From: Lyle Johnson <lyle@...>
Date: 2003-01-07T08:02:37+09:00
Subject: Re: [BUG][FOX] iconlist and multiple icon usage

Pierre Baillet wrote:

> i've encountered a bug in the FOX library from the PragProg installer.
> When using a FXIconList, it does not seem to be possible to use the
> same FXIcon for more than 1 item in the list. Trying to do so result in
> a segfault on win2k (and win98se) at least. 
> 
> Attached you will find a simple test case (you just need to set
> FOLDER_OPEN to a valid png file on your system).

The problem is that you're trying to use an icon before its server-side 
representation has been created. For more information about this issue, 
see this entry from the FOX FAQ:

     http://www.fox-toolkit.org/faq.html#ILLEGALICON

The quick fix for your program is to just add the line:

     icon.create

immediately after the line in Foo#redraw_list that instantiates the new 
FXPNGIcon, i.e.

     def redraw_list
       @iconlist.clearItems
       # display empty boxes
       icon = FXPNGIcon.new(getApp(), @@folder_data)
       icon.create
       (1..3).each{ |f|
         item = FXIconItem.new(f.to_s, icon )
         @iconlist.appendItem(item)
       }
     end

> Apart from reinstancing an icon every time, is there a solution to have
> icons used more than once on with FOX?

As a matter of fact you only need *one* copy of this icon object, and 
can share it amongst all of the list items. If I were to modify your 
example program, it would look like this:

     class Foo < FXMainWindow

       FOLDER_OPEN = "icon/stock_open.png"

       def redraw_list
         @iconlist.clearItems
         (1..3).each{ |f|
           item = FXIconItem.new(f.to_s, @folder_icon)
           @iconlist.appendItem(item)
         }
       end

       def initialize(anApp)
         super(anApp, "COM Marker Viewer " + VERSION, nil, nil,
           DECOR_ALL, 0, 0, 640, 480, 0, 0)

         # Read the image file data and construct the
         # shared icon object
         folder_data = File.open(FOLDER_OPEN, "rb").read()
         @folder_icon = FXPNGIcon.new(getApp(), folder_data)

         frame = FXVerticalFrame.new(self,
                   LAYOUT_FILL_X|LAYOUT_FILL_Y)
         @iconlist = FXIconList.new(frame, nil, 0,
                       ICONLIST_BIG_ICONS|ICONLIST_ROWS|ICONLIST_COLUMNS|
                       LAYOUT_FILL_X|LAYOUT_FILL_Y)
         redraw_list
       end

       def create
         super
         @folder_icon.create
         self.show(PLACEMENT_SCREEN)
       end
     end

     theApp = FXApp.new("foo", "Bar")
     Foo.new(theApp)
     theApp.create
     theApp.run

Apart from moving the app-related stuff out of your main window class, 
the important thing to note is that there is only *one* icon object 
(@folder_icon) that is shared by all of the list items. It gets created 
when the main window (Foo) object is created (see Foo#create).

Hope this helps,

Lyle