gui2: create root window

avr/modules/lcd2/gui2/base/guiapp.asm

@@ -88,9 +88,27 @@ GuiApp_Init:
   ldi r16, HIGH(GuiApp_DefaultSignalmap*2)
   std Y+OBJECT_OFFS_SIGNALMAP_HI, r16
 
+  ; create root window
+  push yl
+    push yh
+      mov xl, yl
+      mov xh, yh
+      ldi r16, 0  ; opts_lo
+      ldi r17, 0  ; opts_hi
+      bigcall RootWindow_new
+      mov xl, yl
+      mov xh, yh
+    pop yh
+  pop yl
+  brcc GuiApp_Init_ret
+
+  std Y+GUIAPP_OFFS_ROOTWINDOW_LO, xl
+  std Y+GUIAPP_OFFS_ROOTWINDOW_HI, xh
+
   ldi r16, GUIAPP_DRAWTIMER
   std Y+GUIAPP_OFFS_DRAWTIMER, r16
-  
+
+GuiApp_Init_ret:
   ret
 ; @end