Utility base class for a button type widgets.
Configurations for the buttons come from :
- html area : corresponds to the web layout command name
- width,height : default are 20,20. Classes should redifine teh getButtonWidth and getButtonHeight to provide othe values
- imageurl : image that will be used when the button is active. Default value is read from the web layout command imageurl parameter. Classes can redifine getImageURL.
- imageurl : image that will be used when the button is active. Default value is read from the web layout command disabledimageurl parameter. Classes can redifine getDisabledImageURL.
Clases inheriting should redefine the function activateTool which is called when the button is clicked