How to convert the numeric keypad dot-key into the DecimalSeparator?

Question

In some applications, like Microsoft Excel, the dot-key from the numeric keypad (VK_DECIMAL) is automatically converted into the current DecimalSeparator.

I'm trying to implement the same feature but I didn't find a way to make it work in the whole application.

Fabrizio · Accepted Answer · 2022-09-14 08:35:32Z

-1

At the form level, it can be done by using the form's KeyPreview property and OnKeyPress event handler, for example:

function IsKeyPressed(const AKey : Word) : Boolean;
begin
  Result := GetKeyState(AKey) < 0;
end;

procedure TMyBaseForm.FormCreate(Sender: TObject);
begin
  inherited;
  KeyPreview := True;
end;

procedure TMyBaseForm.FormKeyPress(Sender: TObject; var Key: Char);
begin
  inherited;
  if(IsKeyPressed(VK_DECIMAL))
  then Key := FormatSettings.DecimalSeparator;
end;

But this solution requires to have a common base form class for all application's forms and won't work with any form/dialog who is not inheriting from that base class (i.e: It will not work with a simple InputQuery either)

answered Sep 14, 2022 at 8:35

Fabrizio

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8 Comments

Andreas Rejbrand Over a year ago

To make it work in all forms, drop a TApplicationEvents on your main form and add an OnMessage handler. Look for WM_CHAR and then replace the Msg.wParam accordingly.

Fabrizio Over a year ago

@AndreasRejbrand: How can I distinguish between VK_DECIMAL and VK_OEM_PERIOD? The wParam is 46 in both cases

Andreas Rejbrand Over a year ago

The ugly solution is to continue to use your IsKeyPressed(VK_DECIMAL) approach. I haven't had time to investigate the alternatives.

HeartWare Over a year ago

Remember to also check for the NumLock state. Otherwise someone might expect "Del" key action when pressing that button, and be confused that a decimal point arrives instead.

Remy Lebeau Over a year ago

OnKeyPress/WM_CHAR deal in translated characters, not in virtual keys. To process virtual keys, you need to handle OnKey(Down|Up)/WM_KEY(DOWN|UP) instead

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