setTabOrder was not considering the case, when a child widget has
its focus proxy set to its parent widget. This happens, for example,
for the QLineEdit that is nested inside the QAbstractSpinBox.
For such cases the lastFocusChild was calculated incorrectly, and, as
a result, such child widgets were not correctly positioned in the
focus chain. This could lead to an error while backtabbing.
Here is a brief example. Suppose we have 3 widgets arranged like this:
auto spinBoxOne = new QDoubleSpinBox;
auto spinBoxTwo = new QDoubleSpinBox;
auto button = new QPushButton;
Then the default widget focus order is:
- spinBoxOne
- lineedit (from spinBoxOne)
- spinBoxTwo
- lineedit (from spinBoxTwo)
- button
Before this commit setting the explicit tab order changed the focus
order in the following way:
QWidget::setTabOrder(spinBoxOne, spinBoxTwo);
QWidget::setTabOrder(spinBoxTwo, button);
- spinBoxOne
- spinBoxTwo
- button
- lineedit (from spinBoxOne)
- lineedit (from spinBoxTwo)
In this case, backtabbing from spinBoxOne actually leads us to
lineedit (from spinBoxTwo), which refers to spinBoxTwo.
And so we're stuck in a loop.
This commit fixes the issue by handling such special case, and
preserving correct focus order.
Note: the actual unit-test in this patch uses QLineEdit instead of
QPushButton, because one can't tab to buttons on macOS by default.
However the general idea is the same.
Pick-to: 6.0 5.15
Fixes: QTBUG-81097
Change-Id: I5d16da7733a4d63f809cab28b8ca9e116b87cffa
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
00505ed2b5