widget(3)

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 wid gets.

Generic methods available to all widgets include the meth
ods 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 applica tion 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. new_
Name 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: 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.; This command also resets the screen saver for the
screen. Some screen savers will ignore this, but oth
ers will reset so that the screen becomes visible
again.
$widget->Busy?(?-recurse => 1?-option = value>?)?: This method configures a -cursor option for $widget and (if -recurse = 1> is specified) all its descen dants. 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->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->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 vir
tual-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 par
ents and among siblings the highest one in the stack
ing 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 $widget continues to exist while ref erences to it still exist, e.g. until variable goes
out of scope. However any attempt to use Tk methods
on the object will fail. Exists($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 widthx height+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 plat
form-specific identifier for $widget. On Unix plat
forms, this is the X window identifier. Under Win
dows, 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 appli
cation ``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 imme
diately, rather than waiting for the script to com
plete. Most display updates are performed as idle
callbacks, so idletasks will cause them to run. How ever, 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) cur
rently 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 sib
lings that overlap it and will not obscure any sib
lings). 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 ances tor 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 wid
get.
$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 man
ager, 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 par ent, as opposed to its full path name). The command
$mainwin->name will return the name of the applica tion.
$widget->OnDestroy(callback);: OnDestroy accepts a standard perl/Tk callback. When the window associated with $widget is destroyed then the callback is invoked. Unlike $wid_
get->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 $wid_ get is the main window of the application.
$widget->PathName: Returns the tk path name of $widget. (This is an
import from the C interface.)
$widget->pathname(id): Returns an object whose X identifier is id. The iden
tifier 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 applica
tion, 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 speci fied 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 coordi
nates 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 ances tor 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 $wid_
get'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 corre
spond 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 cor
ner of $widget's border (or $widget if it has no bor der).
$widget->rooty: Returns a decimal string giving the y-coordinate, in
the root window of the screen, of the upper-left cor
ner of $widget's border (or $widget if it has no bor der).
scaling
$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 num_
ber 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 accomo
date the new scaling factor.
$widget->screen: Returns the name of the screen associated with $wid_
get, 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 $wid_
get's screen, in pixels.
$widget->screenmmheight: Returns a decimal string giving the height of $wid_
get'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: direct color, grayscale, pseudocolor, staticcolor, stat icgray, 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 contain
ing $widget.
$widget->UnmapWindow: Cause $widget to be "unmapped" i.e. removed from the display. This does for any widget what $widget->with draw does for toplevel widgets. May confuse the geome
try manager (pack, grid, place, ...) that thinks it
is managing the widget.
$widget->update: One of two methods which are used to bring the appli
cation ``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->Unbusy: Restores widget state after a call to $widget->Busy.
$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 $wid_
get->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 associ
ated with $widget if there is one; otherwise returns the height of $widget's screen.
$widget->vrootwidth: Returns the width of the virtual root window associ
ated 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 asso
ciated 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 $wid_
get.
$widget->vrooty: Returns the y-offset of the virtual root window asso
ciated 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 $wid_
get.
$widget->waitVariablename) $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 modi
fied. 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 interac
tion. 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 interac
tion. 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 com
plete.
$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 win dow's requested width instead of its actual width.
$widget->x: Returns a decimal string giving the x-coordinate, in
$widget's parent, of the upper-left corner of $wid_ get'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 $wid_ get'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

docs.sk