Add QGraphicsLayout::anchor() overloads and query the default spacing.

This commit fixes several related issues:
1. QGAL::anchor() had a spacing argument that defaulted to 0. That made
   it impossible to know if the user meant that the spacing should be 0
   or if the spacing should be picked from the style.
   Instead we have to overload anchor, so now we have one function that
   does not take spacing as an argument. That one will create an anchor
   where the spacing is queried from the style. The other overload
   allows the user to explicitly set the spacing, thus the default
   spacing is ignored.

2. Make sure we pick up the spacing correctly from the style if needed.
   setAnchorSizeHintsFromDefaults() will set the correct spacing on
   anchors that was created without specifying a spacing value.

3. Add QGAL::anchor(Qt::Corner, ...) convenience function with an
   overload (for the same reason as explained in 1.)

4. Added QGraphicsAnchorLayoutPrivate::anchor() as a helper function
   that is called from all the 4 public API anchor() functions so that
   we don't need to have duplicate code for argument checking etc.

5. Fix autotests. They assumed that anchor() without a spacing argument
   created a spacing of 0.

0 files changed, 0 insertions, 0 deletions