>, my
dearest friend, who has been on this project before even one line was written.
He constantly bombarded me with suggestions and patiently reviewed the whole
text. He also checked each program on Linux and Solaris. </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="WISHLIST"
>1.8. Wish List</A
></H3
><P
>This is the wish list, in the order of priority. If you have a wish or you want
to work on completing the wish, mail <A
HREF="mailto:ppadala@gmail.com"
TARGET="_top"
>me</A
>. </P
><P
></P
><UL
><LI
><P
>Add examples to last parts of forms section.</P
></LI
><LI
><P
>Prepare a Demo showing all the programs and allow the user to browse through
description of each program. Let the user compile and see the program in action.
A dialog based interface is preferred.</P
></LI
><LI
><P
>Add debug info. _tracef, _tracemouse stuff.</P
></LI
><LI
><P
>Accessing termcap, terminfo using functions provided by ncurses
package.</P
></LI
><LI
><P
>Working on two terminals simultaneously.</P
></LI
><LI
><P
>Add more stuff to miscellaneous section.</P
></LI
></UL
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="COPYRIGHT"
>1.9. Copyright</A
></H3
><P
>Copyright &copy; 2001 by Pradeep Padala. </P
><P
>Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, distribute with
modifications, sublicense, and/or sell copies of the Software, and to permit
persons to whom the Software is furnished to do so, subject to the following
conditions:</P
><P
>The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.</P
><P
>THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.</P
><P
>Except as contained in this notice, the name(s) of the above copyright holders
shall not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization. </P
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="HELLOWORLD"
>2. Hello World !!!</A
></H2
><P
>Welcome to the world of curses. Before we plunge into the library and look into
its various features, let's write a simple program and say
hello to the world. </P
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="COMPILECURSES"
>2.1. Compiling With the NCURSES Library</A
></H3
><P
>To use ncurses library functions, you have to include ncurses.h in your
programs. To link the
program with ncurses the flag -lncurses should be added.</P
><PRE
CLASS="PROGRAMLISTING"
> #include &lt;ncurses.h&gt;
.
.
.
compile and link: gcc &lt;program file&gt; -lncurses</PRE
><DIV
CLASS="EXAMPLE"
><A
NAME="BHW"
></A
><P
><B
>Example 1. The Hello World !!! Program </B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62;
int main()
{
initscr(); /* Start curses mode */
printw("Hello World !!!"); /* Print Hello World */
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}</SPAN
></PRE
></DIV
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="DISSECTION"
>2.2. Dissection</A
></H3
><P
>
The above program prints "Hello World !!!" to the screen and exits. This
program shows how to initialize curses and do screen manipulation and
end curses mode. Let's dissect it line by line. </P
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="ABOUT-INITSCR"
>2.2.1. About initscr()</A
></H4
><P
>The function initscr() initializes the terminal in curses mode. In some
implementations, it clears the screen and presents a blank screen. To do any
screen manipulation using curses package this has to be called first. This
function initializes the curses system and allocates memory for our present
window (called <TT
CLASS="LITERAL"
>stdscr</TT
>) and some other data-structures. Under extreme
cases this function might fail due to insufficient memory to allocate memory
for curses library's data structures. </P
><P
>
After this is done, we can do a variety of initializations to customize
our curses settings. These details will be explained <A
HREF="#INIT"
>later </A
>.</P
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="MYST-REFRESH"
>2.2.2. The mysterious refresh()</A
></H4
><P
>The next line printw prints the string "Hello World !!!" on to the screen. This
function is analogous to normal printf in all respects except that it prints
the data on a window called stdscr at the current (y,x) co-ordinates. Since our
present co-ordinates are at 0,0 the string is printed at the left hand corner
of the window.</P
><P
>This brings us to that mysterious refresh(). Well, when we called printw
the data is actually written to an imaginary window, which is not updated
on the screen yet. The job of printw is to update a few flags
and data structures and write the data to a buffer corresponding to stdscr.
In order to show it on the screen, we need to call refresh() and tell the
curses system to dump the contents on the screen.</P
><P
>The philosophy behind all this is to allow the programmer to do multiple updates
on the imaginary screen or windows and do a refresh once all his screen update
is done. refresh() checks the window and updates only the portion which has been
changed. This improves performance and offers greater flexibility too. But, it is
sometimes frustrating to beginners. A common mistake committed by beginners is
to forget to call refresh() after they did some update through printw() class of
functions. I still forget to add it sometimes :-) </P
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="ABOUT-ENDWIN"
>2.2.3. About endwin()</A
></H4
><P
>And finally don't forget to end the curses mode. Otherwise your terminal might
behave strangely after the program quits. endwin() frees the memory taken by
curses sub-system and its data structures and puts the terminal in normal
mode. This function must be called after you are done with the curses mode. </P
></DIV
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="GORY"
>3. The Gory Details</A
></H2
><P
>Now that we have seen how to write a simple curses program let's get into the
details. There are many functions that help customize what you see on screen and
many features which can be put to full use. </P
><P
>Here we go...</P
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="INIT"
>4. Initialization</A
></H2
><P
>We now know that to initialize curses system the function initscr() has to be
called. There are functions which can be called after this initialization to
customize our curses session. We may ask the curses system to set the terminal
in raw mode or initialize color or initialize the mouse etc.. Let's discuss some
of the functions that are normally called immediately after initscr();</P
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ABOUTINIT"
>4.1. Initialization functions</A
></H3
><P
> </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="RAWCBREAK"
>4.2. raw() and cbreak()</A
></H3
><P
>Normally the terminal driver buffers the characters a user types until a new
line or carriage return is encountered. But most programs require that the
characters be available as soon as the user types them. The above two functions
are used to disable line buffering. The difference between these two functions
is in the way control characters like suspend (CTRL-Z), interrupt and quit
(CTRL-C) are passed to the program. In the raw() mode these characters are
directly passed to the program without generating a signal. In the
<TT
CLASS="LITERAL"
>cbreak()</TT
> mode these control characters are
interpreted as any other character by the terminal driver. I personally prefer
to use raw() as I can exercise greater control over what the user does.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ECHONOECHO"
>4.3. echo() and noecho()</A
></H3
><P
>
These functions control the echoing of characters typed by the user to the
terminal. <TT
CLASS="LITERAL"
>noecho()</TT
> switches off echoing. The
reason you might want to do this is to gain more control over echoing or to
suppress unnecessary echoing while taking input from the user through the
getch() etc. functions. Most of the interactive programs call
<TT
CLASS="LITERAL"
>noecho()</TT
> at initialization and do the echoing
of characters in a controlled manner. It gives the programmer the flexibility
of echoing characters at any place in the window without updating current (y,x)
co-ordinates. </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="KEYPAD"
>4.4. keypad()</A
></H3
><P
>This is my favorite initialization function. It enables the reading of function
keys like F1, F2, arrow keys etc. Almost every interactive program enables this,
as arrow keys are a major part of any User Interface. Do
<TT
CLASS="LITERAL"
>keypad(stdscr, TRUE) </TT
> to enable this feature
for the regular screen (stdscr). You will learn more about key management in
later sections of this document.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="HALFDELAY"
>4.5. halfdelay()</A
></H3
><P
>This function, though not used very often, is a useful one at times.
halfdelay()is called to enable the half-delay mode, which is similar to the
cbreak() mode in that characters typed are immediately available to program.
However, it waits for 'X' tenths of a second for input and then returns ERR, if
no input is available. 'X' is the timeout value passed to the function
halfdelay(). This function is useful when you want to ask the user for input,
and if he doesn't respond with in certain time, we can do some thing else. One
possible example is a timeout at the password prompt. </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="MISCINIT"
>4.6. Miscellaneous Initialization functions</A
></H3
><P
>There are few more functions which are called at initialization to
customize curses behavior. They are not used as extensively as those mentioned
above. Some of them are explained where appropriate.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="INITEX"
>4.7. An Example</A
></H3
><P
>Let's write a program which will clarify the usage of these functions.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="BINFU"
></A
><P
><B
>Example 2. Initialization Function Usage example </B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62;
int main()
{ int ch;
initscr(); /* Start curses mode */
raw(); /* Line buffering disabled */
keypad(stdscr, TRUE); /* We get F1, F2 etc.. */
noecho(); /* Don't echo() while we do getch */
printw("Type any character to see it in bold\n");
ch = getch(); /* If raw() hadn't been called
* we have to press enter before it
* gets to the program */
if(ch == KEY_F(1)) /* Without keypad enabled this will */
printw("F1 Key pressed");/* not get to us either */
/* Without noecho() some ugly escape
* charachters might have been printed
* on screen */
else
{ printw("The pressed key is ");
attron(A_BOLD);
printw("%c", ch);
attroff(A_BOLD);
}
refresh(); /* Print it on to the real screen */
getch(); /* Wait for user input */
endwin(); /* End curses mode */
return 0;
}</SPAN
></PRE
></DIV
><P
>This program is self-explanatory. But I used functions which aren't explained
yet. The function <TT
CLASS="LITERAL"
>getch()</TT
> is used to get a
character from user. It is equivalent to normal
<TT
CLASS="LITERAL"
>getchar()</TT
> except that we can disable the line
buffering to avoid &lt;enter&gt; after input. Look for more about
<TT
CLASS="LITERAL"
>getch()</TT
>and reading keys in the <A
HREF="#KEYS"
> key management section </A
>. The functions attron and attroff
are used to switch some attributes on and off respectively. In the example I
used them to print the character in bold. These functions are explained in detail
later.</P
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="AWORDWINDOWS"
>5. A Word about Windows</A
></H2
><P
>
Before we plunge into the myriad ncurses functions, let me clear few things
about windows. Windows are explained in detail in following <A
HREF="#WINDOWS"
> sections </A
></P
><P
>A Window is an imaginary screen defined by curses system. A window does not mean
a bordered window which you usually see on Win9X platforms. When curses is
initialized, it creates a default window named
<TT
CLASS="LITERAL"
>stdscr</TT
> which represents your 80x25 (or the size
of window in which you are running) screen. If you are doing simple tasks like
printing few strings, reading input etc., you can safely use this single window
for all of your purposes. You can also create windows and call functions which
explicitly work on the specified window.</P
><P
>For example, if you call</P
><PRE
CLASS="PROGRAMLISTING"
> printw("Hi There !!!");
refresh();</PRE
><P
>It prints the string on stdscr at the present cursor position. Similarly the
call to refresh(), works on stdscr only. </P
><P
>Say you have created <A
HREF="#WINDOWS"
>windows</A
> then you have to
call a function with a 'w' added to the usual function.</P
><PRE
CLASS="PROGRAMLISTING"
> wprintw(win, "Hi There !!!");
wrefresh(win);</PRE
><P
>As you will see in the rest of the document, naming of functions follow the
same convention. For each function there usually are three more functions.</P
><PRE
CLASS="PROGRAMLISTING"
> printw(string); /* Print on stdscr at present cursor position */
mvprintw(y, x, string);/* Move to (y, x) then print string */
wprintw(win, string); /* Print on window win at present cursor position */
/* in the window */
mvwprintw(win, y, x, string); /* Move to (y, x) relative to window */
/* co-ordinates and then print */</PRE
><P
>Usually the w-less functions are macros which expand to corresponding w-function
with stdscr as the window parameter.</P
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="PRINTW"
>6. Output functions</A
></H2
><P
>I guess you can't wait any more to see some action. Back to our odyssey of
curses functions. Now that curses is initialized, let's interact with
world.</P
><P
>There are three classes of functions which you can use to do output on screen.
<P
></P
><OL
TYPE="1"
><LI
><P
>addch() class: Print single character with attributes </P
></LI
><LI
><P
>printw() class: Print formatted output similar to printf()</P
></LI
><LI
><P
>addstr() class: Print strings</P
></LI
></OL
></P
><P
>These functions can be used interchangeably and it's a matter of style as to
which class is used. Let's see each one in detail.</P
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ADDCHCLASS"
>6.1. addch() class of functions</A
></H3
><P
>These functions put a single character into the current cursor location and
advance the position of the cursor. You can give the character to be printed but
they usually are used to print a character with some attributes. Attributes are
explained in detail in later <A
HREF="#ATTRIB"
> sections </A
> of the
document. If a character is associated with an attribute(bold, reverse video
etc.), when curses prints the character, it is printed in that attribute.</P
><P
>In order to combine a character with some attributes, you have two options:</P
><P
></P
><UL
><LI
><P
>By OR'ing a single character with the desired attribute macros. These attribute
macros could be found in the header file
<TT
CLASS="LITERAL"
>ncurses.h</TT
>. For example, you want to print a
character ch(of type char) bold and underlined, you would call addch() as below.
<PRE
CLASS="PROGRAMLISTING"
> addch(ch | A_BOLD | A_UNDERLINE);</PRE
></P
></LI
><LI
><P
>By using functions like <TT
CLASS="LITERAL"
>attrset(),attron(),attroff()</TT
>. These functions are explained in the <A
HREF="#ATTRIB"
>Attributes</A
> section. Briefly, they manipulate the current attributes of
the given window. Once set, the character printed in the window are associated
with the attributes until it is turned off.</P
></LI
></UL
><P
>Additionally, <TT
CLASS="LITERAL"
>curses</TT
> provides some special
characters for character-based graphics. You can draw tables, horizontal or
vertical lines, etc. You can find all avaliable characters in the header file
<TT
CLASS="LITERAL"
>ncurses.h</TT
>. Try looking for macros beginning
with <TT
CLASS="LITERAL"
>ACS_</TT
> in this file. </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="AEN298"
>6.2. mvaddch(), waddch() and mvwaddch()</A
></H3
><P
><TT
CLASS="LITERAL"
>mvaddch()</TT
> is used to move the cursor to a
given point, and then print. Thus, the calls:
<PRE
CLASS="PROGRAMLISTING"
> move(row,col); /* moves the cursor to row<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>th</I
></SPAN
> row and col<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>th</I
></SPAN
> column */
addch(ch);</PRE
>
can be replaced by
<PRE
CLASS="PROGRAMLISTING"
> mvaddch(row,col,ch);</PRE
></P
><P
><TT
CLASS="LITERAL"
>waddch()</TT
> is similar to
<TT
CLASS="LITERAL"
>addch()</TT
>, except that it adds a character into
the given window. (Note that <TT
CLASS="LITERAL"
>addch()</TT
> adds a
character into the window <TT
CLASS="LITERAL"
>stdscr</TT
>.)</P
><P
>In a similar fashion <TT
CLASS="LITERAL"
>mvwaddch()</TT
> function is
used to add a character into the given window at the given coordinates.</P
><P
>Now, we are familiar with the basic output function
<TT
CLASS="LITERAL"
>addch()</TT
>. But, if we want to print a string, it
would be very annoying to print it character by character. Fortunately,
<TT
CLASS="LITERAL"
>ncurses</TT
> provides <TT
CLASS="LITERAL"
>printf</TT
><SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>-like</I
></SPAN
> or
<TT
CLASS="LITERAL"
>puts</TT
><SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>-like</I
></SPAN
> functions.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="PRINTWCLASS"
>6.3. printw() class of functions</A
></H3
><P
>These functions are similar to <TT
CLASS="LITERAL"
>printf()</TT
> with
the added capability of printing at any position on the screen. </P
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="PRINTWMVPRINTW"
>6.3.1. printw() and mvprintw</A
></H4
><P
>These two functions work much like <TT
CLASS="LITERAL"
>printf()</TT
>.
<TT
CLASS="LITERAL"
>mvprintw()</TT
> can be used to move the cursor to a
position and then print. If you want to move the cursor first and then print
using <TT
CLASS="LITERAL"
>printw()</TT
> function, use
<TT
CLASS="LITERAL"
>move() </TT
> first and then use
<TT
CLASS="LITERAL"
>printw()</TT
> though I see no point why one should
avoid using <TT
CLASS="LITERAL"
>mvprintw()</TT
>, you have the
flexibility to manipulate. </P
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="WPRINTWMVWPRINTW"
>6.3.2. wprintw() and mvwprintw</A
></H4
><P
>These two functions are similar to above two except that they print in the
corresponding window given as argument. </P
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="VWPRINTW"
>6.3.3. vwprintw()</A
></H4
><P
>This function is similar to <TT
CLASS="LITERAL"
>vprintf()</TT
>. This can
be used when variable number of arguments are to be printed.</P
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="SIMPLEPRINTWEX"
>6.3.4. A Simple printw example</A
></H4
><DIV
CLASS="EXAMPLE"
><A
NAME="BPREX"
></A
><P
><B
>Example 3. A Simple printw example </B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62; /* ncurses.h includes stdio.h */
#include &#60;string.h&#62;
int main()
{
char mesg[]="Just a string"; /* message to be appeared on the screen */
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
mvprintw(row-2,0,"This screen has %d rows and %d columns\n",row,col);
printw("Try resizing your window(if possible) and then run this program again");
refresh();
getch();
endwin();
return 0;
}</SPAN
></PRE
></DIV
><P
>Above program demonstrates how easy it is to use <TT
CLASS="LITERAL"
>printw</TT
>. You just feed the coordinates and the message to be appeared
on the screen, then it does what you want.</P
><P
>The above program introduces us to a new function
<TT
CLASS="LITERAL"
>getmaxyx()</TT
>, a macro defined in
<TT
CLASS="LITERAL"
>ncurses.h</TT
>. It gives the number of columns and
the number of rows in a given window.
<TT
CLASS="LITERAL"
>getmaxyx()</TT
> does this by updating the variables
given to it. Since <TT
CLASS="LITERAL"
>getmaxyx()</TT
> is not a function
we don't pass pointers to it, we just give two integer variables. </P
></DIV
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ADDSTRCLASS"
>6.4. addstr() class of functions</A
></H3
><P
><TT
CLASS="LITERAL"
>addstr()</TT
> is used to put a character string into
a given window. This function is similar to calling
<TT
CLASS="LITERAL"
>addch()</TT
> once for each character in a given
string. This is true for all output functions. There are other functions from
this family such as <TT
CLASS="LITERAL"
>mvaddstr(),mvwaddstr()</TT
> and
<TT
CLASS="LITERAL"
>waddstr()</TT
>, which obey the naming convention of
curses.(e.g. mvaddstr() is similar to the respective calls move() and then
addstr().) Another function of this family is addnstr(), which takes an integer
parameter(say n) additionally. This function puts at most n characters into the
screen. If n is negative, then the entire string will be added. </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ACAUTION"
>6.5. A word of caution</A
></H3
><P
>All these functions take y co-ordinate first and then x in their arguments.
A common mistake by beginners is to pass x,y in that order. If you are
doing too many manipulations of (y,x) co-ordinates, think of dividing the
screen into windows and manipulate each one separately. Windows are explained
in the <A
HREF="#WINDOWS"
> windows </A
> section.</P
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="SCANW"
>7. Input functions</A
></H2
><P
>Well, printing without taking input, is boring. Let's see functions which
allow us to get input from user. These functions also can be divided into
three categories.</P
><P
></P
><OL
TYPE="1"
><LI
><P
>getch() class: Get a character</P
></LI
><LI
><P
>scanw() class: Get formatted input</P
></LI
><LI
><P
>getstr() class: Get strings</P
></LI
></OL
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="GETCHCLASS"
>7.1. getch() class of functions</A
></H3
><P
>These functions read a single character from the terminal. But there are several
subtle facts to consider. For example if you don't use the function cbreak(),
curses will not read your input characters contiguously but will begin read them
only after a new line or an EOF is encountered. In order to avoid this, the
cbreak() function must used so that characters are immediately available to your
program. Another widely used function is noecho(). As the name suggests, when
this function is set (used), the characters that are keyed in by the user will
not show up on the screen. The two functions cbreak() and noecho() are typical
examples of key management. Functions of this genre are explained in the
<A
HREF="#KEYS"
>key management section </A
>.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="SCANWCLASS"
>7.2. scanw() class of functions</A
></H3
><P
>These functions are similar to <TT
CLASS="LITERAL"
>scanf()</TT
> with the
added capability of getting the input from any location on the screen.</P
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="SCANWMVSCANW"
>7.2.1. scanw() and mvscanw</A
></H4
><P
>The usage of these functions is similar to that of
<TT
CLASS="LITERAL"
>sscanf()</TT
>, where the line to be scanned is
provided by <TT
CLASS="LITERAL"
>wgetstr()</TT
> function. That is, these
functions call to <TT
CLASS="LITERAL"
>wgetstr()</TT
> function(explained
below) and uses the resulting line for a scan. </P
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="WSCANWMVWSCANW"
>7.2.2. wscanw() and mvwscanw()</A
></H4
><P
>These are similar to above two functions except that they read from a window,
which is supplied as one of the arguments to these functions. </P
></DIV
><DIV
CLASS="SECT3"
><HR><H4
CLASS="SECT3"
><A
NAME="VWSCANW"
>7.2.3. vwscanw()</A
></H4
><P
>This function is similar to <TT
CLASS="LITERAL"
>vscanf()</TT
>. This can
be used when a variable number of arguments are to be scanned.</P
></DIV
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="GETSTRCLASS"
>7.3. getstr() class of functions</A
></H3
><P
>These functions are used to get strings from the terminal. In essence, this
function performs the same task as would be achieved by a series of calls to
<TT
CLASS="LITERAL"
>getch()</TT
> until a newline, carriage return, or
end-of-file is received. The resulting string of characters are pointed to by
<TT
CLASS="LITERAL"
>str</TT
>, which is a character pointer provided by
the user.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="GETSTREX"
>7.4. Some examples</A
></H3
><DIV
CLASS="EXAMPLE"
><A
NAME="BSCEX"
></A
><P
><B
>Example 4. A Simple scanw example </B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62; /* ncurses.h includes stdio.h */
#include &#60;string.h&#62;
int main()
{
char mesg[]="Enter a string: "; /* message to be appeared on the screen */
char str[80];
int row,col; /* to store the number of rows and *
* the number of colums of the screen */
initscr(); /* start the curses mode */
getmaxyx(stdscr,row,col); /* get the number of rows and columns */
mvprintw(row/2,(col-strlen(mesg))/2,"%s",mesg);
/* print the message at the center of the screen */
getstr(str);
mvprintw(LINES - 2, 0, "You Entered: %s", str);
getch();
endwin();
return 0;
}</SPAN
></PRE
></DIV
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="ATTRIB"
>8. Attributes</A
></H2
><P
>We have seen an example of how attributes can be used to print characters with
some special effects. Attributes, when set prudently, can present information in
an easy, understandable manner. The following program takes a C file as input
and prints the file with comments in bold. Scan through the code. </P
><DIV
CLASS="EXAMPLE"
><A
NAME="BSIAT"
></A
><P
><B
>Example 5. A Simple Attributes example </B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>/* pager functionality by Joseph Spainhour" &#60;spainhou@bellsouth.net&#62; */
#include &#60;ncurses.h&#62;
#include &#60;stdlib.h&#62;
int main(int argc, char *argv[])
{
int ch, prev, row, col;
prev = EOF;
FILE *fp;
int y, x;
if(argc != 2)
{
printf("Usage: %s &#60;a c file name&#62;\n", argv[0]);
exit(1);
}
fp = fopen(argv[1], "r");
if(fp == NULL)
{
perror("Cannot open input file");
exit(1);
}
initscr(); /* Start curses mode */
getmaxyx(stdscr, row, col); /* find the boundaries of the screeen */
while((ch = fgetc(fp)) != EOF) /* read the file till we reach the end */
{
getyx(stdscr, y, x); /* get the current curser position */
if(y == (row - 1)) /* are we are at the end of the screen */
{
printw("&#60;-Press Any Key-&#62;"); /* tell the user to press a key */
getch();
clear(); /* clear the screen */
move(0, 0); /* start at the beginning of the screen */
}
if(prev == '/' &#38;&#38; ch == '*') /* If it is / and * then only
* switch bold on */
{
attron(A_BOLD); /* cut bold on */
getyx(stdscr, y, x); /* get the current curser position */
move(y, x - 1); /* back up one space */
printw("%c%c", '/', ch); /* The actual printing is done here */
}
else
printw("%c", ch);
refresh();
if(prev == '*' &#38;&#38; ch == '/')
attroff(A_BOLD); /* Switch it off once we got *
* and then / */
prev = ch;
}
endwin(); /* End curses mode */
fclose(fp);
return 0;
}</SPAN
></PRE
></DIV
><P
>
Don't worry about all those initialization and other crap. Concentrate on
the while loop. It reads each character in the file and searches for the
pattern /*. Once it spots the pattern, it switches the BOLD attribute on with
<TT
CLASS="LITERAL"
> attron()</TT
> . When we get the pattern */ it is
switched off by <TT
CLASS="LITERAL"
> attroff()</TT
> .</P
><P
>
The above program also introduces us to two useful functions
<TT
CLASS="LITERAL"
>getyx() </TT
> and
<TT
CLASS="LITERAL"
>move()</TT
>. The first function gets the
co-ordinates of the present cursor into the variables y, x. Since getyx() is a
macro we don't have to pass pointers to variables. The function
<TT
CLASS="LITERAL"
>move()</TT
> moves the cursor to the co-ordinates
given to it. </P
><P
>
The above program is really a simple one which doesn't do much. On these lines
one could write a more useful program which reads a C file, parses it and prints
it in different colors. One could even extend it to other languages as well.</P
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ATTRIBDETAILS"
>8.1. The details</A
></H3
><P
>Let's get into more details of attributes. The functions <TT
CLASS="LITERAL"
>attron(), attroff(), attrset() </TT
>, and their sister functions
<TT
CLASS="LITERAL"
> attr_get()</TT
> etc.. can be used to switch
attributes on/off , get attributes and produce a colorful display.</P
><P
>The functions attron and attroff take a bit-mask of attributes and switch them
on or off, respectively. The following video attributes, which are defined in
&lt;curses.h&gt; can be passed to these functions. </P
><PRE
CLASS="PROGRAMLISTING"
>
A_NORMAL Normal display (no highlight)
A_STANDOUT Best highlighting mode of the terminal.
A_UNDERLINE Underlining
A_REVERSE Reverse video
A_BLINK Blinking
A_DIM Half bright
A_BOLD Extra bright or bold
A_PROTECT Protected mode
A_INVIS Invisible or blank mode
A_ALTCHARSET Alternate character set
A_CHARTEXT Bit-mask to extract a character
COLOR_PAIR(n) Color-pair number n
</PRE
><P
>
The last one is the most colorful one :-) Colors are explained in the
<A
HREF="#color"
TARGET="_top"
>next sections</A
>.</P
><P
>We can OR(|) any number of above attributes to get a combined effect. If you
wanted reverse video with blinking characters you can use</P
><PRE
CLASS="PROGRAMLISTING"
> attron(A_REVERSE | A_BLINK);</PRE
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ATTRONVSATTRSET"
>8.2. attron() vs attrset()</A
></H3
><P
>Then what is the difference between attron() and attrset()? attrset sets the
attributes of window whereas attron just switches on the attribute given to it.
So attrset() fully overrides whatever attributes the window previously had and
sets it to the new attribute(s). Similarly attroff() just switches off the
attribute(s) given to it as an argument. This gives us the flexibility of
managing attributes easily.But if you use them carelessly you may loose track of
what attributes the window has and garble the display. This is especially true
while managing menus with colors and highlighting. So decide on a consistent
policy and stick to it. You can always use <TT
CLASS="LITERAL"
> standend()</TT
> which is equivalent to <TT
CLASS="LITERAL"
> attrset(A_NORMAL)</TT
> which turns off all attributes and brings you to normal mode.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ATTR_GET"
>8.3. attr_get()</A
></H3
><P
>&#13;The function attr_get() gets the current attributes and color pair of the
window. Though we might not use this as often as the above functions, this is
useful in scanning areas of screen. Say we wanted to do some complex update on
screen and we are not sure what attribute each character is associated with.
Then this function can be used with either attrset or attron to produce the
desired effect.&#13;</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="ATTR_FUNCS"
>8.4. attr_ functions</A
></H3
><P
>There are series of functions like attr_set(), attr_on etc.. These are similar
to above functions except that they take parameters of type
<TT
CLASS="LITERAL"
>attr_t</TT
>.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="WATTRFUNCS"
>8.5. wattr functions</A
></H3
><P
>For each of the above functions we have a corresponding function with 'w' which
operates on a particular window. The above functions operate on stdscr. </P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="CHGAT"
>8.6. chgat() functions</A
></H3
><P
>The function chgat() is listed in the end of the man page curs_attr. It actually
is a useful one. This function can be used to set attributes for a group of
characters without moving. I mean it !!! without moving the cursor :-) It
changes the attributes of a given number of characters starting at the current
cursor location.</P
><P
>We can give -1 as the character count to update till end of line. If you want to
change attributes of characters from current position to end of line, just use
this.</P
><PRE
CLASS="PROGRAMLISTING"
> chgat(-1, A_REVERSE, 0, NULL);</PRE
><P
>
This function is useful when changing attributes for characters that are
already on the screen. Move to the character from which you want to change and
change the attribute. </P
><P
>Other functions wchgat(), mvchgat(), wchgat() behave similarly except that the w
functions operate on the particular window. The mv functions first move the
cursor then perform the work given to them. Actually chgat is a macro which is
replaced by a wchgat() with stdscr as the window. Most of the "w-less" functions
are macros.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="BWICH"
></A
><P
><B
>Example 6. Chgat() Usage example </B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62;
int main(int argc, char *argv[])
{ initscr(); /* Start curses mode */
start_color(); /* Start color functionality */
init_pair(1, COLOR_CYAN, COLOR_BLACK);
printw("A Big string which i didn't care to type fully ");
mvchgat(0, 0, -1, A_BLINK, 1, NULL);
/*
* First two parameters specify the position at which to start
* Third parameter number of characters to update. -1 means till
* end of line
* Forth parameter is the normal attribute you wanted to give
* to the charcter
* Fifth is the color index. It is the index given during init_pair()
* use 0 if you didn't want color
* Sixth one is always NULL
*/
refresh();
getch();
endwin(); /* End curses mode */
return 0;
}</SPAN
></PRE
></DIV
><P
>This example also introduces us to the color world of curses. Colors will be
explained in detail later. Use 0 for no color.</P
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="WINDOWS"
>9. Windows</A
></H2
><P
>Windows form the most important concept in curses. You have seen the standard
window stdscr above where all the functions implicitly operated on this window.
Now to make design even a simplest GUI, you need to resort to windows. The main
reason you may want to use windows is to manipulate parts of the screen
separately, for better efficiency, by updating only the windows that need to be
changed and for a better design. I would say the last reason is the most
important in going for windows. You should always strive for a better and
easy-to-manage design in your programs. If you are writing big, complex GUIs
this is of pivotal importance before you start doing anything.</P
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="WINDOWBASICS"
>9.1. The basics</A
></H3
><P
>A Window can be created by calling the function
<TT
CLASS="LITERAL"
>newwin()</TT
>. It doesn't create any thing on the
screen actually. It allocates memory for a structure to manipulate the window
and updates the structure with data regarding the window like it's size, beginy,
beginx etc.. Hence in curses, a window is just an abstraction of an imaginary
window, which can be manipulated independent of other parts of screen. The
function newwin() returns a pointer to structure WINDOW, which can be passed to
window related functions like wprintw() etc.. Finally the window can be
destroyed with delwin(). It will deallocate the memory associated with the
window structure.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="LETBEWINDOW"
>9.2. Let there be a Window !!!</A
></H3
><P
>What fun is it, if a window is created and we can't see it. So the fun part
begins by displaying the window. The function
<TT
CLASS="LITERAL"
>box()</TT
> can be used to draw a border around the
window. Let's explore these functions in more detail in this example.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="BWIBO"
></A
><P
><B
>Example 7. Window Border example </B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62;
WINDOW *create_newwin(int height, int width, int starty, int startx);
void destroy_win(WINDOW *local_win);
int main(int argc, char *argv[])
{ WINDOW *my_win;
int startx, starty, width, height;
int ch;
initscr(); /* Start curses mode */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
height = 3;
width = 10;
starty = (LINES - height) / 2; /* Calculating for a center placement */
startx = (COLS - width) / 2; /* of the window */
printw("Press F1 to exit");
refresh();
my_win = create_newwin(height, width, starty, startx);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,--startx);
break;
case KEY_RIGHT:
destroy_win(my_win);
my_win = create_newwin(height, width, starty,++startx);
break;
case KEY_UP:
destroy_win(my_win);
my_win = create_newwin(height, width, --starty,startx);
break;
case KEY_DOWN:
destroy_win(my_win);
my_win = create_newwin(height, width, ++starty,startx);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
WINDOW *create_newwin(int height, int width, int starty, int startx)
{ WINDOW *local_win;
local_win = newwin(height, width, starty, startx);
box(local_win, 0 , 0); /* 0, 0 gives default characters
* for the vertical and horizontal
* lines */
wrefresh(local_win); /* Show that box */
return local_win;
}
void destroy_win(WINDOW *local_win)
{
/* box(local_win, ' ', ' '); : This won't produce the desired
* result of erasing the window. It will leave it's four corners
* and so an ugly remnant of window.
*/
wborder(local_win, ' ', ' ', ' ',' ',' ',' ',' ',' ');
/* The parameters taken are
* 1. win: the window on which to operate
* 2. ls: character to be used for the left side of the window
* 3. rs: character to be used for the right side of the window
* 4. ts: character to be used for the top side of the window
* 5. bs: character to be used for the bottom side of the window
* 6. tl: character to be used for the top left corner of the window
* 7. tr: character to be used for the top right corner of the window
* 8. bl: character to be used for the bottom left corner of the window
* 9. br: character to be used for the bottom right corner of the window
*/
wrefresh(local_win);
delwin(local_win);
}</SPAN
></PRE
></DIV
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="BORDEREXEXPL"
>9.3. Explanation</A
></H3
><P
>Don't scream. I know it's a big example. But I have to explain some important
things here :-). This program creates a rectangular window that can be moved
with left, right, up, down arrow keys. It repeatedly creates and destroys
windows as user press a key. Don't go beyond the screen limits. Checking for
those limits is left as an exercise for the reader. Let's dissect it by line by line.</P
><P
>The <TT
CLASS="LITERAL"
>create_newwin()</TT
> function creates a window
with <TT
CLASS="LITERAL"
>newwin() </TT
> and displays a border around it
with box. The function <TT
CLASS="LITERAL"
> destroy_win()</TT
> first
erases the window from screen by painting a border with ' ' character and then
calling <TT
CLASS="LITERAL"
>delwin()</TT
> to deallocate memory related
to it. Depending on the key the user presses, starty or startx is changed and a
new window is created.</P
><P
>In the destroy_win, as you can see, I used wborder instead of box. The reason is
written in the comments (You missed it. I know. Read the code :-)). wborder
draws a border around the window with the characters given to it as the 4 corner
points and the 4 lines. To put it clearly, if you have called wborder as below:
<PRE
CLASS="PROGRAMLISTING"
> wborder(win, '|', '|', '-', '-', '+', '+', '+', '+');</PRE
></P
><P
>it produces some thing like </P
><PRE
CLASS="PROGRAMLISTING"
> +------------+
| |
| |
| |
| |
| |
| |
+------------+</PRE
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="OTHERSTUFF"
>9.4. The other stuff in the example</A
></H3
><P
>You can also see in the above examples, that I have used the variables COLS,
LINES which are initialized to the screen sizes after initscr(). They can be
useful in finding screen dimensions and finding the center co-ordinate of the
screen as above. The function <TT
CLASS="LITERAL"
>getch()</TT
> as usual
gets the key from keyboard and according to the key it does the corresponding
work. This type of switch- case is very common in any GUI based programs.</P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="OTHERBORDERFUNCS"
>9.5. Other Border functions</A
></H3
><P
>Above program is grossly inefficient in that with each press of a key, a window
is destroyed and another is created. So let's write a more efficient program
which uses other border related functions.</P
><P
>The following program uses <TT
CLASS="LITERAL"
>mvhline()</TT
> and
<TT
CLASS="LITERAL"
>mvvline()</TT
> to achieve similar effect. These two
functions are simple. They create a horizontal or vertical line of the specified
length at the specified position.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="BOTBO"
></A
><P
><B
>Example 8. More border functions</B
></P
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62;
typedef struct _win_border_struct {
chtype ls, rs, ts, bs,
tl, tr, bl, br;
}WIN_BORDER;
typedef struct _WIN_struct {
int startx, starty;
int height, width;
WIN_BORDER border;
}WIN;
void init_win_params(WIN *p_win);
void print_win_params(WIN *p_win);
void create_box(WIN *win, bool flag);
int main(int argc, char *argv[])
{ WIN win;
int ch;
initscr(); /* Start curses mode */
start_color(); /* Start the color functionality */
cbreak(); /* Line buffering disabled, Pass on
* everty thing to me */
keypad(stdscr, TRUE); /* I need that nifty F1 */
noecho();
init_pair(1, COLOR_CYAN, COLOR_BLACK);
/* Initialize the window parameters */
init_win_params(&#38;win);
print_win_params(&#38;win);
attron(COLOR_PAIR(1));
printw("Press F1 to exit");
refresh();
attroff(COLOR_PAIR(1));
create_box(&#38;win, TRUE);
while((ch = getch()) != KEY_F(1))
{ switch(ch)
{ case KEY_LEFT:
create_box(&#38;win, FALSE);
--win.startx;
create_box(&#38;win, TRUE);
break;
case KEY_RIGHT:
create_box(&#38;win, FALSE);
++win.startx;
create_box(&#38;win, TRUE);
break;
case KEY_UP:
create_box(&#38;win, FALSE);
--win.starty;
create_box(&#38;win, TRUE);
break;
case KEY_DOWN:
create_box(&#38;win, FALSE);
++win.starty;
create_box(&#38;win, TRUE);
break;
}
}
endwin(); /* End curses mode */
return 0;
}
void init_win_params(WIN *p_win)
{
p_win-&#62;height = 3;
p_win-&#62;width = 10;
p_win-&#62;starty = (LINES - p_win-&#62;height)/2;
p_win-&#62;startx = (COLS - p_win-&#62;width)/2;
p_win-&#62;border.ls = '|';
p_win-&#62;border.rs = '|';
p_win-&#62;border.ts = '-';
p_win-&#62;border.bs = '-';
p_win-&#62;border.tl = '+';
p_win-&#62;border.tr = '+';
p_win-&#62;border.bl = '+';
p_win-&#62;border.br = '+';
}
void print_win_params(WIN *p_win)
{
#ifdef _DEBUG
mvprintw(25, 0, "%d %d %d %d", p_win-&#62;startx, p_win-&#62;starty,
p_win-&#62;width, p_win-&#62;height);
refresh();
#endif
}
void create_box(WIN *p_win, bool flag)
{ int i, j;
int x, y, w, h;
x = p_win-&#62;startx;
y = p_win-&#62;starty;
w = p_win-&#62;width;
h = p_win-&#62;height;
if(flag == TRUE)
{ mvaddch(y, x, p_win-&#62;border.tl);
mvaddch(y, x + w, p_win-&#62;border.tr);
mvaddch(y + h, x, p_win-&#62;border.bl);
mvaddch(y + h, x + w, p_win-&#62;border.br);
mvhline(y, x + 1, p_win-&#62;border.ts, w - 1);
mvhline(y + h, x + 1, p_win-&#62;border.bs, w - 1);
mvvline(y + 1, x, p_win-&#62;border.ls, h - 1);
mvvline(y + 1, x + w, p_win-&#62;border.rs, h - 1);
}
else
for(j = y; j &#60;= y + h; ++j)
for(i = x; i &#60;= x + w; ++i)
mvaddch(j, i, ' ');
refresh();
}</SPAN
></PRE
></DIV
></DIV
></DIV
><DIV
CLASS="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="COLOR"
>10. Colors</A
></H2
><DIV
CLASS="SECT2"
><H3
CLASS="SECT2"
><A
NAME="COLORBASICS"
>10.1. The basics</A
></H3
><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
><PRE
CLASS="PROGRAMLISTING"
><SPAN
CLASS="INLINEMEDIAOBJECT"
>#include &#60;ncurses.h&#62;
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
></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.
<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
></P
></DIV
><DIV
CLASS="SECT2"
><HR><H3
CLASS="SECT2"
><A
NAME="CHANGECOLORDEFS"
>10.2. Changing Color Definitions</A
></H3
><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
><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
><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"
><HR><H3
CLASS="SECT2"
><A
NAME="COLORCONTENT"
>10.3. Color Content</A
></H3
><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="SECT1"
><HR><H2
CLASS="SECT1"
><A
NAME="KEYS"
>11. Interfacing with the key board</A
></H2
><DIV
CLASS="SECT2"
><H3
CLASS="SECT2"
><A
NAME="KEYSBASICS"
>11.1. The Basics</A
></H3
><P
>No GUI is complete without a strong user interface and to interact with the
user, a curses program should be sensitive to key presses or the mouse actions
done by the user. Let's deal with the keys first.</P
><P
>As you have seen in almost all of the above examples, it's very easy to get key
input from the user. A simple way of getting key presses is to use