How to enter a floating-point number ?

[Gan3sh <gan3sh wanadoo fr>]

Hi,

I would like to add a widget in my application to be able to enter a
floating-point number and only that.
If I use a GtkEntry, I didn't see in the doc how to restrict the
available characters to only digits (and also . + -).
And if I use a GtkSpinButton, I didn't see how to set the arrows
unvisible.

Is there another widget for entering only a number ?

I must say that it must run on Linux and Win32 too.

TIA,
Stéphane.