SCALE(9) SCALE(9)
NAME
scale - Create and manipulate scale widgets
SYNOPSIS
scale pathName ?options?
STANDARD OPTIONS
-activebackground -font -relief
-background -foreground
-borderwidth -orient
WIDGET-SPECIFIC OPTIONS
-bigincrement dist
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 Tk 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.
-from frac
A real value corresponding to the left or top end of
the scale.
-label string
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 dist
Specifies the desired long dimension of the scale. For
vertical scales this is the scale's height; for hori-
zontal scales it is the scale's width.
-resolution frac
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
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SCALE(9) SCALE(9)
integral).
-showvalue boolean
Specifies a boolean value indicating whether or not the
current value of the scale is to be displayed.
-sliderlength dist
Specfies the size of the slider along the slider's long
dimension..
-sliderrelief relief
Specifies the relief to use when drawing the slider.
-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 won't activate.
If the scale is active, the slider is displayed using
the colour specified by the activeBackground option.
-tickinterval frac
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.
-to frac
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.
-width dist
Specifies the desired narrow dimension of the trough.
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 path-
Name argument) and makes it into a scale widget. Additional
options, described above, may be specified on the command
line to configure aspects of the scale such as its colours,
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
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SCALE(9) SCALE(9)
the BINDINGS section below. Whenever the scale's value is
changed, a Tk command is invoked (using the command option)
to notify other interested widgets of the change. In addi-
tion, the value of the scale can be linked to a Tk 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 Tk command whose name is
pathName. This command may be used to invoke various opera-
tions on the widget. It has the following general form:
pathName option ?arg arg ...?
Option and the args determine the exact behaviour of the
command. The following commands are possible for scale wid-
gets:
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 wid-
get. If no option is specified, returns a list of all
of the available options for pathName. If one or more
option-value pairs are specified, then the command mod-
ifies 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 coordi-
nates of the point along the centreline 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
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SCALE(9) SCALE(9)
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 bindings for scales that give them
the following default behaviour. Where the behaviour is
different for vertical and horizontal scales, the horizontal
behaviour 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 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.
If the scale is disabled using the state option then none of
the above bindings have any effect.
The behaviour of scales can be changed by defining new bind-
ings for individual widgets.
SEE ALSO
options(9), types(9)
BUGS
The -bigincrement and -tickinterval options are currently
ignored.
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