ChartObject Q&A

• Q1. What is ChartObject?
  
  ChartObject is a powerful object-oriented library of 2D and 3D interactive graphic tools that enable X Windows/Motif developers and end users alike to create a wide range of charts. It goes beyond widget technology to give users a level of interactive real-time performance, flexibility and editing functionality unavailable in any other charting package.

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• Q2. How do I create a plot of type PIE/BAR/... ?
  
  You can create a plot of the type you want by setting the resource XmNchartType to XintCHART_TYPE_PIE/BAR/..., when you are creating the chart object in your program.

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• Q3. How do I create a ComboPlot to share an axis?
  
  ChartObject lets you combine primitive plot types to build a composite plot. The mechanism to combine plots is very flexible. You first create a chart with resource XmNchartType set to XintCHART_TYPE_COMBINATION. Then you retrieve the ID of the combo plot created using the INT convenience function, XintChartGetComponent(). Once this is done, you can create as many new plot types as you want inside the combo plot object using function XintComboPlotCreateNewPlot() . For each plot you can place the axes wherever you want. If several plots have axes displayed on the same side, the axes will be automatically stacked next to each other.

  In the example that follows, we will show you how to create a combo plot which contains two plots. The bar plot is placing its x_axis at the bottom of the combo plot and its y_axis at the left, while the line plot is placing its x_axis at the top and its y_axis at the right.

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• Q4. How do I use DataGroup?
  
  DataGroup allows the definition and manipulation of multiple data objects as a single group. It conceptually serves as a "container" for all other data object classes. For example, in the program for Question No. 1, a DataGroup object contains three DataSampled objects and one DataLabel object.

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• Q5. How do I set attributes for the components of a chart?
  
  All the components created by a chart object can be accessed and modified to fit the application's requirements. Function XintChartGetComponent() allows the application to retreive a component from a chart object. Next we will show you how to use this function to retreive the ID of the legend object of a chart object and how to modify it.

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• Q6. How do I store a chart as a template?
  
  The ChartObject convenience function XintChartSaveTemplate() will allow you to store a chart as a template. The code below shows its simplicity.

     Object  chart;
     :
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     XintChartSaveTemplate("template_file", &chart, 1);
     :
  

  Because only the visual attributes are saved, you can associate the chart with new data when it is restored in another application. Another function, XintChartReadTemplate() , reads the chart objects stored in a template file created by XintChartSaveTemplate().

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• Q7. How do I disable the editing of an individual object?
  
  There are two ways to do this.

  The first method is to find the widget ID of the object for which you want to disable the editing -- either you already have it, or you can get it with the INT convenience function XintChartGetComponent(refer to Question No. 5). Then set the resource XmNsensitive to False. There is, however, one problem with this method. When you set the resource XmNsensitive to False, the object can no longer be selected, so it can not be moved or resized by the end user.

  The following code fragment shows how to disable the editing of the legend of the chart.
  

      :
      :
      legend = XintChartGetComponent(chart, XintCHART_COMPONENT_LEGEND);
      XtVaSetValues((Widget)legend, XmNsensitive, False, NULL);
      :
      :
  

  The second method is to disable the resource dialogs by registering callback XmNresourceDialogCallback on the EditObject Widget and setting the doit flag member of the callback structure to False. In the following example, the editing of the legend is disabled, yet the legend can be selected and moved!

  Code Example

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• Q8. How do I get the limits of a chart?
  
  Get the limit resources of the plot of the chart. The limit resources are specified as a pointer to a data structure of type XintLimits.

  The following code fragment shows how to get the limits with the functin XtVaGetValues().
  

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      Object   chart, plot;
      XintLimits  y_limits;
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      plot = XintChartGetComponent(chart, XintCHART_COMPONENT_PLOT);
      XtVaGetValues((Widget)plot, XmNyLimits, &y_limits, NULL);
      :
  

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• Q9. How do I customize the built-in resource editor?
  
  Each built-in resource editor panel can be customized to some extent. It is possible to remove an item from the panel, remove an item inside an option menu, or rename a component in the resource editor panel. For these purposes, INT offers some convenience functions, such as XintResEditGetBox(), XintResEditGetLabel() and XintResEditGetMenuButton(). For a detailed description of how to use these functions, refer to the Guide pp41.

  In the following example, we will show you how to 1) Remove XmNchartFooter and XmNshowLegend editors from the chart resource editor menu; 2) Change name of option menu "Chart Type" to "My Type"; and 3) Disable High Low and Cell Array choices in chart type.

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• Q10. How do I attach my own resource editor?
  
  First, disable the built-in resource editor of the object to which you want to add your own (see Question No. 7). Then create your own resource editor panel using callback XmNresourceDialogCallback. For detailed info about this, refer to the Guide pp 42

  In the following example, we will show you how to build your own legend object editor, which allows only title editing.

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• Q11. How do I zoom and unzoom a chart?
  
  The Chart library facilitates the creation of zoom applicatons by providing the XmNareaSelectionCallback resource and XintChartZoom() convenience function, which enable the application designer to change the data displayed in the viewport easily.

  To unzoom the chart (i.e. to zoomout to the full viewport), you need only to set both XmNxLimits and XmNyLimits to NULL.

  In the following example, when you hold down button 1 to select an area, the viewport is zoomed to the area you select. To unzoom it, just hold down the Control key and click button 1.

  Code Example

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• Q12. What is the coordinate system for a chart or a plot?
  
  The EditObject class defines a linear coodinate system that is between 0.0 to 100.0 both horizontally and vertically. You can use the functions provided in the CompBase widget class, XintHorizontalPixelToUser(),XintHorizontalUserToPixel(), and XintVerticalPixelToUser(),XintVerticalUserToPixel(), to do transformations between pixel coordinate system and the EditObject Coordinate system.

  Each object class defines a specific resource or set of resources that describe the geometry of the object. The coordinate system used to describe the object geometry is normally the one defined by its parent. In graphic object class, two resources, XmNhorizontalAxis and XmNverticalAxis, can be used to specify a diferent coordinate system vertically, horizontally or both. So, suppose you are placing a graphic object into a chart. If the object is inserted inside the chart, its coordinate system is the Chart coordinate system which is between 0 and 100 in both the horizontal and vertical directions. If the object is inserted inside a Plot2D, its coordinate system is the one defined by the axes (if there are any) attached to the Plot2D object.

  In the following example, we will first get the cursor position, which is in the pixel value, via Locator action, then transform it into EditObject Coordinate system. Please note that the EditObject coordinate is already available in the callback structure. We did not use it simply because we were showing you how to do transformations between the two coordinate systems.

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• Q13. How do I get cursor position?
  
  See the answer to the previous question.

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• Q14. How do I allow only 1-dimensional editing?
  
  Use the resource XmNmoveDirection to constrain the move operation of a Graphic object. In a chart, when the object(s) in the datagroup is(are) DataSeries class object(s), you can get the object ID first by using the INT convenience function XintChartGetSeriesOfData() , then set the resource XmNmoveDirection to whatever you like.

  In the following example, we will specify that the line associated with the DataSeries can only move horizontally. The label strings and positions of the X axis will be changing accordingly.

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• Q15. How do I create a symbol and how do I use it?
  
  The Symbol object class allows the application to define and draw custom symbols. To create a symbol, you must first convert a string containing a symbol description into a parsed symbol data structure with the INT convenience function XintSymbolCreate(), set the resource XmNsymbolData to the symbol data you just created, set other resources, such as XmNSymbolLocation and XmNsymbolScale, and then create the symbol with INT convenience function XintCreateSymbol().

  After you create the symbol, you can modify it with the built-in symbol editor. The symbol editor is invoked by double clicking on the symbol.

  Code Example

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• Q16. What callback can I get from a chart?
  
  The Chart object class does not define any new callbacks. However, the callback structure returned with callback XmNverifyCallback is redefined.

  Now, if you want to keep any component in a chart from being moved, you can do it this way:
  

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  static void NonMoveCallback(widget, data, cb)
    Widget widget;
    XtPointer data;
    XintChartVerifyCallbackStruct *cb;
  {
    if (cb->reason == XintCR_OBJECT_MOVE)
       cb->doit = False;
  }
  
  /* in main() */
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     XtAddCallback((Widget)chart, XmNverifyCallback,
                  (XtCallbackProc) NonMoveCallback, NULL);
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