Hello.
I'm on Qt 5.9.1.
I'm trying to make an application accessible through screen readers. I
have a custom widget (let's call it MyWidget) that contains text. The
text is drawn using QPainter, which is why a custom widget is used
rather than something like QTextBrowser.
I implemented the QAccessibleTextInterface for the widget, and it works
with Orca under Linux, but when used in Windows 7 with NVDA,
QAccessibleInterface::interface_cast() requests the wrong interface
type. With Orca, I get requests for a QAccessible::TextInterface. In
NVDA, it's always QAccessible::ValueInterface.
AccessibleMyWidget is defined as:
class AccessibleMyWidget:
public QAccessibleWidget, public QAccessibleTextInterface {
public:
explicit AccessibleMyWidget(QWidget* w)
: QAccessibleWidget(w, QAccessible::EditableText)
{
Q_ASSERT(isValid());
}
void* interface_cast(QAccessible::InterfaceType t) override
{
if (t == QAccessible::TextInterface) {
// !!! This is never requested with NVDA !!!
return static_cast<QAccessibleTextInterface*>(this);
}
return QAccessibleWidget::interface_cast(t);
}
// QAccessibleTextInterface implementation below this point.
void addSelection(int startOffset, int endOffset) override;
QString attributes(int offset, int* startOffset,
int* endOffset) const override;
// etc.
};
With Orca under Linux, everything seems to work as intended. I get calls
to interface_cast() for a TextInterface, and after that, the various
functions of QAccessibleTextInterface are called. With NVDA under Linux,
I just get interface_cast() calls for ValueInterface, and none of the
QAccessibleTextInterface functions are called. Which means MyWidget is
completely inaccessible, unless I override QAccessibleWidget::text() and
just return all text as a single string, which means no cursor
navigation, no selection support... It basically becomes just a QLabel
at this point, but with a ton of text and thus very hard to use.
What am I missing here?
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