#1719 TK_OPTION_NULL_OK not fully supported

[Joe English]

Tk_SetOptions() does not recognize the
TK_OPTION_NULL_OK flag bit for options of type
TK_OPTION_INT, TK_OPTION_BOOL, and a few others.

This causes a bug in the Tile widgets (current CVS
HEAD), which use null defaults in several places. For
example:

tlabel .l
.l configure -width [.l cget -width]
==> Error 'expected integer but got ""'

Workaround possible but this should be fixed in the core.

[Jan Nijtmans]

Why is this one invalid? If the documentation doesn't
mention this, either the documentation should be modified
to menthion that TK_OPTION_NULL_OK is not supported
for some options, either the implementation should be
modified to allow TK_OPTION_NULL_OK for all options.

(I don't mind which solution is chosen, but I don't
think that this artifact is invalid)

[Joe English]

(Sorry, I added a comment when I changed the status, but it didn't get posted).

The documentation already states "Not all option types support the TK_OPTION_NULL_OK flag; for those that do, there is an explicit indication of that fact in the descriptions below [...]".

[Joe English]

dburns reports on the Tcl'ers chat that this is causing problems for GUIB (a gui builder); if a user selects a value for one of the affected by-default-NULL options, it's imposible to reset it back to the default empty value. Reopening.