By default, the RotateAngleValid property is empty. The RotateAngleValid property has no effect if it is empty, missing or invalid. If the RotateAngleValid property is valid expression, the value of RotateAngle property always matches RotateAngleValid expression. In other words, the RotateAngleValid validates the rotation angle of the layer. Use the DefaultLayer(exDefLayerRotateAngleValid) property to specify the default value for the RotateAngleValid property, before adding any layer. The Change event occurs when the layer's OffsetX property is changed. The DragStart / Drag / DragEnd events notify your application when a layer is dragged. You can debug the rotation angle, using the Debug property of the DragInfo object. During drag operation you can use the RotateAngleValid property to limit the rotation angle.

For instance:

• "0", indicates that no rotation is allowed, or in other words, RotateAngle is always 0.
• "15 * int(value / 15)", specifies that only multiply of 15 degree is allowed for RotateAngle property ( sectorial rotation )
• "value = 0 ? 0 : ( value < 0 ? -180 : +180 )", indicates that valid values for RotateAngle property is -180, 0 and +180 ( discrete rotation )
• "value MIN -90 MAX 90", indicates that values of RotateAngle property are between -90 and +90 degrees ( range movement )
• "value < 90 ? value : (value < 180 ? 90 : ( value < 270 ? 270 : value ))", converts the value to an angle between 270 and 90 degree.
• "int(value / 360 * 100)/100 * 360" converts the value to an integer rotation angle
• "(value)/100 * 360" converts a percent value to an angle

The RotateAngleValid property supports the following keywords:

• value keyword indicates the current value of RotateAngle property ( the value to validate )

Also, this property supports all constants, operators and functions defined here.

The following picture shows the rotation properties of the Layer, relative to the RotateCenterLayer layer:

Any of the following properties can be used to rotate the layer:

• DefaultRotateAngle, specifies the default angle to rotate the layer.
• RotateAngle, specifies the angle to rotate the layer.
• RotateAngleValid, validates / limits the rotation angle of the layer.
• Value and ValueToRotateAngle, specifies the expression to convert the value to rotating angle. The RotateAngleToValue converts the current rotation angle to a value.

The following properties can be used to specify a different rotation center:

• RotateCenterLayer, indicates the index of the layer the rotation is around.
• RotateCenterX, indicates the expression that determines the x-origin of the rotation point relative to the RotateCenterLayer layer.
• RotateCenterY, indicates the expression that determines the y-origin of the rotation point relative to the RotateCenterLayer layer. 

The following properties can be used to change the rotation center, while the layer's OnDrag property is exDoRotamove:

• RotamoveCenterX, specifies the x-position of the layer's center.
• RotamoveCenterY, specifies the y-position of the layer's center. 
• RotamoveOffsetX,  specifies the x-offset of the layer.
• RotamoveOffsetY, specifies the y-offset of the layer.