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

Overview

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

A linear pointer is always used for linear gauges.

Working with Pointers in the UI

Pointer properties can be set by:

1. 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.
2. 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 linear pointer object can be one of three types:  thermometer, bar or marker, as determined by the pointer's Type property. 

Thermometer Pointer

The thermometer represents the most common usage of the linear gauge and the style of thermometer is determined by the ThermometerStyle property. Various thermometer properties can be used to customize its shape and color. The thermometer bulb, located at the extreme end of the thermometer, can also be customized for shape and size.

Note: The thermometer pointer is only available for linear gauges.

Figure 1:  Thermometer pointer. 

Bar Pointer

Bar pointers are effective for displaying a dynamic range of data. The width of the bar is determined by Width. 

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 the developer wishes to only show the range of positive numbers that has been spanned.

Bar pointers are available for circular and linear gauges.

 

Figure 2: Bar pointer.

Marker Pointer

Marker pointers are shapes that represent the current value of the circular pointer. This type of pointer is most effective when displaying milestone values on the gauge. The width of the marker is determined by Width. 

The style of the marker is determined by MarkerStyle. The length of the marker is determined by MarkerLength.

Marker pointers are available for circular and linear gauges. 

Figure 3: Marker pointer.

Images

A linear pointer can be customized so that it is represented by an image, thereby adding a tremendous visual impact to the gauge. It is recommended that the developer review the Working with Images topic for detailed information on how to use images (especially named 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 linear 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.

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

Layout

The linear 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 linear gauge's scale. When Placement is set to Inside, the pointer will be placed above the linear gauge. When Placement is set to Outside, the pointer will be placed below the linear gauge.

Figure 4: Placement = Inside (left figure); Placement = Outside (right figure).

Use DistanceFromScale to set an offset from the Placement where the pointer is placed.

Pointing to Values

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

1. Specify an expression for the Pointer Value in the Gauge Wizard's Data Tab.
2. Specify an expression for the Value in the Pointers Tab of either the Gauge Designer or Sub-Gauge Designer dialogs.
3. 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.

See Also

 

 

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