Summary

We need to define and implement the new interface that will allow accessibility subsystem to properly interact with list components.

Problem

The absence of the dedicated AccessibleList interface does not allow setting selections on lists on MacOS using the accessible shortcuts and external accessibility devices. The current solution severely limits the ability of accessibility subsystem to interact with the list component thus it is not acceptable. Existing implementation uses AccessibleSelection implemented in the JList but it lacks ability to work with multiple selection intervals and side effects of setting singular selection with sequential calling of clearSelection() and addSelection() lead to the the line selection action being repeated by the VoiceOver indefinitely.

Solution

We need a new accessibility interface that will implement the selection model for accessibility lists. Also it should provide additional information about the list, regardless of whether the accessibility list is inherited from JList or impolemented from scratch. New interface should be able to provide system with the additional information such as selection mode and should be flexible enough to allow implementation of both single and multiselection modes. The AccessibleSelection interface does not allow working with index intervals, which will prevent the implementation of multiple selection in the future.

This interface is not yet relevant on windows because the most common readers do not have a screen navigation modes similar to VoiceOver quick navigation and the current functionality is sufficient.

Specification

--- /dev/null
+++ b/src/java.desktop/share/classes/javax/accessibility/AccessibleList.java
+package javax.accessibility;
+
+/**
+ *  This interface provides list specific data.
+ *
+ */
+public interface AccessibleList {
+
+    /**
+     * A value for the selectionMode property: select one list index
+     * at a time.
+     */
+    int SINGLE_SELECTION = 0;
+
+    /**
+     * A value for the selectionMode property: select one contiguous
+     * range of indices at a time.
+     */
+    int SINGLE_INTERVAL_SELECTION = 1;
+
+    /**
+     * A value for the selectionMode property: select one or more
+     * contiguous ranges of indices at a time.
+     */
+    int MULTIPLE_INTERVAL_SELECTION = 2;
+
+    /**
+     * Returns the length of the list.
+     * @return the length of the list
+     */
+    int getSize();
+
+    /**
+     * Changes the selection to be between {@code index0} and {@code index1}
+     *
+     * @param index0 one end of the interval.
+     * @param index1 other end of the interval
+     */
+    void setSelectionInterval(int index0, int index1);
+
+    /**
+     * Changes the selection to be the set union of the current selection
+     * and the indices between {@code index0} and {@code index1} inclusive.
+     *
+     * @param index0 one end of the interval.
+     * @param index1 other end of the interval
+     */
+    void addSelectionInterval(int index0, int index1);
+
+    /**
+     * Changes the selection to be the set difference of the current selection
+     * and the indices between {@code index0} and {@code index1} inclusive.
+     *
+     * @param index0 one end of the interval.
+     * @param index1 other end of the interval
+     */
+    void removeSelectionInterval(int index0, int index1);
+
+    /**
+     * Returns the first selected index or -1 if the selection is empty.
+     *
+     * @return the first selected index or -1 if the selection is empty.
+     */
+    int getMinSelectionIndex();
+
+    /**
+     * Returns the last selected index or -1 if the selection is empty.
+     *
+     * @return the last selected index or -1 if the selection is empty.
+     */
+    int getMaxSelectionIndex();
+
+
+    /**
+     * Returns true if the specified index is selected.
+     *
+     * @param index an index
+     * @return {@code true} if the specified index is selected
+     */
+    boolean isSelectedIndex(int index);
+
+    /**
+     * Returns true if no indices are selected.
+     *
+     * @return {@code true} if no indices are selected.
+     */
+    boolean isSelectionEmpty();
+
+    /**
+     * Insert {@code length} indices beginning before/after {@code index}. This is typically
+     * called to sync the selection model with a corresponding change
+     * in the data model.
+     *
+     * @param index the beginning of the interval
+     * @param length the length of the interval
+     * @param before if {@code true}, interval inserts before the {@code index},
+     *               otherwise, interval inserts after the {@code index}
+     */
+    void insertIndexInterval(int index, int length, boolean before);
+
+    /**
+     * Remove the indices in the interval {@code index0,index1} (inclusive) from
+     * the selection model. This is typically called to sync the selection
+     * model width a corresponding change in the data model.
+     *
+     * @param index0 the beginning of the interval
+     * @param index1 the end of the interval
+     */
+    void removeIndexInterval(int index0, int index1);
+
+    /**
+     * Sets the selection mode. The following list describes the accepted
+     * selection modes:
+     * <ul>
+     * <li>{@code AccessibleList.SINGLE_SELECTION} -
+     *   Only one list index can be selected at a time. In this mode,
+     *   {@code setSelectionInterval} and {@code addSelectionInterval} are
+     *   equivalent, both replacing the current selection with the index
+     *   represented by the second argument (the "lead").
+     * <li>{@code AccessibleList.SINGLE_INTERVAL_SELECTION} -
+     *   Only one contiguous interval can be selected at a time.
+     *   In this mode, {@code addSelectionInterval} behaves like
+     *   {@code setSelectionInterval} (replacing the current selection),
+     *   unless the given interval is immediately adjacent to or overlaps
+     *   the existing selection, and can therefore be used to grow it.
+     * <li>{@code AccessibleList.MULTIPLE_INTERVAL_SELECTION} -
+     *   In this mode, there's no restriction on what can be selected.
+     * </ul>
+     *
+     * @param selectionMode the selection mode
+     */
+    void setSelectionMode(int selectionMode);
+
+    /**
+     * Returns the current selection mode.
+     *
+     * @return the current selection mode
+     * @see #setSelectionMode
+     */
+    int getSelectionMode();
+
+    /**
+     * Returns an array of all of the selected indices in the selection model,
+     * in increasing order.
+     *
+     * @return all of the selected indices, in increasing order,
+     *         or an empty array if nothing is selected
+     */
+    int[] getSelectedIndices();
+
+    /**
+     * Returns the number of selected items.
+     *
+     * @return the number of selected items, 0 if no items are selected
+     */
+    int getSelectedItemsCount();
+}