An experiment to evaluate the suitability of the four techniques described above was devised. There are two main aims. The first was to measure the comparative performance in terms of string echo time for each of the communication techniques. The second aim is to gain insight into the engineering costs associated with implementing each method. GUIs are assembled using sub-components called widgets.
Widgets represent items such as buttons, sliders and menu items.
In response to user actions widgets generate callbacks. For example a user clicking on a button generates a callback which then invokes the appropriate response in the application - perhaps to open a dialog box. In a distributed GUI these callbacks need to be forwarded to the server. Callbacks from some widgets can also contain parameters reflecting their current state. A slider's callback may for example pass an integer representing the current position of the slider.