Re: [Fxruby-users] Dialogues, and create.

[Lyle J. <jl...@cf...>]

Hugh Sasse Staff Elec Eng wrote:

> The next thing I'll need to know is: Where can I generalize this
> behaviour: are there other calls that propagate like this?

The other two that immediately come to mind are the detach() and 
destroy() methods.

You may already understand that the purpose of calling create() is to 
create and then bind a native windowing-system entity (e.g. a X window, 
or a Win32 GDI font) to an already-existing FOX object (like an FXWindow 
or FXFont instance).

Calling detach() on a FOX object reverses part of the effect of 
create(); it breaks this binding between the FOX object and its 
window-system entity, but it doesn't actually destroy either of them. 
And like create(), detach() does its thing recursively, from parent to 
child windows.

Calling destroy() goes one step further (if you want to think of it that 
way) and actually destroys the window-system entity. Note that it 
doesn't destroy (garbage-collect) the FOX object, just the X window or 
whatever that was backing it up. An important distinction, though, is 
that destroy() is not as aggressive as create() and detach() in terms of 
its recursive behavior. Specifically, calling destroy() on a widget will 
not destroy any of its shared resources, like fonts or icons. Suppose 
you create an icon:

     anIcon = FXPNGIcon.new(getApp(), ...)

and then associate it with two different widgets (a label and a button):

     aLabel.icon = anIcon
     aButton.icon = anIcon

Now suppose that at some point later you call destroy() on the button:

     aButton.destroy

It is clear that you want to blow away the X window (or Win32 window) 
underlying that FXButton instance, but you don't want to destroy the 
icon too since someone else may still be using that resource. And in 
this case, of course, that "someone else" is the label.

There are other behaviors in FOX that are recursive, e.g. the manner in 
which the layout algorithm works, but right offhand I can't think of any 
other APIs that you'd deal with directly that have a recursive nature. I 
am sure that as soon as I send this post, someone will point out some 
cases I forgot about, though ;)

Hope this helps,

Lyle