Framed glasslike: Fix and document top/base textures feature (minetes…

…t#7824)

doc/lua_api.txt

@@ -1082,6 +1082,11 @@ Look for examples in `games/minimal` or `games/minetest_game`.
       size: 1 pixel for 16x16, 2 pixels for 32x32 etc.
     * The glass 'shine' (or other desired detail) on each node face is supplied
       by the second texture specified in `tiles`.
+    * If a third texture is specified in `tiles` it will be used for the top and
+      base of the glass volume.
+    * If third and fourth textures are specified in `tiles`, the third will be
+      used for the top of the glass volume and the fourth will be used for the
+      base of the glass volume.
 * `glasslike_framed_optional`
     * This switches between the above 2 drawtypes according to the menu setting
       'Connected Glass'.

src/content_mapblock.cpp

@@ -702,7 +702,7 @@ void MapblockMeshGenerator::drawGlasslikeFramedNode()
 			tiles[2].layers[0].texture &&
 			tiles[3].layers[0].texture) {
 		glass_tiles[0] = tiles[4];
-		glass_tiles[1] = tiles[0];
+		glass_tiles[1] = tiles[2];
 		glass_tiles[2] = tiles[4];
 		glass_tiles[3] = tiles[4];
 		glass_tiles[4] = tiles[3];