Widget
Section: User Contributed Perl Documentation (3)
Updated: 2021-01-27
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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 reenable 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
accomodate 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 documentaion on generic methods is incomplete.
KEYWORDS
atom, children, class, geometry, height, identifier, information, interpreters,
mapped, parent, path name, screen, virtual root, width, window