Suppose the following usecase: you scan the first product of the
picking. A server onchange is then triggered. You scan the same product
a second time, before the first onchange has returned. You expect that
the first onchange is completely executed before running the second one.
This was not the case. Moreover, some onchanges were not be able to
work with the invalid state of the formview at some times, and crashed.
The previous implementation was wrong because id didn't run the main
barcode processing mechanism inside a Mutex. It was also wrong because
it didn't correctly wait for the onchange to execute (a previous barcode
onchanges or some classic ones) before setting the barcode field.
Simon Lejeune
17adc2e09e