Add possibility to iterate over all selected items in wxSelectionStore.

This is necessary for retrieving all the selected items at once: while doing
this is not recommended for a control with a potentially very large number of
items, it must be possible to allow using wxSelectionStore for wxDataViewCtrl
implementation as wxDataViewCtrl must implement its GetSelections() method.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77902 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/selstore.h

@@ -78,6 +78,19 @@ public:
                               : m_itemsSel.GetCount();
     }
 
+    // type of a "cookie" used to preserve the iteration state, this is an
+    // opaque type, don't rely on its current representation
+    typedef size_t IterationState;
+
+    // constant representing absence of selection and hence end of iteration
+    static const unsigned NO_SELECTION = static_cast<unsigned>(-1);
+
+    // get the first selected item in index order, return NO_SELECTION if none
+    unsigned GetFirstSelectedItem(IterationState& cookie) const;
+
+    // get the next selected item, return NO_SELECTION if no more
+    unsigned GetNextSelectedItem(IterationState& cookie) const;
+
 private:
     // (re)init
     void Init() { m_count = 0; m_defaultState = false; }

src/generic/selstore.cpp

@@ -229,3 +229,42 @@ void wxSelectionStore::SetItemCount(unsigned count)
     // remember the new number of items
     m_count = count;
 }
+
+// ----------------------------------------------------------------------------
+// Iteration
+// ----------------------------------------------------------------------------
+
+unsigned wxSelectionStore::GetFirstSelectedItem(IterationState& cookie) const
+{
+    cookie = 0;
+
+    return GetNextSelectedItem(cookie);
+}
+
+unsigned wxSelectionStore::GetNextSelectedItem(IterationState& cookie) const
+{
+    if ( m_defaultState )
+    {
+        // We have no choice but to iterate over all items in this case. It
+        // shouldn't be that bad in practice because (almost) all items are
+        // supposed to be selected if m_defaultState == true anyhow.
+        for ( unsigned item = cookie; ; item++ )
+        {
+            if ( item >= m_count )
+                return NO_SELECTION;
+
+            if ( IsSelected(item) )
+            {
+                cookie = item + 1;
+                return item;
+            }
+        }
+    }
+    else // Simple case when we directly have the selected items.
+    {
+        if ( cookie >= m_itemsSel.size() )
+            return NO_SELECTION;
+
+        return m_itemsSel[cookie++];
+    }
+}

tests/misc/selstoretest.cpp

@@ -45,12 +45,14 @@ private:
         CPPUNIT_TEST( SelectRange );
         CPPUNIT_TEST( SetItemCount );
         CPPUNIT_TEST( Clear );
+        CPPUNIT_TEST( Iterate );
     CPPUNIT_TEST_SUITE_END();
 
     void SelectItem();
     void SelectRange();
     void SetItemCount();
     void Clear();
+    void Iterate();
 
     // NB: must be even
     static const unsigned NUM_ITEMS;
@@ -131,3 +133,19 @@ void SelStoreTestCase::Clear()
     CPPUNIT_ASSERT_EQUAL( 0u, m_store->GetSelectedCount() );
 }
 
+void SelStoreTestCase::Iterate()
+{
+    m_store->SelectRange(NUM_ITEMS/2 - 1, NUM_ITEMS/2 + 1);
+
+    wxSelectionStore::IterationState cookie;
+    CPPUNIT_ASSERT_EQUAL(NUM_ITEMS/2 - 1, m_store->GetFirstSelectedItem(cookie));
+    CPPUNIT_ASSERT_EQUAL(NUM_ITEMS/2, m_store->GetNextSelectedItem(cookie));
+    CPPUNIT_ASSERT_EQUAL(NUM_ITEMS/2 + 1, m_store->GetNextSelectedItem(cookie));
+
+    CPPUNIT_ASSERT_EQUAL(wxSelectionStore::NO_SELECTION, m_store->GetNextSelectedItem(cookie));
+
+
+    m_store->SelectRange(0, NUM_ITEMS - 1);
+    m_store->SelectItem(0, false);
+    CPPUNIT_ASSERT_EQUAL(1, m_store->GetFirstSelectedItem(cookie));
+}