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.
- 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.
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