Read the whole line and strip the redundant blanks

in_wstr() reads a line to its end, so gather() no longer needs move() +
_end_of_line() to work out how much of it to ask for: strip the trailing
blanks instead, keeping the one the cursor rests on.

Author: fedonman

Lib/curses/textpad.py

@@ -200,12 +200,16 @@ def gather(self):
         result = ""
         self._update_max_yx()
         for y in range(self.maxy+1):
-            self.win.move(y, 0)
-            stop = self._end_of_line(y)
-            if stop == 0 and self.stripspaces:
-                continue
-            count = stop+1 if self.stripspaces else self.maxx+1
-            result = result + str(self.win.in_wchstr(y, 0, count))
+            # The whole line: in_wstr() reads a double-width character once,
+            # skipping the continuation cell that holds its other half.
+            line = self.win.in_wstr(y, 0)
+            if self.stripspaces:
+                stripped = line.rstrip(' ')
+                if not stripped:
+                    continue
+                # Keep the blank the cursor rests on past the last character.
+                line = stripped + ' ' if len(stripped) < len(line) else stripped
+            result = result + line
             if self.maxy > 0:
                 result = result + "\n"
         return result