WheelMouse

[Hermann Kofler]

Wenn ich in der DBLookupCombox mit dem Rad der WheelMouse scrolle, so verabschiedet sich das Programm. Dieser Fehler ist bei verschiedenen Betriebssysteme, Computer und Mäuse aufgetreten.
Weiß jemand woran das liegt.

Vielen Dank
Hermann

[Patrick Sack]

<br>Hi,...
<br>
<br>ich habe irgend wo schon mal was darüber gelesen (ggf. hier im Forum). Ich glaube das ist ein BUG. Wenn du in Delphi 5 unter Hilfe - Info gehst und da eine Compilierung < 6.18 steht dann Versuch mal ein Update.
<br>
<br>MfG
<br>P

[Andreas Kosch]

Hallo,

Borland hat am 28.09.1999 einen <b>Delphi Tech Allert</b> zu diesem Problem als eMail verschickt:

Product: Delphi <br>
Version: 5.0 <br>
Description: Conflict between latest InteliMouse
driver and TDBLookupComboBox.<br>
Severity: Serious/Highly Visible

<b>Steps to Reproduce:</b><br>
Install InteliMouse Driver v2.2d.
Create or open an application which uses a
TDBLookupComboBox. Click on the arrow in the
box to show the drop down list. Now move the
mouse wheel, and the application freezes.
The application must be killed to recover.
This issue does not occur with a TComboBox
(TDBLookupComboBox is not a TComboBox descendent).

<b>Workaround</b>:<br>
A permanent solution to this issue is currently
in development. Here is a workaround which
requires adding a couple lines to DBCTRLS.PAS:
<pre>
{ This part takes care of the AV. ListLink.DataSet
could be nil after the WM_MOUSEWHEEL wasn't
handled and the Intellimouse driver decided to
send a WM_VSCROLL }
procedure TDBLookupListBox.WMVScroll(var Message: TWMVScroll);
begin
SearchText := '';
<<<< ADD >>>>
if ListLink.DataSet = nil then Exit;
<<<< END ADD >>>>
with Message, ListLink.DataSet do
case ScrollCode of
SB_LINEUP: MoveBy(-FRecordIndex - 1);
SB_LINEDOWN: MoveBy(FRecordCount - FRecordIndex);
SB_PAGEUP: MoveBy(-FRecordIndex - FRecordCount+ 1);
SB_PAGEDOWN: MoveBy(FRecordCount - FRecordIndex+ FRecordCount - 2);
SB_THUMBPOSITION:
begin
case Pos of
0: First;
1: MoveBy(-FRecordIndex - FRecordCount + 1);
2: Exit;
3: MoveBy(FRecordCount - FRecordIndex + FRecordCount - 2);
4: Last;
end;
end;
SB_BOTTOM: Last;
SB_TOP: First;
end;
end;
{ This takes care of the "hang". For some unknown
reason, the control gets a WM_KILLFOCUS immediately
after the *second* WM_MOUSEWHEEL. I wasn't able to
determine where the message came from. However,
focus is retained by the drop-down list, making it
appear that the application had stopped responding }
procedure TDBLookupComboBox.CloseUp(Accept: Boolean);
var
Msg: TMsg;
ListValue: Variant;
begin
if FListVisible then
begin
if GetCapture <> 0 then SendMessage(GetCapture,WM_CANCELMODE, 0, 0);
<<<< ADD >>>>
SetFocus;
<<<< END ADD >>>>
ListValue := FDataList.KeyValue;
SetWindowPos(FDataList.Handle, 0, 0, 0, 0, 0, SWP_NOZORDERor
SWP_NOMOVE or SWP_NOSIZE or SWP_NOACTIVATEor SWP_HIDEWINDOW);
FListVisible := False;
FDataList.ListSource := nil;
Invalidate;
SearchText := '';
if Accept and CanModify then SelectKeyValue(ListValue);
if Assigned(FOnCloseUp) then FOnCloseUp(Self);
end;
end;
</pre>
Mit der Installation des <b>UpdatePack#1</b> zu Delphi 5 sollte das Problem aus der Welt sein.
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