The latching button element works much like the parameter button element described earlier in this document, but is specialized to show and control an enumeration parameter which knows exactly two states (e.g. on/off or true/false).
When the operator changes the state of the button by clicking it once, the latching button sends the 'other' parameter value to the device. On the other hand, if some other instance in the system changes the parameter state, the latching button recognizes this and changes the up/down state of the button accordingly.
Like the parameter button, the latching button may be labeled with text or an image. To reflect the actual state, the latching button always is configured with two text string or two image names which are shown according to the actual parameter value.
The latching button element never uses a button label and an icon at the same time. Either iconUp / iconDown or labelUp / labelDown contain empty strings.
The valueUp and valueDown values are not only sent when the button is pressed or released. They also are used to set the button state when a parameter value is received though id: If the value matches valueDown the button goes to 'pressed' state, in all other cases the button gets released. Labels or icons change an this moment according to the new state.