opengeode.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# pylint: disable=C0302
"""
    OpenGEODE - A tiny, free SDL Editor for TASTE

    SDL is the Specification and Description Language (Z100 standard from ITU)

    Copyright (c) 2012-2013 European Space Agency

    Designed and implemented by Maxime Perrotin

    Contact: maxime.perrotin@esa.int
"""

import signal
import sys
import os
import argparse
import logging
import traceback
import re
import code
import pprint
import random
from functools import partial
from itertools import chain

# To freeze the application on Windows, all modules must be imported even
# when they are not directly used from this module (py2exe bug)
# NOQA makes flake8 ignore locally-ununsed modules
# pylint: disable=W0611
import enum  # NOQA
import string  # NOQA
import fnmatch  # NOQA
import operator  # NOQA
import subprocess  # NOQA
import distutils  # NOQA
import tempfile  # NOQA
import uuid  # NOQA
import importlib  # NOQA
import antlr3  # NOQA
import antlr3.tree  # NOQA
import importlib  # NOQA
import PySide  # NOQA
import PySide.QtCore  # NOQA
import PySide.QtGui  # NOQA
import PySide.QtUiTools  # NOQA
import undoCommands  # NOQA
import sdl92Lexer  # NOQA
import sdl92Parser  # NOQA
import genericSymbols  # NOQA
import PySide.QtXml  # NOQA
import singledispatch  # NOQA
import Asn1scc  # NOQA
import Connectors  # NOQA
import TextInteraction  # NOQA
import pygraphviz  # NOQA
import sdlSymbols
import AdaGenerator
import ogParser
import ogAST
import Renderer
import Clipboard
import Statechart
import Lander
import Helper
import Pr
import CGenerator

# Enable mypy type checking
try:
    from typing import List, Union, Dict, Set
except ImportError:
    pass

try:
    import stringtemplate3  # NOQA
except ImportError:
    pass

#from PySide import phonon

from PySide import QtGui, QtCore
from PySide.QtCore import Qt, QSize, QFile, QIODevice, QRectF, QTimer, QPoint

from PySide.QtUiTools import QUiLoader
from PySide import QtSvg

from genericSymbols import(Symbol, Comment, Cornergrabber, Connection)
from sdlSymbols import(Input, Output, Decision, DecisionAnswer, Task,
        ProcedureCall, TextSymbol, State, Start, Join, Label, Procedure,
        ProcedureStart, ProcedureStop, StateStart, Connect, Process,
        ContinuousSignal)
from TextInteraction import EditableText

# Icons and png files generated from the resource file:
import icons  # NOQA

# Logging: ist of properly loaded modules that will use it
LOG = logging.getLogger(__name__)
MODULES = [
    sdlSymbols,
    genericSymbols,
    ogAST,
    ogParser,
    Lander,
    AdaGenerator,
    undoCommands,
    Renderer,
    Clipboard,
    Statechart,
    Helper,
    Asn1scc,
    Connectors,
    Pr,
    TextInteraction,
    Connectors,
    CGenerator,
] # type: List[module]

try:
    import LlvmGenerator
    MODULES.append(LlvmGenerator)
except ImportError:
    pass

try:
    import StgBackend
    MODULES.append(StgBackend)
except ImportError:
    pass


__all__ = ['opengeode', 'SDL_Scene', 'SDL_View', 'parse']
__version__ = '1.3.29'

if hasattr(sys, 'frozen'):
    # Detect if we are running on Windows (py2exe-generated)
    try:
        CUR_DIR = os.path.dirname(unicode
                (sys.executable, sys.getfilesystemencoding()))
    except TypeError:
        CUR_DIR = os.path.dirname(os.path.realpath(__file__))
    else:
        # Redirect stderr to a log file - to avoid py2exe error message
        # that pops up at application closure when app logs errors
        sys.stdout = open('opengeode_stdout.log', 'w')
        sys.stderr = open('opengeode_stderr.log', 'w')
else:
    CUR_DIR = os.path.dirname(os.path.realpath(__file__))


# Global handling all top-level elements
# It seems that if we don't keep a global list of these elements
# (START, STATE, and Text symbols)
# they sometimes get destroyed and disappear from the scene.
# As if a GC was deleting these object *even if they belong to the scene*
# (but have no parentItem). Most likely a Qt/Pyside bug.
G_SYMBOLS = set()


# Other Qt bug:
# QGraphicsTextItem don't stand that their parent item (usually an
# SDL symbol) is removed from the scene (scene.removeItem()). It
# provokes segfault when application exits.
# Workaround is to use hide()/show() to make items disappear
# from the scene (when deleted). Seems OK (MP 2013-03-26)

# Lookup table used to configure the context-dependent toolbars
ACTIONS = {
    'block': [Process, Comment, TextSymbol],
    'process': [Start, State, Input, Connect, ContinuousSignal, Task, Decision,
                DecisionAnswer, Output, ProcedureCall, TextSymbol, Comment,
                Label, Join, Procedure],
    'procedure': [ProcedureStart, Task, Decision,
                  DecisionAnswer, Output, ProcedureCall, TextSymbol,
                  Comment, Label, Join, ProcedureStop],
    'statechart': [],
    'state': [StateStart, State, Input, Connect, ContinuousSignal, Task,
              Decision, DecisionAnswer, Output, ProcedureCall, TextSymbol,
              Comment, Label, Join, ProcedureStop, Procedure],
    'clipboard': [Start, State, Input, Connect, Task, Decision, DecisionAnswer,
                  Output, ProcedureCall, TextSymbol, Comment, Label,
                  Join, Procedure, Process, StateStart, ProcedureStop,
                  ContinuousSignal],
    'lander': [],
    'asn1': []
}


def log_errors(window, errors, warnings, clearfirst=True):
    ''' Report Error and Warnings on the console and in the log window '''
    if window and clearfirst:
        window.clear()
    for error in errors:
        if type(error[0]) == list:
            # should be fixed now, CHECKME - NO, NOT FULLY FIXED
            # problem is in decision answers branches
            error[0] = 'Internal error - ' + str(error[0])
        LOG.error(error[0])
        item = QtGui.QListWidgetItem(u'[ERROR] ' + error[0])
        if len(error) == 3:
            item.setData(Qt.UserRole, error[1])
            #found = self.scene().symbol_near(QPoint(*error[1]), 1)
            # Pyside bug: setData cannot store 'found' directly
            #item.setData(Qt.UserRole + 1, id(found))
            item.setData(Qt.UserRole + 1, error[2])
        if window:
            window.addItem(item)
    for warning in warnings:
        LOG.warning(warning[0])
        item = QtGui.QListWidgetItem(u'[WARNING] ' + str(warning[0]))
        if len(warning) == 3:
            item.setData(Qt.UserRole, warning[1])
            item.setData(Qt.UserRole + 1, warning[2])
        if window:
            window.addItem(item)
    if not errors and not warnings and window:
        window.addItem('No errors, no warnings!')



class Vi_bar(QtGui.QLineEdit, object):
    ''' Line editor for the Vi-like command mode '''
    def __init__(self):
        ''' Create the bar - no need for parent '''
        super(Vi_bar, self).__init__()

    def keyPressEvent(self, key_event):
        ''' Handle key press - in particular Escape '''
        super(Vi_bar, self).keyPressEvent(key_event)
        if key_event.key() == Qt.Key_Escape:
            self.clearFocus()


class File_toolbar(QtGui.QToolBar, object):
    ''' Toolbar with file open, save, etc '''
    def __init__(self, parent):
        ''' Create the toolbar using standard icons '''
        super(File_toolbar, self).__init__(parent)
        self.setMovable(False)
        self.setFloatable(False)
        self.new_button = self.addAction(self.style().standardIcon(
            QtGui.QStyle.SP_FileIcon), 'New model')
        self.open_button = self.addAction(self.style().standardIcon(
            QtGui.QStyle.SP_DialogOpenButton), 'Open model')
        self.save_button = self.addAction(self.style().standardIcon(
            QtGui.QStyle.SP_DialogSaveButton), 'Save model')
        self.check_button = self.addAction(self.style().standardIcon(
            QtGui.QStyle.SP_DialogApplyButton), 'Check model')
        self.addSeparator()
        # Up arrow to come back from a subscene (e.g. procedure)
        self.up_button = self.addAction(self.style().standardIcon(
            QtGui.QStyle.SP_ArrowUp), 'Go one level above')
        self.up_button.setEnabled(False)


class Sdl_toolbar(QtGui.QToolBar, object):
    '''
        Toolbar with SDL symbols
        The list of symbols is passed as paramters at creation time ; the class
        looks for icons for the name of the symbols and .png extension.
        The buttons activation is context dependent. Configuration is done
        directly at symbol leval (using the "allowed_followers" property)
    '''
    def __init__(self, parent):
        ''' Create the toolbar, get icons and link actions '''
        super(Sdl_toolbar, self).__init__(parent)
        self.setMovable(False)
        self.setFloatable(False)
        self.setIconSize(QSize(35, 35))
        self.actions = {}

    def set_actions(self, bar_items):
        ''' Set the acons and actions on the toolbar '''
        self.actions = {}
        self.clear()
        for item in bar_items:
            item_name = item.__name__
            self.actions[item_name] = self.addAction(
                           QtGui.QIcon(':icons/{icon}'.format(
                           icon=item_name.lower() + '.png')), item_name)
        self.update_menu()

    def enable_action(self, action):
        ''' Used as a slot to allow a scene to enable a menu action,
            e.g. if the Start symbol is deleted, the Start button
            shall be activated '''
        self.actions[action].setEnabled(True)

    def disable_action(self, action):
        ''' See description in enable_action '''
        self.actions[action].setEnabled(False)

    def update_menu(self, scene=None):
        ''' Context-dependent enabling/disabling of menu buttons '''
        try:
            selection = list(scene.selected_symbols)
        except AttributeError:
            selection = []
        if not selection:
            # Second chance, check if an item has focus (editable text)
            try:
                selection.append(scene.focusItem().parentItem())
            except AttributeError:
                pass
        if len(selection) > 1:
            # When several items are selected, disable all menu entries
            for _, action in self.actions.viewitems():
                action.setEnabled(False)
        elif not selection:
            # When nothing is selected:
            # activate everything, and when user selects an icon,
            # keep the action on hold until he clicks on the scene
            for action in self.actions.viewkeys():
                self.actions[action].setEnabled(True)

            # Check for singletons (e.g. START symbol)
            try:
                for item in scene.visible_symb:
                    try:
                        if item.is_singleton:
                            self.actions[
                                    item.__class__.__name__].setEnabled(False)
                    except (AttributeError, KeyError) as error:
                        LOG.debug(str(error))
            except AttributeError:
                pass
        else:
            # Only one selected item
            selection, = selection
            for action in self.actions.viewkeys():
                self.actions[action].setEnabled(False)
            for action in getattr(selection, 'allowed_followers', []):
                try:
                    self.actions[action].setEnabled(True)
                except KeyError:
                    LOG.debug('No menu item for symbol "' + action + '"')


class SDL_Scene(QtGui.QGraphicsScene, object):
    ''' Main graphic scene (canvas) where the user can place SDL symbols '''
    # Signal to be emitted when the scene is left (e.g. UP button)
    scene_left = QtCore.Signal()

    def __init__(self, context='process'):
        '''
            Create an SDL Scene for a given context:
            process, procedure or composite state
        '''
        super(SDL_Scene, self).__init__()
        # Reference to the parent scene
        self.parent_scene = None
        self.mode = 'idle'
        self.context = context
        self.allowed_symbols = ACTIONS[context]
        # Configure the action menu
        all_possible_actions = set()
        for action in ACTIONS.viewvalues():
            all_possible_actions |= set(action)
        self.actions = {action.__name__: partial(self.add_symbol, action)
                for action in all_possible_actions}

        # Create a stack for handling undo/redo commands
        # (defined in undoCommands.py)
        self.undo_stack = QtGui.QUndoStack(self)
        # buttonSelected is used to set which symbol to draw
        # on next scene click (see mousePressEvent)
        self.button_selected = None
        self.setBackgroundBrush(QtGui.QBrush(
                                           QtGui.QImage(':icons/texture.png')))
        self.messages_window = None
        self.click_coordinates = None
        self.orig_pos = None
        self.process_name = 'opengeode'
        # Scene name is used to update the tab window name when scene changes
        self.name = ''
        # search_item/search_pattern are used for search/replace function
        self.search_item = None
        self.search_pattern = None
        # Selection rectangle when user clicks on the scene and moves mouse
        self.select_rect = None
        # Keep a list of composite states: {'stateName': SDL_Scene}
        self._composite_states = {}
        # Keep a track of highlighted symbols: { symbol: brush }
        self.highlighted = {}


    def is_aggregation(self):
        ''' Determine if the current scene is a state aggregation, i.e. if
        if contains only floating states without children
        '''
        for each in self.visible_symb:
            if each.hasParent:
                return False
            if not isinstance(each, State):
                # At the moment do not support Text Areas
                return False
            if any(child for child in each.childSymbols()
                    if isinstance(child, (Input, ContinuousSignal))):
                return False
        return True


    @property
    def visible_symb(self):
        ''' Return the visible items of a scene '''
        return (it for it in self.items() if it.isVisible() and
                isinstance(it, Symbol))


    @property
    def editable_texts(self):
        ''' Return all EditableText areas of a scene '''
        return (it for it in self.items() if it.isVisible() and
                isinstance(it, EditableText))


    @property
    def floating_symb(self):
        ''' Return the top level floating items of a scene '''
        return (it for it in self.visible_symb if not it.hasParent)


    @property
    def processes(self):
        ''' Return visible processes components of the scene '''
        return (it for it in self.visible_symb if isinstance(it, Process) and
                not isinstance(it, Procedure))


    @property
    def procedures(self):
        ''' Return visible procedures components of the scene '''
        return (it for it in self.visible_symb if isinstance(it, Procedure))


    @property
    def states(self):
        ''' Return visible state components of the scene '''
        return (it for it in self.visible_symb if isinstance(it, State))


    @property
    def texts(self):
        ''' Return visible text areas components of the scene '''
        return (it for it in self.visible_symb if isinstance(it, TextSymbol))


    @property
    def procs(self):
        ''' Return visible procedure declaration components of the scene '''
        return (it for it in self.visible_symb if isinstance(it, Procedure))


    @property
    def start(self):
        ''' Return visible start components of the scene '''
        return (it for it in self.visible_symb if isinstance(it, Start))


    @property
    def floating_labels(self):
        ''' Return visible floating label components of the scene '''
        return (it for it in self.floating_symb if isinstance(it, Label))


    @property
    def returns(self):
        ''' Return visible return components of the scene '''
        return (it for it in self.visible_symb if isinstance(it,
                                                              ProcedureStop))


    @property
    def composite_states(self):
        ''' Return states that contain a composite part '''
        # Update the list first
        for each in self.states:
            if each.is_composite() and \
                  each.nested_scene not in self._composite_states.viewvalues():
                self._composite_states[unicode(each).split()[0].lower()] = \
                                                            each.nested_scene
        return self._composite_states


    @composite_states.setter
    def composite_states(self, value):
        ''' Attribute setter '''
        self._composite_states = value


    @property
    def all_nested_scenes(self):
        ''' Return all nested scenes, recursively '''
        for each in self.visible_symb:
            if each.nested_scene and isinstance(each.nested_scene, SDL_Scene):
                yield each.nested_scene
                for sub in each.nested_scene.all_nested_scenes:
                    yield sub


    @property
    def path(self):
        ''' Get the path to the current scene as a list
        e.g. ['BLOCK a', 'PROCESS b', ...]
        '''
        if not self.parent_scene:
            return [self.name[0:-3]]
        return self.parent_scene.path + [self.name[0:-3]]


    @property
    def selected_symbols(self):
        ''' Generate the list of selected symbols (excluding grabbers) '''
        for selection in self.selectedItems():
            if isinstance(selection, Symbol):
                yield selection
            elif isinstance(selection, Cornergrabber):
                yield selection.parent


    def quit_scene(self):
        ''' Called in case of scene switch (e.g. UP button) '''
        pass


    def render_everything(self, ast):
        ''' Render a process and its children scenes, recursively '''
        already_created = []

        def recursive_render(content, dest_scene):
            ''' Process the rendering in scenes and nested scenes '''
            if isinstance(content, ogAST.Process):
                # XXX - should be set when entering the process
                self.process_name = ast.processName

            try:
                # Render top-level items and their children:
                for each in Renderer.render(content, dest_scene):
                    G_SYMBOLS.add(each)
                # Refreshing the scene may result in resizing some symbols
                dest_scene.refresh()
                for each in dest_scene.floating_symb:
                    # Once everything is rendered, adjust position of each
                    # symbol to the value from the AST (positions may be
                    # slightly altered by the reshaping functions)
                    def fix_pos_from_ast(symbol):
                        try:
                            if symbol.ast.pos_x and symbol.ast.pos_y:
                                relpos = symbol.mapFromScene(symbol.ast.pos_x,
                                                           symbol.ast.pos_y)
                                symbol.pos_x += relpos.x()
                                symbol.pos_y += relpos.y()
                                symbol.update_connections()
                                # Update_position is called here because it
                                # is not possible to be sure that the
                                # positionning stored in the file will be
                                # rendered correctly on the host plaform.
                                # Font rendering may cause slight differences
                                # between Linux and Windows for example.
                                symbol.update_position()
                            else:
                                # No CIF coordinates: (1) fix COMMENT position
                                # and (2) if floating call CAM
                                if isinstance(symbol, genericSymbols.Comment):
                                    symbol.pos_x = \
                                      symbol.parent.boundingRect().width() + 15
                                    symbol.pos_y = 0
                                if not symbol.hasParent:
                                    #print 'Positionning', unicode(symbol)[slice(0,20)]
                                    sc_br = dest_scene.itemsBoundingRect()
                                    sy_br = symbol.mapRectToScene(
                                                symbol.boundingRect() |
                                                symbol.childrenBoundingRect())
                                    symbol.pos_x += (sc_br.width() - sy_br.x())
#                                   symbol.cam(symbol.position,
#                                              symbol.position)
                        except AttributeError:
                            # no AST, ignore (e.g. Connections, Cornergrabbers)
                            pass
                        else:
                            # Recursively fix pos of sub branches and followers
                            for branch in (elm for elm in symbol.childSymbols()
                                       if isinstance(elm,
                                             genericSymbols.HorizontalSymbol)):
                                fix_pos_from_ast(branch)
                            fix_pos_from_ast(symbol.next_aligned_symbol())
                            fix_pos_from_ast(symbol.comment)
                    fix_pos_from_ast(each)
            except TypeError:
                LOG.error(traceback.format_exc())

            # Render nested scenes, recursively:
            for each in (item for item in dest_scene.visible_symb
                         if item.nested_scene):
                LOG.debug(u'Recursive scene: ' + unicode(each))
                if isinstance(each.nested_scene, ogAST.CompositeState) \
                        and (not each.nested_scene.statename
                             or each.nested_scene in already_created):
                    # Ignore nested state scenes that already exist
                    LOG.debug('Subscene "{}" ignored'.format(unicode(each)))
                    continue
                subscene = \
                        self.create_subscene(each.__class__.__name__.lower(),
                                             dest_scene)
                already_created.append(each.nested_scene)
                subscene.name = unicode(each)
                LOG.debug('Created scene: {}'.format(subscene.name))
                recursive_render(each.nested_scene.content, subscene)
                each.nested_scene = subscene

            # Make sure all composite states are initially up to date
            # (Needed for the symbol shape to have dashed lines)
            for each in dest_scene.states:
                if unicode(each).lower() in \
                        dest_scene.composite_states.viewkeys():
                    each.nested_scene = dest_scene.composite_states[
                                                         unicode(each).lower()]

        recursive_render(ast, self)


    def refresh(self):
        ''' Refresh the symbols and connections in the scene '''
        LOG.debug('scene refresh')
        for symbol in self.visible_symb:
            symbol.updateConnectionPointPosition()
            symbol.updateConnectionPoints()
        for symbol in self.editable_texts:
            # EditableText refreshing - design explanation:
            # The first one is tricky: at symbol initialization,
            # the bounding rect of the text is computed from the raw
            # text value, without any formatting. However, it can
            # happen that text (especially when a model is loaded)
            # contains highlighted data (bold), which has the effect
            # of making the width of the text in fact wider than
            # the bounding rect. The set_text_alignment function,
            # that is applying the aligment of the text within its
            # bounding rect, can work only if the text width is fixed.
            # It has to set it according to the bounding rect, which,
            # therefore can be too small, and this has the effect of
            # pushing the exceeding character to the next line.
            # The only way to avoid this is to call setTextWidth
            # with the value -1 before the aligment is computed.
            # This has the effect of re-computing the bounding rect
            # and fixing the width issue.
            symbol.setTextWidth(-1)
            symbol.set_textbox_position()
            symbol.try_resize()
            symbol.set_text_alignment()
        for symbol in self.visible_symb:
            symbol.update_connections()


    def set_cursor(self, follower):
        ''' Set the cursor shape depending on the selected menu item '''
        for item in self.items():
            try:
                if follower.__name__ not in item.allowed_followers:
                    item.setCursor(Qt.ForbiddenCursor)
                else:
                    item.setCursor(Qt.PointingHandCursor)
            except AttributeError:
                # if there are items not having allowed_followers
                pass


    def reset_cursor(self):
        ''' Reset the default cursor of an item '''
        for item in self.items():
            try:
                item.setCursor(item.default_cursor)
            except AttributeError:
                pass


    def translate_to_origin(self):
        '''
            Translate all items to coordinate system starting at (0,0),
            in order to avoid negative coordinates
        '''
        try:
            min_x = min(item.x() for item in self.floating_symb)
            min_y = min(item.y() for item in self.floating_symb)
        except ValueError:
            # No item in the scene
            return 0, 0
        delta_x = -min_x if min_x < 0 else 0
        delta_y = -min_y if min_y < 0 else 0
        for item in self.floating_symb:
            item.pos_x += delta_x
            item.pos_y += delta_y
        return delta_x, delta_y


    def set_selection(self, toolbar):
        ''' When the selection has changed, update menu, etc '''
        toolbar.update_menu(self)
        for item in self.selected_symbols:
            item.grabber.display()


    def syntax_errors(self, symb):
        ''' Parse a symbol and return a list of syntax errors '''
        return symb.check_syntax('\n'.join(Pr.generate(symb, recursive=False)))


    def check_syntax(self, symbol):
        ''' Check syntax of a symbol and display a pop-up in case of errors '''
        errors = self.syntax_errors(symbol)

        if not errors:
            return

        for view in self.views():
            errs = []
            for error in errors:
                split = error.split()
                if split[0] == 'line' and len(split) > 1:
                    line_col = split[1].split(':')
                    if len(line_col) == 2:
                        # Get line number and column..to locate error
                        # line_nb, col = line_col
                        errs.append(' '.join(split[2:]))
                    else:
                        errs.append(error)
                else:
                    errs.append(error)
            self.clear_focus()
            msg_box = QtGui.QMessageBox(view)
            msg_box.setIcon(QtGui.QMessageBox.Warning)
            msg_box.setWindowTitle('OpenGEODE - Syntax Error')
            msg_box.setInformativeText('\n'.join(errs))
            msg_box.setText("Syntax error!")
            msg_box.setStandardButtons(QtGui.QMessageBox.Discard)
            msg_box.setDefaultButton(QtGui.QMessageBox.Discard)
            msg_box.exec_()


    def global_syntax_check(self, ignore=set()):
        ''' Parse each visible symbol in the current scene and its children
            and check syntax using the parser
            Use a mutable parameter to avoid recursion on already visited
            scenes
        '''
        res = True
        reset = not ignore
        ignore.add(self)
        for each in self.visible_symb:
            errors = self.syntax_errors(each)
            if errors:
                res = False
            for err in errors:
                split = err.split()
                if split[0] == 'line' and len(split) > 1:
                    line_col = split[1].split(':')
                    if len(line_col) == 2:
                        # get line and col. line must be decremented because
                        # line 1 is the CIF comment which is not visible
                        line_nb, col = line_col
                        line_nb = int(line_nb) - 1
                        split[1] = '{}:{}'.format(line_nb, col)
                pos = each.scenePos()
                fmt = [[' '.join(split), [pos.x(), pos.y()], self.path]]
                log_errors(self.messages_window, fmt, [], clearfirst=False)

        for each in self.all_nested_scenes:
            if each not in ignore:
                if not each.global_syntax_check():
                    res = False
        if reset:
            ignore.clear()
        return res


    def update_completion_list(self, symbol):
        ''' When text has changed on a symbol, update the data dictionnary '''
        pr_text = '\n'.join(Pr.generate(symbol,
                                        recursive=False,
                                        nextstate=False, cpy=True))
        symbol.update_completion_list(pr_text=pr_text)


    def highlight(self, item):
        ''' Highlight a symbol '''
        if item in self.highlighted:
            return
        bound = item.boundingRect()
        center = bound.center().x()
        gradient = QtGui.QLinearGradient(center, 0, center, bound.height())
        gradient.setColorAt(0, Qt.cyan)
        gradient.setColorAt(1, Qt.white)
        self.highlighted[item] = item.brush()
        item.setBrush(QtGui.QBrush(gradient))

    def clear_highlight(self, item=None, reset=True):
        ''' Remove the highlighting of one item or all items on the scene '''
        if item in self.highlighted:
            self.setBrush(self.highlighted.pop(item))
        if reset:
            for item, brush in self.highlighted.viewitems():
                item.setBrush(brush)
            self.highlighted = {}


    def find_text(self, pattern):
        ''' Return all symbols with matching text '''
        for item in (symbol for symbol in self.items()
                     if isinstance(symbol, EditableText)
                     and symbol.isVisible()):
            if re.search(pattern, unicode(item), flags=re.IGNORECASE):
                yield item.parentItem()


    def search(self, pattern, replace_with=None):
        ''' Search and replace function ; get next search result with key n '''
        self.clearSelection()
        self.clear_focus()
        if pattern.endswith('\\'):
            # Avoid buggy pattern ending with a single backslash
            pattern += '\\'
        self.search_item = self.find_text(pattern)
        self.search_pattern = pattern
        if replace_with:
            with undoCommands.UndoMacro(self.undo_stack, 'Search and Replace'):
                for item in self.search_item:
                    new_string = re.sub(pattern,
                                        replace_with,
                                        unicode(item.text),
                                        flags=re.IGNORECASE)
                    undo_cmd = undoCommands.ReplaceText(
                                     item.text, unicode(item.text), new_string)
                    self.undo_stack.push(undo_cmd)
                    item.select()
            self.refresh()
        else:
            try:
                item = self.search_item.next()
                item.select()
                item.ensureVisible()
            except StopIteration:
                LOG.info('Pattern not found')


    def delete_selected_symbols(self):
        '''
            Remove selected symbols from the scene, with proper re-connections
        '''
        self.undo_stack.beginMacro('Delete items')
        for item in self.selected_symbols:
            if not item.scene():
                # Ignore if item has already been deleted
                # (in case of multiple selection)
                continue
            undo_cmd = undoCommands.DeleteSymbol(item)
            self.undo_stack.push(undo_cmd)
            try:
                item.branchEntryPoint.parent.updateConnectionPointPosition()
                item.branchEntryPoint.parent.updateConnectionPoints()
            except AttributeError:
                pass
        self.undo_stack.endMacro()


    def copy_selected_symbols(self):
        '''
            Create a copy of selected symbols to a buffer (in AST form)
            Called when user presses Ctrl-C
        '''
        self.click_coordinates = None
        try:
            Clipboard.copy(self.selected_symbols)
        except TypeError as error_msg:
            try:
                self.messages_window.addItem(unicode(error_msg))
            except AttributeError:
                LOG.error(unicode(error_msg))
            raise


    def cut_selected_symbols(self):
        '''
            Create a copy of selected symbols, then delete them
        '''
        try:
            self.copy_selected_symbols()
        except TypeError:
            LOG.error('Copy error - Cannot cut')
        else:
            self.delete_selected_symbols()


    def paste_symbols(self):
        '''
            Paste previously copied symbols at selection point
        '''
        parent = list(self.selected_symbols)
        if len(parent) > 1:
            self.messages_window.addItem(
                    'Cannot paste when several items are selected')
        else:
            parent_item, = parent or [None]
            try:
                new_items = Clipboard.paste(parent_item, self)
            except TypeError as error_msg:
                LOG.error(str(error_msg))
                try:
                    self.messages_window.addItem(str(error_msg))
                except AttributeError:
                    pass
            else:
                self.undo_stack.beginMacro('Paste')
                for item in new_items:
                    # Allow pasting inputs when input is selected
                    # Same for decision answers and connections
                    if(isinstance(parent_item, genericSymbols.HorizontalSymbol)
                            and type(parent_item) == type(item)):
                        parent_item = parent_item.parentItem()

                    undo_cmd = undoCommands.InsertSymbol(item, parent_item,
                            pos=None if parent_item
                                     else self.click_coordinates or item.pos())

                    self.undo_stack.push(undo_cmd)
                    if parent_item:
                        parent_item = item
                    else:
                        G_SYMBOLS.add(item)
                    item.cam(item.pos(), item.pos())
                self.undo_stack.endMacro()
                self.refresh()


    def sdl_to_statechart(self, basic=True):
        ''' Create a graphviz representation of the SDL model '''
        pr_raw = Pr.parse_scene(self)
        pr_data = unicode('\n'.join(pr_raw))
        ast, _, _ = ogParser.parse_pr(string=pr_data)
        try:
            process_ast, = ast.processes
        except ValueError:
            LOG.debug('No statechart to render')
            return None
        # Flatten nested states (no, because neato does not support it,
        # dot supports only vertically-aligned states, and fdp does not
        # support curved edges and is buggy with pygraphviz anyway)
        # Helper.flatten(process_ast)
        return Statechart.create_dot_graph(process_ast, basic)


    def export_branch_to_picture(self, symbol, filename, doc_format):
        ''' Save a symbol and its followers to a file '''
        temp_scene = SDL_Scene(context=self.context)
        temp_scene.messages_window = self.messages_window
        self.clearSelection()
        symbol.select()
        try:
            self.copy_selected_symbols()
            temp_scene.paste_symbols()
            temp_scene.export_img(filename, doc_format)
        except AttributeError:
            pass


    def export_img(self, filename=None, doc_format='png', split=False):
        ''' Save the scene as a PNG/SVG or PDF document
            If specified, split the diagram in multiple files, one
            per top-level floating item
        '''
        if not filename:
            return

        if split:
            # Save in multiple files
            index = 0
            for item in self.floating_symb:
                name = '{}-{}'.format(filename, str(index))
                LOG.info('Saving {ext} file: {name}.{ext}'
                         .format(ext=doc_format, name=name))
                self.export_branch_to_picture(item, name, doc_format)
                index += 1

        if filename.split('.')[-1] != doc_format:
            filename += '.' + doc_format

        self.clearSelection()
        self.clear_focus()
        # Copy in a different scene to get the smallest rectangle
        other_scene = SDL_Scene(context=self.context)
        other_scene.messages_window = self.messages_window
        other_scene.setBackgroundBrush(QtGui.QBrush())
        for each in self.floating_symb:
            each.select()
            try:
                self.copy_selected_symbols()
            except AttributeError as err:
                LOG.debug(str(traceback.format_exc()))