Record information about other key modifiers on X11/GTK

In particular, Mod4 is used for the Command button when you run Linux
on Mac hardware. I don't know how to get the others, but added them
for safety.

pkgs/gui-pkgs/gui-doc/scribblings/gui/key-event-class.scrbl

@@ -20,6 +20,9 @@ See also @|mousekeydiscuss|.
                  [shift-down any/c #f]
                  [control-down any/c #f]
                  [meta-down any/c #f]
+                 [mod3-down any/c #f]
+                 [mod4-down any/c #f]
+                 [mod5-down any/c #f]
                  [alt-down any/c #f]
                  [x exact-integer? 0]
                  [y exact-integer? 0]
@@ -28,8 +31,9 @@ See also @|mousekeydiscuss|.
 
 See the corresponding @racketidfont{get-} and @racketidfont{set-}
  methods for information about @racket[key-code], @racket[shift-down],
- @racket[control-down], @racket[meta-down], @racket[alt-down],
+ @racket[control-down], @racket[meta-down], @racket[mod3-down], @racket[mod4-down],
- @racket[x], @racket[y], @racket[time-stamp], @racket[caps-down].
+ @racket[mod5-down], @racket[alt-down], @racket[x], @racket[y], 
+ @racket[time-stamp], @racket[caps-down].
 
 The release key code, as returned by @method[key-event%
 get-key-release-code], is initialized to @racket['press].
@@ -205,6 +209,27 @@ Returns @racket[#t] if the Meta (Unix), Alt (Windows), or Command (Mac OS
 
 }
 
+@defmethod[(get-mod3-down)
+           boolean?]{
+
+Returns @racket[#t] if the Mod3 (Unix) key was down for the event.
+
+}
+
+@defmethod[(get-mod4-down)
+           boolean?]{
+
+Returns @racket[#t] if the Mod4 (Unix) key was down for the event.
+
+}
+
+@defmethod[(get-mod5-down)
+           boolean?]{
+
+Returns @racket[#t] if the Mod5 (Unix) key was down for the event.
+
+}
+
 @defmethod[(get-other-altgr-key-code)
            (or/c char? key-code-symbol? #f)]{
 
@@ -339,6 +364,27 @@ Sets whether the Meta (Unix), Alt (Windows), or Command (Mac OS X) key
 
 }
 
+@defmethod[(set-mod3-down [down? any/c])
+           void?]{
+
+Sets whether the Mod3 (Unix) key was down for the event.
+
+}
+
+@defmethod[(set-mod4-down [down? any/c])
+           void?]{
+
+Sets whether the Mod4 (Unix) key was down for the event.
+
+}
+
+@defmethod[(set-mod5-down [down? any/c])
+           void?]{
+
+Sets whether the Mod5 (Unix) key was down for the event.
+
+}
+
 @defmethod[(set-other-altgr-key-code [code (or/c char? key-code-symbol? #f)])
            void?]{
 

pkgs/gui-pkgs/gui-lib/mred/private/wx/common/event.rkt

@@ -77,6 +77,9 @@
                    [[bool? shift-down] #f]
                    [[bool? control-down] #f]
                    [[bool? meta-down] #f]
+                   [[bool? mod3-down] #f]
+                   [[bool? mod4-down] #f]
+                   [[bool? mod5-down] #f]
                    [[bool? alt-down] #f]
                    [[exact-integer? x] 0]
                    [[exact-integer? y] 0])

pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/window.rkt

@@ -233,6 +233,9 @@
                         [shift-down (bit? modifiers GDK_SHIFT_MASK)]
                         [control-down (bit? modifiers GDK_CONTROL_MASK)]
                         [meta-down (bit? modifiers GDK_MOD1_MASK)]
+                        [mod3-down (bit? modifiers GDK_MOD3_MASK)]
+                        [mod4-down (bit? modifiers GDK_MOD4_MASK)]
+                        [mod5-down (bit? modifiers GDK_MOD5_MASK)]
                         [alt-down (bit? modifiers GDK_META_MASK)]
                         [x 0]
                         [y 0]