Re: [Fxruby-users] Usage FXList : makeItemVisible

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

SIMOKAWA hajime wrote:

> Another Question:
> The 'makeItemVisible' is not working just after 'clearItems'.
> A 'create' is need before 'makeItemVisible'.

When you call clearItems() and, subsequently appendItem(), on the list, 
the list's layout is marked as dirty but it is not immediately 
reconciled. FOX uses a technique of delayed layout, which is described 
on this page from the FOX documentation:

	http://www.fox-toolkit.org/guiupdate.html

Under normal circumstances, the GUI layout will not actually be 
reconciled until we return to the main FOX event loop, i.e. until we 
exit the callback for @btnV9. The problem in your case is that 
makeItemVisible() assumes that the list's layout has already been 
reconciled, which it hasn't. So the solution is to do *something* to 
force the layout to be reconciled immediately, before the call to 
makeItemVisible(). Calling create() on the main window is one way to do 
this, but the more proper way is to call the FXApp#forceRefesh method:

	@btnV9.connect(SEL_COMMAND) {
		update_list
		app.forceRefresh	# reconcile layout immediately!
		@lst.makeItemVisible 9
	}

> But when not just after, the 'create' is needless.

Correct. In this case, the calls to clearItems() and appendItem() in 
@btnUp's callback:

	@btnUp.connect(SEL_COMMAND) {
		update_list
	}

Mark the list's layout as dirty, and shortly after we re-enter FOX's 
main event loop, the GUI layout is reconciled. Now any subsequent call 
to makeItemVisible() will work properly.

Hope this helps,

Lyle