scale(n) Tk Built-In Commands scale(n)______________________________________________________________________________NAME
scale - Create and manipulate scale widgets
scale pathName ?options?
See the options manual entry for details on the standard options.
[-bigincrement 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. [-command command] Specifies
the prefix of a Tcl command to invoke whenever the scale's value is
changed via a widget command. The actual command consists of this
option followed by a space and a real number indicating the new value
of the scale. [-digits digits] An integer specifying how many signifi‐
cant 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. [-from from] A real
value corresponding to the left or top end of the scale.
[-label label] A string to display as a label for the scale. For ver‐
tical 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. [-length length] Specifies the desired long
dimension of the scale in screen units (i.e. any of the forms accept‐
able to Tk_GetPixels). For vertical scales this is the scale's height;
for horizontal scales it is the scale's width. [-resolution resolu‐
tion] 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 round‐
ing occurs. Defaults to 1 (i.e., the value will be integral). [-show‐
value showValue] Specifies a boolean value indicating whether or not
the current value of the scale is to be displayed. [-slider‐
length sliderLength] Specifies the size of the slider, measured in
screen units along the slider's long dimension. The value may be spec‐
ified in any of the forms acceptable to Tk_GetPixels. [-sliderre‐
lief sliderRelief] Specifies the relief to use when drawing the slider,
such as raised or sunken. [-state 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 will not activate. If
the scale is active, the slider is displayed using the color specified
by the activeBackground option. [-tickinterval tickInterval] Must be a
real value. Determines the spacing between numerical tick marks dis‐
played below or to the left of the slider. If 0, no tick marks will be
displayed. [-to 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. [-variable 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. When‐
ever the scale is manipulated interactively, the variable will be modi‐
fied to reflect the scale's new value. [-width 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.
The scale command creates a new window (given by the pathName 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 con‐
figure aspects of the scale such as its colors, orientation, and
relief. The scale command returns its pathName argument. At the time
this command is invoked, there must not exist a window named pathName,
but pathName'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 appear‐
ing 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.
The scale command creates a new Tcl command whose name is pathName.
This command may be used to invoke various operations on the widget.
It has the following general form:
pathName option ?arg arg ...?
Option and the args determine the exact behavior of the command. The
following commands are possible for scale widgets:
pathName cget option
Returns the current value of the configuration option given by
option. Option may have any of the values accepted by the scale
pathName configure ?option? ?value option value ...?
Query or modify the configuration options of the widget. If no
option is specified, returns a list describing all of the avail‐
able options for pathName (see Tk_ConfigureInfo for information
on the format of this list). If option is specified with no
value, then the command returns a list describing the one named
option (this list will be identical to the corresponding sublist
of the value returned if no option is specified). If one or
more option-value pairs are specified, then the command modifies
the given widget option(s) to have the given value(s); in this
case the command returns an empty string. Option may have any
of the values accepted by the scale command.
pathName 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
pathName 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.
pathName 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
is not over one of these elements, an empty string is returned.
pathName 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.
Tk automatically creates class bindings for scales that give them the
following default behavior. Where the behavior is different for verti‐
cal and horizontal scales, the horizontal behavior is described in
 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.
 If button 1 is pressed over the slider, the slider can be
dragged with the mouse.
 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.
 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.
 The Up and Left keys move the slider up (left) by the value of
the resolution option.
 The Down and Right keys move the slider down (right) by the
value of the resolution option.
 Control-Up and Control-Left move the slider up (left) by the
value of the bigIncrement option.
 Control-Down and Control-Right move the slider down (right) by
the value of the bigIncrement option.
 Home moves the slider to the top (left) end of its range.
 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.
scale, slider, trough, widget
Tk 4.1 scale(n)