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Newt(3) 		       User Contributed Perl Documentation			  Newt(3)

       Newt - Perl bindings for Red Hat newt library

	 use Newt;


	 #A lot of Newt operations...


       The Newt module implements perl bindings for the Red Hat newt windowing system, a
       terminal-based window and widget library for writing applications with a simple, but user-
       friendly, interface.

Basic Newt functions
	   Starts Newt services. You must use this command first.

	   Ends Newt services.

	   Clears the background.

	   Foreces an inmediate update of the modified portions of the screen.

	   Sends a beep to the terminal.

	   Returns a tuple containing the screen dimensions.

Keyboard input
	   Stops program execution until a key is pressed.

	   Discards the contents of the terminal's input buffer without waiting for additional

Drawing text on the root window
       "Newt::DrawRootText($left, $top, $text)"
	   Displays the text in the indicated position.

	   Saves the current help line on a stack and displays the new line. If the text is null,
	   Newt's default help line is displayed. If text is a string of length 0, the help line
	   is cleared.

	   Replaces the current help line with the previous one. It is important not to pop more
	   lines than the ones pushed.

Suspending Newt applications
       By default, Newt programs cannot be suspended by the user. Instead, programs can specify a
       callback function which gets invoked whe the user presses the suspend key. To register
       such function, you can do something like this:

	   sub my_cb {


       If the application should suspend and continue like most user applications, the suspend
       callback needs two other newt functions:


       The first one tells Newt to return the terminal to its initial state. Once this is done,
       the application can suspend itself by sending SIGSTP, fork a child program or whatever.
       When it wants to resume using the Newt interface, is must call "Newt::Resume()" before
       doing so.

       For more information on suspending newt applications, read the original newt

       Components are the basic blocks for construction of Newt interfaces.  They all are created
       in a similar manner. You just have to call the constructor to receive a blessed object of
       the specified class:

	   $object = Newt::Foo();

       Once you have a component, you can add it to a panel to create a complex user input

   General component manipulation
       You can attach a callback for a component like this:

	   sub comp_cb {


       Exactly when (if ever) the callback is invoked depens on the type of the component.

       Yo can tell if a component takes or not focus when traversing a form with the following


       It is handy to set some arbitrary information on a component for later retrieval. You do
       this by setting its tag:


       If you call this function without an argument, it replies with the actual tag for that

       In general when the return value of any method of a component isn't described the method
       returns the component itself to allow constructions like:

	       ->Add(0,0, $componet1->Set( .... ) )
	       ->Add(0,1, Newt::Label( .... ) )
	       ->Add(0,2, Newt::Panel( .... )
		   ->Add( .... )
		   ->Add( .... ) )
	       ->Add( .... );

       There are two kinds of buttons: full and compact:

	   $normal_button = Newt::Button($text);
	   $compact_button = Newt::CompactButton($text);

       Labels are quite simple:

	   $label = Newt::Label($text);

       You can set the text of an existing label like this:


   Entry boxes
       Entry boxes are used to enter text:

	   $entry = Newt::Entry($width, $flags, $initial_text);

       The initial text is optional. After an entry has been created, it's contents can be set by

	   $entry->Set($text, $cursor_at_end);

       The last parameter is optional, and signals if the cursor should be moved to the end of
       the new value.

       To get the current value of the entry box, you do this:


       You can filter the characters that may be entered by using a callback filter like this:

	   sub my_filter {
	     my ($proposed_char, $cursor_position) = @_;


	     return(0) if $char_shoud_be_ignored;
	     return($proposed_char)    # Accept the char


       As can be seen, filter callbacks receive a char and an integer which indicates the
       position that the proposed char would take on the entry.  The filter function can return
       the very same char to indicate that it was accepted, but it can also return another char,
       to actually substitute the original one. If the filter wants to simply reject the
       keystroke, it only returns 0.

       When an entry is created, some flags may be specified. The flags are the following and may
       be "OR"ed:

	   If not specified, the user cannot enter text into the entry box which is wider than
	   the entry box itself. This flag removes this limitation, and lets the user enter data
	   of an arbitrary length.

	   If specified, the value of the entry is not displayed. Useful when an applications
	   needs a password.

	   When specified, the entry will cause the form to stop running if the user pressed
	   return inside the entry box. Nice shortcut for users.

       Newt checkboxes are peculiar, since they may have more than two states. To create a normal
       one (checked or unchecked), do this:

	   $check = Newt::Checkbox("Normal checkbox");

       But you can create, for example, a checkbox that switches from not checked to checked with
       an asterisk and then to checked with an 'M':

	   $check = Newt::Checkbox("Normal checkbox", " ", " *M");

       As you can see, you can use the two optional parameters to tell the default char first and
       then the possible chars.

       To know if a checkbox is checked after the for is ran, you use the following:

	   print "Is checked\n" if $check->Checked();

       And you can always get the actual state like this:

	   $state = $check->Get();

   Radio groups
       You create two kinds of radio button groups, vertical and horizontal, by doing this:

	   $radio_group1 = Newt::VRadiogroup('Red', 'Green', 'Blue');
	   $radio_group2 = Newt::HRadiogroup('Red', 'Green', 'Blue');

       You can put any number of options and the first one will always be preselected. To know
       the index of the selected option after the form has run, you do this:

	   $index = $radio_group->Get();

       Listboxes are the most complicated components Newt provides. They can allow single or
       multiple selection, and are easy to update. They are created as follows:

	   $listbox = Newt::Listbox($height, $flags);

       A listbox is created at a certain position and a given height. The $height is used for two
       things. First of all, it is the minimum height the listbox will use. If there are less
       items in the listbox then the height, suggests the listbox will still take up that minimum
       amount of space. Secondly, if the listbox is set to be scrollable (by setting the
       "NEWT_FLAG_SCROLL" flag, $height is also the maximum height of the listbox. If the listbox
       may not scroll, it increases its height to display all of its items.

       The following flags may be used when creating a listbox:

	   The listbox should scroll to display all of the items it contains.

	   When the user presses return on an item in the list, the form should return.

	   A frame is drawn around the listbox, which can make it easier to see which listbox has
	   the focus when a form contains multiple listboxes.

	   By default, a listbox only lets the user select one item in the list at a time. When
	   this flag is specified, they may select multiple items from the list.

       Once a listbox has been created, items are appended to the bottom like this:

	   $listbox->Append($item1, $item2, ...);

       Appending is not the only way to add items to the list. You can insert items in any
       position by telling the item that should be before with the following command:

	   $listbox->Insert($before, $item1, $item2, ...);

       And you can change any item just by telling:

	   $listbox->Set($original, $new);

       Of course you can delete entries:

	   $listbox->Delete($item1, $item2, ...);

       Or just clear out the listbox:


       You can select and unselect items, with the following:

	   $listbox->Select($item1, $item2, ...);

	   $listbox->Unselect($item1, $item2, ...);


       but if you did not sepecify the flag "NEWT_FLAG_MULTIPLE" when constructing your listbox,
       only the last item on the argument list of "Unselect()" will remain selected.

       To get a list of the selected items, just issue:

	   @selected_items = $listbox->Get();

       Scales provide an easy way for telling the user the advance on some lengthy operation. It
       is a horizontal bar graph which the application updates as the operation continues:

	   $scale = Newt::Scale($width, $fullvalue);

       It is set as expected:


       A text box is used for displaying large amounts of text. They are created as follows:

	   $textbox = Newt::Textbox($width, $height, $flags, $text, ...);

       The $text parameter is optional, and if not supplied, the textbox is created only, but it
       does not fill it with data. To do so, use:

	   $textbox->Set($text, ...);

       All the arguments are simply concatenated using the double quote operator.

       The flags that can be passed to the constructor are the following:

	   All text in the textbox should be wrapped to fit the width of the textbox. If this
	   flag is not specified, each newline-delimited line in the text is truncated if it is
	   too long to fit.

	   When Newt wraps text, it tries not to break lines on spaces or tabs. Literal newline
	   characters are respected, and may be used to force line breaks.

	   The text should be scrollable. When this option is used, the scrollbar which is added
	   increases the width of the area used by the textbox by 2 characters.

   Reflowing text
       When applications need to display large amounts of text, it is common not to know exactly
       where the linebreaks should go. While textboxes are quite willing to scroll the text, the
       programmer still must know what width the text will look ``best'' at (where ``best'' means
       most exactly rectangular; no lines much shorter or much longer then the rest). This common
       is specially prevalent in internationalized programs, which need to make a wide variety of
       message string look good on a screen.

       To help with this, Newt provides routines to reformat text to look good. It tries
       different widths to figure out which one will look ``best'' to the user. As these commons
       are almost always used to format text for textbox components, Newt makes it easy to
       construct a textbox with reflowed text.

       The following function reflows the provided text to a target width. the actual width of
       the longest line in the returned text is between "$width - $flexdown" and "$width +
       $flexup"; the actual maximum line length is chosen to make displayed text look
       rectangular. The function returns a tuple consisting of the reflowed text and the actual
       width and height of it.

	   ($r_text, $width, $height) = Newt::ReflowText($width,

       When the reflowed text is being placed in a textbox it may be easier to use the following:

	   $textbox = Newt::TextboxReflowed($width, $flexdown,
					    $flexup, $flags,
					    $text, ...);

       which creates a textbox, reflows the text, and places the reflowed text in the listbox.
       Its parameters consist of the position of the final textbox, the width and flex values for
       the text (which are identical to the parameters passed to "Newt::Reflow()", and the flags
       for the textbox (which are the same as the flags for "Newt::Textbox()". This function does
       not let you limit the height of the textbox, however, making limiting its use to
       constructing textboxes which do not need to scroll.

       To find out how tall the textbox created by "Newt::TextboxReflowed()" is, use
       "Newt::GetNumLines()", which returns the number of lines in the textbox. For textboxes
       created by "Newt::TextboxReflowed()", this is always the same as the height of the

       Please note that the order of the parameters of Newt::ReflowText and Newt::TextboxReflowed
       differs from the C API to allow lists of text but currently only TextboxReflowed allows

       Scrollbars may be attached to forms to let them contain more data than they have space
       for. Currently, there can only be vertical scrollbars:

	   $scroll = Newt::VScrollbar($height,

       When a scrollbar is created, it is given a position on the screen, a height, and two
       colors. The first color is the color used for drawing the scrollbar, and the second color
       is used for drawing the thumb. This is the only place in newt where an application
       specifically sets colors for a component. It s done here to let the colors a scrollbar use
       match the colors of the component the scrollbar is mated too. When a scrollbar is being
       used with a form, $normalColorset is often "NEWT_COLORSET_WINDOW" and $thumbColorset

       If you do not want to bother with colors, you can omit the last two parameters and let
       Newt use the defaults.

       As the scrollbar is normally updated by the component it is mated with, there is no public
       interface for moving the thumb.

       Panels are high level grid-like constructs that are used to group components. You create
       them by specifying the number of columns and rows you want, as well as a caption to be
       used when the panel is displayed as a toplevel:

	   $panel = Newt::Panel(2, 3, "Panel example");

       When run, panels are centered by default, but you can specify a position relative to the
       topleft corner of the screen by appending two optional integers:

	   $panel = Newt::Panel(2, 3, "Panel example", 5, 5);

       Adding components to a panel is straightforward, you just have to indicate the position
       the component will take in the grid:

	  $panel1->Add(0, 0, $mycomponent);

       Several optional parameters my however be used when adding components:


       You can specify the side of the cell to which the component will be aligned by specifying
       an anchor. The anchor values avalaible are "NEWT_ANCHOR_LEFT", "NEWT_ANCHOR_RIGHT",

       You can ask for more space on the sides of the component, perhaps to get a cleaner, less
       cluttered presentation using the padding parameters, and specifiying an integer value.

       Panels may be nested. For this to be done you only have to add a panel to another as you
       would with any other component.

       To run a panel as a toplevel and get user input, you may do the following:

	   ($reason, $data) = $panel->Run();

	   if ($reason eq NEWT_EXIT_HOTKEY) {
	     if ($data eq NEWT_KEY_F12) {
	       print "F12 hotkey was pressed\n";
	     } else {
	       print "Some hotkey other than F12 was pressed\n";
	   } else {
	     print 'Form terminated by button ', $data->Tag(), "\n";

       As can be seen on the example, when called in a list context "Run()" returns two values,
       one is the reason why the form terminated and the other is an associated data. In a scalar
       context only the data is returned. Posible values for the reason are:

	   The form exited because a hotkey was pressed. The associated data contains the key
	   pressed, that is, one of NEWT_KEY_* values. See Hotkeys later for more information.

	   The form exited because a component was activated, a button, for instance a button.
	   The associated data is a reference to the component involved.

       Normally, a panel terminates when the user presses a button, but you can define some keys
       as "hotkeys" that will make the "Run()" function return with "NEWT_EXIT_HOTKEY". Yo do
       this by issuing the folowing:


       F12 is always defined to be a hotkey.

   Drawing panels instead of running them
       When you run a panel the terminal is blocked until the user presses a component or a key
       that causes the panel to exit. Sometimes is useful to present the interface to the user
       without blocking the execution of code. This can be done by only drawing the panel, not
       running it. It is easy to show an advance status for a lengthy operation like this:

	  $i = 1;
	  foreach (@items) {
	     $label->Set("Processing item $i");

   Hiding panels
       Panels can be hidden in case you want by using the following:


       You can import all the constants exported by this package as needed or using several
       predefined tags, with the following syntax:

	   use Newt qw(:exits :keys);

       exits NEWT_EXIT_* constants
       keys NEWT_KEY_* constants
       anchors NEWT_ANCHOR_* constants
       colorsets NEWT_COLORSET_* constanst
       flags NEWT_FLAG_* constants
       entry NEWT_ENTRY_* constants
       fd NEWT_FD_* constants
       grid NEWT_GRID_* constants
       textbox NEWT_TEXTBOX_* constants
	   macros to make useful buttons and panels: OK_BUTTON, CANCEL_BUTTON, QUIT_BUTTON,
	   BACK_BUTTON, OK_CANCEL_PANEL, OK_BACK_PANEL. This macros only create components which
	   are properly tagged.

       Scrollable panels.
       Some forms stuff, like watching file descriptors.

       Writing programs using Newt, by Erik Troan.

       Erik Troan, for writing this useful library. Thanks for his tutorial, too, from where I
       stole complete paragraphs for this documentation, I'm afraid.

       The original author of the Red Hat newt library is Erik Troan, <ewt@redhat.com> The author
       of this Perl bindings is Alejandro Escalante Medina, <amedina@msg.com.mx>

       Version 0.1, 5th Nov 1998

perl v5.16.3				    2014-06-10					  Newt(3)
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