scale - Create and manipulate scale widgets
SYNOPSIS
scale pathName ?options?
STANDARD OPTIONS
activeBackground font highlightThickness repeatInterval
background foreground orient takeFocus
borderWidth highlightBackground relief troughColor
cursor highlightColor repeatDelay
See the options manual entry for details on the standard options.
WIDGET-SPECIFIC OPTIONS
Name: bigIncrement
Class: BigIncrement
Command-Line 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
Command-Line Switch: -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.
Name: digits
Class: Digits
Command-Line 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
Command-Line Switch: -from
A real value corresponding to the left or top end of the scale.
Name: label
Class: Label
Command-Line 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
Command-Line 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
Command-Line 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
Command-Line Switch: -showvalue
Specifies a boolean value indicating whether or not the current
value of the scale is to be displayed.
Name: sliderLength
Class: SliderLength
Command-Line 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: state
Class: State
Command-Line 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
Command-Line 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
Command-Line 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
Command-Line Switch: -variable
Specifies the name of a global variable to link to the scale. Whenever the
value of the variable changes, the scale will upate 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
Command-Line 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 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 configure 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
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 COMMAND
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
command.
- 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 available 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 used.
- 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 isn't 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.
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]
The Up and Left keys move the slider up (left) by the value
of the resolution option.
[5]
The Down and Right keys move the slider down (right) by the value
of the resolution option.
[6]
Control-Up and Control-Left move the slider up (left) by the
value of the bigIncrement option.
[7]
Control-Down and Control-Right move the slider down (right) by the
value of the bigIncrement option.
[8]
Home moves the slider to the top (left) end of its range.
[9]
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