<AWT Dev> [9] Review request for 8046495: KeyEvent can not be accepted in quick mouse clicking

[Petr Pchelko]

Hello, Anton.

Thank you for the cleanup, the new version still looks good to me.

With best regards. Petr.

On 18 июля 2014 г., at 14:28, anton nashatyrev <anton.nashatyrev at oracle.com> wrote:

> Hello, 
> 
>     in offline discussion with Artem and Petr we decided to further clean up the code and completely remove TimeHelper functions from awt_Component.cpp in JDK9. 
> 
>     Could you please review the updated fix: http://cr.openjdk.java.net/~anashaty/8046495/9/webrev.01/
> 
> bug: https://bugs.openjdk.java.net/browse/JDK-8046495
> 
> Thank you!
> Anton.
> 
> On 17.07.2014 13:14, anton nashatyrev wrote:
>> Hello All, 
>> 
>>     could please anyone else take a look at the fix? 
>> 
>> Thanks!
>> Anton.
>> 
>> On 02.07.2014 19:37, Petr Pchelko wrote:
>>> Hello, Anton.
>>> 
>>> Thanks for clarifications and additional testing.
>>> The fix looks good to me too.
>>> 
>>> With best regards. Petr.
>>> 
>>> On 02 июля 2014 г., at 19:34, Anton V. Tarasov <anton.tarasov at oracle.com> wrote:
>>> 
>>>> On 02.07.2014 19:28, anton nashatyrev wrote:
>>>>> Hello, Anton
>>>>> 
>>>>> On 02.07.2014 18:13, Anton V. Tarasov wrote:
>>>>>> On 02.07.2014 11:44, Petr Pchelko wrote:
>>>>>>> Hello, Anton.
>>>>>>> 
>>>>>>> I'm not sure I have a detailed understanding of what's happening. 
>>>>>>> 
>>>>>>> Before your fix the timestamp of the event represented the time when the event was created, and now it's the time when it's sent to java.
>>>>>>> This might be important if some events cause other events to be issued on the java side. 
>>>>>>> 
>>>>>>> So suppose the following:
>>>>>>> Toolkit thread: InputEvent#1 created      - timestamp 0
>>>>>>> Toolkit thread: InputEvent#2 created      - timestamp 1
>>>>>>> Toolkit thread: InputEvent#1 sent           - timestamp 2
>>>>>>> EDT:                InputEvent#1 dispatched - timestamp 3
>>>>>>> EDT:               FocusEvent  created        - timestamp 4
>>>>>>> Toolkit thread: InputEvent#2 sent           - timestamp 5
>>>>>>> 
>>>>>>> Before you fix we had the following event order: InputEvent#1(ts=0), InputEvent#2(ts=1), FocusEvent(ts=4).
>>>>>>> But after your fix we will have a different order: InputEvent#1(ts=2), FocusEvent(ts=4), InputEvent#2(ts=5).
>>>>>>> So now we would have troubles, because the Input Event will go to the new focused component instead of the old one. 
>>>>>>> Do you think that my arguments are correct? I understand that the likelihood of such a situation is very low, but for me it looks possible? Am I missing something?
>>>>>> 
>>>>>> A timestamp for a FocusEvent is taken from the_most_recent_KeyEvent_time which is set on EDT when the event is dispatched. So the fix shouldn't affect it.
>>>>>> 
>>>>>> Also, in awt_Window.cpp, when a TimedWindowEvent is created it is passed a timestamp got with TimeHelper::getMessageTimeUTC(). It appears, that the fix makes key events times even more consistent with it. So, from the kbd focus perspective, it shouldn't make any harm.
>>>>>> 
>>>>>> Anton, could you just please run the following tests, at least:
>>>>>> 
>>>>>> test/java/awt/Focus/6981400/*
>>>>>> test/java/awt/KeyboardFocusManager/TypeAhead/*
>>>>> 
>>>>> I've tested with the following set: 
>>>>> [closed]/java/awt/event/* 
>>>>> [closed]/java/awt/Focus/* 
>>>>> [closed]java/awt/KeyboardFocusManager/*
>>>>> 
>>>>> : no unexpected failures here.
>>>>> 
>>>>> I've also verified that my regression test which comes with the fix works fine on Linux and Mac (despite the fix is Win specific). 
>>>> 
>>>> Great, thanks!
>>>> 
>>>> Anton.
>>>> 
>>>>> 
>>>>> Thanks for review!
>>>>> Anton.
>>>>> 
>>>>>> 
>>>>>> Thanks,
>>>>>> Anton.
>>>>>> 
>>>>>>> 
>>>>>>> Another thing I do not understand is why we were used to use the complicated formula instead of initializing the msg.time field with the JVM current time and using it when sending the event?
>>>>>>> Wouldn't that resolve both your issue and the issue the original fix was made for?
>>>>>>> 
>>>>>>> I have a couple of comments about the code, but let's postpone that until we decide on the approach.
>>>>>>> 
>>>>>>> Thank you.
>>>>>>> With best regards. Petr.
>>>>>>> 
>>>>>>> On 01 июля 2014 г., at 21:20, anton nashatyrev <anton.nashatyrev at oracle.com> wrote:
>>>>>>> 
>>>>>>>> Hello, 
>>>>>>>>     could you please review the following fix:
>>>>>>>> 
>>>>>>>> fix: http://cr.openjdk.java.net/~anashaty/8046495/9/webrev.00/
>>>>>>>> bug: https://bugs.openjdk.java.net/browse/JDK-8046495
>>>>>>>> 
>>>>>>>>     Problem: 
>>>>>>>> On Windows the later InputEvent may have earlier timestamp (getWhen()), which results in incorrect processing of enqueued input events and may also potentially be the reason of other artifacts 
>>>>>>>> 
>>>>>>>>     Evaluation: 
>>>>>>>> On Windows we have some algorithm for calculating input event timestamp: jdk/src/windows/native/sun/windows/awt_Component.cpp:2100
>>>>>>>> Shortly the timestamp is calculated by the following formula: 
>>>>>>>>     when = JVM_CurrentTimeMillis() - (GetTickCount() - GetMessageTime())
>>>>>>>> 
>>>>>>>> Where: 
>>>>>>>>   JVM_CurrentTimeMillis() - the same as System.currentTimeMillis()
>>>>>>>>   GetTickCount() - Win32 function, current millis from boot time
>>>>>>>>   GetMessageTime() - Win32 function, millis from boot time of the latest native Message
>>>>>>>> 
>>>>>>>> In theory the formula looks good: we are trying our best to calculate the actual time of the OS message by taking the current JVM time (JVM_CurrentTimeMillis) and adjusting it with the offset (GetTickCount - GetMessageTime) which should indicate how many milliseconds ago from the current moment (GetTickCount) the message has been actually issued (GetMessageTime).
>>>>>>>> In practice due to usage of different system timers by the JVM_CurrentTimeMillis and GetTickCount their values are not updated synchronously and we may get an earlier timestamp for the later event. 
>>>>>>>> 
>>>>>>>>     Fix: 
>>>>>>>> Just to use JVM_CurrentTimeMillis only as events timestamp. On Mac this is done in exactly the same way: CPlatformResponder.handleMouse/KeyEvent()
>>>>>>>> 
>>>>>>>> The message time offset calculation has been introduced with the fix for JDK-4434193 and it seems that the issue has addressed very similar problem (At times getWhen()in ActionEvent returns higher value than the CurrentSystemTime) which has not been completely resolved in fact.
>>>>>>>> I also didn't find any benefits in using the existing approach: 
>>>>>>>> - all the usages of the TimerHelper are in fact reduced to the mentioned formula: when = JVM_CurrentTimeMillis() - (GetTickCount() - GetMessageTime())
>>>>>>>> - GetMessageTime() always increases (except of the int overflow moments), thus we couldn't get earlier OS messages after later ones
>>>>>>>> - TimerHelper::windowsToUTC(DWORD windowsTime) doesn't guarantee returning the same timestamp across different calls for the same message time 
>>>>>>>> 
>>>>>>>> Thanks! 
>>>>>>>> Anton. 
>>>>>>> 
>>>>>> 
>>>>> 
>>>> 
>>> 
>> 
> 

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