Suggestions for TJvDateTimePicker and TJvDBDateTimePicker

For those of us who didn't have anything else to do,
I needed some changes to these controls to fix some issues
that I was having.  These are by no means a final solution,
but are submitted to provide some support for others who
are more in tune with the official version of this code.

In order to add to the capabilities of these controls,
the following are submitted as suggestions,
but can only be considered a 'work in progress'.

//-----------------------------------------------------------------
//  TJvDBDateTimePicker
//  fixes 'must be in showcheckbox mode' errors for database usage
//  notes:
//  sets default (arbitrary) date/time part for 'other' part DB field
//      (date or time) to make the working value non-zero
//  does not fix when DB field value is both 'date AND time',
//      and happens to be null or equal to the NullDate value
// add 'FDKeepDate: TDateTime' in private section of class
//-----------------------------------------------------------------
procedure TJvDBDateTimePicker.DataChange(Sender: TObject);
begin
  if FDataLink.Field <> nil then
  begin
    if Kind = dtkDate then
    begin
      if IsDateAndTimeField then
        DateTime := FDataLink.Field.AsDateTime
      else
//  changed line
        DateTime := Trunc(FDataLink.Field.AsDateTime) + EncodeTime(12, 0, 0, 0);
    end
    else
    begin
      if IsDateAndTimeField then
      begin
//  added/changed lines
        DateTime := FDataLink.Field.AsDateTime;
        FKeepDate := Trunc(DateTime);
        DateTime := Trunc(Now) + Frac(DateTime);
      end
      else
        DateTime := Trunc(Now) + Frac(FDataLink.Field.AsDateTime);
    end;
  end
  else
  if csDesigning in ComponentState then
  begin
    DateTime := Now;
  end;
  CheckNullValue;
end;

//-----------------------------------------------------------------
//  TJvDBDateTimePicker
//  fixes non-editing response for first up/down click on control
//  notes:
//  added 'CNNotify' to class
//-----------------------------------------------------------------

procedure TJvDBDateTimePicker.CNNotify(var Msg: TWMNotify);
begin
  with Msg, NMHdr^ do
    case code of
      MCN_LAST:
        begin
          FDataLink.Edit;
        end;
    end;
    inherited;
end;


//-----------------------------------------------------------------
//  TJvDateTimePicker
//  fixes disabled control when value becomes equal to NullDate during editing
//  notes:
//  removes null text for duration of editing
//  add 'FDKeepNullText: String' in private section of class
//-----------------------------------------------------------------

procedure TJvDateTimePicker.CNNotify(var Msg: TWMNotify);
...
begin
  with Msg, NMHdr^ do
    case code of
        ...

//  added lines
      NM_SETFOCUS:
        begin
            FKeepNullText := NullText;
            NullText := '';
            inherited;
        end;
      NM_KILLFOCUS:
        begin
            NullText := FKeepNullText;
            inherited;
        end;
        ...

    else
        inherited;

    end;
end;

Suggestions for TJvDateTimePicker and TJvDBDateTimePicker

For those of us who didn't have anything else to do,
I needed some changes to these controls to fix some issues
that I was having.  These are by no means a final solution,
but are submitted to provide some support for others who
are more in tune with the official version of this code.

In order to add to the capabilities of these controls,
the following are submitted as suggestions,
but can only be considered a 'work in progress'.

//-----------------------------------------------------------------
//  TJvDBDateTimePicker
//  fixes 'must be in showcheckbox mode' errors for database usage
//  notes:
//  sets default (arbitrary) date/time part for 'other' part DB field
//      (date or time) to make the working value non-zero
//  does not fix when DB field value is both 'date AND time',
//      and happens to be null or equal to the NullDate value
// add 'FDKeepDate: TDateTime' in private section of class
//-----------------------------------------------------------------
procedure TJvDBDateTimePicker.DataChange(Sender: TObject);
begin
  if FDataLink.Field <> nil then
  begin
    if Kind = dtkDate then
    begin
      if IsDateAndTimeField then
        DateTime := FDataLink.Field.AsDateTime
      else
//  changed line
        DateTime := Trunc(FDataLink.Field.AsDateTime) + EncodeTime(12, 0, 0, 0);
    end
    else
    begin
      if IsDateAndTimeField then
      begin
//  added/changed lines
        DateTime := FDataLink.Field.AsDateTime;
        FKeepDate := Trunc(DateTime);
        DateTime := Trunc(Now) + Frac(DateTime);
      end
      else
        DateTime := Trunc(Now) + Frac(FDataLink.Field.AsDateTime);
    end;
  end
  else
  if csDesigning in ComponentState then
  begin
    DateTime := Now;
  end;
  CheckNullValue;
end;

//-----------------------------------------------------------------
//  TJvDBDateTimePicker
//  fixes non-editing response for first up/down click on control
//  notes:
//  added 'CNNotify' to class
//-----------------------------------------------------------------

procedure TJvDBDateTimePicker.CNNotify(var Msg: TWMNotify);
begin
  with Msg, NMHdr^ do
    case code of
      MCN_LAST:
        begin
          FDataLink.Edit;
        end;
    end;
    inherited;
end;


//-----------------------------------------------------------------
//  TJvDateTimePicker
//  fixes disabled control when value becomes equal to NullDate during editing
//  notes:
//  removes null text for duration of editing
//  add 'FDKeepNullText: String' in private section of class
//-----------------------------------------------------------------

procedure TJvDateTimePicker.CNNotify(var Msg: TWMNotify);
...
begin
  with Msg, NMHdr^ do
    case code of
        ...

//  added lines
      NM_SETFOCUS:
        begin
            FKeepNullText := NullText;
            NullText := '';
            inherited;
        end;
      NM_KILLFOCUS:
        begin
            NullText := FKeepNullText;
            inherited;
        end;
        ...

    else
        inherited;

    end;
end;