The StripChart Widget
Author: Roland Krause 2002, roland_krause@freenet.de
Description: Documentation to XawPlus

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### The StripChart Widget

Application Header file Class Header file Class Class Name Superclass | <X11/XawPlus/StripChart.h> <X11/XawPlus/StripChartP.h> stripChartWidgetClass StripChart Simple

The StripChart widget is used to provide a real time graphical chart of a single value. This widget is used by xload to provide the load graph. It will read data from an application, and update the chart at the update interval specified.

### Differences between Xaw and XawPlus

Since the 3D extensions of Simple are inserted, the StripChart widget has the additional (but at this time not used) resources highlightColor, shadowColor and buttonBorderWidth. The default background color is now grey75.

### Resources

When creating a Simple widget instance, the following resources are retrieved from the argument list of XtSetValues() or XtVaSetValues() or from the resource database:

Name | Class | Type | Default Value
OBJECT: |  |  |
destroyCallback | Callback | Pointer | NULL
RECTANGLE: |  |  |
borderWidth height sensitive width x y | BorderWidth Height Sensitive Width Position Position | Dimension Dimension Boolean Dimension Position Position | 0 120 True 120 0 0
CORE: |  |  |
border background mappedWhenManaged | BorderColor Background MappedWhenManaged | Pixel Pixel Boolean | XtDefaultForeground grey75 True
SIMPLE: |  |  |
cursor cursorName pointerColor pointerColorBackground insensitiveBorder international highlightColor shadowColor buttonBorderWidth | Cursor Cursor Foreground Background Insensitive International Background Background Width | Cursor String Pixel Pixel Pixmap Boolean Pixel Pixel Dimension | None NULL XtDefaultForeground XtDefaultBackground NULL False grey90 grey40 2
STRIPCHART: |  |  |
foreground getValue highlight jumpScroll minScale update | Foreground Callback Foreground JumpScroll Scale Interval | Pixel XtCallbackList Pixel int int int | XtDefaultForeground NULL XtDefaultForeground 1/2 width 1 10 (seconds)

foreground | A pixel value which indexes the widget's colormap to derive the color that will be used to draw the graph.
getValue | This is a list of functions to call every update seconds. This function will get the value to be graphed by the StripChart widget. The section Getting the StripChart Value will describe the calling interface in more detail. This callback list should contain only one function. If this callback list contains more than one function, the behavior is undefined.
highlight | A pixel value which indexes the widget's colormap to derive the color that will be used to draw the scale lines on the graph.
jumpScroll | When the graph reaches the right edge of the window it must be scrolled to the left. This resource specifies the number of pixels it will jump. Smooth scrolling can be achieved by setting this resource to 1.
minScale | The minimum scale for the graph. The number of divisions on the graph will always be greater than or equal to this value.
update | The number of seconds between graph updates. Each update is represented on the graph as a 1 pixel wide line. Every update seconds the getValue procedure will be used to get a new graph point, and this point will be added to the right end of the StripChart.

### Getting The StripChart Value

The StripChart widget will call the application routine passed to it as the getValue callback function every update seconds to obtain another point for the StripChart graph.

The calling interface for the getValue callback is:

> void (*getValueProc)(w, client_data, value)
> Widget w;
> XtPointer client_data;
> XtPointer value; /* double * */

> w | Specifies the StripChart widget.
> client_data | Specifies the client data.
> value | Returns a pointer to a double. The application should set the address pointed to by this argument to a double containing the value to be graphed on the StripChart.

This function is used by the StripChart to call an application routine. The routine will pass the value to be graphed back to the the StripChart in the value field of this routine.

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