Fix for issue5194, based on a patch by Ned Deily.
diff --git a/Lib/idlelib/MultiCall.py b/Lib/idlelib/MultiCall.py
index 1c40638..47f402d 100644
--- a/Lib/idlelib/MultiCall.py
+++ b/Lib/idlelib/MultiCall.py
@@ -32,6 +32,7 @@
import sys
import re
import tkinter
+from idlelib import macosxSupport
# the event type constants, which define the meaning of mc_type
MC_KEYPRESS=0; MC_KEYRELEASE=1; MC_BUTTONPRESS=2; MC_BUTTONRELEASE=3;
@@ -44,7 +45,7 @@
MC_OPTION = 1<<6; MC_COMMAND = 1<<7
# define the list of modifiers, to be used in complex event types.
-if sys.platform == "darwin" and sys.executable.count(".app"):
+if macosxSupport.runningAsOSXApp():
_modifiers = (("Shift",), ("Control",), ("Option",), ("Command",))
_modifier_masks = (MC_SHIFT, MC_CONTROL, MC_OPTION, MC_COMMAND)
else: