a11y: Add new relations DescriptionFor, Described, Flows{From,To}

This is equivalent to the corresponding relation types defined
in the IAccessible2 spec [1] (IA2_RELATION_DESCRIPTION_FOR,
IA2_RELATION_DESCRIBED_BY, IA2_RELATION_FLOWS_FROM,
IA2_RELATION_FLOWS_TO) and for AT-SPI on Linux [2]
(relation types ATSPI_RELATION_DESCRIPTION_FOR,
ATSPI_RELATION_DESCRIBED_BY, ATSPI_RELATION_FLOWS_FROM,
ATSPI_RELATION_FLOWS_TO).

User Interface Automation (UIA) on Windows also has corresponding
properties for 3 of them [3]: UIA_DescribedByPropertyId,
UIA_FlowsFromPropertyId, UIA_FlowsToPropertyId.

This commit adds the new flags and implements the mapping for
the AT-SPI case.
Note that the relation type is conceptually always "inverted"
when comparing Qt and AT-SPI (or Qt and UIA)
as clarified in afbfe30093d49eff0ec4c28c220d33c233b9f807.

"QAccessible::Description" instead of "QAccessible::DescriptionFor"
would align better with the naming scheme of the other relations, but
that is already used in the Text enum.

[1] https://accessibility.linuxfoundation.org/a11yspecs/ia2/docs/html/group__grp_relations.html
[2] https://lazka.github.io/pgi-docs/Atspi-2.0/enums.html#Atspi.RelationType
[3] https://docs.microsoft.com/en-us/windows/win32/winauto/uiauto-automation-element-propids

[ChangeLog][QtGui][QAccessible::RelationFlag] Added new relation
flags DescriptionFor, Described, FlowsFrom and FlowsTo.

Fixes: QTBUG-105864
Change-Id: If2d46099eeea75e177358c821d1ae833a553bd0e
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

src/gui/accessible/linux/qspi_constant_mappings.cpp

@@ -97,6 +97,7 @@ QSpiUIntList spiStateSetFromSpiStates(quint64 states)
 
 AtspiRelationType qAccessibleRelationToAtSpiRelation(QAccessible::Relation relation)
 {
+    // direction of the relation is "inversed" in Qt and AT-SPI
     switch (relation) {
     case QAccessible::Label:
         return ATSPI_RELATION_LABELLED_BY;
@@ -106,6 +107,14 @@ AtspiRelationType qAccessibleRelationToAtSpiRelation(QAccessible::Relation relat
         return ATSPI_RELATION_CONTROLLED_BY;
     case QAccessible::Controlled:
         return ATSPI_RELATION_CONTROLLER_FOR;
+    case QAccessible::DescriptionFor:
+        return ATSPI_RELATION_DESCRIBED_BY;
+    case QAccessible::Described:
+        return ATSPI_RELATION_DESCRIPTION_FOR;
+    case QAccessible::FlowsFrom:
+        return ATSPI_RELATION_FLOWS_TO;
+    case QAccessible::FlowsTo:
+        return ATSPI_RELATION_FLOWS_FROM;
     default:
         qWarning() << "Cannot return AT-SPI relation for:" << relation;
     }

src/gui/accessible/qaccessible.cpp

@@ -367,12 +367,16 @@ Q_LOGGING_CATEGORY(lcAccessibilityCore, "qt.accessibility.core");
     the returned list, and the \c origin object is the one represented
     by the calling interface.
 
-    \value Label            The \c returned object is the label for the \c origin object.
-    \value Labelled         The \c returned object is labelled by the \c origin object.
-    \value Controller       The \c returned object controls the \c origin object.
-    \value Controlled       The \c returned object is controlled by the \c origin object.
-    \value AllRelations     Used as a mask to specify that we are interesting in information
-                            about all relations
+    \value Label                        The \c returned object is the label for the \c origin object.
+    \value Labelled                     The \c returned object is labelled by the \c origin object.
+    \value Controller                   The \c returned object controls the \c origin object.
+    \value Controlled                   The \c returned object is controlled by the \c origin object.
+    \value [since 6.6] DescriptionFor   The \c returned object provides a description for the \c origin object.
+    \value [since 6.6] Described        The \c returned object is described by the \c origin object.
+    \value [since 6.6] FlowsFrom        Content logically flows from the \c returned object to the \c origin object.
+    \value [since 6.6] FlowsTo          Content logically flows to the \c returned object from the \c origin object.
+    \value AllRelations                 Used as a mask to specify that we are interesting in information
+                                        about all relations
 
     Implementations of relations() return a combination of these flags.
     Some values are mutually exclusive.

src/gui/accessible/qaccessible_base.h

@@ -331,6 +331,10 @@ public:
         Labelled      = 0x00000002,
         Controller    = 0x00000004,
         Controlled    = 0x00000008,
+        DescriptionFor = 0x00000010,
+        Described     = 0x00000020,
+        FlowsFrom     = 0x00000040,
+        FlowsTo       = 0x00000080,
         AllRelations  = 0xffffffff
     };
     Q_DECLARE_FLAGS(Relation, RelationFlag)