When formatting numbers, if the fill character used to left-pad to
field widths is '0', the code delegates that padding to the
QLocaleData's ZeroPadded formatting option. Since we want the zeros
before any minus sign, and don't want to subsequently add more zeros
before it, check that this has worked as expected when calling
replaceArgEscapes(), to confirm that it doesn't need to worry about
that.
Add some tests that verify the expected behavior.
In the process, tidy up the code doing this. Rename a local variable
to match our coding style, split a long line.
Pick-to: 6.2
Change-Id: I7cc430c5bceb006cf4e226bca33da16bd2bb1937
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
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