Add QStyle::SH_SpinBox_StepModifier style hint

This patch allows the developer to pick which keyboard modifier
increases the number of steps a QAbstractSpinBox takes when the user
interacts with it.

The modifier can be either Qt::ControlModifier (default),
Qt::ShiftModifier or Qt::NoModifier. Qt::NoModifier disables the step
modifier. Note that on macOS, Control corresponds to the Command key.

Holding the modifier increases the step rate when:
- scrolling;
- pressing the up/down keys;
- pressing the spin box up/down buttons.

[ChangeLog][QtWidgets][QStyle] QStyle::SH_SpinBox_StepModifier allows
the developer to pick which keyboard modifier increases the number of
steps a QAbstractSpinBox takes for the following interactions:
scrolling, up/down keyboard keys and the spin box buttons. The
Qt::ShiftModifier can now be used, or the feature can be disabled
using Qt::NoModifier. Previously, only Qt::ControlModifier could be
used as the modifier.

Change-Id: Ib5518127e86a8f67798a9a1d6e860c6e35896e6f
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/widgets/widgets/qabstractspinbox.cpp b/src/widgets/widgets/qabstractspinbox.cpp
index 0459eadfff..822d896ee6 100644
--- a/src/widgets/widgets/qabstractspinbox.cpp
+++ b/src/widgets/widgets/qabstractspinbox.cpp
@@ -106,6 +106,10 @@ QT_BEGIN_NAMESPACE
     the spinbox buttons. Note that on macOS, Control corresponds to the
     Command key.
 
+    Since Qt 5.12, QStyle::SH_SpinBox_StepModifier can be used to select
+    which Qt::KeyboardModifier increases the step rate. Qt::NoModifier
+    disables this feature.
+
     QAbstractSpinBox also provide a virtual function stepEnabled() to
     determine whether stepping up/down is allowed at any point. This
     function returns a bitset of StepEnabled.
@@ -840,6 +844,7 @@ void QAbstractSpinBox::changeEvent(QEvent *event)
                 style()->styleHint(QStyle::SH_SpinBox_ClickAutoRepeatThreshold, 0, this);
             if (d->edit)
                 d->edit->setFrame(!style()->styleHint(QStyle::SH_SpinBox_ButtonsInsideFrame, nullptr, this));
+            d->stepModifier = static_cast<Qt::KeyboardModifier>(style()->styleHint(QStyle::SH_SpinBox_StepModifier, nullptr, this));
             d->reset();
             d->updateEditFieldGeometry();
             break;