On Thu, 26 Nov 2020 04:52:17 GMT, Sergey Bylokhov <s...@openjdk.org> wrote:
>> Here is a fix for one of the annoying bug, which causes random test failures
>> in the CI.
>>
>> We have a method Robot.waitForIdle(), which supposed to wait until the java
>> and the native queue stabilized. The common use case is to click on the
>> button or show the window, and call waitForIdle() which will wait until the
>> native event will be dispatched by the X11/Windows/macOS as well as followed
>> Java event(paint/focus/etc event) will be dispatched to the EDT.
>>
>> Currently, it is implemented in this way:
>> 1. Flush the EventQueue, so all old events will be posted to EDT.
>> 2. Flush the native event queue, by posting the native event.
>> 3. Flush the EDT, by posting a java event.
>> 4. If some events(unrelated to waitForIdle machinery) were dispatched on
>> steps 2. or 3. then repeat since step 1.
>>
>> It is implemented that they because the native events caused by the OS
>> usually generate the java events, and the java events may generate native
>> events. So we have to wait for both queues (java/native).
>>
>> But it has the next disadvantages:
>> - It is implemented as a busy loop, which does not give a chance for the
>> application to proceed further since it blocks 3 threads EDT/native toolkit
>> thread like appkit/main thread.
>> - It throws the InfiniteLoop exception if the number of attempts is bigger
>> than 20. And this limitation is too small because some tests generate much
>> more events during startup.
>> - Note that the timeout value for the realSync method is 10 seconds, and it
>> was assumed that this method will not be executed longer, but it uses this
>> timeout for all events flushing which can lead up to 600 seconds (20 iters *
>> 3 calls * 10 seconds).
>>
>>
>> The fix:
>> - Add a small delay to the method, so the app can do something useful when
>> waitForIdle() is called
>> - The timeout=10 second is taken care of, we calculate the "end" time and
>> exits if it is exceeded
>> - The maximum number of attempts is increased to 100 and InfiniteLoop is
>> removed.
>>
>> Note that I have made one additional change to the new realSync
>> implementation. At the beginning of the method I call:
>> EventQueue.invokeAndWait(() -> {/*dummy implementation*/});
>> It is needed to be sure that we flush the first event on EDT even if we
>> spend more time than 10 seconds.
>
> Sergey Bylokhov has updated the pull request incrementally with one
> additional commit since the last revision:
>
> Update test/jdk/java/awt/Robot/InfiniteLoopException.java
Marked as reviewed by kizune (Reviewer).
-------------
PR: https://git.openjdk.java.net/jdk/pull/1424
