Moves iter one row before where it already is (synchronizes the values of the parameters in iter
with the values at the new row).
If the iterator was on the data model's first row, then it can't be moved backwards
anymore, and the returned value is false; note also that the "current-row" property
is set to -1 (which means that gda.data_model_iter.DataModelIter.isValid would return false).
This function can return false if it was not allowed to be moved (as it emits the
"validate-set" signal before being moved).
When this function returns true, then iter has actually been moved to the next row,
but some values may not have been read correctly in the row, in which case the
correcsponding #GdaHolder will be left invalid.
Moves iter one row before where it already is (synchronizes the values of the parameters in iter with the values at the new row).
If the iterator was on the data model's first row, then it can't be moved backwards anymore, and the returned value is false; note also that the "current-row" property is set to -1 (which means that gda.data_model_iter.DataModelIter.isValid would return false).
This function can return false if it was not allowed to be moved (as it emits the "validate-set" signal before being moved).
When this function returns true, then iter has actually been moved to the next row, but some values may not have been read correctly in the row, in which case the correcsponding #GdaHolder will be left invalid.