By default, the LayerOfValue property is -1, which indicates that the last visible layer whose OnDrag property is not exDoNothing, is the layer that specifies the control's value. The LayerOfValue property specifies the index of the layer whose value represents the control's Value property. The layer's Value could indicate its offset or its rotation angle, based on the OnDrag property. The OnDrag property indicates the action to be performed when the user drags the layer ( dragable ).  Use the Value property of the Clip object to associate a value with the layer's clipping region. Each layer can associate a value with it, while the control's Value property can be associated through the LayerOfValue property with the value of one of the layers within the control.

For instance:

• the control displays a clock, the value could be the current-time
• the control shows a switch, so the value could indicate the state of the switch
• the control shows a thermometer, so the value could be the current temperature
• the control displays a gauge, so the value could be the value on the gauge pointed by the needle

The Change event occurs when the layer's Value property is changed. During the Change event, you can change values of other layers as well. For instance, if the second-hand of the clock is rotated, you can rotate the hour and the minute-hands of the clock as well. The DragStart / Drag / DragEnd events notify your application when a layer is dragged. You can call DragInfo.Debug = -1 during the DragStart event to display debugging information like current movement, rotation angle when drag operation is performed.

The Value property indicates the value keyword in the following properties:

• ValueToOffsetX, Specifies the expression to convert the value to x-offset. The layer's OffsetX property is the result of evaluating the ValueToOffsetX expression, while the OnDrag property is exDoMove. The OffsetToValue converts the current offset to a value.
• ValueToOffsetY, Specifies the expression to convert the value to y-offset. The layer's OffsetY property is the result of evaluating the ValueToOffsetY expression, while the OnDrag property is exDoMove. The OffsetToValue converts the current offset to a value.
• ValueToRotateAngle, Specifies the expression to convert the value to rotating angle. The layer's RotateAngle property is the result of evaluating the ValueToRotateAngle expression, while the OnDrag property is exDoRotate or exDoRotamove. The RotateAngleToValue converts the current rotation angle to a value.

The Value property works in association with the layer's OnDrag property like follows:

• If the OnDrag property is exDoMove, evaluating the ValueToOffsetX property indicates the layer's OffsetX property.
• If the OnDrag property is exDoMove, evaluating the ValueToOffsetY property indicates the layer's OffsetY property.
• If the OnDrag property is exDoRotate or exDoRotamove, evaluating the ValueToRotateAngle property indicates the layer's RotateAngle property.