- I am not sure you can assume the LOWORD value is non-negative.
It seems to me that the 0XFFFF we got back is meant to be
interpreted as "-1"
which is what I wrote below.
I do note that it appears that in issue #2 you are seeing that up to
65534 items
may be allowed and it wraps if you add more than 65535 ..
So *perhaps* we can interpret 0xFFFF as meaning positive 65535 but I
think
*only* if HIWORD is "0".
- Issue #1 : I am not sure that a "1" in HIWORD automatically means it
is off the
end of the list ... just "outside the client area". I think if HIWORD is
1 we just
bail don't we ?
Then you don't have to worry about whether 0xFFFF meant -1 or 65536
- Issue #2 : There is always *some* limit in cases like this. 32767
(2^15-1) or 65535 (2^16-1)
are very typical in these platform APIs. Often the platform doesn't
explicitly document it
and you have to infer it from the data type. I think it was all very
moot when these APIs
were designed because you'd run out of memory before you could get that
many items :-)
I'd be surprised if there were not already some open bug pointing out
that we accept "int"
for index and don't have any feedback when exceeding platform limits.
From a compatibility point of view, I don't think it is worth doing
anything that would
break ancient applications to provide that feedback.
-phil.
On 11/2/18, 10:23 AM, Ambarish Rapte wrote:
Hi Phil,
Thanks for guiding with the documentation.
The fix is modified after a relook at the documentation, and
observed two issues [mentioned below].
webrev: http://cr.openjdk.java.net/~arapte/8198000/webrev.02
<http://cr.openjdk.java.net/%7Earapte/8198000/webrev.02>
Fix Justification:
LB_ITEMFROMPOINT
documentation(https://docs.microsoft.com/en-us/windows/desktop/controls/lb-itemfrompoint):
1. Message LB_ITEMFROMPOINT returns a LONG value.
2. There is no mention of LB_ERR as return value, like it is
mentioned clearly for some of the other messages as LB_GETCOUNT,
LB_SETITEMHEIGHT, LB_GETTEXT, LB_GETCURSEL.
* So the existing comparison against LB_ERR is incorrect.
3. The two parts LOWORD and HIWORD of return value are of type
WORD(unsigned short), so the return value can never be negative.
* It is another reason to not to compare the returned index
value with LB_ERR which is defined as (-1).
Fix:
Extract the index from LOWORD into a WORD variable and verify only
if the index is smaller than the list size. (webrev.02)
This fixes both JDK-8198000 & below mentioned Issue 1.
2 other Issues:
Issue 1: NON selection of an item.
1. Currently the returned LONG value is used without extracting the
LOWORD.
2. As far as the HIWORD is 0, the LONG return value would be same as
index of item(LOWORD).
3. But when HIWORD is 1, the LONG return value would be a large
unexpected value. If it is used as an index, then it would result
in NON selection of the item.
4. Test program:
http://cr.openjdk.java.net/~arapte/8198000/ListSize3.java
<http://cr.openjdk.java.net/%7Earapte/8198000/ListSize3.java>
5. Steps:
1. Compile and execute the test program with release build JDK.
2. Click in the list's client area below the last item, i.e. do
not click on any item.
6. Expected behavior: Last item should get selected.
7. Actual behavior: Last item does not get selected on first click.
But the focused item gets selected after few clicks.
Issue 2: Incorrect selection when list size exceeds sizeof(WORD)
[0xFFFF].
Steps:
1. Compile and execute the program with release build JDK (with or
without the fix) :
http://cr.openjdk.java.net/~arapte/8198000/List65544.java
<http://cr.openjdk.java.net/%7Earapte/8198000/List65544.java>
2. Click the first item in list, press End key.
3. Click the last item 65544.
4. Expected behavior: The item 65544 should get selected.
5. Actual behavior: The item 65544 does not get selected and instead
item 8 gets selected.
6. Verified only windows behavior.
7. I suggest to file a new JBS for this issue.
Regards,
Ambarish
*From:*Phil Race
*Sent:* Thursday, November 01, 2018 1:51 AM
*To:* Ambarish Rapte <ambarish.ra...@oracle.com>; awt-dev@openjdk.java.net
*Subject:* Re: <AWT Dev> [12] RFR : JDK-8198000 :
java/awt/List/EmptyListEventTest/EmptyListEventTest.java debug assert
on Windows
That adds what I suggested, but I had also suggested you leave in what you
had added as it also adds some protection.
Additionally I read the MS docs and they do explain the 131071 return
value.
The message this code is sending is LB_ITEMFROMPOINT and the docs say
here
https://docs.microsoft.com/en-us/windows/desktop/controls/lb-itemfrompoint
that
>The return value contains the index of the nearest item in the
*LOWORD*
<https://msdn.microsoft.com/library/windows/desktop/ms632659>. The
*HIWORD* <https://msdn.microsoft.com/library/windows/desktop/ms632657>
is zero if the > specified point is in the client area of the list
box, or one if it is outside the client area"
You got 131071 which is, in hex 0X1FFFF.
So you got "1" for hi-word, meaning "outside client area" and "-1" for
loword,
meaning the index. And a return index of "-1" doubtless means an error ..
-phil.
On 10/31/18 12:49 PM, Ambarish Rapte wrote:
Hi Phil & Sergey,
This issue was introduced with the fix for JDK-6806217
<https://bugs.openjdk.java.net/browse/JDK-6806217>, in 7b55, which
modified AwtList::HandleEvent(), so It was not observed with JDK6.
Please review the updated change as discussed
offline: http://cr.openjdk.java.net/~arapte/8198000/webrev.01/
<http://cr.openjdk.java.net/%7Earapte/8198000/webrev.01/>
Regards,
Ambarish
*From:*Phil Race
*Sent:* Tuesday, October 30, 2018 2:09 AM
*To:* Ambarish Rapte <ambarish.ra...@oracle.com>
<mailto:ambarish.ra...@oracle.com>; awt-dev@openjdk.java.net
<mailto:awt-dev@openjdk.java.net>
*Subject:* Re: <AWT Dev> [12] RFR : JDK-8198000 :
java/awt/List/EmptyListEventTest/EmptyListEventTest.java debug
assert on Windows
On 10/29/18 7:31 AM, Ambarish Rapte wrote:
Hi,
Please review this Windows only fix,
JBS:
https://bugs.openjdk.java.net/browse/JDK-8198000
Webrev:
http://cr.openjdk.java.net/~arapte/8198000/webrev.00/
<http://cr.openjdk.java.net/%7Earapte/8198000/webrev.00/>
Issue:
1. Test asserts with debug build jdk, only on windows.
Only the debug build turns on asserts.
But I think JDK 6 always turned on asserts, and this test was
introduced in 6,
so something must have changed else we'd have seen this test fail
a long time ago.
Can you identify what it was ?
Also same comment as the other bug - you need to add the bug id to
the test.
2.
3. Assert at Line no 77, awt_List.h :: IsItemSelected()
4. awt_List.cpp :: AwtList::HandleEvent() calls
IsItemSelected() with an incorrect index value.
Why ?
5.
6. In AwtList::HandleEvent() , the call
SendListMessage(LB_ITEMFROMPOINT, 0, msg->lParam) returns
an arbitrary value 131071, which gets passed to
IsItemSelected().
7. Could not find any relevance to the value 131071, from
LB_ITEMFROMPOINT doc.
That is (128*1024)-1, so it is probably not "arbitrary".
Please add the eval above to the bug report .. once we have a
complete understanding.
-phil.
8.
Fix: Index should be verified before making call to
IsItemSelected() :
http://cr.openjdk.java.net/~arapte/8198000/webrev.00/
<http://cr.openjdk.java.net/%7Earapte/8198000/webrev.00/>
Verification: All list tests pass.
Regards,
Ambarish
