Currently, the orientation of a QScrollBar (and other controls) is not reported on the accessibility level, even though corresponding states or attributes/properties exist in most platform accessibility APIs.

Corresponding states/attributes in platform a11y APIs:

• Linux/AT-SPI2: states ATSPI_STATE_HORIZONTAL [1] and
  ATSPI_STATE_VERTICAL [2]
• Windows/UIA: UIA_OrientationPropertyId [3]
• macOS: NSAccessibilityOrientation [4]
• web/ARIA: "aria-orientation" attribute [5]

Not reporting the orientation e.g. makes it hard for users of assistive technology to identify what orientation the scrollbar has, and thus also which keyboard shortcuts apply for changing the position (up/down key for vertical scrollbar, left/right for horizontal one).

Sample steps to reproduce with AT-SPI2 on Linux:

1. Build and run this sample application

   #include <QApplication>
   #include <QMainWindow>
   #include <QScrollArea>
   
   int main(int argc, char *argv[])
   {
       QApplication a(argc, argv);
   
       QMainWindow w;
   
       QScrollArea* scrollArea = new QScrollArea(&w);
       w.setCentralWidget(scrollArea);
       w.resize(400, 400);
   
       QWidget* dummyWidget = new QWidget;
       dummyWidget->resize(10000, 10000);
       scrollArea->setWidget(dummyWidget);
   
       w.show();
   
       return a.exec();
   }
   

1. start Accerciser Accessibility Explorer
2. in Accerciser's treeview of the a11y hierarchy, select the object for the horizontal scrollbar
3. in Accerciser's "Interface Viewer", check the "States" section

Actual result:

No "horizontal" state is reported.

Expected result:

The "horizontal" state should be reported for the horizontal scroll bar (and the vertical state for the vertical scrollbar).

Further information:

When using a similar program using GTK 3 or GTK 4 instead of Qt, the state is reported as expected.

[1] https://gnome.pages.gitlab.gnome.org/at-spi2-core/libatspi/enum.StateType.html#horizontal
[2] https://gnome.pages.gitlab.gnome.org/at-spi2-core/libatspi/enum.StateType.html#vertical
[3] https://learn.microsoft.com/en-us/windows/win32/winauto/uiauto-automation-element-propids
[4] https://developer.apple.com/documentation/appkit/nsaccessibilityorientationNSAccessibilityOrientation
[5] https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Reference/Attributes/aria-orientation