How do I prevent users from entering values that exceed TSpinEdit.MaxValue? - delphi

Question

I set the MaxValue of a TSpinEdit to 100000 but when I run the program it lets me enter values over 100000 if I enter it manually (instead of using the spins).
There is any way to limit the value to MaxValue without writing code? Otherwise the MaxValue property is 100% useless.
The problem is that when the user enters a huge value this gives an RageCheckError because BigFileThreshis Cardinal.
procedure TFrmMain.spnMaxFileSizeChange(Sender: TObject);
begin
PlaylistCtrl.BigFileThresh:= spnMaxFileSize.Value * KB;
end;
This new behavior of TSpinEdit can cause Delphi programs to crash in many places. I liked the one from Delphi 7 better.
It would be easy for THE CURRENT situation to add a line like:
if spnMaxFileSize.Value> spnMaxFileSize.MaxValue
then spnMaxFileSize.Value:= spnMaxFileSize.MaxValue;
But to add this line from now on or to open all my programs and add this line? This is crazy!

Answer 1

As you've found, the SpinEdit's "onChange" event will be called, even if the currently entered number is outside the range. When you change focus to a different control, the value gets
limited correctly.
You could try making a new (derived) version of TSpinEdit which doesn't work this way, oryou can just add the required checking to your OnChange event handler.

Answer 2

Since the only place checkvalue is called is the message handler of CM_Exit you could use
procedure TFrmMain.spnMaxFileSizeChange(Sender: TObject);
begin
SendMessage(TSpinEdit(Sender).Handle,CM_EXIT,0,0);
PlaylistCtrl.BigFileThresh:= spnMaxFileSize.Value * KB;
end;
to recieve the desired behavior.
investigate ..\source\Win32\Samples\Source.

Answer 3

Two possible solution:
TYPE
TMySpinEdit = class(TSpinEdit) { Fixes the OnChange MinValue/MaxValue issue }
private
Timer: TTimer;
FOnChanged: TNotifyEvent;
procedure TimesUp(Sender: TObject);
public
constructor Create (AOwner: TComponent);override;
destructor Destroy;override;
procedure Change; override;
published
property OnChanged: TNotifyEvent read FOnChanged write FOnChanged;
end;
constructor TMySpinEdit.Create(AOwner: TComponent);
begin
inherited;
Timer:= TTimer.Create(Self);
Timer.OnTimer:= TimesUp;
Timer.Interval:= 2500; { allow user 2.5 seconds to enter a new correct value }
end;
destructor TMySpinEdit.Destroy;
begin
FreeAndNil(Timer);
inherited;
end;
procedure TMySpinEdit.Change;
begin
Timer.Enabled:= FALSE;
Timer.Enabled:= TRUE;
end;
procedure TMySpinEdit.TimesUp;
begin
Timer.Enabled:= FALSE;
if (MaxValue<> 0) AND (Value> MaxValue) then Value:= MaxValue;
if (MinValue<> 0) AND (Value< MinValue) then Value:= MinValue;
if Assigned(FOnChanged) then FOnChanged(Self);
end;
Code not tested yet (to be compiled).
The other solution would be:
TYPE
TMySpinEdit = class(TSpinEdit)
public
procedure Change; override;
end;
IMPLEMENTATION
procedure TMySpinEdit .Change;
begin
if (Value > MaxValue) OR (Value < MinValue) then
begin
Color:= clRed;
EXIT; { Out of range value. Don't trigger the OnChange event. }
end;
Color:= clWindow;
inherited;
end;