Report the position of a painted list item within its set

ui/accessible/ui_accessible_item.cpp

@@ -198,20 +198,49 @@ QAccessibleInterface *Item::parent() const {
 }
 
 void *Item::interface_cast(QAccessible::InterfaceType type) {
+	const auto parent = _parent.get();
+	const auto index = parent ? currentIndex() : -1;
 	if (type == QAccessible::ActionInterface) {
 		// Expose the action interface only when the owner opted in for this
 		// child. Otherwise the Windows UIA bridge would advertise Invoke /
 		// SetFocus / SelectionItem and report success while doing nothing.
-		const auto parent = _parent.get();
-		const auto index = parent ? currentIndex() : -1;
 		if (index >= 0
 			&& parent->accessibilityChildSupportsActions(index)) {
 			return static_cast<QAccessibleActionInterface*>(this);
 		}
+	} else if (type == QAccessible::AttributesInterface) {
+		// Only a row that is one of the set reports a position, a divider
+		// between the rows has none - see accessibilityChildSetPosition.
+		if (index >= 0
+			&& parent->accessibilityChildSetPosition(index).position > 0) {
+			return static_cast<QAccessibleAttributesInterface*>(this);
+		}
 	}
 	return nullptr;
 }
 
+QList<QAccessible::Attribute> Item::attributeKeys() const {
+	return {
+		QAccessible::Attribute::PositionInSet,
+		QAccessible::Attribute::SizeOfSet,
+	};
+}
+
+QVariant Item::attributeValue(QAccessible::Attribute key) const {
+	const auto parent = _parent.get();
+	const auto index = parent ? currentIndex() : -1;
+	if (index < 0) {
+		return QVariant();
+	}
+	const auto position = parent->accessibilityChildSetPosition(index);
+	if (key == QAccessible::Attribute::PositionInSet) {
+		return position.position;
+	} else if (key == QAccessible::Attribute::SizeOfSet) {
+		return position.size;
+	}
+	return QVariant();
+}
+
 QStringList Item::actionNames() const {
 	const auto parent = _parent.get();
 	const auto index = parent ? currentIndex() : -1;

ui/accessible/ui_accessible_item.h

@@ -86,7 +86,8 @@ struct SubItems {
 
 class Item final
 	: public QAccessibleInterface
-	, public QAccessibleActionInterface {
+	, public QAccessibleActionInterface
+	, public QAccessibleAttributesInterface {
 public:
 	Item(not_null<RpWidget*> parent, int index);
 
@@ -131,6 +132,10 @@ class Item final
 	QStringList keyBindingsForAction(
 		const QString &actionName) const override;
 
+	// QAccessibleAttributesInterface.
+	QList<QAccessible::Attribute> attributeKeys() const override;
+	QVariant attributeValue(QAccessible::Attribute key) const override;
+
 private:
 	base::weak_qptr<RpWidget> _parent;
 	mutable std::unique_ptr<SubItems> _subitems;

ui/rp_widget.cpp

@@ -402,6 +402,11 @@ QAccessible::Role RpWidget::accessibilityChildRole() const {
 	return QAccessible::Role::NoRole;
 }
 
+AccessibilitySetPosition RpWidget::accessibilityChildSetPosition(
+		int index) const {
+	return { index + 1, accessibilityChildCount() };
+}
+
 QString RpWidget::accessibilityChildName(int index) const {
 	return QString();
 }

ui/rp_widget.h

@@ -380,6 +380,15 @@ class RpWidgetBase : public Widget, public RpWidgetWrap {
 // Add required fields from QAccessible::State when necessary.
 // Don't forget to amend the AccessibilityState::writeTo implementation.
 // This one allows universal initialization, like { .checkable = true }.
+// The "x of y" of a child of a painted list, reported to a screen reader
+// as PositionInSet / SizeOfSet: the 1-based position of the child within
+// the set of its siblings and the size of that set. A zero position means
+// the child is not one of the set, like a divider row between the items.
+struct AccessibilitySetPosition {
+	int position = 0;
+	int size = 0;
+};
+
 struct AccessibilityState {
 	bool checkable : 1 = false;
 	bool checked : 1 = false;
@@ -458,6 +467,12 @@ class RpWidget : public RpWidgetBase<QWidget> {
 	[[nodiscard]] virtual QAccessible::State accessibilityChildState(int index) const;
 	void accessibilityChildStateChanged(int index, AccessibilityState changes);
 	[[nodiscard]] virtual QAccessible::Role accessibilityChildRole() const;
+
+	// By default every child is one of the set; a list with rows outside
+	// it overrides this to skip them, see AccessibilitySetPosition.
+	[[nodiscard]] virtual AccessibilitySetPosition accessibilityChildSetPosition(
+		int index) const;
+
 	[[nodiscard]] virtual QRect accessibilityChildRect(int index) const;
 	[[nodiscard]] virtual int accessibilityChildColumnCount(int row) const;
 	[[nodiscard]] virtual QAccessible::Role accessibilityChildSubItemRole() const;