Bug Report Q370950

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An AV occasionally occurs when modifying Screen.Cursor if the View is currently locked for updates (for instance, via the BeginUpdate/EndUpdate method block)

AG AG

Anton Grabmayr Anton Grabmayr

created 12 years ago (modified 12 years ago)

since 2012.2.2 I run into AV.
Code:

#01 Screen.Cursor := crHourglass;
#02 tvQReZu_Real.BeginUpdate(lsimImmediate);
…
#39 Screen.Cursor := crDefault; --> AV
#40 tvQReZu_Real.EndUpdate;

When I move #39 below #40 it works fine.

Here the detailed bugreport:

exception class : EAccessViolation
exception message : Zugriffsverletzung bei Adresse 008C4137 in Modul 'ZLALGMVW.exe'. Lesen von Adresse 00000000.

main thread ($1018):
008c4137 +023 ZLALGMVW.exe cxGridCustomTableView TcxCustomGridRecordsViewInfo.GetHitTest
0092839f +00b ZLALGMVW.exe cxGridTableView TcxGridRowsViewInfo.GetHitTest
008c4de8 +094 ZLALGMVW.exe cxGridCustomTableView TcxCustomGridTableViewInfo.DoGetHitTest
00928b06 +032 ZLALGMVW.exe cxGridTableView TcxGridTableViewInfo.DoGetHitTest
008f9fcb +093 ZLALGMVW.exe cxGridCustomView TcxCustomGridViewInfo.GetHitTest
008f5871 +035 ZLALGMVW.exe cxGridCustomView TcxCustomGridController.GetCursor
008f725b +023 ZLALGMVW.exe cxGridCustomView TcxGridSite.GetCurrentCursor
006e76ac +044 ZLALGMVW.exe cxControls TcxControl.WMSetCursor
00533535 +2bd ZLALGMVW.exe Vcl.Controls TControl.WndProc
00537e93 +5b3 ZLALGMVW.exe Vcl.Controls TWinControl.WndProc
006e7cbd +151 ZLALGMVW.exe cxControls TcxControl.WndProc
008f78af +023 ZLALGMVW.exe cxGridCustomView TcxGridSite.WndProc
005374e8 +02c ZLALGMVW.exe Vcl.Controls TWinControl.MainWndProc
00498ddc +014 ZLALGMVW.exe System.Classes StdWndProc
77050107 +02b ntdll.dll KiUserCallbackDispatcher
754696c0 +047 USER32.dll SendMessageW
00620fee +086 ZLALGMVW.exe Vcl.Forms TScreen.SetCursor
01f5890c +03c ZLALGMVW.exe FglFrRez__ZuLi 443 +9 TFglFrRez_ZuLi.DspDataLoad

Show previous comments (10) Comments (13)

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

i have the same problem in v2012 vol 2.3 version
Martin

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

Hello Martin,
Thank you for your message. Our tests and customers' feedback confirm that the issue is resolved. Perhaps the problem you faced is different. Would you please provide us with a small sample project to precisely replicate your scenario on our side?

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

Ok i will try create some project as soon as possible
Martin

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

Thank you for your research. I appreciate it greatly. By the way, would you please take a look at the update from VCLProduct-12.1.6 to VCLProduct -12.2.2 or 12.2.3 - application crash ticket? Perhaps, your scenario is the same and the solution from there will help you overcome the issue…

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

Thank
now i think that problem is (maybe) in old version of cxStatusKeeper. I try it with new version
Martin

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

We look forward to hearing of your progress.

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

To Martin:
Would you please apply the fix from the An AV occasionally occurs when modifying Screen.Cursor if the grid is currently locked for updates (for instance, via the BeginUpdate/EndUpdate method block) issue? It may help.

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

Thank
i will try it.
Martin

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

Now i have another problem in this version of the components. When i use subgrid in tcxgrid and open dataset before master dataset and detail dataset have any data get error bookmark not found. In older version was ok.
(I know that's not a solution to cite but use it in large portions of code of my system)
Martin

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

Sorry, my previous message was not properly

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

Now it seems that when the first record on the master view has data in subview get an error bookmark not found (0). As data components use DOA so do not know if the fault is in DOA or in cxgrid
Martin

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

Hello Martin,
Thank you for your reply. Posting multiple different questions within a report makes it difficult to correctly track and process such items. May we ask you to open a new issue for each question you want to post. Thank you for your cooperation.
For now, I have created a separate issue on your behalf:

Bookmark error in master-detail mode

Please refer to this report for further correspondence on this problem.

JB JB

Private Jan Bednar Private Jan Bednar 12 years ago

Ok, sorry
BTW i use the fix (Would you please apply the fix from the AV under certain circumstances (Regression from 12.1.7) issue? It may help.) and now looks better for now
Martin

Answers approved by DevExpress Support

DevExpress Support Team DevExpress Support Team

created 12 years ago (modified 12 years ago)

Hello,
Thank you for your message. In this case, I recommend you change a cursor type after calling the End Update method, because the TableView is locked at this moment and HitTest returns invalid information.

Show previous comments (11) Comments (14)

AM AM

Private Anders Melander (CodeGroup) Private Anders Melander (CodeGroup) 12 years ago

FWIW I've encountered this exact problem too a little while ago. IMO it's a bug in the grid.
AFAIR the steps that caused the problem was something like:

Populate a grid.
Place cursor over a grid cell.
Set Screen.Cursor=crHourGlass ( or something).
Empty the grid.
Set Screen.Cursor=crDefault (must be crDefault) -> Access Violation.

AG AG

Private Anton Grabmayr Private Anton Grabmayr 12 years ago

Hi,
as this worked before 12.2.2 and due to the fact that just changing the cursor from Hourglass to Default I'd also say that this is a bug within the grid. Propably this also will resolve the other issue as well (Q370951).
A public fix is appreciated asap.
Regards
Toni

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

Hi Toni,
We understand that this issue is critical for you. However, our attempts to reproduce the issue were unsuccessful. Would you please provide us with a sample project to demonstrate the issue? We will examine it and do our best to find a solution.
We appreciate your cooperation.

AG AG

Private Anton Grabmayr Private Anton Grabmayr 12 years ago

Hi,
I managed to reproduce the AV. Please do the following:
Switch the Bar's ComboBox to "Kat B", back to "Kat A" and then to "Kat B" again --> AV
The AV didn't occure at first; then I added TWideString & TWideMemo-fields to the MemData and now I run into the AV…
Regards
Toni

xx.zip

AG AG

Private Anton Grabmayr Private Anton Grabmayr 12 years ago

…one further thing to do:
Please let the mouse cursor within the Grid while this is loading.
Regards
Toni

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

Hello,
Thank you for your sample project. I have reproduced the AV and forwarded this ticket to our developers for research.

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

We have fixed this issue. The code fix is rather complicated. Please be careful applying it.

AG AG

Private Anton Grabmayr Private Anton Grabmayr 12 years ago

Hi,
I successfully applied your fix. No AVs appeared so far.
Thanks
Toni

FL FL

Private Fredrik Loftheim Private Fredrik Loftheim 12 years ago

It seems that if you use the gridviews beginupdate/endupdate the error is now fixed in v2012 vol 2.3.
BUT if you are using the grids (TcxGrid) beginupdate/endupdate the error is still the same as before .
Try changing TV.BeginUpdate/TV.EndUpdate to cxGrid1.BeginUpdate.EndUpdate in Antons attached sample application to see what I mean. Please confirm if you are experiencing the same.

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

Hello Fredrik,
Thank you for your comment. This issue is fixed in the context of the An AV occasionally occurs when modifying Screen.Cursor if the grid is currently locked for updates (for instance, via the BeginUpdate/EndUpdate method block) issue (at least I believe that it is the same as the one you faced). I suggest you apply a fix from there. It should help.
Important note:
It is not a good idea to change the Screen.Cursor property within the BeginUpdate/EndUpdate block (neither for a view nor a grid). Within this block the object is locked and its visual representation is not refreshed. It is refreshed only when calling the EndUpdate method. Thus, changing the cursor type before the EndUpdate method you actually have the default cursor when the "visual refresh" operation is performed (applying filtering, grouping and calculating summaries). This confuses end-users as they see the default cursor while the grid is still freezed. I believe that it is not what you wish to achieve.
So, I suggest you move the cursor changing code outside the BeginUpdate/EndUpdate block.

FL FL

Private Fredrik Loftheim Private Fredrik Loftheim 12 years ago

Actually I am not Changing the Cursor explicitly at all. One example where I get the error is like this:
Grid.BeginUpdate;
try
  Dataset.Close;
  Dataset.Open;
finally
  Grid.EndUpdate;
end;
The Dataset is of type TOracleDataset and probably changes the Cursor during its Open method.
I am not sure if the beginupdate/endupdate is necessary (old code). I temporarily removed it and it seems to function fine without anything being slowed down.
I also have another examle where i dont even call beginupdate/update explicitly, but it is called from the linked dataset during Dataset.EnableControls/Dataset.EnableControls.
By the way, the hotfix from "AV under certain circumstances (Regression from 12.1.7) seems to fix the problem for us.

Private DevExpress Support Team Private DevExpress Support Team 12 years ago

Hello Fredrik,
Thank you for informing us that the problem is now resolved. I am glad to hear that you have found our patch helpful.

AV AV

Private Alisson Vieira Private Alisson Vieira 12 years ago

How can i download this patch ??? it ́s a hot fix ???

J J

Private Jens Fudickar [DX-Squad] Private Jens Fudickar [DX-Squad] 12 years ago

Have a look at the orange box in the upper right corner. There you can download the update.
Regards
Jens

Created: January 11, 2013 12:46 PM

Modified: February 24, 2013 12:57 PM

Platform: VCL

Product: ExpressQuantumGrid Suite

Reproduced: True

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An AV occasionally occurs when modifying Screen.Cursor if the View is currently locked for updates (for instance, via the BeginUpdate/EndUpdate method block)

Answers approved by DevExpress Support

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