| Events are FIDL calls initiated from the server. Because these calls have no |
| built-in client-side response, they are not flow controlled: a server could |
| queue up a very large number of such calls, and flood the client. One solution |
| to this problem is the *throttled event pattern*. This pattern involves adding a |
| client-called FIDL method to serve as an acknowledgement point for one or more |
| events to sync to. |
| |
| Servers should refrain from sending more of the throttled events (the exact |
| semantics here are specific to the implementing protocol) until they have |
| received the next acknowledgement call from the client. Similarly, clients |
| should close the connection the if servers send more throttled events than |
| allowed before the client has acknowledged them. These restrictions are not |
| built into the FIDL runtime, and require some manual implementation on the part |
| of client/server implementers to ensure correct behavior. |
| |
| <<../examples/canvas/_callout.md>> |
| <<../examples/canvas/_client_requested_draw_tutorial.md>> |
