Provided by: libcurses-ui-perl_0.9609-1_all 
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 useful 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.