[Fxruby-users] segfault in GC::start after accessing verticalScrollbar.position from overloaded moveContents

[Oliver S. <ol...@mo...>]

(sorry Lyle, forgot to switch addresses the first time :)

Hello,

I'm trying to bypass a bug in FXScintilla which causes the widget to scroll
up forever when you try
to scroll with a mouse wheel, and I figured out through trial and error that
if I subclass FXScintilla (which is a subclass of FXScrollArea), overload
moveContents and reimplement it with the following:

def moveContents(new_x, new_y)
	old_position = verticalScrollbar.position
	super
	verticalScrollbar.position = old_position
end

the erratic behavior goes away.  I thought I was pretty clever for a while,
but now it turns out that I'm getting a weird segfault when I initiate
garbage collection later in my program.  I can play around with the code in
other ways to make it appear or disappear, but it seems to be pretty hard to
pin down.  I'm guessing that the ruby garbage collector thinks it needs to
free verticalScrollbar, and the segfault occurs because the C++ destructor
has already taken care of it?  If I comment out the two lines that access
verticalScrollbar, it starts working.  If I call the same two lines outside
of the overloaded moveContents, no segfault (but of course the original bug
is still there).

Any ideas?  If I'm not supposed to be overloading moveContents or accessing
verticalScrollbar.position, is there another way to accomplish the same
effect?

Thanks,

Oliver Smith