#  Copyright (c) 1990-1994 The Regents of the University of California.
#  Copyright (c) 1994-1997 Sun Microsystems, Inc.
#  See the file "license.terms" for information on usage and redistribution
#  of this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
#

=head1 NAME

Tk::Widget - Base class of all widgets

=for pm Tk/Widget.pm

=for category Tk Generic Methods

=head1 SYNOPSIS

   package Tk::Whatever;
   require Tk::Widget;
   @ISA = qw(Tk::Widget);
   Construct Tk::Widget 'Whatever';

   sub Tk_cmd { \&Tk::whatever }

S<   >I<$widget>-E<gt>I<method>(?I<arg, arg, ...>?)

=head1 DESCRIPTION

The B<Tk::Widget> is an abstract base class for all Tk widgets.

Generic methods available to all widgets include the methods based on core
C<winfo> mechanism and are used to retrieve information about windows managed by
Tk. They can take any of a number of different forms, depending on the I<method>.
The legal forms are:

=over 4

=item I<$widget>-E<gt>B<appname>?(I<newName>)?

If I<newName> isn't specified, this method returns the name
of the application (the name that may be used in B<send>
commands to communicate with the application).
If I<newName> is specified, then the name of the application
is changed to I<newName>.
If the given name is already in use, then a suffix of the form
``B< #2>'' or ``B< #3>'' is appended in order to make the name unique.
The method's result is the name actually chosen.
I<newName> should not start with a capital letter.
This will interfere with L<option|Tk::option> processing, since names starting with
capitals are assumed to be classes;  as a result, Tk may not
be able to find some options for the application.
If sends have been disabled by deleting the B<send> command,
this command will reenable them and recreate the B<send>
command.

=item I<$widget>-E<gt>B<atom>(I<name>)

Returns a decimal string giving the integer identifier for the
atom whose name is I<name>.  If no atom exists with the name
I<name> then a new one is created.

=item I<$widget>-E<gt>B<atomname>(I<id>)

Returns the textual name for the atom whose integer identifier is
I<id>.
This command is the inverse of the I<$widget>-E<gt>B<atom> command.
It generates an error if no such atom exists.

=item I<$widget>-E<gt>B<bell>

This command rings the bell on the display for I<$widget> and
returns an empty string.
The command uses the current bell-related settings for the display, which
may be modified with programs such as B<xset>.

This command also resets the screen saver for the screen.  Some
screen savers will ignore this, but others will reset so that the
screen becomes visible again.

=item I<$widget>-E<gt>B<Busy>?(?-recurse => 1?I<-option => value>?)?

This method B<configure>s a B<-cursor> option for I<$widget> and 
(if B<-recurse => 1> is specified) all its descendants. The cursor to 
be set may be passed as S<B<-cursor> => I<cursor>> or defaults to 'watch'.
Additional B<configure> options are applied to I<$widget> only.
It also adds a special tag B<'Busy'> to the B<bindtags> of the widgets so
configured so that  B<KeyPress>, B<KeyRelease>, B<ButtonPress> and
B<ButtonRelease> events are ignored (with press events generating a call to
B<bell>). It then acquires a local B<grab> for I<$widget>.
The state of the widgets and the grab is restored by a call to 
I<$widget>-E<gt>B<Unbusy>.


=item I<$widget>-E<gt>B<cells>

Returns a decimal string giving the number of cells in the
color map for I<$widget>.

=item I<$widget>-E<gt>B<children>

I<$widget->>B<children>
Returns a list containing all the children
of $widget.  The list is in stacking order, with the lowest
window first.  Top-level windows are returned as children
of their logical parents.

=item I<$widget>-E<gt>B<class>

Returns the class name for I<$widget>.

=item I<$widget>-E<gt>B<colormapfull>

Returns 1 if the colormap for I<$widget> is known to be full, 0
otherwise.  The colormap for a window is ``known'' to be full if the last
attempt to allocate a new color on that window failed and this
application hasn't freed any colors in the colormap since the
failed allocation.

=item I<$widget>-E<gt>B<containing>(I<rootX,rootY>)

Returns the window containing the point given
by I<rootX> and I<rootY>.
I<RootX> and I<rootY> are specified in screen units (i.e.
any form acceptable to B<Tk_GetPixels>) in the coordinate
system of the root window (if a virtual-root window manager is in
use then the coordinate system of the virtual root window is used).
If no window in this application contains the point then an empty
string is returned.
In selecting the containing window, children are given higher priority
than parents and among siblings the highest one in the stacking order is
chosen.

=item I<$widget>-E<gt>B<depth>

Returns a decimal string giving the depth of I<$widget> (number
of bits per pixel).

=item I<$widget>-E<gt>B<destroy>

This command deletes the window related to
I<$widget>, plus all its descendants.
If all the B<MainWindows> are deleted then the entire application
will be destroyed.

The perl object I<$widget> continues to exist while references
to it still exist, e.g. until variable goes out of scope.
However any attempt to use Tk methods on the object will fail.
B<Exists>(I<$widget>) will return false on such objects.

Note however that while a window exists for I<$widget> the
perl object is maintained (due to "references" in perl/Tk internals)
even though original variables may have gone out of scope.
(Normally this is intuitive.)

=item B<Exists>(I<$widget>)

Returns 1 if there exists a window for I<$widget>, 0 if no such
window exists.

=item I<$widget>-E<gt>B<font>(I<option>?, I<arg, arg, ...>?)

Create and inspect fonts. See L<Tk::Font> for further details.

=item I<$widget>-E<gt>B<fpixels>(I<number>)

Returns a floating-point value giving the number of pixels
in I<$widget> corresponding to the distance given by I<number>.
I<Number> may be specified in any of the forms acceptable
to B<Tk_GetScreenMM>, such as ``2.0c'' or ``1i''.
The return value may be fractional;  for an integer value, use
I<$widget>-E<gt>B<pixels>.

=item I<$widget>-E<gt>B<Getimage>(I<name>)

Given I<name>, look for an image file with that base name and return
a L<Tk::Image>.  File extensions are tried in this order: F<xpm>,
F<gif>, F<ppm>, F<xbm> until a valid iamge is found.  If no image is
found, try a builtin image with that name.

=item I<$widget>-E<gt>B<geometry>

Returns the geometry for I<$widget>, in the form
I<width>B<x>I<height>B<+>I<x>B<+>I<y>.  All dimensions are
in pixels.

=item I<$widget>-E<gt>B<height>

Returns a decimal string giving I<$widget>'s height in pixels.
When a window is first created its height will be 1 pixel;  the
height will eventually be changed by a geometry manager to fulfill
the window's needs.
If you need the true height immediately after creating a widget,
invoke B<update> to force the geometry manager to arrange it,
or use I<$widget>-E<gt>B<reqheight> to get the window's requested height
instead of its actual height.

=item I<$widget>-E<gt>B<id>

Returns a hexadecimal string giving a low-level platform-specific
identifier for $widget.  On Unix platforms, this is the X
window identifier.  Under Windows, this is the Windows
HWND.  On the Macintosh the value has no meaning outside Tk. 

=item I<$widget>-E<gt>B<idletasks>        

One of two methods which are used to bring the application ``up to date''
by entering the event loop repeated until all pending events
(including idle callbacks) have been processed.

If the B<idletasks> method is specified, then no new events or errors
are processed; only idle callbacks are invoked. This causes operations
that are normally deferred, such as display updates and window layout
calculations, to be performed immediately.

The B<idletasks> command is useful in scripts where changes have been
made to the application's state and you want those changes to appear
on the display immediately, rather than waiting for the script to
complete. Most display updates are performed as idle callbacks, so
B<idletasks> will cause them to run. However, there are some kinds of
updates that only happen in response to events, such as those
triggered by window size changes; these updates will not occur in
B<idletasks>.

=item I<$widget>-E<gt>B<interps>

Returns a list whose members are the names of all Tcl interpreters
(e.g. all Tk-based applications) currently registered for
a particular display.
The return value refers
to the display of I<$widget>.

=item I<$widget>-E<gt>B<ismapped>

Returns B<1> if I<$widget> is currently mapped, B<0> otherwise.

=item I<$widget->>B<lower>(?I<belowThis>?)

If the I<belowThis> argument is omitted then the command lowers
$widget so that it is below all of its siblings in the stacking
order (it will be obscured by any siblings that overlap it and
will not obscure any siblings).
If I<belowThis> is specified then it must be the path name of
a window that is either a sibling of $widget or the descendant
of a sibling of $widget.
In this case the B<lower> command will insert
$widget into the stacking order just below I<belowThis>
(or the ancestor of I<belowThis> that is a sibling of $widget);
this could end up either raising or lowering $widget.

=item I<$widget>-E<gt>B<manager>

Returns the name of the geometry manager currently
responsible for I<$widget>, or an empty string if I<$widget>
isn't managed by any geometry manager.
The name is usually the name of the method for the geometry
manager, such as B<pack> or B<place>.
If the geometry manager is a widget, such as canvases or text, the
name is the widget's class command, such as B<canvas>.

=item I<$widget>-E<gt>B<name>

Returns I<$widget>'s name (i.e. its name within its parent, as opposed
to its full path name).
The command I<$mainwin>-E<gt>B<name> will return the name of the application.

=item I<$widget>-E<gt>B<OnDestroy>(I<callback>);

OnDestroy accepts a standard perl/Tk I<callback>.
When the window associated with I<$widget> is destroyed then
the callback is invoked. Unlike I<$widget->>bind('E<lt>DestroyE<gt>',...)
the widgets methods are still available when I<callback> is executed,
so (for example) a B<Text> widget can save its contents to a file.

OnDestroy was required for new B<after> mechanism.

=item I<$widget>-E<gt>B<parent>

Returns I<$widget>'s parent, or an empty string
if I<$widget> is the main window of the application.

=item I<$widget>-E<gt>B<PathName>

Returns the tk path name of I<$widget>. (This is an import from the
C interface.)

=item I<$widget>-E<gt>B<pathname>(I<id>)

Returns an object whose X identifier is I<id>.
The identifier is looked up on the display of I<$widget>.
I<Id> must be a decimal, hexadecimal, or octal integer and must
correspond to a window in the invoking application, or an error
occurs which can be trapped with C<eval { }> or C<Tk::catch { }>.
If the window belongs to the application, but is not an object
(for example wrapper windows, HList header, etc.) then C<undef>
is returned.

=item I<$widget>-E<gt>B<pixels>(I<number>)

Returns the number of pixels in I<$widget> corresponding
to the distance given by I<number>.
I<Number> may be specified in any of the forms acceptable
to B<Tk_GetPixels>, such as ``2.0c'' or ``1i''.
The result is rounded to the nearest integer value;  for a
fractional result, use I<$widget>-E<gt>B<fpixels>.

=item I<$widget>-E<gt>B<pointerx>

If the mouse pointer is on the same screen as I<$widget>, returns the
pointer's x coordinate, measured in pixels in the screen's root window.
If a virtual root window is in use on the screen, the position is
measured in the virtual root.
If the mouse pointer isn't on the same screen as I<$widget> then
-1 is returned.

=item I<$widget>-E<gt>B<pointerxy>

If the mouse pointer is on the same screen as I<$widget>, returns a list
with two elements, which are the pointer's x and y coordinates measured
in pixels in the screen's root window.
If a virtual root window is in use on the screen, the position
is computed in the virtual root.
If the mouse pointer isn't on the same screen as I<$widget> then
both of the returned coordinates are -1.

=item I<$widget>-E<gt>B<pointery>

If the mouse pointer is on the same screen as I<$widget>, returns the
pointer's y coordinate, measured in pixels in the screen's root window.
If a virtual root window is in use on the screen, the position
is computed in the virtual root.
If the mouse pointer isn't on the same screen as I<$widget> then
-1 is returned.

=item I<$widget>-E<gt>B<raise>(?I<aboveThis>?)

If the I<aboveThis> argument is omitted then the command raises
$widget so that it is above all of its siblings in the stacking
order (it will not be obscured by any siblings and will obscure
any siblings that overlap it).
If I<aboveThis> is specified then it must be the path name of
a window that is either a sibling of $widget or the descendant
of a sibling of $widget.
In this case the B<raise> command will insert
$widget into the stacking order just above I<aboveThis>
(or the ancestor of I<aboveThis> that is a sibling of $widget);
this could end up either raising or lowering $widget.

=item I<$widget>-E<gt>B<reqheight>

Returns a decimal string giving I<$widget>'s requested height,
in pixels.  This is the value used by I<$widget>'s geometry
manager to compute its geometry.

=item I<$widget>-E<gt>B<reqwidth>

Returns a decimal string giving I<$widget>'s requested width,
in pixels.  This is the value used by I<$widget>'s geometry
manager to compute its geometry.

=item I<$widget>-E<gt>B<rgb>(I<color>)

Returns a list containing three decimal values, which are the
red, green, and blue intensities that correspond to I<color> in
the window given by I<$widget>.  I<Color>
may be specified in any of the forms acceptable for a color
option.

=item I<$widget>-E<gt>B<rootx>

Returns a decimal string giving the x-coordinate, in the root
window of the screen, of the
upper-left corner of I<$widget>'s border (or I<$widget> if it
has no border).

=item I<$widget>-E<gt>B<rooty>

Returns a decimal string giving the y-coordinate, in the root
window of the screen, of the
upper-left corner of I<$widget>'s border (or I<$widget> if it
has no border).

=item B<scaling>

=item I<$widget>-E<gt>B<scaling>?(I<number>)?

Sets and queries the current scaling factor used by Tk to convert between
physical units (for example, points, inches, or millimeters) and pixels.  The
I<number> argument is a floating point number that specifies the number of
pixels per point on $widget's display. If the I<number> argument is
omitted, the current value of the scaling factor is returned.

A ``point'' is a unit of measurement equal to 1/72 inch.  A scaling factor
of 1.0 corresponds to 1 pixel per point, which is equivalent to a standard
72 dpi monitor.  A scaling factor of 1.25 would mean 1.25 pixels per point,
which is the setting for a 90 dpi monitor; setting the scaling factor to
1.25 on a 72 dpi monitor would cause everything in the application to be
displayed 1.25 times as large as normal.  The initial value for the scaling
factor is set when the application starts, based on properties of the
installed monitor (as reported via the window system),
but it can be changed at any time.  Measurements made
after the scaling factor is changed will use the new scaling factor, but it
is undefined whether existing widgets will resize themselves dynamically to
accomodate the new scaling factor.

=item I<$widget>-E<gt>B<screen>

Returns the name of the screen associated with I<$widget>, in
the form I<displayName>.I<screenIndex>.

=item I<$widget>-E<gt>B<screencells>

Returns a decimal string giving the number of cells in the default
color map for I<$widget>'s screen.

=item I<$widget>-E<gt>B<screendepth>

Returns a decimal string giving the depth of the root window
of I<$widget>'s screen (number of bits per pixel).

=item I<$widget>-E<gt>B<screenheight>

Returns a decimal string giving the height of I<$widget>'s screen,
in pixels.

=item I<$widget>-E<gt>B<screenmmheight>

Returns a decimal string giving the height of I<$widget>'s screen,
in millimeters.

=item I<$widget>-E<gt>B<screenmmwidth>

Returns a decimal string giving the width of I<$widget>'s screen,
in millimeters.

=item I<$widget>-E<gt>B<screenvisual>

Returns one of the following strings to indicate the default visual
class for I<$widget>'s screen: B<directcolor>, B<grayscale>,
B<pseudocolor>, B<staticcolor>, B<staticgray>, or
B<truecolor>.

=item I<$widget>-E<gt>B<screenwidth>

Returns a decimal string giving the width of I<$widget>'s screen,
in pixels.

=item I<$widget>-E<gt>B<server>

Returns a string containing information about the server for
I<$widget>'s display.  The exact format of this string may vary
from platform to platform.  For X servers the string
has the form ``B<X>I<major>B<R>I<minor vendor vendorVersion>''
where I<major> and I<minor> are the version and revision
numbers provided by the server (e.g., B<X11R5>), I<vendor>
is the name of the vendor for the server, and I<vendorRelease>
is an integer release number provided by the server.

=item I<$widget>-E<gt>B<toplevel>

Returns the reference of the top-level window containing I<$widget>.

=item I<$widget>-E<gt>B<update> 

One of two methods which are used to bring the application ``up to date''
by entering the event loop repeated until all pending events
(including idle callbacks) have been processed.

The B<update> method is useful in scripts where you are performing a
long-running computation but you still want the application to respond
to events such as user interactions; if you occasionally call
B<update> then user input will be processed during the next call to
B<update>.

=item I<$widget>-E<gt>B<Unbusy>

Restores widget state after a call to  I<$widget>-E<gt>B<Busy>.

=item I<$widget>-E<gt>B<viewable>

Returns 1 if I<$widget> and all of its ancestors up through the
nearest toplevel window are mapped.  Returns 0 if any of these
windows are not mapped.

=item I<$widget>-E<gt>B<visual>

Returns one of the following strings to indicate the visual
class for I<$widget>: B<directcolor>, B<grayscale>,
B<pseudocolor>, B<staticcolor>, B<staticgray>, or
B<truecolor>.

=item I<$widget>-E<gt>B<visualid>

Returns the X identifier for the visual for $widget.

=item I<$widget>-E<gt>B<visualsavailable>(?B<includeids>?)

Returns a list whose elements describe the visuals available for
I<$widget>'s screen.
Each element consists of a visual class followed by an integer depth.
The class has the same form as returned by I<$widget>-E<gt>B<visual>.
The depth gives the number of bits per pixel in the visual.
In addition, if the B<includeids> argument is provided, then the
depth is followed by the X identifier for the visual.

=item I<$widget>-E<gt>B<vrootheight>

Returns the height of the virtual root window associated with I<$widget>
if there is one;  otherwise returns the height of I<$widget>'s screen.

=item I<$widget>-E<gt>B<vrootwidth>

Returns the width of the virtual root window associated with I<$widget>
if there is one;  otherwise returns the width of I<$widget>'s screen.

=item I<$widget>-E<gt>B<vrootx>

Returns the x-offset of the virtual root window associated with I<$widget>,
relative to the root window of its screen.
This is normally either zero or negative.
Returns 0 if there is no virtual root window for I<$widget>.

=item I<$widget>-E<gt>B<vrooty>

Returns the y-offset of the virtual root window associated with I<$widget>,
relative to the root window of its screen.
This is normally either zero or negative.
Returns 0 if there is no virtual root window for I<$widget>.

=item I<$widget->>B<waitVariable>(\$I<name>)

=item I<$widget->>B<waitVisibility>

=item I<$widget->>B<waitWindow>

The B<tk wait> methods wait for one of several things to happen,
then it returns without taking any other actions.
The return value is always an empty string.
B<waitVariable> expects a reference to a perl
variable and the command waits for that variable to be modified.
This form is typically used to wait for a user to finish interacting
with a dialog which sets the variable as part (possibly final)
part of the interaction.
B<waitVisibility> waits for a change in I<$widget>'s
visibility state (as indicated by the arrival of a VisibilityNotify
event).  This form is typically used to wait for a newly-created
window to appear on the screen before taking some action.
B<waitWindow> waits for I<$widget> to be destroyed.
This form is typically used to wait for a user to finish interacting
with a dialog box before using the result of that interaction.
Note that creating and destroying the window each time a dialog is required
makes code modular but imposes overhead which can be avoided by B<withdrawing>
the window instead and using B<waitVisibility>.

While the B<tk wait> methods are waiting they processes events in
the normal fashion, so the application will continue to respond
to user interactions.
If an event handler invokes B<tkwait> again, the nested call
to B<tkwait> must complete before the outer call can complete.

=item I<$widget>-E<gt>B<width>

Returns a decimal string giving I<$widget>'s width in pixels.
When a window is first created its width will be 1 pixel;  the
width will eventually be changed by a geometry manager to fulfill
the window's needs.
If you need the true width immediately after creating a widget,
invoke B<update> to force the geometry manager to arrange it,
or use I<$widget>-E<gt>B<reqwidth> to get the window's requested width
instead of its actual width.

=item I<$widget>-E<gt>B<x>

Returns a decimal string giving the x-coordinate, in I<$widget>'s
parent, of the upper-left corner of I<$widget>'s border (or I<$widget>
if it has no border).

=item I<$widget>-E<gt>B<y>

Returns a decimal string giving the y-coordinate, in I<$widget>'s
parent, of the
upper-left corner of I<$widget>'s border (or I<$widget> if it
has no border).

=back

=head1 CAVEATS

The above documentaion on generic methods is incomplete.

=head1 KEYWORDS

atom, children, class, geometry, height, identifier, information, interpreters,
mapped, parent, path name, screen, virtual root, width, window

=cut

