Tk::Scale - Create and manipulate Scale widgets
$scale =
$parent->Scale(?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.
- 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.
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.
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.
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.
scale, slider, trough, widget