[wxruby-users] Segfault with GridCellChoiceEditor

[Alex Fenton]

Hi Glen

Glen Holcomb wrote:
> In my application I have a few Grid objects in a Notebook.  The Grid 
> objects are populated via GridTableBase.  Certain Grid cells need to 
> have a choice interface (I'm artificially enforcing foreign key 
> constraints).  All this works to the point where you try to edit the 
> value for that cell.  The choice box renders (i.e. the drop down arrow 
> appears) then the application segfaults.  Unfortunately I'm stuck 
> developing this in a Windows (XP) environment so I can't do much with 
> the segfault.  Any help would be most appreciated.
The problem here is the combination of GridTableBase and cell editors / 
renderers, which makes the memory management very tricky. It's noted as 
a bug here:
http://rubyforge.org/tracker/index.php?func=detail&aid=19187&group_id=35&atid=218

I don't know how to fix it in the library, but you should be able to 
work around it by storing the cell editor in an instance variable 
somewhere. Then ruby will mark it and preserve it from GC. From the code 
you posted on c.l.r (please do post code on this mailing list as well)

def get_attr(row, col, attr_kind)
  attr = Wx::GridCellAttr.new

  if @db_table == "computers" and col == 4
    ## INSTEAD OF THIS
    # attr.set_editor(Wx::GridCellChoiceEditor.new(["CAD", "GIS", "CMT"]))
    ## TRY THIS
    @editors ||= []
    @editors << Wx::GridCellChoiceEditor.new(["CAD", "GIS", "CMT"])
    attr.set_editor(@editors.last)
  end

  attr
end

hth
alex