Provides a rotary knob control for Mootools
This widget aims to provide a rotary knob control for MooTools.
A Knob object can be instantiated with a variety of options, and the library also parses the DOM for elements with class .mooknob, replacing each with an instance of the Knob control.
All knobs require user-supplied styling.
Knobs can be controlled with keyboard and/or mouse, and provide WIA-ARIA attributes.
Knobs can monitor and reflect a field with a value attribute.
By default, the control increments and decrements by 1. If the control receives keyboard focus, the cursor keys may be used to increment and decrement the value - by 10 if if the shift key is depressed. If the alt/meta key is depressed whilst a cursor key is pressed, the value of the control is set to its maximum or minimum, dependent on the cursor key..
A control can monitor and reflect values of another element's value fileld: such element should be supplied via the monotpr field, as described in 'Options', below.
The initial value of the control comes from either the monitor elements' value, or the options.value (which may come from the data-value attribute of the element), or from the element's value field, in that order.
As seems to be usual for MooTools, no CSS is supplied. However, the Docs/index.html page contains some examples. A basic gray and round knob can be achieved without graphics if you client supports the border-radius property of CSS3:
<style>
.rotary {
border: 1px solid black;
background: silver;
text-align: center;
border-radius: 50%;
font-weight: bold;
font-size:28pt;
width: 32pt;
height: 32pt;
}
</style>
If select the addpointer option (below), the widget will contain a UTF-8 up-arrow.
The widget can be configued using the attribute of any element which it consumes.
The range of values the widget will supports defaults to +/-100, but can be set with the aria-valuemin and aria-valuemax attributes of the element.
The initial value can be set via the value attribute or data-value attribute.
The chosen value of the control will be placed in the aria-valuenow and aria-valuetext attributes, and in the value attribute, if present, otherwise in the data-value attribute.
For example, the following element will produce a rotary knob with an up-arrow (↑), an initial value of 10, and range between -20 and 20:
<span id='knob1'
data-value='10'
aria-valuemin='-20'
aria-valuemax='20'
>↑</span>
The equivalent to the above HTML would be:
new Knob({
element: 'knob1',
range: [-20, 20],
value: 10
});
The following options are available. Some may be supplied as dataset- attributes when their values are literal.
element
: the DOM element to replace with this controlvalue
: (0) The iInitial value of the control. If not supplied, taken from attributes value or data-valuerange
: ([-100, 100]) The minimum and maximum values. May be supplied in HTML as aria-valuemin and aria-valuemax.scale
: (1) Multiplier applied to the number of pixels the mosue may be moved, to acheive change in thevalue
field (see Events, below)keychangeby
: (1) When arrow keys control the knob, thevalue
field is increased by this factorkeychangebywithshift
: (10) Askeychangeby
, above, but for when shift is held.monitor
: A name for, or instance of, a DOM element that has avalue
field that shoudl be monitored for changes, to be reflected by this control. Intended for text input elements.monitorMs
: (250) The interval, in milliseconds, at which to check themonitor
element, if supplied. The monitor element's value (an aria-related) attribute will also be updated with changes to the control.addpointer
: (↑) By default the module (since 0.3) replaceselement
's content with an up-arrow to the element. Disable this by setting this option to null or false.forceint
: (false) Force all values to be integersdegreesoffset
: (0) Offset, in degrees, to apply to the rotation of the knob. This does not effect the value of the control, only its appearance, and can change the style of the control form a pan control to a volume control, for example. The default is 0 but this may change.
In addition to the above options, the following events are supplied:
onMousedown
: fired when the knob is clickedonMouseup
: fired when the knob is released but before it is renderedonTick
: fired as the knob is turned
The onTick
event is intended to allow the user to adjust the behaviour
of the widget, using the following object fields:
x
andy
represent the position of the mouse curosr relative to the knobmovement
contains the greater of these two,value
contains the previous value incremented bymovement
multiplied by the value of thescale
option (this.options.scale).degrees
contains the amount by which the knob will be rotated, and can be set in accordance with the values accepted by the CSS3 Transform/rotate property (0-360, afik)
The onTick
event could just be used to update a text display field.
render
: Update the control to reflect the current state of thevalue
field, which may be set by supply a single, numeric argumentattach
: Called at instantiation to attach eveents to allow the control to operatedetach
: Removes events
- Double click support is nearly available, but how to convert an angle to a value?
When using HTML mark-up to create a knob, why do *valuemin* and *valuemax* not work?
The acceptable range of inputs should be specified through aria-valuemin
and aria-valuemax*, not
data-valueminand
data-valuemax`.
Why are arguments all lower case, rather than camel case?
To make parsing of dataset
attributes easier: these are all forced to lower case by the browser.