Widget(3pm) User Contributed Perl Documentation Widget(3pm)
NAME
Tk::Widget - Base class of all widgets
SYNOPSIS
package Tk::Whatever;
require Tk::Widget;
@ISA = qw(Tk::Widget);
Construct Tk::Widget 'Whatever';
sub Tk_cmd { \&Tk::whatever }
$widget->method(?arg, arg, ...?)
DESCRIPTION
The Tk::Widget is an abstract base class for all Tk widgets.
Generic methods available to all widgets include the methods based on
core "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 method. The legal forms are:
$widget->appname?(newName)?
If newName isn't specified, this method returns the name of the
application (the name that may be used in send commands to
communicate with the application). If newName is specified, then
the name of the application is changed to newName. If the given
name is already in use, then a suffix of the form `` #2'' or `` #3''
is appended in order to make the name unique. The method's result
is the name actually chosen. newName should not start with a
capital letter. This will interfere with 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 send command, this
command will re-enable them and recreate the send command.
$widget->atom(name)
Returns a decimal string giving the integer identifier for the atom
whose name is name. If no atom exists with the name name then a new
one is created.
$widget->atomname(id)
Returns the textual name for the atom whose integer identifier is
id. This command is the inverse of the $widget->atom command. It
generates an error if no such atom exists.
$widget->bell( ?-nice? );
This command rings the bell on the display for $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 xset.
If -nice is not specified, 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.
$widget->bindDump
This command returns a list of strings suitable for printing
detailing binding information for a widget. It prints a widget's
bindtags. For each binding tag it prints all the bindings,
comprised of the event descriptor and the callback. Callback
arguments are printed, and Tk::Ev objects are expanded.
$widget->Busy?(?-recurse => 1?,-option => value?)?
This method configures a -cursor option for $widget and (if -recurse
= 1> is specified) all its descendants. The cursor to be set may be
passed as -cursor = cursor> or defaults to 'watch'. Additional
configure options are applied to $widget only. It also adds a
special tag 'Busy' to the bindtags of the widgets so configured so
that KeyPress, KeyRelease, ButtonPress and ButtonRelease events are
ignored (with press events generating a call to bell). It then
acquires a local grab for $widget. The state of the widgets and the
grab is restored by a call to $widget->Unbusy.
$widget->caret( ?-x => x?, ?-y => y?, ?-height => height? );
Sets and queries the caret location for the display of the specified
Tk window window. The caret is the per-display cursor location used
for indicating global focus (e.g. to comply with Microsoft
Accessibility guidelines), as well as for location of the over-the-
spot XIM (X Input Methods) or Windows IME windows. If no options are
specified, the last values used for setting the caret are return in
option-value pair format. -x and -y represent window-relative
coordinates, and -height is the height of the current cursor
location, or the height of the specified window if none is given.
$widget->cells
Returns a decimal string giving the number of cells in the color map
for $widget.
$widget->children
$widget->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.
$widget->class
Returns the class name for $widget.
$widget->colormapfull
Returns 1 if the colormap for $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.
$widget->ConfigSpecs
Used to perform delegated option configuration for a mega-widget.
Returns, in Tk::Derived::ConfigSpecs notation (see Tk::ConfigSpecs),
all possible options for a widget. For example,
$s = $self->Scale;
$self->ConfigSpecs(
$s->ConfigSpecs,
.... more ConfigSpecs specifications
);
returns a hash of all Tk::Scale options, delegated to $s - e.g. some
representative examples:
-bigincrement => [$s, bigIncrement, BigIncrement, 0, 0]
-digits => [$s, digits, Digits, 0, 0]
-sliderlength => [$s, sliderLength, SliderLength, 10m, 30]
-troughcolor => [$s, troughColor, Background, #c3c3c3, #c3c3c3]
This provides an easy means of populating a mega-widget's
ConfigSpecs with initializers.
$widget->containing(rootX,rootY)
Returns the window containing the point given by rootX and rootY.
RootX and rootY are specified in screen units (i.e. any form
acceptable to 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.
$widget->depth
Returns a decimal string giving the depth of $widget (number of bits
per pixel).
$widget->destroy
This command deletes the window related to $widget, plus all its
descendants. If all the MainWindows are deleted then the entire
application will be destroyed.
The perl object $widget continues to exist while references to it
still exist, e.g. until variable goes out of scope. However any
attempt to use Tk methods on the object will fail. Exists($widget)
will return false on such objects.
Note however that while a window exists for $widget the perl object
is maintained (due to "references" in perl/Tk internals) even though
original variables may have gone out of scope. (Normally this is
intuitive.)
Exists($widget)
Returns 1 if there exists a window for $widget, 0 if no such window
exists.
$widget->font(option?, arg, arg, ...?)
Create and inspect fonts. See Tk::Font for further details.
$widget->fpixels(number)
Returns a floating-point value giving the number of pixels in
$widget corresponding to the distance given by number. Number may
be specified in any of the forms acceptable to Tk_GetScreenMM, such
as ``2.0c'' or ``1i''. The return value may be fractional; for an
integer value, use $widget->pixels.
$widget->Getimage(name)
Given name, look for an image file with that base name and return a
Tk::Image. File extensions are tried in this order: xpm, gif, ppm,
xbm until a valid iamge is found. If no image is found, try a
builtin image with that name.
$widget->geometry
Returns the geometry for $widget, in the form widthxheight+x+y. All
dimensions are in pixels.
$widget->height
Returns a decimal string giving $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 update to force the geometry manager to arrange it,
or use $widget->reqheight to get the window's requested height
instead of its actual height.
$widget->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.
$widget->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 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 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
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
idletasks.
$widget->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
$widget.
$widget->ismapped
Returns 1 if $widget is currently mapped, 0 otherwise.
$widget->lower(?belowThis?)
If the 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 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 lower command
will insert $widget into the stacking order just below belowThis (or
the ancestor of belowThis that is a sibling of $widget); this could
end up either raising or lowering $widget.
$widget->MapWindow
Cause $widget to be "mapped" i.e. made visible on the display. May
confuse the geometry manager (pack, grid, place, ...) that thinks
it is managing the widget.
$widget->manager
Returns the name of the geometry manager currently responsible for
$widget, or an empty string if $widget isn't managed by any geometry
manager. The name is usually the name of the method for the
geometry manager, such as pack or place. If the geometry manager is
a widget, such as canvases or text, the name is the widget's class
command, such as canvas.
$widget->name
Returns $widget's name (i.e. its name within its parent, as opposed
to its full path name). The command $mainwin->name will return the
name of the application.
$widget->OnDestroy(callback);
OnDestroy accepts a standard perl/Tk callback. When the window
associated with $widget is destroyed then the callback is invoked.
Unlike $widget->bind('<Destroy>',...) the widgets methods are still
available when callback is executed, so (for example) a Text widget
can save its contents to a file.
OnDestroy was required for new after mechanism.
$widget->parent
Returns $widget's parent, or an empty string if $widget is the main
window of the application.
$widget->PathName
Returns the Tk path name of $widget. This is the inverse of the
"Widget" method. (This is an import from the C interface.)
$widget->pathname(id)
Returns an object whose X identifier is id. The identifier is
looked up on the display of $widget. 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
"eval { }" or "Tk::catch { }". If the window belongs to the
application, but is not an object (for example wrapper windows,
HList header, etc.) then "undef" is returned.
$widget->pixels(number)
Returns the number of pixels in $widget corresponding to the
distance given by number. Number may be specified in any of the
forms acceptable to Tk_GetPixels, such as ``2.0c'' or ``1i''. The
result is rounded to the nearest integer value; for a fractional
result, use $widget->fpixels.
$widget->pointerx
If the mouse pointer is on the same screen as $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 $widget then -1 is returned.
$widget->pointerxy
If the mouse pointer is on the same screen as $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
$widget then both of the returned coordinates are -1.
$widget->pointery
If the mouse pointer is on the same screen as $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 $widget then -1 is returned.
$widget->raise(?aboveThis?)
If the 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 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 raise command
will insert $widget into the stacking order just above aboveThis (or
the ancestor of aboveThis that is a sibling of $widget); this could
end up either raising or lowering $widget.
$widget->reqheight
Returns a decimal string giving $widget's requested height, in
pixels. This is the value used by $widget's geometry manager to
compute its geometry.
$widget->reqwidth
Returns a decimal string giving $widget's requested width, in
pixels. This is the value used by $widget's geometry manager to
compute its geometry.
$widget->rgb(color)
Returns a list containing three decimal values, which are the red,
green, and blue intensities that correspond to color in the window
given by $widget. Color may be specified in any of the forms
acceptable for a color option.
$widget->rootx
Returns a decimal string giving the x-coordinate, in the root window
of the screen, of the upper-left corner of $widget's border (or
$widget if it has no border).
$widget->rooty
Returns a decimal string giving the y-coordinate, in the root window
of the screen, of the upper-left corner of $widget's border (or
$widget if it has no border).
$widget->scaling?(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 number argument is a floating point number that
specifies the number of pixels per point on $widget's display. If
the 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 accommodate the new scaling
factor.
$widget->screen
Returns the name of the screen associated with $widget, in the form
displayName.screenIndex.
$widget->screencells
Returns a decimal string giving the number of cells in the default
color map for $widget's screen.
$widget->screendepth
Returns a decimal string giving the depth of the root window of
$widget's screen (number of bits per pixel).
$widget->screenheight
Returns a decimal string giving the height of $widget's screen, in
pixels.
$widget->screenmmheight
Returns a decimal string giving the height of $widget's screen, in
millimeters.
$widget->screenmmwidth
Returns a decimal string giving the width of $widget's screen, in
millimeters.
$widget->screenvisual
Returns one of the following strings to indicate the default visual
class for $widget's screen: directcolor, grayscale, pseudocolor,
staticcolor, staticgray, or truecolor.
$widget->screenwidth
Returns a decimal string giving the width of $widget's screen, in
pixels.
$widget->server
Returns a string containing information about the server for
$widget's display. The exact format of this string may vary from
platform to platform. For X servers the string has the form
``XmajorRminor vendor vendorVersion'' where major and minor are the
version and revision numbers provided by the server (e.g., X11R5),
vendor is the name of the vendor for the server, and vendorRelease
is an integer release number provided by the server.
$widget->toplevel
Returns the reference of the top-level window containing $widget.
$widget->Unbusy
Restores widget state after a call to $widget->Busy.
$widget->UnmapWindow
Cause $widget to be "unmapped" i.e. removed from the display. This
does for any widget what $widget->withdraw does for toplevel
widgets. May confuse the geometry manager (pack, grid, place, ...)
that thinks it is managing the widget.
$widget->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 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 update then user input will be processed during the next call
to update.
$widget->useinputmethods( ?boolean? )
Sets and queries the state of whether Tk should use XIM (X Input
Methods) for filtering events. The resulting state is returned.
XIM is used in some locales (ie: Japanese, Korean), to handle
special input devices. This feature is only significant on X. If
XIM support is not available, this will always return 0. If the
boolean argument is omitted, the current state is returned.
This is turned on by default for the main display.
$widget->viewable
Returns 1 if $widget and all of its ancestors up through the nearest
toplevel window are mapped. Returns 0 if any of these windows are
not mapped.
$widget->visual
Returns one of the following strings to indicate the visual class
for $widget: directcolor, grayscale, pseudocolor, staticcolor,
staticgray, or truecolor.
$widget->visualid
Returns the X identifier for the visual for $widget.
$widget->visualsavailable(?includeids?)
Returns a list whose elements describe the visuals available for
$widget's screen. Each element consists of a visual class followed
by an integer depth. The class has the same form as returned by
$widget->visual. The depth gives the number of bits per pixel in
the visual. In addition, if the includeids argument is provided,
then the depth is followed by the X identifier for the visual.
$widget->vrootheight
Returns the height of the virtual root window associated with
$widget if there is one; otherwise returns the height of $widget's
screen.
$widget->vrootwidth
Returns the width of the virtual root window associated with $widget
if there is one; otherwise returns the width of $widget's screen.
$widget->vrootx
Returns the x-offset of the virtual root window associated with
$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 $widget.
$widget->vrooty
Returns the y-offset of the virtual root window associated with
$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 $widget.
$widget->waitVariable(\$name)
$widget->waitVisibility
$widget->waitWindow
The 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. 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. waitVisibility waits for a change in $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.
waitWindow waits for $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
withdrawing the window instead and using waitVisibility.
While the 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 tkwait again, the nested
call to tkwait must complete before the outer call can complete.
$widget->Walk(proc?, arg, ...?)
Traverse a widget hierarchy starting at $widget while executing the
subroutine proc to every visited widget. The arguments arg, ... are
supplied to the subroutine.
$widget->Widget(pathname)
Returns the widget reference for the given Tk path name, or "undef"
if the path name does not match a Tk widget. This is the inverse of
the "PathName" method. (This is an import from the C interface.)
$widget->width
Returns a decimal string giving $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 update to force the geometry manager to arrange it,
or use $widget->reqwidth to get the window's requested width instead
of its actual width.
$widget->windowingsystem
Returns the current Tk windowing system, one of x11 (X11-based),
win32 (MS Windows), classic (Mac OS Classic), or aqua (Mac OS X
Aqua).
$widget->x
Returns a decimal string giving the x-coordinate, in $widget's
parent, of the upper-left corner of $widget's border (or $widget if
it has no border).
$widget->y
Returns a decimal string giving the y-coordinate, in $widget's
parent, of the upper-left corner of $widget's border (or $widget if
it has no border).
CAVEATS
The above documentation on generic methods is incomplete.
KEYWORDS
atom, children, class, geometry, height, identifier, information,
interpreters, mapped, parent, path name, screen, virtual root, width,
window
perl v5.40.1 2025-04-13 Widget(3pm)
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