#13 Changes Tk8.7 -underline type result in runtime errors

[Brian Griffin]

Values for the canvas widget -underline option have changed in Tk8.7 (Tcl 9) from TIP #577. It has changed from type int to type index, which include values like "end-2", and "" (the empty set).
Existing code uses the old form: {$underline != -1} to test for the empty set, These checks need to change to {$underline ne ""}.

Also note that type index is nolonger a simple integer.

[Peter Spjuth]

I made a fix that makes it handle it a bit more gracefully.
End-style index will be treated as not existing for now.

Is there a nice way to parse end-style from Tcl?

[Brian Griffin]

I'm not aware of a specific command for this. However, the following should work:

~~~~
set str "Example String Value"
set index "end-3"
set intIndex [lindex [lseq [string length $str]] $index]

This technique should work for both strings and lists.

proc intIndexForString {stringValue index} {
return [lindex [lseq [string length $stringValue]] $index]
}

proc intIndexForList {listValue index} {
return [lindex [lseq [llength $listValue]] $index]
}
~~~

These functions should have O(1) performance regardless of string length or list length.

[Peter Spjuth]

Fixed it with the lseq trick.