Fixes to the handling of LBS_EXTENDEDSEL style, with tests.

dlls/user/listbox.c

@@ -2010,11 +2010,16 @@ static LRESULT LISTBOX_HandleLButtonDown( LB_DESCR *descr, DWORD keys, INT x, IN
         {
             LISTBOX_MoveCaret( descr, index, FALSE );
 
-            if (descr->style & LBS_MULTIPLESEL)
+            if (descr->style & LBS_EXTENDEDSEL)
+            {
+                LISTBOX_SetSelection( descr, index,
+                               descr->items[index].selected,
+                              (descr->style & LBS_NOTIFY) != 0 );
+            }
+            else
             {
                 LISTBOX_SetSelection( descr, index,
-                              (!(descr->style & LBS_MULTIPLESEL) ||
-                               !descr->items[index].selected),
+                               !descr->items[index].selected,
                               (descr->style & LBS_NOTIFY) != 0 );
             }
         }

dlls/user/tests/listbox.c

@@ -181,6 +181,26 @@ START_TEST(listbox)
      {LB_ERR, LB_ERR,      0, LB_ERR}, {0,0,0,0},
      {     1,      1,      1, LB_ERR}, {0,0,0,0},
      {     2,      2,      2, LB_ERR}, {0,0,0,0}};
+  const struct listbox_test ES =
+    {{LBS_EXTENDEDSEL},
+     {     0, LB_ERR,      0,      0}, {0,0,0,0},
+     {     1,      1,      1,      1}, {0,0,0,0},
+     {     2,      2,      2,      1}, {0,0,0,0}};
+  const struct listbox_test ES_NS =
+    {{LBS_EXTENDEDSEL | LBS_NOSEL},
+     {LB_ERR, LB_ERR,      0, LB_ERR}, {0,0,0,0},
+     {     1,      1,      1, LB_ERR}, {0,0,0,0},
+     {     2,      2,      2, LB_ERR}, {0,0,0,0}};
+  const struct listbox_test EMS =
+    {{LBS_EXTENDEDSEL | LBS_MULTIPLESEL},
+     {     0, LB_ERR,      0,      0}, {0,0,0,0},
+     {     1,      1,      1,      1}, {0,0,0,0},
+     {     2,      2,      2,      1}, {0,0,0,0}};
+  const struct listbox_test EMS_NS =
+    {{LBS_EXTENDEDSEL | LBS_MULTIPLESEL | LBS_NOSEL},
+     {LB_ERR, LB_ERR,      0, LB_ERR}, {0,0,0,0},
+     {     1,      1,      1, LB_ERR}, {0,0,0,0},
+     {     2,      2,      2, LB_ERR}, {0,0,0,0}};
 
   trace (" Testing single selection...\n");
   check (SS);
@@ -190,6 +210,14 @@ START_TEST(listbox)
   check (MS);
   trace (" ... with NOSEL\n");
   check (MS_NS);
+  trace (" Testing extended selection...\n");
+  check (ES);
+  trace (" ... with NOSEL\n");
+  check (ES_NS);
+  trace (" Testing extended and multiple selection...\n");
+  check (EMS);
+  trace (" ... with NOSEL\n");
+  check (EMS_NS);
 
   check_item_height();
 }