Question

The following “explaination” from the Microsoft MSDN is sematically void to me:

Occurs when the focus or keyboard user interface (UI) cues change.

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.changeuicues.aspx

Can anyone provide a substantive definition… or a resource that describes this event?

Even the following references from the MSDN don’t help:

http://msdn.microsoft.com/en-us/library/system.windows.forms.uicues.aspx

OR

http://msdn.microsoft.com/en-us/library/system.windows.forms.uicueseventargs.aspx

All of these assume that the reader knows what a UI Cue is…

Answer 1

This event is fired when the UICues change for a control.

What is a UI Cue? Take a look at the UICuse enumeration documentation:

This enumeration is used to specify which user interface cues will be displayed or changed. For example, when the user presses the ALT key, the keyboard shortcuts on the menu are displayed by underlining the appropriate character. The bitwise combination of UICues for this example would be ShowKeyboard and ChangeKeyboard.

In other words, a UI Cue is a visual indicator for the user of the software’s internal state which might not otherwise be apparent. For example (different from above), when a button has “focus” (meaning pressing the Enter or Return key will initiate the associated Click event), the OS provides a “UI Cue”, usually a dotted rectangle around the edges of the button, indicating that that particular button (and not one of the others on the screen) has keyboard focus.

Without these UI Cues, the user may not have way of determining the internal state of the software, rendering the behavior unpredictable (as in, when I press Enter I won’t know which button will be “clicked”).

According to the documentation (follow the link above), a WinForms control supports the following cues (which can be combined using bitwise logic):

• ShowFocus Focus rectangles are displayed after the change.
• ShowKeyboard Keyboard cues are underlined after the change.
• Shown Focus rectangles are displayed and keyboard cues are underlined after the change.
• ChangeFocus The state of the focus cues has changed.
• ChangeKeyboard The state of the keyboard cues has changed.
• Changed The state of the focus cues and keyboard cues has changed.
• None No change was made.