<Swing Dev> Unexpected NullPointerException by endComposition()
Charles Lee
littlee at linux.vnet.ibm.com
Thu Nov 10 01:16:14 UTC 2011
On 11/10/2011 02:37 AM, Pavel Porvatov wrote:
> Hi Charles,
>
> The fix looks good, but the test should use EDT in the main method
> because Swing components are used. Don't worry about that, I'll fix it
> and commit the fix soon
>
> Thanks, Pavel
>> On 11/03/2011 10:41 PM, Pavel Porvatov wrote:
>>> Hi Charles,
>>>> On 10/27/2011 09:12 PM, Pavel Porvatov wrote:
>>>>> Hi Charles,
>>>>>> On 10/14/2011 04:06 PM, Pavel Porvatov wrote:
>>>>>>> Hi Charles,
>>>>>>>> On 10/11/2011 05:50 PM, Pavel Porvatov wrote:
>>>>>>>>> Hi Charles,
>>>>>>>>>> On 10/08/2011 05:41 PM, Pavel Porvatov wrote:
>>>>>>>>>> I got your point. What about this solution:
>>>>>>>>>> If in the compose mode, endCompositoin just sendComposedText
>>>>>>>>>> instead of sendCommittedText.
>>>>>>>>>>
>>>>>>>>>> The patch is attached
>>>>>>>>>>
>>>>>>>>> Could you please explain the fix? May be it removes NPE but it
>>>>>>>>> puzzles me. So if buffer.length() == 0 you invoke
>>>>>>>>> sendCommittedText, right? But sendCommittedText commits
>>>>>>>>> buffer, but buffer is empty. Looks strange...
>>>>>>>>>
>>>>>>>>> BTW: the code like "if (!notInCompositionMode) {" a little bit
>>>>>>>>> difficult to understand =) I'd preffer to avoid two negations
>>>>>>>>> and use "if (notInCompositionMode)" and swap if/else blocks...
>>>>>>>>>
>>>>>>>>> Regards, Pavel
>>>>>>>>>
>>>>>>>> Hi Pavel,
>>>>>>>>
>>>>>>>> Sorry for the confusion. Here is some explanation, please
>>>>>>>> correct me if I am wrong:
>>>>>>>> 1. There two modes which is judge from the buffer size:
>>>>>>>> composed mode when the buffer size is not zero and normal mode
>>>>>>>> when the buffer size is zero.
>>>>>>> Right
>>>>>>>> 2. The original code make no difference whether it is in the
>>>>>>>> composed mode or normal mode. In the normal mode, which buffer
>>>>>>>> size is zero, it sends the committed text. In the composed
>>>>>>>> mode, which buffer size is not zero, it also sends the
>>>>>>>> committed code. And NPE occurred here.
>>>>>>>> 3. In the patch, I do not change the logic when in the normal
>>>>>>>> mode. (notInCompositionMode branch) Why? I guess it is the
>>>>>>>> logic of "Ends any input composition that may currently be
>>>>>>>> going on in this context. Depending on the platform and
>>>>>>>> possibly user preferences, this may commit or delete
>>>>>>>> uncommitted text." from the api spec....
>>>>>>> Yes. But after your change the following code looks strange for me:
>>>>>>> if (!notInCompositionMode) {
>>>>>>> ....
>>>>>>> } else {
>>>>>>> >>>> sendCommittedText();
>>>>>>> }
>>>>>>> So if we are not in composition mode we send something (empty
>>>>>>> string actually). Logically we shouldn't send anything (IMO),
>>>>>>> because buffer is empty. Why should we do something at all if
>>>>>>> endComposition is invoked and we are not in composition mode?
>>>>>>>> 4. In the patch, the logic in the composed mode is that: if it
>>>>>>>> is in the composed mode, keep every thing as just composed :-)
>>>>>>>
>>>>>>> I found a new bug (???) in the fix. If you apply the patch, run
>>>>>>> the MouseEventTest2 test and follow the instructions from the
>>>>>>> bug description NPE will not be thrown, but the JTextArea
>>>>>>> remains in composition mode even after endComposition completion.
>>>>>>
>>>>>> Right. It seems that we have to do some thing in the jdk :-).
>>>>>> Here it is:
>>>>>>
>>>>>> The patch attached is just adding a null check at the beginning
>>>>>> of the mouseClicked method in DefaultCaret. So why the component
>>>>>> is null in the DefaultCaret? That because the caret has already
>>>>>> been deinstalled. It seems to be an order problem of mouse event
>>>>>> and the event which endCompositon sent. The endComposition will
>>>>>> exchange the caret and deinstall the old one. On the other hand,
>>>>>> mouse click event was happening on the old caret. So the
>>>>>> component of the old caret is null now. NPE happens.
>>>>> It looks that you are trying to fix the consequence, but not the
>>>>> root of the problem. The endComposition method shouldn't send
>>>>> anything to deinstalled DefaultCaret. I think the previous version
>>>>> of the fix was much closer than this one.
>>>>>
>>>>> Regards, Pavel
>>>> Hi Pavel,
>>>>
>>>> The problem is how should we deal with the uncommitted compose
>>>> character when endComposition.
>>>> 1. Remain the character. Not good, will remain in compose mode
>>>> after endComposition.
>>>> 2. Delete the character. I think it just like the
>>>> cancelComposition. We have to send some thing to delete the
>>>> characters which are already shown on the text area.
>>>>
>>>> Here is a new patch which add a little bit logic in the
>>>> endComposition method:
>>>> 1. It still remain the null check in the mouseClick
>>>> 2. It use cancelCompostion in the endComposition when in the
>>>> compose mode.
>>>>
>>>> Any idea?
>>>
>>> I deeply analyzed the problem and found out that I agree with your
>>> last fix *without* changing in the CodePointInputMethod.java class
>>> (you sent such version on 10/19/2011). I answered on that mail "It
>>> looks that you are trying to fix the consequence, but not the root
>>> of the problem. The endComposition method shouldn't send anything to
>>> deinstalled DefaultCaret." Actually we shouldn't send anything to
>>> deinstalled DefaultCaret and I found code that removes listener of
>>> deinstalled DefaultCaret. But at the same time deinstalled
>>> DefaultCaret gets mouseClick notification because AWT makes copy of
>>> all listeners before notifications. Unfortunately we can't change
>>> such functionality and the best and simplest way to fix the problem
>>> is to skip mouseClicked notification for deinstalled carets.
>>>
>>> Could you please write an automatic test, please?
>>>
>>> BTW: I didn't catch "problem is how should we deal with the
>>> uncommitted compose character when endComposition". Current
>>> implementation works fine, IMO: it commits entered characters and
>>> ends composition.
>>>
>>> Regards, Pavel
>> Hi Pavel,
>>
>> />>> "problem is how should we deal with the uncommitted compose
>> character when endComposition"/
>> I am talking about what user will when the endComposition calls. To
>> me, it is more reasonable when the uncommitted character go away if
>> the composition is not complete :-). That's the reason I am using
>> cancelComposition. Thanks for pointing out the AWT copy things. Would
>> you like to point me where it is? It is kind of hard to debug in the
>> awt/swing code :-P
>>
>> Below is the patch and simple test case (attached):
>>
>> --
>> Yours Charles
That's great. Thanks a lot, Pavel.
--
Yours Charles
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