Fix accessibility-related performance regressions

Before 089dd16f, we had a QQuickControlPrivate::accessibleAttached
member that indicated whether accessibility was active. Since 4be38ab
in qtdeclarative, it was possible to access QQuickAccessibleAttached::
attachedProperties() directly, but we ended up accidentally accessing
it even when accessibility was not active, which added noticeable
overhead.

This improves those qmlbench test cases that call accessibility-aware
setters such as QQuickAbstractButton::setChecked() a lot. For example,
the test cases for CheckBox and RadioButton create large amounts of
controls with a "checked: index % 2" binding.

- CheckBox: 84 => 93 frames
- RadioButton: 98 => 113 frames

QAccessible::setActive(true) only notifies the observers, but does not
really make accessibility active in the sense that the consequent calls
to QAccessible::isActive() still return false. tst_accessible had to be
changed to use QPlatformAccessible::setActive() instead.

Change-Id: I8fd0fe2dddfd5633ce22a080bcda459f2d6e443e
Reviewed-by: Liang Qi <liang.qi@qt.io>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/quicktemplates2/qquickcontrol_p_p.h b/src/quicktemplates2/qquickcontrol_p_p.h
index e990e44f..e7e9d46f 100644
--- a/src/quicktemplates2/qquickcontrol_p_p.h
+++ b/src/quicktemplates2/qquickcontrol_p_p.h
@@ -60,6 +60,8 @@
 
 QT_BEGIN_NAMESPACE
 
+class QQuickAccessibleAttached;
+
 class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickControlPrivate : public QQuickItemPrivate
 #if QT_CONFIG(accessibility)
     , public QAccessible::ActivationObserver
@@ -100,6 +102,7 @@ public:
 #if QT_CONFIG(accessibility)
     void accessibilityActiveChanged(bool active) override;
     QAccessible::Role accessibleRole() const override;
+    static QQuickAccessibleAttached *accessibleAttached(const QObject *object);
 #endif
 
     virtual void resolveFont();