WebGMaps Access Violation

VCL TMS VCL WebGMaps
1

Hi,

I am using VCL version 2.9.4.6 and am getting an access violation when closing the form that the map is on.

I cannot debug it as it keeps crashing Delphi (Tokyo 10.2.2 February 2018 patch).

It is happening in procedure TWebGMaps.HookWndProc on line:
  Msg.Result := CallWindowProc(OldWndProc, frm.Handle, Msg.Msg, Msg.wParam, Msg.lParam);

The form it is on is an MDI Child and I am using DevEx Ribbons, etc.

Any help would be greatly appreciated.

Thanks,

Ken

2

Please use the latest version v2.9.4.7

https://www.tmssoftware.com/site/webgmaps.asp
3

This is actually the version I installed yesterday. The setup says it is v2.9.4.7 but after install the component version is still v2.9.4.6 and has the same problem.

4

I cannot reproduce a problem here. Does this problem happen with any of our demos? Does it happen when you just place TWebGMaps on a new VCL application?

5

I will investigate and reply but as per my message above. Is it possible that it is still v2.9.4.6?

6

If the installer mentioned 2.9.4.7 , it is the latest. I see in the repo version nr. was overlooked in the source.

7

Thanks, I cannot replicate this either. I think it is connected with the DevEx components although this was not happening previously.

8

It seems that when the form is closed and this line is executed:

Msg.Result := CallWindowProc(OldWndProc, frm.Handle, Msg.Msg, Msg.wParam, Msg.lParam);

that the form has already been freed.

9

But how can we reproduce this?

10

I would suspect that DevEx are also using hooks but not sure if changes on DevEx's part or yours have caused this to start happening. For now I have patched your code to stop this happening.

11

Could you inform about your patch so we can investigate whether this could be applicable in our release?

12

I'm afraid that I was too optimistic. Everything I have tried so far fails to work consistently.

13

As long as we cannot reproduce this here, it is very hard to investigate.

Does this help in HookWndproc():

  if Assigned(frm) and not (csDestroying in frm.ComponentState) then
    Msg.Result := CallWindowProc(OldWndProc, frm.Handle, Msg.Msg, Msg.wParam, Msg.lParam);

?
14

I understand the difficulty.

This does not help I'm afraid.

I don't know if this helps but the block after is never entered.

  if Msg.Msg = WM_CLOSE then

15

We'd really need to be able to reproduce this here.

16

If you are willing to download the DevEx trial I can provide some code.

17

I would prefer if this can be isolated with a project just using standard Delphi controls and our controls and there is a proof this way the problem is really in our code.

18

Ok. I will start stripping out code until I find the problem then, starting with the hook.

19

I need a bit of assistance please. I am only getting a problem if I load markers, if not, there is no error. I get an error when FMarkers id freed.Do you have any idea what could cause this?

20

And if I comment out FreeAndNil(FMarkers); in TWebGMaps.Destroy there is no problem when I have added Markers!