tdf#146626 catch IndexOutOfBoundsException when fetching accessible children

com::sun::star::accessibility::XAccessibleContext::getAccessibleChild()
can throw an IndexOutOfBoundsException exception even when fetching with
an index that is positive and less than the value returned by a call to
the accessible context's getAccessibleChildCount() method so put every
getAccessibleChild() call in a try/catch block.

Note: this is actually expected behavior even though it is rare. For
example, accessibility::AccessibleTextHelper_Impl::getAccessibleChild()
uses the following code snippet to throw such an exception:

if( 0 > i || i >= getAccessibleChildCount() ||
GetTextForwarder().GetParagraphCount() <= i )

In the case of tdf#146626, getAccessibleChildCount() returns 22 but
getAccessibleChild(1) throws such an exception due to the last
condition in the above code snippet.

Change-Id: If974afb7b9178faa99b91dcd79eb5f169bbfe13e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/153160
Tested-by: Jenkins
Reviewed-by: Patrick Luby <plubius@neooffice.org>

1 files changed, 18 insertions, 8 deletions

diff --git a/vcl/osx/a11yrolehelper.mm b/vcl/osx/a11yrolehelper.mm
index 5cb75c94a86f..e95036dbebd9 100644
--- a/vcl/osx/a11yrolehelper.mm
+++ b/vcl/osx/a11yrolehelper.mm
@@ -24,8 +24,12 @@
 
 #include <com/sun/star/accessibility/AccessibleRole.hpp>
 #include <com/sun/star/accessibility/AccessibleStateType.hpp>
+#include <com/sun/star/lang/IndexOutOfBoundsException.hpp>
+
+#include <sal/log.hxx>
 
 using namespace ::com::sun::star::accessibility;
+using namespace ::com::sun::star::lang;
 using namespace ::com::sun::star::uno;
 
 @implementation AquaA11yRoleHelper
@@ -153,17 +157,23 @@ using namespace ::com::sun::star::uno;
             }
         }
     } else if ( accessibleContext -> getAccessibleRole() == AccessibleRole::COMBO_BOX ) {
-        Reference < XAccessible > rxAccessible = accessibleContext -> getAccessibleChild(0);
-        if ( rxAccessible.is() ) {
-            Reference < XAccessibleContext > rxAccessibleContext = rxAccessible -> getAccessibleContext();
-            if ( rxAccessibleContext.is() && rxAccessibleContext -> getAccessibleRole() == AccessibleRole::TEXT ) {
-                sal_Int64 nStateSet = rxAccessibleContext -> getAccessibleStateSet();
-                if ( !(nStateSet & AccessibleStateType::EDITABLE ) ) {
-                    [ nativeRole release ];
-                    nativeRole = NSAccessibilityPopUpButtonRole;
+        try {
+            Reference < XAccessible > rxAccessible = accessibleContext -> getAccessibleChild(0);
+            if ( rxAccessible.is() ) {
+                Reference < XAccessibleContext > rxAccessibleContext = rxAccessible -> getAccessibleContext();
+                if ( rxAccessibleContext.is() && rxAccessibleContext -> getAccessibleRole() == AccessibleRole::TEXT ) {
+                    sal_Int64 nStateSet = rxAccessibleContext -> getAccessibleStateSet();
+                    if ( !(nStateSet & AccessibleStateType::EDITABLE ) ) {
+                        [ nativeRole release ];
+                        nativeRole = NSAccessibilityPopUpButtonRole;
+                    }
                 }
             }
         }
+        catch (const IndexOutOfBoundsException&)
+        {
+            SAL_WARN("vcl", "No valid accessible objects in parent");
+        }
     }
     return nativeRole;
 }