hgk: update backgroud colour when Ttk is available

Ttk doesn't automatically set up Tk colour palette.
Because of that, Ttk controls look differently when used
together with old Tk controls. When we use Ttk controls,
we first query if we have any setting for the client
background, and if we do, we update Tk palette as well.

contrib/hgk

@@ -30,6 +30,8 b' if {[catch {package require Ttk}]} {'
     interp alias {} ttk::label {} label
     interp alias {} ttk::scrollbar {} scrollbar
     interp alias {} ttk::optionMenu {} tk_optionMenu
+
+    proc updatepalette {} {}
 } else {
     proc ::ttk::optionMenu {w varName firstValue args} {
         upvar #0 $varName var
@@ -46,6 +48,11 b' if {[catch {package require Ttk}]} {'
         }
         return $w.menu
     }
+    proc updatepalette {} {
+        catch {
+            tk_setPalette background [ttk::style lookup client -background]
+        }
+    }
 }
 
 if {[tk windowingsystem] eq "win32"} {
@@ -120,6 +127,7 b' if {$theme eq "default"} {'
 
 }
 
+updatepalette
 
 # Unify right mouse button handling.
 # See "mouse buttons on macintosh" thread on comp.lang.tcl