a11y: Add XAccessibleValue::getMinimumIncrement method

Add a method 'getMinimumIncrement' to the XAccessibleValue interface.
The method returns the minimal increment by which the value represented by
the object can be adjusted.

The main motivation is to expose this to AT-SPI, so it can be retrieved e.g.
by libatspi's 'atspi_value_get_minimum_increment' function [1],
s. the note in Change-Id: I8af326c2d24c1801147a56ea2e2a886ab42ac634
"a11y: Expose FormattedField as spinbox" for more details.

The implementation relevant for the 'FormattedField' class is in
'SVTXAccessibleNumericField::getMinimumIncrement', which returns
the spin size.

While at it, also move the comment in sw/source/core/access/acccell.hxx
mentioning what methods are overriden for the 'XAccessibleValue' interface
to the right place.

[1] https://developer.gnome.org/libatspi/stable/libatspi-atspi-value.html#atspi-value-get-minimum-increment

Change-Id: Ie148a4e1cedbdbb5964f8565c81611d3480465cb
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/119596
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 14 insertions, 0 deletions

diff --git a/offapi/com/sun/star/accessibility/XAccessibleValue.idl b/offapi/com/sun/star/accessibility/XAccessibleValue.idl
index d25c814354f0..db66c039b68a 100644
--- a/offapi/com/sun/star/accessibility/XAccessibleValue.idl
+++ b/offapi/com/sun/star/accessibility/XAccessibleValue.idl
@@ -89,6 +89,20 @@ interface XAccessibleValue : ::com::sun::star::uno::XInterface
             returned.
     */
     any getMinimumValue ();
+
+    /** Returns the minimal increment by which the value represented by this
+        object can be adjusted.
+
+        <p>The type of the returned value is implementation dependent. It
+        does not have to be the same type as that returned by
+        getCurrentAccessibleValue().</p>
+
+        @return
+            Returns the minimal increment value in an implementation dependent type.
+            If this object has no minimum increment value, then an empty object is
+            returned.
+    */
+    any getMinimumIncrement ();
 };
 
 }; }; }; };