'Update' Is Wasting Processor Time

The old implementation since wish8.6 is doing superfluous update computations, test this script:

These are the measurements with memtime (Linux):

Revised: 0.84 s
wish8.5: 1.08 s
wish8.6: 14.80 s
wish8.7: 68.58 s

Note that the revised version is based on wish8.6 (pl 6), so we can conclude that the text widget implementation is the causer of this processor load.