Make lua selection negate return a new selection

... instead of modifying the one given as a parameter.

Also add tests for it.

src/nhlsel.c

@@ -113,6 +113,7 @@ lua_State *L;
     return 1;
 }
 
+/* Replace the topmost selection in the stack with a clone of it. */
 /* local sel = selection.clone(sel); */
 static int
 l_selection_clone(L)
@@ -120,7 +121,6 @@ lua_State *L;
 {
     struct selectionvar *sel = l_selection_check(L, 1);
     struct selectionvar *tmp;
-    /* int x,y; */   /* REVIEW: unreferenced */
     lua_pop(L, 1);
     (void) l_selection_new(L);
     tmp = l_selection_check(L, 1);
@@ -207,17 +207,24 @@ lua_State *L;
 
 /* local s = selection.negate(sel); */
 /* local s = selection.negate(); */
+/* local s = sel:negate(); */
 static int
 l_selection_not(L)
 lua_State *L;
 {
     int argc = lua_gettop(L);
-    struct selectionvar *sel;
+    struct selectionvar *sel, *sel2;
 
-    if (argc == 0)
+    if (argc == 0) {
         (void) l_selection_new(L);
-    sel = l_selection_check(L, 1);
-    selection_not(sel);
+        sel = l_selection_check(L, 1);
+        selection_not(sel);
+    } else {
+        sel = l_selection_check(L, 1);
+        (void) l_selection_clone(L);
+        sel2 = l_selection_check(L, 1);
+        selection_not(sel2);
+    }
     lua_settop(L, 1);
     return 1;
 }

test/test_sel.lua

@@ -1,8 +1,8 @@
 
-
 -- Test the selection
 
-function test_selection()
+-- test selection parameters
+function test_selection_params()
    local sel = selection.new();
 
    -- test set & get
@@ -79,7 +79,28 @@ function test_selection()
 
    local sel2 = selection.clone(sel);
    local sel3 = sel2:clone();
-end -- selection_tests()
+
+end -- test_selection_params
+
+-- test negation
+function test_sel_negate()
+   local sela = selection.negate();
+   local selb = sela:negate();
+
+   for x = 0,nhc.COLNO - 2 do
+      for y = 0,nhc.ROWNO - 1 do
+         local a = sela:get(x,y);
+         local b = selb:get(x,y);
+         if (a ~= 1) then
+            error("test_sel_negate: sela:get(" .. x .. "," .. y .. ")==" .. a);
+         end
+         if (b ~= 0) then
+            error("test_sel_negate: selb:get(" .. x .. "," .. y .. ")==" .. b);
+         end
+      end
+   end
+end -- test_sel_negate
 
 
-test_selection();
+test_selection_params();
+test_sel_negate();