RFR: 8159048: Null PulseReciever in AbstractMasterTimer

[Kevin Rushforth]

On Mon, 3 Jul 2023 15:49:31 GMT, Jose Pereda <jpereda at openjdk.org> wrote:

> This PR adds a check to the Animation and AnimationTimer public methods to verify that these are called from the JavaFX Application thread. If the call is done from any other thread, an IllegalStateException will be thrown.
> 
> This will prevent users from getting unexpected errors (typically NPE, like the one posted in the JBS issue), and will fail fast with a clear exception and reason for it.
> 
> The javadoc of the Animation and AnimationTimer classes and public methods has been updated accordingly.
> 
> Tests for both classes have been included, failing (as in no exceptions were thrown when calling from a background thread) before this patch, and passing (as in ISE was thrown).

@jperedadnr In case you missed it, this PR is not `rfr` due to white space errors.

At first glance, this looks like a good fix. Since this enforces a new threading restriction on existing animation methods, it will need a CSR.

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PR Comment: https://git.openjdk.org/jfx/pull/1167#issuecomment-1656735642
PR Comment: https://git.openjdk.org/jfx/pull/1167#issuecomment-1656736296