Caret Ownership

Within a frame, only one object can contain the keyboard focus. This property must be maintained when a frame contains multiple editors in multiple displays, and when a single editor contains other editors as items.

When a editor has the keyboard focus, it will usually display the current selection, or a line indicating the insertion point; this line is called the caret.

When a editor contains other editors, it keeps track of caret ownership among the sub-editors it contains. When the caret is taken away from the main editor, it will take away caret ownership from the appropriate sub-editor.

When a editor or snip is drawn, an argument to the drawing method specifies whether the caret should be drawn with the data. This argument can be any of (in increasing order):

• 'no-caret -- The caret should not be drawn at all.
• 'show-inactive-caret -- The caret should be drawn as inactive; items may be identified as the local current selection, but the keyboard focus is elsewhere.
• 'show-caret -- The caret should be drawn to show keyboard focus ownership.