Provided by: perl-tk_804.033-2build1_amd64 
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