Re: CellRendererSpinButton and negative values

[muppet <scott asofyet org>]

On Sep 30, 2004, at 1:45 AM, Daniel Kasak wrote:

> Is it possible to get negative values supported?
> Where is the data type set in the source of CellRendererSpinButton?

(assuming you're looking at 
Gtk2-1.061/examples/cellrenderer-spinbutton.pl)

the "value" property is a GObject property.  this is created in the 
Glib::Object::Subclass 'use' starting at line 37.  specifically, the 
'properties' key is a reference to a list of Glib::ParamSpec objects, 
and the one named 'value' is created as part of the map statement from 
line 49 to line 60.  a map is used there because we have four 
properties of the same type with common values, and the map removes 
some duplicated code.  the array reference at line 57 is

   ['value', 'Value', 'How much is the fish', 0.0],

and the Glib::ParamSpec::double call places those values respectively 
in the "name", "nickname", "blurb", and "default_value" parameters.  
three other parameters are hard-coded there --- "minimum" ('0.0' at 
line 53), "maximum" (DBL_MAX at line 54), and "flags" (readable & 
writable, at line 56).

thus, this defines those four parameters to be doubles with legal 
values being the set [0.0, DBL_MAX].

if you want to change the legal range, you'll want to pull 'step' out 
of the map statement (negative values are not sensible for the 'step' 
parameter, which is passed to the SpinButton's step parameter to 
determine the increment used by the arrow buttons), and change the min 
& max to taste.

(Glib::ParamSpec::double is documented in the Glib::ParamSpec manpage, 
and the stuff you pass through Glib::Object::Subclass is documented in 
the Glib::Object::Subclass manpage.)

--
I think it worked on the Wiley Coyote model of project management - if
at any point you looked down and realised what you were doing was
impossible then you'd instantly fail.
  -- Simon Wistow