SCALE(9) Kernel Developer's Manual SCALE(9)

scale - Create and manipulate scale widgets

scale pathName ?options?

-activebackground -font               -orient
-background       -foreground         -relief
-borderwidth      -highlightcolor     -takefocus
-disabledcolor    -highlightthickness

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.
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.
A real value corresponding to the left or top end of the scale.
Specifies a desired height for the scale. If this option isn't specified, the scale is given a default height.
A string to display as a label for the scale. If the option is specified as an empty string, no label is displayed.
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).
Specifies a boolean value indicating whether or not the current value of the scale is to be displayed.
Specfies the size of the slider along the slider's long dimension..
Specifies the relief to use when drawing the slider.
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.
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.
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.
Specifies a desired width for the scale. If this option isn't specified, the scale is given a default width.

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 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.

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 Tk command is invoked (using the command option) to notify other interested widgets of the change.

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 right of the trough (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 Tk 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 behaviour of the command. The following commands are possible for scale widgets:
Returns the current value of the configuration option given by option. Option may have any of the values accepted by the scale command.
Query or modify the configuration options of the widget. 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 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.
Returns a list whose elements are the x and y coordinates 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.
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.
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.
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 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 bigincrement 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 the widget receives Up-arrow or Left-arrow key events, the scale's value will be incremented or decremented so as to adjust the value towards the fromvalue.
[4]
If the widget receives Down-arrow or Right-arrow key events, the scale's value will be incremented or decremented so as to adjust the value towards the tovalue.

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 bindings for individual widgets.

options (9), types (9)