Larry Clapp reported a panic from failing to start the display link.
Ignore the error and hope the error is transient.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
Recent changes to the macOS threading exposed a problem where a
window's display link may fail to start after being started and stopped
in rapid succession.
Introduce a displayLink type that waits a while after the last stop
request before stopping its display link. That seems to be the way
other projects are using display links.
As a bonus, the new implementation avoids the potentially expensive
overhead of frequent starting and stopping the underlying OS thread.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
pierre