NIL is valid value for reading only. A run time error results, if an attempt is made to assign NIL to the :selUnderline instance variable.
Member variable XbpRtf():selUnderline Foundation
Configures underlined type face for the selection.
The property contains .T. (true) when the text at the selection is displayed underlined, otherwise .F. (false). Assigning a logical value to the property changes the type face of the text beginning at the position :selStart accordingly.
If the text in the current selection contains sections with both underlined and normal text, the instance variable :selUnderline contains the value NIL. This value represents an indeterminate state that the Xbase++ application may chose to visualize in its user interface. Some word processor applications use grayed controls to visualize conflicting properties in the current selection, for example.
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