This topic discusses circular pointers, which are used for circular gauges.

Overview

A circular pointer "points" to a value along a circular scale, and every pointer is associated with a particular scale. By default, this scale is called "Default".

A circular pointer is always used for circular gauges.

Working with Pointers in the UI

Pointer properties can be set by:

Using the Pointers Tab of either the Gauge or Sub-Gauge Designer dialog. Select the pointer to be modified and then set its properties using this tab.
Using the Advanced Tab of either the Gauge or Sub-Gauge Designer dialog. Select a pointer object and then set its properties.

Types and Styles

A circular pointer can be one of three types: needle, bar or marker. This is determined by the Type property.

Needle Pointer

Needle pointers are the most common type of circular gauge pointers.

The style of the needle is determined by the NeedleStyle property, and the width of the needle is determined by the Width property.

All needles can optionally display a needle cap by setting CapVisible to True. If desired you can also set various properties relating to the cap's size and appearance. The needle cap is always placed in the center of the scale's radius.

The needle pointer is only available for circular gauges.

Figure 1: Needle pointers.

Bar Pointer

Bar pointers are effective for displaying a dynamic range of data.

The width of the bar is determined by the Width property.

The bar will start at the scale minimum when the BarStart property is set to ScaleStart. If you wish to explicitly start the bar pointer at zero, the BarStart property must be set to Zero. This may be useful in situations where the scale has negative values and you wish to only show the range of positive numbers that has been spanned.

Bar pointers are available for both circular and linear gauges.

Figure 2: Bar pointers.

Marker Pointer

Marker pointers are shapes that represent the current value of the circular pointer, and they are most effective when displaying milestone values on a gauge.

The width of the marker is determined by the Width property, the style of the marker is determined by the MarkerStyle property, and the length of the marker is determined by the MarkerLength property.

Marker pointers are available for both circular and linear gauges.

Figure 3: Marker pointers.

Images

A circular pointer can be customized to be represented by an image, which adds tremendous visual impact to the gauge. It is recommended that you review the Working with Images topic for detailed information on how to use images.

To customize the pointer with an image:

Set the Image property of a pointer object:
- by specifying the file location of the image on the local machine (this will add the image to the named images collection for future reference), OR.
- by specifying the name of an image that has already been added to the control's NamedImages collection (accomplished by selecting the control in the Advanced Tab of either the Gauge or Sub-Gauge Designer dialog and then using the NamedImages property).
Set a pivot point by specifying a coordinate set as the ImageOrigin. This corresponds to the point on the image around which the circular pointer will pivot.
Where appropriate set the ImageTransColor property to a background color contained in the image. This will set the color to be transparent, allowing the image to properly blend with the background.

These steps can also be applied to customize the pointer cap with an image.

PointerImage

Figure 4: Gauge with customized pointer.

Layout

The circular pointer is placed at a point on the scale as determined by the Placement and DistanceFromScale properties. Placement determines the positioning of the pointer relative to the circular gauge's scale, and DistanceFromScale determines the offset from the Placement where the pointer is placed.

The following summarizes the layout options for a circular pointer:

When DistanceFromScale is not set the circular pointer is positioned based on the Placement property only.
When DistanceFromScale is set the circular pointer will offset the Placement property with the value of DistanceFromScale.

Figure 5: Placement = Inside, DistanceFromScale = 0 (left image) and DistanceFromScale = 25 (right image).

Pointing to Values

A pointer's value is represented by its Value property, which can be set one of three ways:

Specify an expression for the Pointer Value in the Gauge Wizard's Data Tab.
Specify an expression for the Value in the Pointers Tab of either the Gauge Designer or Sub-Gauge Designer dialogs.
Set the Value property of a pointer in the Code Editor.

Dropping a value field from the Datasets window onto the control's Data Field landing zone will automatically set the value of the control's first pointer to the last value of that field.

Snapping

When a value is generated for the pointer to display, the pointer can snap to a SnappingInterval on the scale by setting SnappingEnabled to True. This is useful to display equal incremental changes to values that are displayed on the gauge.

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Circular Pointers
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