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Curses::UI::Widget(3) User Contributed Perl DocumentationCurses::UI::Widget(3)

NAME
       Curses::UI::Widget - The base class for all widgets

CLASS HIERARCHY
	Curses::UI::Widget - base class

SYNOPSIS
       This class is not used directly by somebody who is building an
       application using Curses::UI. It's a base class that is expanded by the
       Curses::UI widgets.  See WIDGET STRUCTURE below for a basic widget
       framework.

	   use Curses::UI::Widget;
	   my $widget = new Curses::UI::Widget(
	       -width  => 15,
	       -height => 5,
	       -border => 1,
	   );

STANDARD OPTIONS
       The standard options for (most) widgets are the options that are
       enabled by this class. So this class doesn't really have standard
       options.

WIDGET-SPECIFIC OPTIONS
   GENERAL:
       ·   -parent < OBJECTREF >

	   This option specifies parent of the object. This parent is the
	   object (Curses::UI, Window, Widget(descendant), etc.)  in which the
	   widget is drawn.

       ·   -intellidraw < BOOLEAN >

	   If BOOLEAN has a true value (which is the default), the intellidraw
	   method (see below) will be suported. This option is mainly used in
	   widget building.

       ·   -userdata < SCALAR >

	   This option specifies a user data that can be retrieved with the
	   userdata() method.  It is usefull to store application's internal
	   data that otherwise would not be accessible in callbacks.

       ·   -border < BOOLEAN >

	   Each widget can be drawn with or without a border. To enable the
	   border use a true value and to disable it use a false value for
	   BOOLEAN. The default is not to use a border.

       ·   -sbborder < BOOLEAN >

	   If no border is used, a square bracket border may be used.  This is
	   a border which is constructed from '[' and ']' characters. This
	   type of border is especially useful for single line widgets (like
	   text entries and popup boxes).  A square bracket border can only be
	   enabled if -border is false. The default is not to use a square
	   bracket border.

   POSITIONING:
	+---------------------------------------------------+
	| parent		     ^			    |
	|			     |			    |
	|			     y			    |
	|			     |			    |
	|			     v			    |
	|			     ^			    |
	|			     |			    |
	|			   padtop		    |
	|			     |			    |
	|			     v			    |
	|		     +- TITLE -------+		    |
	|		     | widget	^    |		    |
	|		     |		|    |		    |
	|		     |		|    |		    |
	|<--x--><--padleft-->|<----width---->|<--padright-->|
	|		     |		|    |		    |
	|		     |		|    |		    |
	|		     |	      height |		    |
	|		     |		v    |		    |
	|		     +---------------+		    |
	|				^		    |
	|				|		    |
	|			    padbottom		    |
	|				|		    |
	|				v		    |
	+---------------------------------------------------+

       ·   -x < VALUE >

	   The x-position of the widget, relative to the parent. The default
	   is 0.

       ·   -y < VALUE >

	   The y-position of the widget, relative to the parent. The default
	   is 0.

       ·   -width < VALUE >

	   The width of the widget. If the width is undefined or -1, the
	   maximum available width will be used. By default the widget will
	   use the maximum available width.

       ·   -height < VALUE >

	   The height of the widget. If the height is undefined or -1, the
	   maximum available height will be used. By default the widget will
	   use the maximum available height.

   PADDING:
       ·   -pad < VALUE >

       ·   -padtop < VALUE >

       ·   -padbottom < VALUE >

       ·   -padleft < VALUE >

       ·   -padright < VALUE >

	   With -pad you can specify the default padding outside the widget
	   (the default value for -pad is 0). Using one of the -pad... options
	   that have a direction in them, you can override the default
	   padding.

       ·   -ipad < VALUE >

       ·   -ipadtop < VALUE >

       ·   -ipadbottom < VALUE >

       ·   -ipadleft < VALUE >

       ·   -ipadright < VALUE >

	   These are almost the same as the -pad... options, except these
	   options specify the padding _inside_ the widget. Normally the
	   available effective drawing area for a widget will be the complete
	   area if no border is used or else the area within the border.

   TITLE:
       Remark:

       A title is drawn in the border of a widget. So a title will only be
       available if -border is true.

       ·   -title < TEXT >

	   Set the title of the widget to TEXT. If the text is longer then the
	   available width, it will be clipped.

       ·   -titlereverse < BOOLEAN >

	   The title can be drawn in normal or in reverse type. If
	   -titlereverse is true, the text will be drawn in reverse type. The
	   default is to use reverse type.

       ·   -titlefullwidth < BOOLEAN >

	   If -titlereverse is true, the title can be stretched to fill the
	   complete width of the widget by giving -titlefullwidth a true
	   value.  By default this option is disabled.

   SCROLLBARS:
       Remark:

       Since the user of a Curses::UI program has no real control over the so
       called "scrollbars", they aren't really scrollbars. A better name would
       be something like "document location indicators".  But since they look
       so much like scrollbars I decided I could get away with this naming
       convention.

       ·   -vscrollbar < VALUE >

	   VALUE can be 'left', 'right', another true value or false.

	   If -vscrollbar has a true value, a vertical scrollbar will be drawn
	   by the widget. If this true value happens to be "left", the
	   scrollbar will be drawn on the left side of the widget. In all
	   other cases it will be drawn on the right side. The default is not
	   to draw a vertical scrollbar.

	   For widget programmers: To control the scrollbar, the widget data
	   -vscrolllen (the total length of the content of the widget) and
	   -vscrollpos (the current position in the document) should be set.
	   If Curses::UI::Widget::draw is called, the scrollbar will be drawn.

       ·   -hscrollbar < VALUE >

	   VALUE can be 'top', 'bottom', another true value or false.

	   If -hscrollbar has a true value, a horizontal scrollbar will be
	   drawn by the widget. If this true value happens to be "top", the
	   scrollbar will be drawn at the top of the widget. In all other
	   cases it will be drawn at the bottom. The default is not to draw a
	   horizontal scrollbar.

	   For widget programmers: To control the scrollbar, the widget data
	   -hscrolllen (the maximum width of the content of the widget) and
	   -hscrollpos (the current horizontal position in the document)
	   should be set. If Curses::UI::Widget::draw is called, the scrollbar
	   will be drawn.

   EVENTS
       ·   -onfocus < CODEREF >

	   This sets the onFocus event handler for the widget.	If the widget
	   gets the focus, the code in CODEREF will be executed. It will get
	   the widget reference as its argument.

       ·   -onblur < CODEREF >

	   This sets the onBlur event handler for the widget.  If the widget
	   loses the focus, the code in CODEREF will be executed. It will get
	   the widget reference as its argument.

METHODS
       ·   new ( OPTIONS )

	   Create a new Curses::UI::Widget instance using the options in HASH.

       ·   layout ( )

	   Layout the widget. Compute the size the widget needs and see if it
	   fits. Create the curses windows that are needed for the widget (the
	   border and the effective drawing area).

       ·   draw ( BOOLEAN )

	   Draw the Curses::UI::Widget. If BOOLEAN is true, the screen will
	   not update after drawing. By default this argument is false, so the
	   screen will update after drawing the widget.

       ·   intellidraw ( )

	   If the widget is visible (it is not hidden and it is in the window
	   that is currently on top) and if intellidraw is not disabled for it
	   (-intellidraw has a true value) it is drawn and the curses routine
	   doupdate() will be called to update the screen.

	   This is useful if you change something in a widget and want it to
	   update its state. If you simply call draw() and doupdate()
	   yourself, then the widget will also be drawn if it is on a window
	   that is currently not on top. This would result in the widget being
	   drawn right through the contents of the window that is currently on
	   top.

       ·   focus ( )

	   Give focus to the widget. In Curses::UI::Widget, this method
	   immediately returns, so the widget will not get focused.  A derived
	   class that needs focus, must override this method.

       ·   focusable ( [BOOLEAN] )

	   If BOOLEAN is set to a true value the widget will be focusable,
	   false will make it unfocusable. If not argument is given, it will
	   return the current state.

       ·   lose_focus ( )

	   This method makes the current widget lose it's focus.  It returns
	   the current widget.

       ·   modalfocus ( )

	   Gives the widget a modal focus, i.e. no other widget can be active
	   till this widget is removed.

       ·   title ( TEXT )

	   Change the title that is shown in the border of the widget to TEXT.

       ·   width ( )

       ·   height ( )

	   These methods return the total width and height of the widget.
	   This is the space that the widget itself uses plus the space that
	   is used by the outside padding.

       ·   borderwidth ( )

       ·   borderheight ( )

	   These methods return the width and the height of the border of the
	   widget.

       ·   canvaswidth ( )

       ·   canvasheight ( )

	   These methods return the with and the height of the effective
	   drawing area of the widget. This is the area where the draw()
	   method of a widget may draw the contents of the widget (BTW: the
	   curses window that is associated to this drawing area is
	   $this->{-canvasscr}).

       ·   width_by_windowscrwidth ( NEEDWIDTH, OPTIONS )

       ·   height_by_windowscrheight ( NEEDHEIGHT, OPTIONS )

	   These methods are exported by this module. These can be used in
	   child classes to easily compute the total width/height the widget
	   needs in relation to the needed width/height of the effective
	   drawing area ($this->{-canvasscr}). The OPTIONS contains the
	   options that will be used to create the widget. So if we want a
	   widget that has a drawing area height of 1 and that has a border,
	   the -height option can be computed using something like:

	     my $height = height_by_windowscrheight(1, -border => 1);

       ·   generic_focus ( BLOCKTIME, CTRLKEYS, CURSOR, PRECALLBACK )

	   For most widgets the generic_focus method will be enough to handle
	   focusing. This method will do the following:

	   It starts a loop for reading keyboard input from the user.  At the
	   start of this loop the PRECALLBACK is called. This callback can for
	   example be used for layouting the widget. Then, the widget is
	   drawn.

	   Now a key is read or if the DO_KEY:<key> construction was used, the
	   <key> will be used as if it was read from the keyboard (you can
	   find more on this construction below). If the DO_KEY:<key>
	   construction was not used, a key is read using the get_key method
	   which is in Curses::UI::Common.  The arguments BLOCKTIME, CTRLKEYS
	   and CURSOR are passed to get_key.

	   Now the key is checked. If the value of the key is -1, get_key did
	   not read a key at all. In that case, the program will go back to
	   the start of the loop.

	   As soon as a key is read, this key will be handed to the
	   process_bindings method (see below). The returnvalue of this method
	   (called RETURN from now on) will be used to determine what to do
	   next. We have the following cases:

	   * RETURN matches DO_KEY:<key>

	   The <key> is extracted from RETURN. The loop is restarted and <key>
	   will be used as if it was entered using the keyboard.

	   * RETURN is a CODE reference

	   RETURN will be returned to the caller of generic_focus.  This will
	   have the widget lose its focus. The caller then can execute the
	   code.

	   * RETURN is a SCALAR value

	   RETURN will be returned to the caller of generic_focus.  This will
	   have the widget lose its focus.

	   * anything else

	   The widget will keep its focus. The loop will be restarted all over
	   again. So, if you are writing a binding routine for a widget, you
	   can have the focus to stay at the widget by returning the widget
	   instance itself. Example:

	       sub myroutine() {
		   my $this = shift;
		   .... do your thing ....
		   return $this;
	       }

       ·   process_bindings ( KEY )

	   KEY -> maps via binding to -> ROUTINE -> maps to -> VALUE

	   This method will try to find out if there is a binding defined for
	   the KEY. If no binding is found, the method will return the widget
	   object itself.  If a binding is found, the method will check if
	   there is an corresponding ROUTINE. If the ROUTINE can be found it
	   will check if it's VALUE is a code reference. If it is, the code
	   will be executed and the returnvalue of this code will be returned.
	   Else the VALUE will directly be returned.

       ·   clear_binding ( ROUTINE )

	   Clear all keybindings for routine ROUTINE.

       ·   set_routine ( ROUTINE, VALUE )

	   Set the routine ROUTINE to the VALUE. The VALUE may either be a
	   scalar value or a code reference. If process_bindings (see above)
	   sees a scalar value, it will return this value. If it sees a
	   coderef, it will execute the code and return the returnvalue of
	   this code.

       ·   set_binding ( ROUTINE, KEYLIST )

	   Bind the keys in the list KEYLIST to the ROUTINE. If you use an
	   empty string for a key, then this routine will become the default
	   routine (in case no other keybinding could be found). This is for
	   example used in the TextEditor widget.

       ·   set_event ( EVENT, [CODEREF] )

	   This routine will set the callback for event EVENT to CODEREF. If
	   CODEREF is omitted or undefined, the event will be cleared.

       ·   clear_event ( EVENT )

	   This will clear the callback for event EVENT.

       ·   run_event ( EVENT )

	   This routine will check if a callback for the event EVENT is set
	   and if is a code reference. If this is the case, it will run the
	   code and return its return value.

       ·   onFocus ( CODEREF )

	   This method can be used to set the -onfocus event handler (see
	   above) after initialization of the widget.

       ·   onBlur ( CODEREF )

	   This method can be used to set the -onblur event handler (see
	   above) after initialization of the widget.

       ·   parentwindow ( )

	   Returns this parent window for the widget or undef if no parent
	   window can be found (this should not happen).

       ·   in_topwindow ( )

	   Returns true if the widget is in the window that is currently on
	   top.

       ·   userdata ( [ SCALAR ] )

	   This method will return the user internal data stored in this
	   widget.  If a SCALAR parameter is specified it will also set the
	   current user data to it.

       ·   beep_on ( )

	   This sets the data member $this->{-nobeep} of the class instance to
	   a false value.

       ·   beep_off ( )

	   This sets the data member $this->{-nobeep} of the class instance to
	   a true value.

       ·   dobeep ( )

	   This will call the curses beep() routine, but only if -nobeep is
	   false.

WIDGET STRUCTURE
       Here's a basic framework for creating a new widget. You do not have to
       follow this framework. As long as your widget has the methods new(),
       layout(), draw() and focus(), it can be used in Curses::UI.

	   package Curses::UI::YourWidget

	   use Curses;
	   use Curses::UI::Widget;
	   use Curses::UI::Common; # some common widget routines

	   use vars qw($VERSION @ISA);
	   $VERSION = '0.01';
	   @ISA = qw(Curses::UI::Widget Curses::UI::Common);

	   # For a widget that can get focus, you should define
	   # the routines that are used to control the widget.
	   # Each routine has a name. This name is used in
	   # the definition of the bindings.
	   # The value can be a string or a subroutine reference.
	   # A string will make the widget return from focus.
	   #
	   my %routines = (
	       'return'	   => 'LOSE_FOCUS',
	       'key-a'	   => \&key_a,
	       'key-other' => \&other_key
	   );

	   # Using the bindings, the routines can be binded to key-
	   # presses. If the keypress is an empty string, this means
	   # that this is the default binding. If the key is not
	   # handled by any other binding, it's handled by this
	   # default binding.
	   #
	   my %bindings = (
	       KEY_DOWN()  => 'return',	  # down arrow will make the
					  # widget lose it's focus
	       'a'	   => 'key-a',	  # a-key will trigger key_a()
	       ''	   => 'key-other' # any other key will trigger other_key()
	   );

	   # The creation of the widget. When doing it this way,
	   # it's easy to make optional and forced arguments
	   # possible. A forced argument could for example be
	   # -border => 1, which would mean that the widget
	   # always has a border, which can't be disabled by the
	   # programmer. The arguments can of course be used
	   # for storing the current state of the widget.
	   #
	   sub new () {
	       my $class = shift;
	       my %args = (
		   -optional_argument_1 => "default value 1",
		   -optional_argument_2 => "default value 2",
		   ....etc....
		   @_,
		   -forced_argument_1	=> "forced value 1",
		   -forced_argument_2	=> "forced value 2",
		   ....etc....
		   -bindings		=> {%bindings},
		   -routines		=> {%routines},
	       );

	       # Create the widget and do the layout of it.
	       my $this = $class->SUPER::new( %args );
	   $this->layout;

	   return $this;
	   }

	   # Each widget should have a layout() routine. Here,
	   # the widget itself and it's contents can be layouted.
	   # In case of a very simple widget, this will only mean
	   # that the Widget has to be layouted (in which case the
	   # routine could be left out, since it's in the base
	   # class already). In other cases you will have to add
	   # your own layout code. This routine is very important,
	   # since it will enable the resizeability of the widget!
	   #
	   sub layout () {
	       my $this = shift;

	       $this->SUPER::layout;
	   return $this if $Curses::UI::screen_too_small;

	       ....your own layout stuff....

	       # If you decide that the widget does not fit on the
	       # screen, then set $Curses::UI::screen_too_small
	       # to a true value and return.
	       if ( ....the widget does not fit.... ) {
		   $Curses::UI::screen_too_small++;
		   return $this;
	       }

	       return $this;
	   }

	   # The widget is drawn by the draw() routine. The
	   # $no_update part is used to disable screen flickering
	   # if a lot of widgets have to be drawn at once (for
	   # example on resizing or redrawing). The curses window
	   # which you can use for drawing the widget's contents
	   # is $this->{-canvasscr}.
	   #
	   sub draw(;$) {
	       my $this = shift;
	       my $no_doupdate = shift || 0;
	       return $this if $this->hidden;
	       $this->SUPER::draw(1);

	       ....your own draw stuff....
	       $this->{-canvasscr}->addstr(0, 0, "Fixed string");
	       ....your own draw stuff....

	       $this->{-canvasscr}->noutrefresh;
	       doupdate() unless $no_doupdate;
	   return $this;
	   }

	   # Focus the widget. If you do not override this routine
	   # from Curses::UI::Widget, the widget will not be
	   # focusable. Mostly you will use the generic_focus() method.
	   #
	   sub focus()
	   {
	       my $this = shift;
	       $this->show; # makes the widget visible if it was invisible
	       return $this->generic_focus(
		   undef,	      # delaytime, default = 2 (1/10 second).
		   NO_CONTROLKEYS,    # disable controlkeys like CTRL+C. To enable
				      # them use CONTROLKEYS instead.
		   CURSOR_INVISIBLE,  # do not show the cursor (if supported). To
				      # show the cursor use CURSOR_VISIBLE.
		   \&pre_key_routine, # optional callback routine to execute
				      # before a key is read. Mostly unused.
	       );
	   }

	   ....your own widget handling routines....

SEE ALSO
       Curses::UI

AUTHOR
       Copyright (c) 2001-2002 Maurice Makaay. All rights reserved.

       Maintained by Marcus Thiesen (marcus@cpan.thiesenweb.de)

       This package is free software and is provided "as is" without express
       or implied warranty. It may be used, redistributed and/or modified
       under the same terms as perl itself.

perl v5.16.3			  2014-02-10		 Curses::UI::Widget(3)
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