> -----Original Message----- > From: Tristan Van Berkom [mailto:tvb@xxxxxxxxx] > Sent: Tuesday, June 14, 2005 8:11 AM > To: Shay Harding > Cc: gtk-list@xxxxxxxxx > Subject: Re: Glib - Object Properties > > Shay Harding wrote: > > > > Currently, I can get/set properties no problem. The issues > I am having > > pertain to how to trap errors during object construction for > > CONSTRUCT_ONLY properties. If I have a property with flags set to: > > > > G_PARAM_CONSTRUCT_ONLY | G_PARAM_READWRITE > > > > then I supposedly can only set the property while calling > > g_object_new(). This is only kind of true. If I attempt to set the > > property after g_object_new() is called, Glib simply emits > a warning, > > but still allows the property to be set. Actually, this is > only true > > if I call g_object_set_property() within my > xxx_set_property() function. > > The problem is g_object_set_property() returns void so I > have no way > > to catch errors (i.e. property set outside of a constructor). > > > > How can CONSTRUCT_ONLY actually be enforced and not emit > warnings to > > stdout/stderr? From what I can tell, I can't even write my > own code to > > do this since I have no access to the static global > 'pspec_pool' and > > the GParamSpec passed to my xxx_set_property() function after > > construct is NULL (incidentally it seems to always be NULL > after the > > object is constructed even without CONSTRUCT_ONLY set in flags). > > > > Thanks for any insight as to why this all works like this and any > > advice on enforcing policies. > > Hi, > "Construct only" properties were only enforced in GTK+ >= > 2.4, If you are using the latest GTK+, then your > xxx_set_property method "shouldn't get envoked" when setting > properties on your object. > > You should never call g_object_set_property () from inside > your xxx_set_property method, this will result in endless > recursion, the set_property method is a private method used > only to actualy persist the transported GValue on your actual > instance. > > Cheers, > -Tristan > Thanks for the reply. I am using glib 2.6.4 and did finally figure out what I was doing wrong for the CONSTRUCT_ONLY properties. It was basically me not understanding what was going on. After looking at the source code some more in gobject.c, I realized I didn't need to call my own xxx_set_property() function, but simply call g_object_set/get_property(), which then called my xxx_set_property() method and checked on CONSTRUCT_ONLY flags and such. I think I have all that sorted out now. I am still having serious troubles trying to get my test objects to work (just to figure out how the glib code works). I basically created an "Option" object (to store command line options as objects; is an easy way to get familiar with the glib code). I figured I could have a base abstract class "Option" and then implement things like IntOption, BoolOption, StringOption. The only difference between all of them is the type of data to store. I created the Option class as (standard typedefs and macros left out): struct _Option { GObject parent_instance; OptionPrivate *priv; }; struct _OptionClass { GObjectClass parent_class; }; struct _OptionPrivate { gchar *name; gpointer value; }; // The GET_PRIVATE macro for this simply tells it // to return the OptionPrivate struct type. struct _IntOption { Option parent_instance; OptionPrivate *priv; }; struct _IntOptionClass { OptionClass *parent_class; }; I have the option_class_init() which installs the properties and adds the private struct. It all works for the base Option type (until I set it to abstract anyway). When I try to create an "IntOption" type and tell it to use "Option" as a parent, it kind of falls apart (can't find any good examples of this; the testobject.c code is not much help). I have it working, but it's pretty hacked IMO. I have an option_init both types use as their class_init function (I figure out which type called it via IS_XXX_CLASS macro. I couldn't figure out how to get the properties installed if IntOption had its own class_init function. They don't seem to chain up automatically and I didn't see a way to do it manually (constructor perhaps?). I created option_set/get_property() functions that set the value gpointer with g_value_get_pointer(). This is fine for setting, but I wanted to return the actual data type on the get() call (i.e. int, boolean, gchar*). I can do it by writing an init function and get function for each type, but that seems pretty redundant. I have currently accomplished it with macros (i.e. INT_OPTION_GET_VALUE(obj)) which just calls g_object_get_property() and casts the returned gpointer appropriately. This seems kind of messy and a hack. I was wondering if there is a "proper" way to do it within the glib object framework without duplicating a lot of code? Thanks for any insight you can provide. Shay _______________________________________________ gtk-list@xxxxxxxxx http://mail.gnome.org/mailman/listinfo/gtk-list
