new prefs for window sizing

build/shared/lib/preferences.txt

@@ -72,8 +72,15 @@ platform.auto_file_type_associations = true
 
 
 # default size for the main window
-default.window.width = 500
-default.window.height = 600
+editor.window.width.default = 500
+editor.window.height.default = 600
+
+editor.window.width.min = 400
+editor.window.height.min = 500
+# tested as approx 440 on OS X
+editor.window.height.min.macosx = 450
+# tested to be 515 on Windows XP, this leaves some room
+editor.window.height.min.windows = 530
 
 # font size for editor
 editor.font=Monospaced,plain,12