One problem for many developers new to IRIS IM is the amount of knowledge required to build working applications. Although RapidApp significantly reduces the knowledge needed to create application interfaces, you still need significant knowledge of IRIS IM to begin getting values from widgets, displaying data, or dynamically configuring widgets.

For example, the simple calculator program described in Chapter 1, “RapidApp Tour,” requires that you know how to extract the contents of two text fields, convert the strings to integers, and add them back to the third text field. To do this simple operation, you must either know about the XtSetValues()/XtGetValues() functions and that the text widgets have an XmNvalue resource, or you must know about the XmTextFieldGetString()/XmTextFieldSetString() functions.

Neither of these approaches is hard, but the fact that you have to know the interface for each type of widget can make seemingly simple tasks difficult. There are over 700 functions in IRIS IM, Xt, and Xlib, and although XmTextFieldGetString() and XmTextFieldSetString() are easy to use, you have to know they exist before you can actually use them.

The VkEZ package is a utility that makes it easier to perform simple operations in some cases. The package is not a general-purpose “widget wrapper” library and normally you shouldn't use it in production code—especially if you are concerned about the performance of your application. The VkEZ utility provides an easy-to-remember API for common operations. It is suitable for use in prototypes, demos, and applications in which performance isn't a concern. Instead of memorizing dozens or perhaps hundreds of IRIS IM functions, VkEZ requires that you remember only a few simple operations that you can apply to all widgets.

At its simplest, the VkEZ package provides a few operations you can apply to nearly any widget. You can use the “=”, “<<“, or “+=” operators to assign, or append data to a widget. The exact meaning of the operator varies with the widget but should normally “do the right thing.” You can also retrieve the “value” of a widget simply by an implicit or explicit cast to the desired type. Again, the actual data returned depends on the widget. Retrieving the “String” of a Text widget yields the contents of the text field; retrieving the “String” of a List widget yields the text of the selected item. Retrieving an integer from a Scale widget gets the current value of the scale. Asking for the integer value of a text field returns the results of calling atoi() on the contents of the field.

To use a VkEZ operation, you must enclose the widget to be used in “EZ()”, like this:

EZ(widget)

Then you can use the VkEZ operators to set and retrieve data from the widgets. For example, in the calculator example you can set the value of the _result text field to be the sum of the _value1 and _value2 widgets, like this:

EZ(_result) = (int) EZ(_value1) + (int) EZ(_value2);

You can also use the C++ “<<” operator to append data. For example, you can implement a more verbose form of the above example as follows:

EZ(_result) = "";  // Clear the text field
EZ(_result) << "The result of " << EZ(_value1) << " + "
            << EZ(_value2) << " = "
            << (int) EZ(_value1) + (int) EZ(_value2);

If the _value1 widget contains the string “10” and _value2 contains “20,” this places the following string in the _result text field:

The result of 10 + 20 = 30

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Note: The VkEZ package is designed for quick prototypes and ease of learning. The implementation is inefficient and offers no real advantage over the IRIS IM API other than simplicity. Use the VkEZ utilities sparingly, and for production-quality programs, plan to replace all uses with the more direct mechanisms supported by IRIS IM. When you are ready to replace the EZ functions with production code, you should be able to find all occurrences of “EZ” quite easily in your editor.

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For more detailed information about the widgets and operations supported, see “VkEZ Operators.”

EZ(_dial) += 10;

EZ(_dial2) = (int) EZ(_dial1) / 2;

EZ(_list) = "red, green, blue";

EZ(_list) += "yellow, orange";

EZ(_list) << "yellow, orange";

EZ(_text) = "The width of the button is "
             << EZ(_button).width << " pixels";

EZ(_label).width = EZ(_longlabel).width;

EZ(_label).foreground = "blue";

EZ(_label).background =
                     "SGI_DYNAMIC AlternateBackgroundColor1";

VkEZ has two kinds of operators:

The description of each operator lists the widgets that support that operator and defines how the operator works on each widget.

strcpy(buffer, EZ(text));

int value = EZ(dial);

EZ& operator=(int); 
EZ& operator=(float); 
EZ& operator=(const char *);

EZ(text) = 12345;

EZ& operator+=(int); 
EZ& operator+=(float); 
EZ& operator+=(const char *); 
EZ& operator<<(int); 
EZ& operator<<(float); 
EZ& operator<<(const char *);

EZ(toggle) += 0;

EZ(toggle) +=1;

EZ& operator-=(int);

EZ(toggle) -= 0;

EZ(toggle) -= 1;

int width = EZ(widget).width;
EZ(widget).width = 20;
EZ(widget).foreground = "red";
Pixel index = EZ(widget).background;