bpo-33642: IDLE: Use variable number of lines in CodeContext. (GH-7106)

Instead of displaying a fixed number of lines, some blank, Code Context
now displays the variable number of actual context lines.  When there
are no context lines, it shows a single blank line to indicate that the
feature is turned on.

The Code Context configuration option is changed from 'numlines'
(default 3) to 'maxlines' (default 15) to avoid possible interference
between user settings for the old and new versions of Code Context.
(cherry picked from commit 29996a1)

Co-authored-by: Cheryl Sabella <cheryl.sabella@gmail.com>

Lib/idlelib/codecontext.py

@@ -4,7 +4,7 @@
 determine which block you are in.  This extension implements a pane at the top
 of each IDLE edit window which provides block structure hints.  These hints are
 the lines which contain the block opening keywords, e.g. 'if', for the
-enclosing block.  The number of hint lines is determined by the numlines
+enclosing block.  The number of hint lines is determined by the maxlines
 variable in the codecontext section of config-extensions.def. Lines which do
 not open blocks are not shown in the context hints pane.
 
@@ -80,7 +80,7 @@ def __init__(self, editwin):
     def reload(cls):
         "Load class variables from config."
         cls.context_depth = idleConf.GetOption("extensions", "CodeContext",
-                                       "numlines", type="int", default=3)
+                                       "maxlines", type="int", default=15)
 ##        cls.bgcolor = idleConf.GetOption("extensions", "CodeContext",
 ##                                     "bgcolor", type="str", default="LightGray")
 ##        cls.fgcolor = idleConf.GetOption("extensions", "CodeContext",
@@ -116,7 +116,7 @@ def toggle_code_context_event(self, event=None):
                 padx += widget.tk.getint(widget.cget('padx'))
                 border += widget.tk.getint(widget.cget('border'))
             self.label = tkinter.Label(
-                    self.editwin.top, text="\n" * (self.context_depth - 1),
+                    self.editwin.top, text="",
                     anchor=W, justify=LEFT, font=self.textfont,
                     bg=self.bgcolor, fg=self.fgcolor,
                     width=1,  # Don't request more than we get.
@@ -191,11 +191,10 @@ def update_code_context(self):
                                                  stopindent)
         self.info.extend(lines)
         self.topvisible = new_topvisible
-        # Empty lines in context pane.
-        context_strings = [""] * max(0, self.context_depth - len(self.info))
-        # Followed by the context hint lines.
-        context_strings += [x[2] for x in self.info[-self.context_depth:]]
-        self.label["text"] = '\n'.join(context_strings)
+        # Last context_depth context lines.
+        context_strings = [x[2] for x in self.info[-self.context_depth:]]
+        showfirst = 0 if context_strings[0] else 1
+        self.label["text"] = '\n'.join(context_strings[showfirst:])
 
     def timer_event(self):
         "Event on editor text widget triggered every UPDATEINTERVAL ms."

Lib/idlelib/config-extensions.def

@@ -7,10 +7,7 @@
 popupwait= 2000
 
 [CodeContext]
-numlines= 3
-visible= False
-bgcolor= LightGray
-fgcolor= Black
+maxlines= 15
 
 [FormatParagraph]
 max-width= 72

Lib/idlelib/configdialog.py

@@ -1843,7 +1843,7 @@ def create_page_general(self):
         self.format_width = tracers.add(
                 StringVar(self), ('extensions', 'FormatParagraph', 'max-width'))
         self.context_lines = tracers.add(
-                StringVar(self), ('extensions', 'CodeContext', 'numlines'))
+                StringVar(self), ('extensions', 'CodeContext', 'maxlines'))
 
         # Create widgets:
         # Section frames.
@@ -1910,7 +1910,7 @@ def create_page_general(self):
                 frame_format, textvariable=self.format_width, width=4)
 
         frame_context = Frame(frame_editor, borderwidth=0)
-        context_title = Label(frame_context, text='Context Lines :')
+        context_title = Label(frame_context, text='Max Context Lines :')
         self.context_int = Entry(
                 frame_context, textvariable=self.context_lines, width=3)
 
@@ -2012,7 +2012,7 @@ def load_general_cfg(self):
         self.format_width.set(idleConf.GetOption(
                 'extensions', 'FormatParagraph', 'max-width', type='int'))
         self.context_lines.set(idleConf.GetOption(
-                'extensions', 'CodeContext', 'numlines', type='int'))
+                'extensions', 'CodeContext', 'maxlines', type='int'))
 
         # Set additional help sources.
         self.user_helplist = idleConf.GetAllExtraHelpSourcesList()
@@ -2204,6 +2204,9 @@ def detach(self):
 'opener' - opener '({[' corresponding to closer; 'parens' - both chars;
 'expression' (default) - also everything in between.  Flash-delay is how
 long to highlight if cursor is not moved (0 means forever).
+
+CodeContext: Maxlines is the maximum number of code context lines to
+display when Code Context is turned on for an editor window.
 '''
 }
 

Lib/idlelib/idle_test/test_codecontext.py

@@ -110,7 +110,7 @@ def test_del(self):
 
     def test_reload(self):
         codecontext.CodeContext.reload()
-        self.assertEqual(self.cc.context_depth, 3)
+        self.assertEqual(self.cc.context_depth, 15)
 
     def test_toggle_code_context_event(self):
         eq = self.assertEqual
@@ -127,7 +127,7 @@ def test_toggle_code_context_event(self):
         eq(cc.label['font'], cc.textfont)
         eq(cc.label['fg'], cc.fgcolor)
         eq(cc.label['bg'], cc.bgcolor)
-        eq(cc.label['text'], '\n' * 2)
+        eq(cc.label['text'], '')
 
         # Toggle off.
         eq(toggle(), 'break')
@@ -193,24 +193,26 @@ def test_update_code_context(self):
         eq(cc.info, [(0, -1, '', False)])
         eq(cc.topvisible, 1)
 
+        # Scroll down to line 1.
+        cc.text.yview(1)
+        cc.update_code_context()
+        eq(cc.info, [(0, -1, '', False)])
+        eq(cc.topvisible, 2)
+        eq(cc.label['text'], '')
+
         # Scroll down to line 2.
         cc.text.yview(2)
         cc.update_code_context()
         eq(cc.info, [(0, -1, '', False), (2, 0, 'class C1():', 'class')])
         eq(cc.topvisible, 3)
-        # context_depth is 3 so it pads with blank lines.
-        eq(cc.label['text'], '\n'
-                             '\n'
-                             'class C1():')
+        eq(cc.label['text'], 'class C1():')
 
         # Scroll down to line 3.  Since it's a comment, nothing changes.
         cc.text.yview(3)
         cc.update_code_context()
         eq(cc.info, [(0, -1, '', False), (2, 0, 'class C1():', 'class')])
         eq(cc.topvisible, 4)
-        eq(cc.label['text'], '\n'
-                             '\n'
-                             'class C1():')
+        eq(cc.label['text'], 'class C1():')
 
         # Scroll down to line 4.
         cc.text.yview(4)
@@ -219,8 +221,7 @@ def test_update_code_context(self):
                      (2, 0, 'class C1():', 'class'),
                      (4, 4, '    def __init__(self, a, b):', 'def')])
         eq(cc.topvisible, 5)
-        eq(cc.label['text'], '\n'
-                             'class C1():\n'
+        eq(cc.label['text'], 'class C1():\n'
                              '    def __init__(self, a, b):')
 
         # Scroll down to line 11.  Last 'def' is removed.
@@ -232,7 +233,8 @@ def test_update_code_context(self):
                      (8, 8, '        if a > b:', 'if'),
                      (10, 8, '        elif a < b:', 'elif')])
         eq(cc.topvisible, 12)
-        eq(cc.label['text'], '    def compare(self):\n'
+        eq(cc.label['text'], 'class C1():\n'
+                             '    def compare(self):\n'
                              '        if a > b:\n'
                              '        elif a < b:')
 
@@ -245,7 +247,8 @@ def test_update_code_context(self):
                      (8, 8, '        if a > b:', 'if'),
                      (10, 8, '        elif a < b:', 'elif')])
         eq(cc.topvisible, 12)
-        eq(cc.label['text'], '    def compare(self):\n'
+        eq(cc.label['text'], 'class C1():\n'
+                             '    def compare(self):\n'
                              '        if a > b:\n'
                              '        elif a < b:')
 

Lib/idlelib/idle_test/test_configdialog.py

@@ -1170,7 +1170,7 @@ def test_paragraph(self):
     def test_context(self):
         self.page.context_int.delete(0, 'end')
         self.page.context_int.insert(0, '1')
-        self.assertEqual(extpage, {'CodeContext': {'numlines': '1'}})
+        self.assertEqual(extpage, {'CodeContext': {'maxlines': '1'}})
 
     def test_source_selected(self):
         d = self.page

Misc/NEWS.d/next/IDLE/2018-05-24-20-42-44.bpo-33642.J0VQbS.rst

@@ -0,0 +1,9 @@
+IDLE: Only display actual code context lines.
+Instead of displaying a fixed number of lines, some blank, Code Context
+now displays the variable number of actual context lines.  When there
+are no context lines, it shows a single blank line to indicate that the
+feature is turned on.
+
+The Code Context configuration option is changed from 'numlines'
+(default 3) to 'maxlines' (default 15) to avoid possible interference
+between user settings for the old and new versions of Code Context.