a11y: Get UnoControl accessible without implementing XAccessible

By now, almost all a11y implementations implement both,
the XAccessible and XAccessibleContext interfaces themselves,
and they do so via the OAccessible base class.

One remaining case that only implements the XAccessible interface
directly is UnoControl. XAccessible::getAccessibleContext
is used from within AccessibleControlShape::Init to get the
accessible context. That accessible context however
is an OAccessible and implements both, the XAccessible
and XAccessibleContext interfaces again.

Stop requiring that UnoControl implements XAccessible
by instead adding a dedicated new method UnoControl::getAccessible
to directly get the OAccessible without relying on
the XAccessible interface being implemented by UnoControl.

In AccessibleControlShape::Init, cast to UnoControl
instead of querying for the XAccessible interface
and call the new method directly.

Stop implementing the XAccessible interface in
UnoControl as it is no longer needed now.

This aligns the UnoControl a11y logic more with how
a11y is implemented elsewhere across the code base.

Sample steps to trigger the modified code
when using the gtk3 vcl plugin on Linux:

* start the Orca screen reader
* start Writer
* insert a few push button controls using
  "Form" -> "Push Button" and then clicking into
  the document and dragging to insert
* disable design mode using "Form" -> "Design Mode"
* focus one of the controls by clicking on it
* press the Tab key to move focus between the controls

No differences in behavior were observed when
doing this with or without this change in place.

Side note: Announcement of the controls when they
receive focus didn't work (reliably) when opening an
existing document containing form controls instead of
inserting them into a new one, but that is preexisting
and unrelated to this commit.

Also adjust test AccessibleFixedTextTest::testFixedText
of the CppunitTest_toolkit_a11y test suite
accordingly that was assuming that it can
query the XAccessible interface directly
from the UNO control.

Change-Id: I8cc3902a8de725eda3d810920f1da2d390c06f73
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/210464
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

include/toolkit/controls/unocontrol.hxx

@@ -33,7 +33,7 @@
 #include <tools/long.hxx>
 #include <comphelper/interfacecontainer3.hxx>
 #include <comphelper/OAccessible.hxx>
-#include <cppuhelper/implbase9.hxx>
+#include <cppuhelper/implbase8.hxx>
 #include <unotools/weakref.hxx>
 #include <com/sun/star/util/XModeChangeBroadcaster.hpp>
 #include <memory>
@@ -61,12 +61,11 @@ struct UnoControlComponentInfos
 struct UnoControl_Data;
 
 
-typedef ::cppu::WeakAggImplHelper9  <   css::awt::XControl
+typedef ::cppu::WeakAggImplHelper8  <   css::awt::XControl
                                     ,   css::awt::XWindow2
                                     ,   css::awt::XView
                                     ,   css::beans::XPropertiesChangeListener
                                     ,   css::lang::XServiceInfo
-                                    ,   css::accessibility::XAccessible
                                     ,   css::util::XModeChangeBroadcaster
                                     ,   css::awt::XUnitConversion
                                     ,   css::awt::XStyleSettingsSupplier
@@ -199,9 +198,6 @@ public:
     sal_Bool SAL_CALL supportsService( const OUString& ServiceName ) override;
     css::uno::Sequence< OUString > SAL_CALL getSupportedServiceNames(  ) override;
 
-    // XAccessible
-    virtual css::uno::Reference< css::accessibility::XAccessibleContext > SAL_CALL getAccessibleContext(  ) override;
-
     // XModeChangeBroadcaster
     virtual void SAL_CALL addModeChangeListener( const css::uno::Reference< css::util::XModeChangeListener >& _rxListener ) override;
     virtual void SAL_CALL removeModeChangeListener( const css::uno::Reference< css::util::XModeChangeListener >& _rxListener ) override;
@@ -217,6 +213,7 @@ public:
     // XStyleSettingsSupplier
     virtual css::uno::Reference< css::awt::XStyleSettings > SAL_CALL getStyleSettings() override;
 
+    rtl::Reference<comphelper::OAccessible> getAccessible();
     css::uno::Reference< css::awt::XVclWindowPeer > getVclWindowPeer();
 
 protected:

svx/source/accessibility/AccessibleControlShape.cxx

@@ -201,10 +201,9 @@ void AccessibleControlShape::Init()
         else
         {
             Reference< XModeChangeBroadcaster > xControlModes( m_xUnoControl, UNO_QUERY );
-            Reference< XAccessible > xControlAccessible( xControlModes, UNO_QUERY );
             Reference< XAccessibleContext > xNativeControlContext;
-            if ( xControlAccessible.is() )
-                xNativeControlContext = xControlAccessible->getAccessibleContext();
+            if (UnoControl* pUnoControl = dynamic_cast<UnoControl*>(xControlModes.get()))
+                xNativeControlContext = pUnoControl->getAccessible();
             OSL_ENSURE( xNativeControlContext.is(), "AccessibleControlShape::Init: no AccessibleContext for the control!" );
             m_aControlContext = WeakReference< XAccessibleContext >( xNativeControlContext );
 

toolkit/qa/cppunit/a11y/AccessibleFixedTextTest.cxx

@@ -34,6 +34,7 @@
 #include <test/a11y/XAccessibleEventBroadcasterTester.hxx>
 #include <test/a11y/XAccessibleTextTester.hxx>
 #include <test/a11y/accessibletestbase.hxx>
+#include <toolkit/controls/unocontrol.hxx>
 #include <vcl/scheduler.hxx>
 
 using namespace css;
@@ -101,7 +102,10 @@ void AccessibleFixedTextTest::testFixedText()
 
     Scheduler::ProcessEventsToIdle();
 
-    css::uno::Reference<css::accessibility::XAccessible> xRoot(xWinDlg, css::uno::UNO_QUERY_THROW);
+    UnoControl* pControl = dynamic_cast<UnoControl*>(xWinDlg.get());
+    CPPUNIT_ASSERT(pControl);
+
+    css::uno::Reference<css::accessibility::XAccessible> xRoot = pControl->getAccessible();
     test::AccessibleTestBase::dumpA11YTree(xRoot);
 
     css::uno::Reference<css::accessibility::XAccessibleContext> xContext

toolkit/source/controls/unocontrol.cxx

@@ -1461,7 +1461,7 @@ Sequence< OUString > UnoControl::getSupportedServiceNames(  )
 }
 
 
-Reference< XAccessibleContext > SAL_CALL UnoControl::getAccessibleContext(  )
+rtl::Reference<comphelper::OAccessible> UnoControl::getAccessible()
 {
     // creation of the context will certainly require the SolarMutex ...
     SolarMutexGuard aSolarGuard;
@@ -1485,7 +1485,7 @@ Reference< XAccessibleContext > SAL_CALL UnoControl::getAccessibleContext(  )
             pCurrentAccessible = ::toolkit::OAccessibleControlContext::create(this);
 
         DBG_ASSERT(pCurrentAccessible.is(),
-                   "UnoControl::getAccessibleContext: invalid context (invalid peer?)!");
+                   "UnoControl::getAccessible: invalid context (invalid peer?)!");
         mpAccessible = unotools::WeakReference<comphelper::OAccessible>(pCurrentAccessible);
 
         // get notified when the accessible is disposed