Rename 'defineMask' to 'newMask'. Add inverted mask (issue #226).

src/modules/graphics/opengl/Graphics.cpp

@@ -437,9 +437,9 @@ namespace opengl
 		glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
 	}
 
-	void Graphics::useMask()
+	void Graphics::useMask(bool invert)
 	{
-		glStencilFunc(GL_EQUAL, 1, 1);
+		glStencilFunc(GL_EQUAL, (int)(!invert), 1); // invert ? 0 : 1
 		glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
 		glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
 	}

src/modules/graphics/opengl/Graphics.h

@@ -242,8 +242,10 @@ namespace opengl
 		/**
 		 * Set stencil function to mask the following drawing calls using
 		 * the current stencil buffer
+		 * @param invert Invert the mask, i.e. draw everywhere expect where
+		 *               the mask is defined.
 		 */
-		void useMask();
+		void useMask(bool invert = false);
 
 		/**
 		 * Disables the stencil buffer

src/modules/graphics/opengl/wrap_Graphics.cpp

@@ -144,7 +144,7 @@ namespace opengl
 		return instance->getScissor(L);
 	}
 
-	int w_defineMask(lua_State * L)
+	int w_newMask(lua_State * L)
 	{
 		// just return the function
 		if (!lua_isfunction(L, 1))
@@ -153,7 +153,7 @@ namespace opengl
 		return 1;
 	}
 
-	int w_setMask(lua_State * L)
+	static int setMask(lua_State * L, bool invert)
 	{
 		// no argument -> clear mask
 		if (lua_isnoneornil(L, 1)) {
@@ -166,11 +166,21 @@ namespace opengl
 
 		instance->defineMask();
 		lua_call(L, lua_gettop(L) - 1, 0); // call mask(...)
-		instance->useMask();
+		instance->useMask(invert);
 
 		return 0;
 	}
 
+	int w_setMask(lua_State * L)
+	{
+		return setMask(L, false);
+	}
+
+	int w_setInvertedMask(lua_State * L)
+	{
+		return setMask(L, true);
+	}
+
 	int w_newImage(lua_State * L)
 	{
 		// Convert to File, if necessary.
@@ -1047,8 +1057,9 @@ namespace opengl
 		{ "setScissor", w_setScissor },
 		{ "getScissor", w_getScissor },
 
-		{ "defineMask", w_defineMask },
+		{ "newMask", w_newMask },
 		{ "setMask", w_setMask },
+		{ "setInvertedMask", w_setInvertedMask },
 
 		{ "point", w_point },
 		{ "line", w_line },