Scale(3pm) User Contributed Perl Documentation Scale(3pm)
NAME
Tk::Scale - Create and manipulate Scale widgets
SYNOPSIS
$scale = $parent->Scale(?options?);
STANDARD OPTIONS
-activebackground -font -highlightthickness -repeatinterval
-background -foreground -orient -takefocus
-borderwidth -highlightbackground -relief -troughcolor
-cursor -highlightcolor -repeatdelay
See Tk::options for details of the standard options.
WIDGET-SPECIFIC OPTIONS
Name: bigIncrement
Class: BigIncrement
Switch: -bigincrement
Some interactions with the scale cause its value to change by
``large'' increments; this option specifies the size of the large
increments. If specified as 0, the large increments default to 1/10
the range of the scale.
Name: command
Class: Command
Switch: -command
Specifies the prefix of a perl/Tk callback to invoke whenever the
scale's value is changed via a method. The actual command consists
of this option followed by a space and a real number indicating the
new value of the scale.
Name: digits
Class: Digits
Switch: -digits
An integer specifying how many significant digits should be retained
when converting the value of the scale to a string. If the number
is less than or equal to zero, then the scale picks the smallest
value that guarantees that every possible slider position prints as
a different string.
Name: from
Class: From
Switch: -from
A real value corresponding to the left or top end of the scale.
Name: label
Class: Label
Switch: -label
A string to display as a label for the scale. For vertical scales
the label is displayed just to the right of the top end of the
scale. For horizontal scales the label is displayed just above the
left end of the scale. If the option is specified as an empty
string, no label is displayed.
Name: length
Class: Length
Switch: -length
Specifies the desired long dimension of the scale in screen units
(i.e. any of the forms acceptable to Tk_GetPixels). For vertical
scales this is the scale's height; for horizontal scales it is the
scale's width.
Name: resolution
Class: Resolution
Switch: -resolution
A real value specifying the resolution for the scale. If this value
is greater than zero then the scale's value will always be rounded
to an even multiple of this value, as will tick marks and the
endpoints of the scale. If the value is less than zero then no
rounding occurs. Defaults to 1 (i.e., the value will be integral).
Name: showValue
Class: ShowValue
Switch: -showvalue
Specifies a boolean value indicating whether or not the current
value of the scale is to be displayed.
Name: sliderLength
Class: SliderLength
Switch: -sliderlength
Specfies the size of the slider, measured in screen units along the
slider's long dimension. The value may be specified in any of the
forms acceptable to Tk_GetPixels.
Name: sliderRelief
Class: SliderRelief
Switch: -sliderrelief
Specifies the relief to use when drawing the slider, such as raised
or sunken.
Name: state
Class: State
Switch: -state
Specifies one of three states for the scale: normal, active, or
disabled. If the scale is disabled then the value may not be
changed and the scale won't activate. If the scale is active, the
slider is displayed using the color specified by the
activeBackground option.
Name: tickInterval
Class: TickInterval
Switch: -tickinterval
Must be a real value. Determines the spacing between numerical tick
marks displayed below or to the left of the slider. If 0, no tick
marks will be displayed.
Name: to
Class: To
Switch: -to
Specifies a real value corresponding to the right or bottom end of
the scale. This value may be either less than or greater than the
from option.
Name: variable
Class: Variable
Switch: -variable
Specifies the name of a global variable to link to the scale.
Whenever the value of the variable changes, the scale will update to
reflect this value. Whenever the scale is manipulated
interactively, the variable will be modified to reflect the scale's
new value.
Name: width
Class: Width
Switch: -width
Specifies the desired narrow dimension of the trough in screen units
(i.e. any of the forms acceptable to Tk_GetPixels). For vertical
scales this is the trough's width; for horizontal scales this is
the trough's height.
DESCRIPTION
The Scale method creates a new window (given by the $widget argument)
and makes it into a scale widget. Additional options, described above,
may be specified on the command line or in the option database to
configure aspects of the scale such as its colors, orientation, and
relief. The scale command returns its $widget argument. At the time
this command is invoked, there must not exist a window named $widget,
but $widget's parent must exist.
A scale is a widget that displays a rectangular trough and a small
slider. The trough corresponds to a range of real values (determined by
the from, to, and resolution options), and the position of the slider
selects a particular real value. The slider's position (and hence the
scale's value) may be adjusted with the mouse or keyboard as described
in the "BINDINGS" section below. Whenever the scale's value is changed,
a Tcl command is invoked (using the command option) to notify other
interested widgets of the change. In addition, the value of the scale
can be linked to a Tcl variable (using the variable option), so that
changes in either are reflected in the other.
Three annotations may be displayed in a scale widget: a label appearing
at the top right of the widget (top left for horizontal scales), a
number displayed just to the left of the slider (just above the slider
for horizontal scales), and a collection of numerical tick marks just to
the left of the current value (just below the trough for horizontal
scales). Each of these three annotations may be enabled or disabled
using the configuration options.
WIDGET METHODS
The Scale method creates a widget object. This object supports the
configure and cget methods described in Tk::options which can be used to
enquire and modify the options described above. The widget also
inherits all the methods provided by the generic Tk::Widget class.
The following additional methods are available for scale widgets:
$scale->coords(?value?)
Returns a list whose elements are the x and y coordinates of the
point along the centerline of the trough that corresponds to value.
If value is omitted then the scale's current value is used.
$scale->get(?x, y?)
If x and y are omitted, returns the current value of the scale. If
x and y are specified, they give pixel coordinates within the
widget; the command returns the scale value corresponding to the
given pixel. Only one of x or y is used: for horizontal scales y
is ignored, and for vertical scales x is ignored.
$scale->identify(x, y)
Returns a string indicating what part of the scale lies under the
coordinates given by x and y. A return value of slider means that
the point is over the slider; trough1 means that the point is over
the portion of the slider above or to the left of the slider; and
trough2 means that the point is over the portion of the slider below
or to the right of the slider. If the point isn't over one of these
elements, an empty string is returned.
$scale->set(value)
This command is invoked to change the current value of the scale,
and hence the position at which the slider is displayed. Value
gives the new value for the scale. The command has no effect if the
scale is disabled.
BINDINGS
Tk automatically creates class bindings for scales that give them the
following default behavior. Where the behavior is different for
vertical and horizontal scales, the horizontal behavior is described in
parentheses.
[1] If button 1 is pressed in the trough, the scale's value will be
incremented or decremented by the value of the resolution option so
that the slider moves in the direction of the cursor. If the button
is held down, the action auto-repeats.
[2] If button 1 is pressed over the slider, the slider can be dragged
with the mouse.
[3] If button 1 is pressed in the trough with the Control key down, the
slider moves all the way to the end of its range, in the direction
towards the mouse cursor.
[4] If button 2 is pressed, the scale's value is set to the mouse
position. If the mouse is dragged with button 2 down, the scale's
value changes with the drag.
[5] The Up and Left keys move the slider up (left) by the value of the
resolution option.
[6] The Down and Right keys move the slider down (right) by the value of
the resolution option.
[7] Control-Up and Control-Left move the slider up (left) by the value
of the bigIncrement option.
[8] Control-Down and Control-Right move the slider down (right) by the
value of the bigIncrement option.
[9] Home moves the slider to the top (left) end of its range.
[10]
End moves the slider to the bottom (right) end of its range.
If the scale is disabled using the state option then none of the
above bindings have any effect.
The behavior of scales can be changed by defining new bindings for
individual widgets or by redefining the class bindings.
KEYWORDS
scale, slider, trough, widget
perl v5.40.1 2025-04-13 Scale(3pm)
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