public interface StatefulImages
stateful components may
 display different media depending on the current state of the component. See the Img.src attribute or Button.icon attribute for examples of such
 "stateful images". In general the media to load for each state may be specified in two ways:
image URL, this value will be treated as a
 default, or base URL. When a new state is applied, this filename will be combined with the state name to form a combined URL.
 This in turn changes the media that gets loaded and updates the image to reflect the new
 state.sprite configuration documentation for a discussion of
 how sprites can be used for stateful images.  The following table lists out the standard set
 of combined URLs that  may be generated. Subclasses may support additional state-derived media
 of course. Note that the src URL will be split such that the extension is always applied to the
 end of the combined string. For example in the following table, if src was set to
 "blank.gif", the Selected+Focused URL would be 
 "blank_Selected_Focused.gif". 
| URL for Img source | Description | 
| src+extension | Default URL | 
| src+"_Selected"+extension | Applied when StatefulCanvas.selectedis set to
 true | 
| src+"_Focused"+extension | Applied when the component has keyboard focus, if StatefulCanvas.showFocusedis true,
 andStatefulCanvas.showFocusedAsOveris not true. | 
| src+"_Over"+extension | Applied when the user
 rolls over the component if StatefulCanvas.showRollOveris set
 to true | 
| src+"_Down"+extension | Applied when the user presses the mouse button over over the component if StatefulCanvas.showDownis set to
 true | 
| src+"_Disabled"+extension | Applied to Canvas.disabledcomponent
 ifStatefulCanvas.showDisabledis true. | 
| Combined states | |
| src+"_Selected_Focused"+extension | Combined Selected and focused state | 
| src+"_Selected_Over"+extension | Combined Selected and rollOver state | 
| src+"_Focused_Over"+extension | Combined Focused and rollOver state | 
| src+"_Selected_Focused_Over"+extension | Combined Selected, Focused and rollOver state | 
| src+"_Selected_Down"+extension | Combined Selected and mouse-down state | 
| src+"_Focused_Down"+extension | Combined Focused and mouse-down state | 
| src+"_Selected_Focused_Down"+extension | Combined Selected, Focused and mouse-down state | 
| src+"_Selected_Disabled"+extension | Combined Selected and Disabled state | 
SCStatefulImgConfig object allows
 developers to specify a set of explicit  image URLs, one for each state to be displayed, rather
 than relying on an automatically generated combined URL. This pattern is useful for cases where
 the filename of the stateful versions of the image doesn't match up with the auto-generated
 format.