The Angle property contains the angle of the pointer in tenths of degrees, clockwise, starting at the bottom of the dial. This orientation corresponds with the orientation of most turn dials. This means the MinAngle value is at the bottom left at 30°, the MaxAngle at the bottom right, at 330° from the negative Y axis. If you change the value of Angle, the Position is updated automatically. Every change will fire the OnChange event. 

type   TRadioAngle = 0..3600;

Use the Bitmap in the event handler for the OnDrawPointer event. It contains the bitmap, on which the dial face is drawn. To draw your own pointer, you'll need the Canvas property of the bitmap.

Note: This property can only be used at run time and is read-only.

ButtonEdge is the width of the edge of the dial. It can have a value between rcMinEdge and rcMaxEdge. The Radius property is not changed by this, because Radius is controls size of the entire button, so the edge is included. 

const   rcMaxEdge = 10;   rcMinEdge = 2;

Use Center in the event handler for the OnDrawPointer event to draw a custom pointer. It contains the center point of the dial. It is important for the AngleToPoint method.

Note: This property can only be used at run time and is read-only.

Use DefaultPos to set the standard Position for the component. The user can select this position by double-clicking the dial.

Use Frequency to specify the spacing of the tick marks, using the logical units used by the Position property. For example, a Frequency of 5 sets a tick mark at every fifth possible increment. To provide visual feedback about the units used by the radio control, set Frequency to SmallChange or LargeChange.

Note: If the value of the TickStyle property is not set to tsAuto, the value of Frequency is ignored.

Set LargeChange to specify how much to change the value of Position when the user clicks on the dial while pressing Shift simultaneously. The Max and Min properties define the total range over which Position can vary.

For example, if Max is 30000 and Min is 0, the scale pointer can assume 30,000 positions. If the LargeChange property setting is 10000 and the Position property is 0, the user can click the dial three times after the thumb tab before it moves all the way to the end of the scale.

LargeChange should correspond to the portion of this range that the user sees as a useful change, expressed in the logical units used by the Max, Min, and Position properties.

Use Max to set an upper limit to the value that can be represented using the radio control. The scale pointer indicates the current Position in a range between Min and Max.

Use MaxAngle to set an upper limit to the scale position that can be represented using the radio control. The pointer indicates the current Angle in a range between MinAngle and MaxAngle.

Use Min to set a lower limit to the value that can be represented using the radio control. The scale pointer indicates the current Position in a range between Min and Max.

Use MinAngle to set a lower limit to the scale position that can be represented using the radio control. The pointer indicates the current Angle in a range between MinAngle and MaxAngle.

Set PointerColor to specify the color of the pointer on the dial.

Set PointerSize to specify the size of the dial pointer relative to the radius of the dial. The size is expressed as a percentage of the Radius property.

Set PointerShape to specify the geometric shape of the dial pointer. 

type   TRadioPointerShape = (psLine, psTriangle, psDot, psOwnerDraw);

PointerShape has these possible values: 

Value	Meaning
psLine	The pointer is a single line
psTriangle	The pointer is a triangle
psDot	The pointer is a round dot
psOwnerDraw	The pointer is drawn in the OnDrawPointer event

Read Position to determine the current value represented by the radio control. Position is a value in the range between Min and Max (inclusive). Set Position to programmatically move the dial pointer of the radio control to a new value. 

Note: On every position change, the The Angle property is updated and the OnChange event is called.

Use Radius to control the size of the dial on the component. There is a minimum radius the dial can have, which is defined by the rcMinRadius constant. 

const   rcMinRadius = 15;

Use RepeatDelay to get or set the delay in milliseconds between when the dial is clicked and the auto-repeat function will set in.

Use RepeatRate to get or set the time in milliseconds between two repeats of the auto-repeat function.

Set SmallChange to specify how much to change the value of Position when the user clicks on the dial. The Max and Min properties define the total range over which Position can vary.

For example, if Max is 100 and Min is 0, the pointer can assume 100 positions. If the SmallChange property setting is 5 and the Position property is 0, the user can click the down or right arrow button 20 times before the pointer is moved all the way to the end of the scale.

SmallChange should correspond to the portion of this range that the user sees as one item or tick, expressed in the logical units used by the Max, Min, and Position properties.

Set TickStyle to specify whether the radio control should display tick marks, and if so, how those tick marks are set.  

type   TTickStyle = (tsNone, tsAuto, tsManual);

TickStyle has these possible values: 

Value	Meaning
tsNone	No tick marks are displayed.
tsAuto	Tick marks are automatically displayed at increments equal to the value of the Frequency property.
tsManual	Tick marks are displayed at the Min and Max values. Additional tick marks can be set using the SetTick method.

Use SetTick to place a tick mark on the bar at the position that corresponds to the Value parameter. Tick marks specified in this manner are only displayed when the TickStyle is set to tsManual. 

The Length parameter defines one of three possible lenghts, a tick mark can have. 

const   tlLongLen = 10;   tlMiddleLen = 6;   tlShortLen = 4; type   TTickLength = (tlShort, tlMiddle, tlLong);

Length has these possible values: 

Value	Meaning
tlShort	A tick is tlShortLen pixels.
tlMiddle	A tick is tlMiddleLen pixels.
tl Long	A tick is tlLongLen pixels.

Use AngleToPoint to calculate the point, which is at a given angle and radius from a center point. This method was specifically designed to be used in the OnDrawPointer event.

This event is called whenever Position and/or Angle change.

This event is called, when the user should draw the position pointer. This event will only be generated, if the PointerShape property has the psOwnerDraw value.

During this event, the drawing is restricted to the face of the dial button.

To draw the pointer, you can use the Bitmap, Position, Angle, Radius, ButtonEdge, Center, PointerColor and PointerSize properties and the AngleToPoint method. 

type   TRadioDrawEvent = procedure (Sender: TRadioControl; ARect: TRect)                       of object;