reload method
Reads path again — a material file, or a map one uses — after it
changed on disk. What it was is drawn until it arrives.
Implementation
void reload(String path) {
final source = _sources[path];
if (source != null) _load(path, source);
for (final srgb in const [true, false]) {
if (_textures.remove((path, srgb)) != null) _textureChanged(path);
}
}