retry method
Explicitly retries a failed resource. Successful or active loads are left intact; repainting alone never causes an automatic retry loop.
Implementation
bool retry(DiagramImageSource source) {
if (_disposed) throw StateError('Image cache is disposed.');
if (!_failed.remove(source.uri)) return false;
_errors.remove(source.uri);
imageFor(source);
_changed(source.uri);
return true;
}