[3.6] bpo-30495: IDLE: improve textview with docstrings, PEP8 names, more tests. (GH-2283) (#2496)

Split TextViewer class into ViewWindow, ViewFrame, and TextFrame classes so that instances
of the latter two can be placed with other widgets within a multiframe window.
Patch by Cheryl Sabella.
(cherry picked from commit 42bc8be)

Lib/idlelib/idle_test/htest.py

@@ -8,7 +8,7 @@ callable in the module named in the spec.  Close the window to skip or
 end the test.
 
 In a tested module, let X be a global name bound to a callable (class
-or function) whose .__name__ attrubute is also X (the usual situation).
+or function) whose .__name__ attribute is also X (the usual situation).
 The first parameter of X must be 'parent'.  When called, the parent
 argument will be the root window.  X must create a child Toplevel
 window (or subclass thereof).  The Toplevel may be a test widget or
@@ -306,15 +306,6 @@ _tabbed_pages_spec = {
            "<nothing> is an invalid add page and remove page name.\n"
     }
 
-TextViewer_spec = {
-    'file': 'textview',
-    'kwds': {'title': 'Test textview',
-             'text':'The quick brown fox jumps over the lazy dog.\n'*35,
-             '_htest': True},
-    'msg': "Test for read-only property of text.\n"
-           "Text is selectable. Window is scrollable.",
-     }
-
 _tooltip_spec = {
     'file': 'tooltip',
     'kwds': {},
@@ -338,6 +329,15 @@ _undo_delegator_spec = {
            "by printing to the console or the IDLE shell.\n"
     }
 
+ViewWindow_spec = {
+    'file': 'textview',
+    'kwds': {'title': 'Test textview',
+             'text': 'The quick brown fox jumps over the lazy dog.\n'*35,
+             '_htest': True},
+    'msg': "Test for read-only property of text.\n"
+           "Select text, scroll window, close"
+     }
+
 _widget_redirector_spec = {
     'file': 'redirector',
     'kwds': {},