Issue #75 and #87 - added filter_offset attribute and filter-grid layout

- All filters are now loaded when a display list is first shown
- a filter_offset attribute for script object can now be used in much the
  same way as index_offset, to pull artworks and information from filters
  other than the current filter
- The filter-grid layout has been added, which allows for multiple filters
  to be shown at once (for example, if you set up filters for each letter
  of the alphabet then each column of the grid will contain a letter)
- Includes some fiddling with the scrolling speed when a key is held down

.gitignore

@@ -1,7 +1,20 @@
-attract
+/attract
 *.o
 *.a
 obj
 core
 *.dll
 *.exe
+/*.cfg
+/*.am
+*.layout
+*.depend
+/emulators
+/layouts
+/plugins
+/language
+/romlists
+/sounds
+/stats
+/modules
+/history.idx

Layouts.md

@@ -38,12 +38,14 @@ Contents
       * [`fe.list`](#list)
       * [`fe.overlay`](#overlay)
       * [`fe.obj`](#obj)
+      * [`fe.filters`](#filters)
       * [`fe.script_dir`](#script_dir)
       * [`fe.script_file`](#script_file)
    * [Classes](#classes)
       * [`fe.LayoutGlobals`](#LayoutGlobals)
       * [`fe.CurrentList`](#CurrentList)
       * [`fe.Overlay`](#Overlay)
+      * [`fe.Filter`](#Filter)
       * [`fe.Image`](#Image)
       * [`fe.Text`](#Text)
       * [`fe.ListBox`](#ListBox)
@@ -500,6 +502,7 @@ Return Value:
 
     fe.game_info( id )
     fe.game_info( id, index_offset )
+    fe.game_info( id, index_offset, filter_offset )
 
 Get information about the selected game.
 
@@ -526,6 +529,9 @@ Parameters:
    * index_offset - the offset (from the current selection) of the game to
      retrieve info on.  i.e. -1=previous game, 0=current game, 1=next game...
      and so on.  Default value is 0.
+   * filter_offset - the offset (from the current filter) of the filter
+     containing the selection to retrieve info on.  i.e. -1=previous filter,
+     0=current filter.  Default value is 0.
 
 Return Value:
 
@@ -856,6 +862,13 @@ functionality may be accessed.
 `fe.Text` and `fe.ListBox` instances.
 
 
+<a name="filters" />
+#### `fe.filters` ####
+
+`fe.filters` contains information on the available filters.  It is an array
+of `fe.Filter` instances.
+
+
 <a name="script_dir" />
 #### `fe.script_dir` ####
 
@@ -946,6 +959,7 @@ Attributes:
      reversed.
    * `list_limit` - Get the value of the list limit applied to the current
      list.
+   * `filter_index` - Get/set the current filter index.
 
 <a name="Overlay" />
 #### `fe.Overlay` ####
@@ -978,6 +992,20 @@ Member Functions:
      This could be useful to provide feedback during time-intensive operations.
 
 
+<a name="Filter" />
+#### `fe.Filter` ####
+
+This class is a container for information about the avaiable filters.  Instances
+of this class are contained in the `fe.filters` array.  This class cannot
+otherwise be instantiated in a script.
+
+Attributes:
+
+   * `name` - Get the filter name.
+   * `index` - Get the index of the currently selected game in this filter.
+   * `size` - Get the size of the game list in this filter.
+
+
 <a name="Image" />
 #### `fe.Image` ####
 
@@ -1011,6 +1039,10 @@ Attributes:
      for the artwork to display.  For example, set to -1 for the image
      corresponding to the previous list entry, or 1 for the next list entry,
      etc.  Default value is 0.
+   * `filter_offset` - [artwork only] Get/set filter offset from current
+     filter for the artwork to display.  For example, set to -1 for an image
+     indexed in the previous filter, or 1 for the next filter, etc.  Default
+     value is 0.
    * `skew_x` - Get/set the amount of x-direction image skew (in layout
      coordinates).  Default value is 0.  Use a negative value to skew the
      image to the left instead.
@@ -1154,6 +1186,10 @@ Attributes:
    * `index_offset` - Get/set offset from current game selection for text
      info to display.  For example, set to -1 to show text info for the
      previous list entry, or 1 for the next list entry.  Default value is 0.
+   * `filter_offset` - Get/set filter offset from current filter for the
+     text info to display.  For example, set to -1 to show text info for
+     a selection in the previous filter, or 1 for the next filter, etc.
+     Default value is 0.
    * `bg_red` - Get/set red colour level for text background. Range is
      [0 ... 255].  Default value is 0.
    * `bg_green` - Get/set green colour level for text background. Range is
@@ -1220,6 +1256,9 @@ Attributes:
    * `alpha` - Get/set alpha level for text. Range is [0 ... 255].
      Default value is 255.
    * `index_offset` - Not used.
+   * `filter_offset` - Get/set filter offset from current filter for the
+     text info to display.  For example, set to -1 to show info for the
+     previous filter, or 1 for the next filter, etc.  Default value is 0.
    * `bg_red` - Get/set red colour level for background. Range is
      [0 ... 255].  Default value is 0.
    * `bg_green` - Get/set green colour level for background. Range is