Fix SF bug # 602259, 3rd parameter for Tkinter.scan_dragto

Add the optional gain parameter and pass it to Tk.

Lib/lib-tk/Tkinter.py

@@ -2139,11 +2139,11 @@ class Canvas(Widget):
     def scan_mark(self, x, y):
         """Remember the current X, Y coordinates."""
         self.tk.call(self._w, 'scan', 'mark', x, y)
-    def scan_dragto(self, x, y):
-        """Adjust the view of the canvas to 10 times the
+    def scan_dragto(self, x, y, gain=10):
+        """Adjust the view of the canvas to GAIN times the
         difference between X and Y and the coordinates given in
         scan_mark."""
-        self.tk.call(self._w, 'scan', 'dragto', x, y)
+        self.tk.call(self._w, 'scan', 'dragto', x, y, gain)
     def select_adjust(self, tagOrId, index):
         """Adjust the end of the selection near the cursor of an item TAGORID to index."""
         self.tk.call(self._w, 'select', 'adjust', tagOrId, index)

Misc/NEWS

@@ -88,6 +88,9 @@ Library
 
 - urlparse can now parse imap:// URLs.  See SF feature request #618024.
 
+- Tkinter.Canvas.scan_dragto() provides an optional parameter to support
+  the gain value which is passed to Tk.  SF bug# 602259.
+
 Tools/Demos
 -----------