XControl
XControls are introduced in LabVIEW 8.0 and enhance the power of front panel objects in great ways.
Essentially an XControl is a front panel object with dedicated code linked to react on certain user events.
An XControl exists of several parts, managed in a .xctl file. The .xctl file is a XML-file like the project-file. Other parts of the XControl are abilities. The following abilities are obliged
| Ability | Function | Called if/when | LabVIEW file type | Optional? |
|---|---|---|---|---|
| Init | To initialize memory, convert from previous version, load data from a previous session | The first time a Xcontrol is added to a VI, an Xcontrol is upgraded, a VI with an XControl is opened | Instrument (VI) | No |
| Data | Interface to the calling VI | NA | Control (ctl) | No |
| State | Contains local data for the XControl | NA | Control (ctl) | No |
| Facade | Contains the code running when the XControl is active | Every time an event inside the Facade VI is triggered | Instrument (VI) | No |
| Uninit | To close items allocated in Init | The XControl is unloaded from memory | Instrument (VI) | Yes |
| Convert state for save | Change the data that is saved inside a VI | The VI containing the XControl is saved | Instrument (VI) | Yes |
Facade Ability VI
The Facade VI is the running heart of the XControl. It decides on which events applied to the XControl should be reacted in which ways.
The Facade Ability VI has several data in- and outputs to fit in the XControl framework.
| Name | Description | Type |
|---|---|---|
| Data In | Returns last saved value of 'Data Out' | Control |
| Data Out | Outputs the value for use inside the containing VI | Indicator |
| Display State In | Holds internal data of the XControl | Control |
| Display State Out | Placeholder for internal data | Indicator |
| Container State | Holds information about the XControl for use inside the XControl | Control |
| Container State.Indicator? | Returns True if the XControl is an indicator | NA |
| Container State.Runmode? | Returns True if the VI containing the XControl is in Runmode. | NA |
| Container State.Refnum | Reference to the control representing the XControl | NA |
| Action | Contains commands for LabVIEW about the current XControl event session | Indicator |
| Action.DataChanged? | If this boolean is true LabVIEW will save te 'Data Out' value, if false the value will revert to 'Data In' | NA |
| Action.StateChanged? | If this boolean is true LabVIEW will save te 'Display State Out' value, if false the value will revert to 'Display State In' | NA |
| Action.Action Name | Can be used to track changes made by XControls for undo for instance |