tdf#135922 a11y: Prepare reporting text attrs as IA2 obj attrs

According to the IAccessible2 specification, some
of the attributes that LibreOffice handles as text
attributes are mapped to IAccessible2 text attributes
as well [1], but others should be reported as object
attributes [2], e.g. text alignment
is reported via the "text-align" object attribute on
the paragraph object.

So far, `AccessibleTextAttributeHelper` was only handling
attributes that are mapped to IAccessible2 text attributes.

Prepare for reporting object attributes as well, which
will be required to report text alignment on Windows
in a compliant way (s. tdf#135922).

On the other hand, Qt also expects
`QAccessibleTextInterface::attributes` to return
text formatting using the attributes specified in the
IAccessible2 attribute specifications and maps that to the
platform-specific attributes (AT-SPI text attributes
on Linux), but currently does not provide any way
to report object attributes in addition to text
attributes. It however supports e.g. the
"text-align" attribute mentioned in the
IAccessible2 object attribute specification
when it's reported as a text attribute [3].

Therefore, add a new `IA2AttributeType` enum
that can be used to specify what kind of
IAccessible2 attributes (text attributes,
object attributes) to report.

Only request IA2 text attributes on Windows
when text attributes are requested, but
both types for Qt.

So far, support for none of the object attributes
has been implemented, but an upcoming change
will do that.

[1] https://wiki.linuxfoundation.org/accessibility/iaccessible2/textattributes
[2] https://wiki.linuxfoundation.org/accessibility/iaccessible2/objectattributes
[3] https://code.qt.io/cgit/qt/qtbase.git/tree/src/gui/accessible/linux/atspiadaptor.cpp?id=546208f0ff23819d216cbb5bf0b5daded79b454e#n2193

Change-Id: Ief7c840d3c5274714a914ca0e56df0c5eaffb06d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/158255
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 29 insertions, 3 deletions

diff --git a/include/vcl/accessibility/AccessibleTextAttributeHelper.hxx b/include/vcl/accessibility/AccessibleTextAttributeHelper.hxx
index c5e02a04e85c..d0d49c3209b3 100644
--- a/include/vcl/accessibility/AccessibleTextAttributeHelper.hxx
+++ b/include/vcl/accessibility/AccessibleTextAttributeHelper.hxx
@@ -22,23 +22,49 @@
 #include <com/sun/star/accessibility/XAccessibleText.hpp>
 #include <com/sun/star/beans/PropertyValue.hdl>
 #include <com/sun/star/uno/Sequence.hxx>
+#include <o3tl/typed_flags_set.hxx>
 #include <rtl/ustring.hxx>
 #include <vcl/dllapi.h>
 
+/**
+ * According to the IAccessible2 specification, some of the attributes that LibreOffice
+ * handles as text attributes are mapped to IAccessible2 text attributes as well,
+ * but others should be reported as object attributes (e.g. text alignment is reported
+ * via the "text-align" object attribute on the paragraph object).
+ *
+ * https://wiki.linuxfoundation.org/accessibility/iaccessible2/textattributes
+ * https://wiki.linuxfoundation.org/accessibility/iaccessible2/objectattributes
+ *
+ * This enum class is used to specify the type(s) of attributes of interest.
+ */
+enum class IA2AttributeType
+{
+    None = 0x0000,
+    ObjectAttributes = 0x0001,
+    TextAttributes = 0x0002
+};
+
+template <> struct o3tl::typed_flags<IA2AttributeType> : is_typed_flags<IA2AttributeType, 0x003>
+{
+};
+
 class VCL_DLLPUBLIC AccessibleTextAttributeHelper
 {
 public:
     /** Converts UNO text attribute properties to a string holding
      *  the corresponding IAccessible2 text attributes.
      * @param rUnoAttributes A sequence holding the UNO text attributes.
+     * @param eAttributeType: Thy type(s) of attributes of interest.
      * @returns String holding the corresponding IAccessible2 text properties.
      */
     static OUString ConvertUnoToIAccessible2TextAttributes(
-        const css::uno::Sequence<css::beans::PropertyValue>& rUnoAttributes);
+        const css::uno::Sequence<css::beans::PropertyValue>& rUnoAttributes,
+        IA2AttributeType eAttributeType);
 
     /**
      * Get the IAccessible2 text attributes and the span of the attributes at the given index.
      * @param xText The interface to query for the information.
+     * @param eAttributeType: Thy type(s) of attributes of interest.
      * @param nOffset Character offset for which to retrieve the information.
      * @param rStartOffset Out param that is set to the start index of the attribute run.
      * @param rEndOffset Out param that is set to the end index of the attribute run.
@@ -46,8 +72,8 @@ public:
      */
     static OUString
     GetIAccessible2TextAttributes(css::uno::Reference<css::accessibility::XAccessibleText> xText,
-                                  sal_Int32 nOffset, sal_Int32& rStartOffset,
-                                  sal_Int32& rEndOffset);
+                                  IA2AttributeType eAttributeType, sal_Int32 nOffset,
+                                  sal_Int32& rStartOffset, sal_Int32& rEndOffset);
 };
 
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