Revert "background grid"

This reverts commit 1dd3fdfba3.

src/map/source.cpp

@@ -57,19 +57,6 @@ size_t Source::getTileCount() const {
     return tiles.size();
 }
 
-bool Source::viewportTileParsed() {
-    bool parsed = false;
-
-    for (auto &pair : tiles) {
-        Tile::ID id = pair.first;
-        if (hasTile(id) == TileData::State::parsed) {
-            parsed = true;
-        }
-    }
-
-    return parsed;
-}
-
 void Source::drawClippingMasks() {
     for (std::pair<const Tile::ID, std::unique_ptr<Tile>> &pair : tiles) {
         Tile &tile = *pair.second;