Issue #24782: Limit width of canvas and hence IDLE settings dialog.
diff --git a/Lib/idlelib/configDialog.py b/Lib/idlelib/configDialog.py
index d7c4dfb..579b9b3 100644
--- a/Lib/idlelib/configDialog.py
+++ b/Lib/idlelib/configDialog.py
@@ -1406,7 +1406,7 @@
         vscrollbar = Scrollbar(self, orient=VERTICAL)
         vscrollbar.pack(fill=Y, side=RIGHT, expand=FALSE)
         canvas = Canvas(self, bd=0, highlightthickness=0,
-                        yscrollcommand=vscrollbar.set)
+                        yscrollcommand=vscrollbar.set, width=240)
         canvas.pack(side=LEFT, fill=BOTH, expand=TRUE)
         vscrollbar.config(command=canvas.yview)