"""CodeContext - Extension to display the block context above the edit window

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Once code has scrolled off the top of a window, it can be difficult to

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determine which block you are in. This extension implements a pane at the top

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of each IDLE edit window which provides block structure hints. These hints are

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the lines which contain the block opening keywords, e.g. 'if', for the

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enclosing block. The number of hint lines is determined by the numlines

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variable in the CodeContext section of config-extensions.def. Lines which do

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not open blocks are not shown in the context hints pane.

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"""

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import Tkinter

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from Tkconstants import TOP, LEFT, X, W, SUNKEN

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import re

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from sys import maxint as INFINITY

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from idlelib.configHandler import idleConf

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BLOCKOPENERS = {"class", "def", "elif", "else", "except", "finally", "for",

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"if", "try", "while", "with"}

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UPDATEINTERVAL = 100 # millisec

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FONTUPDATEINTERVAL = 1000 # millisec

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getspacesfirstword =\

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lambda s, c=re.compile(r"^(\s*)(\w*)"): c.match(s).groups()

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class CodeContext:

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menudefs = [('options', [('!Code Conte_xt', '<<toggle-code-context>>')])]

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context_depth = idleConf.GetOption("extensions", "CodeContext",

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"numlines", type="int", default=3)

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bgcolor = idleConf.GetOption("extensions", "CodeContext",

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"bgcolor", type="str", default="LightGray")

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fgcolor = idleConf.GetOption("extensions", "CodeContext",

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"fgcolor", type="str", default="Black")

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def __init__(self, editwin):

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self.editwin = editwin

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self.text = editwin.text

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self.textfont = self.text["font"]

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self.label = None

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# self.info is a list of (line number, indent level, line text, block

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# keyword) tuples providing the block structure associated with

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# self.topvisible (the linenumber of the line displayed at the top of

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# the edit window). self.info[0] is initialized as a 'dummy' line which

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# starts the toplevel 'block' of the module.

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self.info = [(0, -1, "", False)]

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self.topvisible = 1

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visible = idleConf.GetOption("extensions", "CodeContext",

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"visible", type="bool", default=False)

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if visible:

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self.toggle_code_context_event()

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self.editwin.setvar('<<toggle-code-context>>', True)

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# Start two update cycles, one for context lines, one for font changes.

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self.text.after(UPDATEINTERVAL, self.timer_event)

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self.text.after(FONTUPDATEINTERVAL, self.font_timer_event)

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def toggle_code_context_event(self, event=None):

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if not self.label:

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# Calculate the border width and horizontal padding required to

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# align the context with the text in the main Text widget.

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#

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# All values are passed through int(str(<value>)), since some

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# values may be pixel objects, which can't simply be added to ints.

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widgets = self.editwin.text, self.editwin.text_frame

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# Calculate the required vertical padding

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padx = 0

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for widget in widgets:

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padx += int(str( widget.pack_info()['padx'] ))

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padx += int(str( widget.cget('padx') ))

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# Calculate the required border width

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border = 0

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for widget in widgets:

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border += int(str( widget.cget('border') ))

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self.label = Tkinter.Label(self.editwin.top,

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text="\n" * (self.context_depth - 1),

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anchor=W, justify=LEFT,

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font=self.textfont,

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bg=self.bgcolor, fg=self.fgcolor,

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width=1, #don't request more than we get

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padx=padx, border=border,

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relief=SUNKEN)

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# Pack the label widget before and above the text_frame widget,

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# thus ensuring that it will appear directly above text_frame

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self.label.pack(side=TOP, fill=X, expand=False,

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before=self.editwin.text_frame)

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else:

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self.label.destroy()

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self.label = None

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idleConf.SetOption("extensions", "CodeContext", "visible",

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str(self.label is not None))

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idleConf.SaveUserCfgFiles()

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def get_line_info(self, linenum):

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"""Get the line indent value, text, and any block start keyword

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If the line does not start a block, the keyword value is False.

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The indentation of empty lines (or comment lines) is INFINITY.

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"""

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text = self.text.get("%d.0" % linenum, "%d.end" % linenum)

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spaces, firstword = getspacesfirstword(text)

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opener = firstword in BLOCKOPENERS and firstword

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if len(text) == len(spaces) or text[len(spaces)] == '#':

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indent = INFINITY

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else:

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indent = len(spaces)

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return indent, text, opener

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def get_context(self, new_topvisible, stopline=1, stopindent=0):

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"""Get context lines, starting at new_topvisible and working backwards.

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Stop when stopline or stopindent is reached. Return a tuple of context

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data and the indent level at the top of the region inspected.

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"""

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assert stopline > 0

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lines = []

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# The indentation level we are currently in:

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lastindent = INFINITY

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# For a line to be interesting, it must begin with a block opening

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# keyword, and have less indentation than lastindent.

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for linenum in xrange(new_topvisible, stopline-1, -1):

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indent, text, opener = self.get_line_info(linenum)

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if indent < lastindent:

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lastindent = indent

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if opener in ("else", "elif"):

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# We also show the if statement

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lastindent += 1

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if opener and linenum < new_topvisible and indent >= stopindent:

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lines.append((linenum, indent, text, opener))

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if lastindent <= stopindent:

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break

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lines.reverse()

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return lines, lastindent

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def update_code_context(self):

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"""Update context information and lines visible in the context pane.

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"""

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new_topvisible = int(self.text.index("@0,0").split('.')[0])

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if self.topvisible == new_topvisible: # haven't scrolled

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return

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if self.topvisible < new_topvisible: # scroll down

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lines, lastindent = self.get_context(new_topvisible,

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self.topvisible)

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# retain only context info applicable to the region

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# between topvisible and new_topvisible:

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while self.info[-1][1] >= lastindent:

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del self.info[-1]

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elif self.topvisible > new_topvisible: # scroll up

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stopindent = self.info[-1][1] + 1

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# retain only context info associated

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# with lines above new_topvisible:

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while self.info[-1][0] >= new_topvisible:

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stopindent = self.info[-1][1]

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del self.info[-1]

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lines, lastindent = self.get_context(new_topvisible,

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self.info[-1][0]+1,

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stopindent)

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self.info.extend(lines)

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self.topvisible = new_topvisible

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# empty lines in context pane:

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context_strings = [""] * max(0, self.context_depth - len(self.info))

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# followed by the context hint lines:

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context_strings += [x[2] for x in self.info[-self.context_depth:]]

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self.label["text"] = '\n'.join(context_strings)

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def timer_event(self):

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if self.label:

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self.update_code_context()

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self.text.after(UPDATEINTERVAL, self.timer_event)

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def font_timer_event(self):

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newtextfont = self.text["font"]

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if self.label and newtextfont != self.textfont:

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self.textfont = newtextfont

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self.label["font"] = self.textfont

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self.text.after(FONTUPDATEINTERVAL, self.font_timer_event)

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