WebGMaps Access Violation

VCL TMS VCL WebGMaps
21

Can I please ask you to provide a sample source app with which we can reproduce this here. In our demo apps using markers, no error can be seen here.

22

Ok, time for me to come clean and eat humble pie. In my application I was inadvertently indirectly freeing FBounds after the markers had been loaded. This had been in my code for years but only just started causing problems. After changing this everything works fine. I apologise for the inconvenience caused and infering that the problem was in WebGMaps.

23

We are experiencing the same issue. 


Our findings, if you comment out the new hooks stuff, the AV goes away (or exit early)

<DELPHI>
procedure TWebGMaps.InstallHook;
var
  frm: TCustomForm;
begin
  exit; //<- Bail out to avoid AV

  if not Assigned(HookedForms) then
    HookedForms := TList.Create;

  if not Assigned(HookedClients) then
    HookedClients := TList.Create;

  frm := GetParentForm(Self);
  HookedClients.Add(self);

  if HookedForms.IndexOf(frm) = -1 then
  begin
    HookedForms.Add(frm);

    {$IFDEF DELPHI_UNICODE}
    OldWndProc := TFarProc(GetWindowLongPtr(frm.Handle, GWL_WNDPROC));
    NewWndProc := MakeObjectInstance(HookWndProc);
    SetWindowLongPtr(frm.Handle, GWL_WNDPROC, LInteger(NewWndProc));
    {$ENDIF}

    {$IFNDEF DELPHI_UNICODE}
    OldWndProc := TFarProc(GetWindowLong(frm.Handle, GWL_WNDPROC));
    NewWndProc := MakeObjectInstance(HookWndProc);
    SetWindowLong(frm.Handle, GWL_WNDPROC, LInteger(NewWndProc));
    {$ENDIF}

    FHooked := true;
  end;
end;

procedure TWebGMaps.HookWndProc(var Msg: TMessage);
var
  i: integer;
  wgm: TWebGMaps;
  frm: TCustomForm;
begin
  exit; // <-Bail out to avoid AV

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

  if Msg.Msg = WM_CLOSE then
  begin
    RemoveHook;

    if Assigned(HookedClients) then
    begin
      for i := HookedClients.Count - 1 downto 0 do
      begin
        wgm := TWebGMaps(HookedClients.Items);
        frm := GetParentForm(wgm);

        if (frm = GetParentForm(Self)) and (frm = Application.MainForm) then
        begin
          wgm.Free;
          HookedClients.Delete(i);
        end;
      end;

      if HookedClients.Count = 0 then
        FreeAndNil(HookedClients);
    end;
  end;
end;

24

Not sure what this hook stuff is for but seems to work pretty good without ... and as a bonus no AV.

25

This was introduced for issues with specific updates of the Microsoft IE TWebBrowser control. For specific Windows 10 updates, Microsoft had broken this control and the implementation with the hooks was a workaround for the Microsoft breaking change.

26

I also had to comment out (Exit;) the hooks, giving AV on Windows 7.