Support for composite states

AdaGenerator.py

@@ -136,7 +136,7 @@ def _process(process):
             else:
                 term.next_id = context.mapping[term.inputString.lower()
                                                + '_'
-                                               + term.via.lower()
+                                               + term.entrypoint.lower()
                                                + '_START']
 
     def update_composite_state(state, process):
@@ -163,20 +163,39 @@ def _process(process):
             if each.kind == 'next_state':
                 each.inputString = state.statename + '_' + each.inputString
                 update_terminator(state, each, process)
+
+    def propagate_inputs(nested_state, inputlist):
+        ''' Nested states: Inputs at level N but be handled at level N-1
+            that is, all inputs of a composite states (the ones that allow
+            to exit the composite state from the outer scope) must be
+            processed by each of the substates.
+        '''
+        for _, val in nested_state.mapping.viewitems():
+            try:
+                val.extend(inputlist)
+            except AttributeError:
+                pass
+        for each in nested_state.composite_states:
+            # do the same recursively
+            propagate_inputs(each, nested_state.mapping[nested.statename])
+            del nested_state.mapping[nested.statename]
+
     for each in process.composite_states:
         update_composite_state(each, process)
+        propagate_inputs(each, process.mapping[each.statename])
+        del process.mapping[each.statename]
 
     # Update terminators at process level
     for each in process.terminators:
         if each.kind == 'next_state':
             update_terminator(process, each, process)
 
-
     # Add the process states list to the process-level variables
     states_decl = 'type states is ('
-    states_decl += ', '.join(process.mapping.iterkeys()) + ');'
+    states_decl += ', '.join(name for name in process.mapping.iterkeys()
+                             if not name.endswith('START')) + ');'
     process_level_decl.append(states_decl)
-    process_level_decl.append('state : states := START;')
+    process_level_decl.append('state : states;')
 
     # Add function allowing to trace current state as a string
     process_level_decl.append('function get_state return String;')

Renderer.py

@@ -34,6 +34,7 @@ import ogAST
 import sdlSymbols
 import genericSymbols
 import logging
+from itertools import chain
 from singledispatch import singledispatch
 
 LOG = logging.getLogger(__name__)
@@ -130,8 +131,8 @@ def _state(ast, scene, states, terminators, parent=None):
     if new_state not in scene.items():
         scene.addItem(new_state)
 
-    for inp in ast.inputs:
-        render(inp, scene=scene, parent=new_state, states=states)
+    for exit in chain(ast.inputs, ast.connects):
+        render(exit, scene=scene, parent=new_state, states=states)
 
     new_state.nested_scene = ast.composite or ogAST.CompositeState()
 
@@ -328,3 +329,19 @@ def _input(ast, scene, parent, states):
                parent=inp,
                states=states)
     return inp
+
+@render.register(ogAST.Connect)
+def _input(ast, scene, parent, states):
+    ''' Add connect symbol from the AST to the scene '''
+    # Note: PROVIDED clause is not supported
+    conn = sdlSymbols.Connect(parent, ast=ast)
+    if conn not in scene.items():
+        scene.addItem(inp)
+    if not parent:
+        conn.setPos(ast.pos_x, ast.pos_y)
+    if ast.transition:
+        render(ast.transition,
+               scene=scene,
+               parent=conn,
+               states=states)
+    return conn

Statechart.py

@@ -60,6 +60,8 @@ class Record(genericSymbols.HorizontalSymbol, object):
             property_box = QtGui.QGraphicsTextItem(self)
             property_box.setPos(5, 30)
             property_box.setPlainText(node['properties'])
+        # Text in statecharts is read-only:
+        self.text.setTextInteractionFlags(QtCore.Qt.TextBrowserInteraction)
 
     def set_shape(self, width, height):
         ''' Define the polygon shape from width and height '''

genericSymbols.py

@@ -286,6 +286,9 @@ class EditableText(QGraphicsTextItem, object):
             Slot connected to the autocompletion popup,
             invoked when selection is made
         '''
+        if not(self.textInteractionFlags() & Qt.TextEditable):
+            self.completer.hide()
+            return
         text_cursor = self.textCursor()
         # Go back to the previously saved cursor position
         text_cursor.setPosition(self.cursor_position)
@@ -537,6 +540,8 @@ class Symbol(QObject, QGraphicsPathItem, object):
     _unique_followers = []  # unique : e.g. comment symbol
     _insertable_followers = []  # no limit to insert below current symbol
     _terminal_followers = []  # cannot be inserted between two symbols
+    # By default a symbol is resizeable
+    resizeable = True
     # By default symbol size may expand when inner text exceeds border
     auto_expand = True
     # By default connections between symbols are lines, not arrows
@@ -561,8 +566,8 @@ class Symbol(QObject, QGraphicsPathItem, object):
     redbold = ()
     # Specify if the symbol can be drawn with anti-aliasing
     _antialiasing = True
-    # Specify if the symbol text can be edited
-    editable = True
+    # Specify if the symbol has a text area
+    has_text_area = True
 
     def __init__(self, parent=None):
         '''
@@ -615,6 +620,13 @@ class Symbol(QObject, QGraphicsPathItem, object):
 
     position = Property(QPointF, _pos, _set_pos)
 
+    def is_composite(self):
+        ''' Return True if nested scene has something in it '''
+        try:
+            return any(item.isVisible() for item in self.nested_scene.items())
+        except AttributeError:
+            return False
+
     @property
     def allowed_followers(self):
         '''
@@ -714,7 +726,7 @@ class Symbol(QObject, QGraphicsPathItem, object):
             _, syntax_errors, ___, ____, _____ = (
                                 self.parser.parseSingleElement(
                                                 self.common_name, repr(self)))
-        except AssertionError:
+        except (AssertionError, AttributeError):
             LOG.error('Checker failed - no parser for this construct?')
         else:
             try:
@@ -885,6 +897,8 @@ class Symbol(QObject, QGraphicsPathItem, object):
 
     def resize_item(self, rect):
         ''' resize item, e.g. when editing text - move children accordingly '''
+        if not self.resizeable:
+            return
         pos = self.pos()
         delta_x = (self.boundingRect().width() - rect.width()) / 2.0
         delta_y = self.boundingRect().height() - rect.height()
@@ -1170,7 +1184,7 @@ class Comment(Symbol, object):
             Redefinition of the Resize function
             (Comment symbol only resizes in one direction)
         '''
-        if self.grabber.resize_mode.endswith('left'):
+        if not self.resizeable or self.grabber.resize_mode.endswith('left'):
             return
         self.set_shape(rect.width(), rect.height())
         self.update_connections()
@@ -1298,6 +1312,9 @@ class Cornergrabber(QGraphicsPolygonItem, object):
             # Parent item may have changed its cursor (e.g. when inserting
             # items). In that case, don't override the cursor for that area
             cursor = self.parent.cursor()
+        elif not self.parent.resizeable:
+            cursor = self.parent.default_cursor
+            self.resize_mode = ''
         # Left side
         elif 0.0 <= pos.x() <= 10.0:
             # Top-left corner: disabled
@@ -1311,7 +1328,6 @@ class Cornergrabber(QGraphicsPolygonItem, object):
                 self.resize_mode = 'left'
         # Middle of item
         elif 5.0 < pos.x() < self.boundingRect().width() - 10.0 and (
-                     # pos.y() <= 10.0 or
                      pos.y() > self.boundingRect().height() - 10.0):
             cursor = Qt.SizeVerCursor
             self.resize_mode = 'bottom'
@@ -1344,7 +1360,7 @@ class HorizontalSymbol(Symbol, object):
         super(HorizontalSymbol, self).__init__(parent)
         self.minDistanceToSymbolAbove = 20
         self.connection = None
-        if self.editable:
+        if self.has_text_area:
             self.text = EditableText(parent=self, text=text,
                     hyperlink=hyperlink)
         if parent:
@@ -1412,7 +1428,8 @@ class HorizontalSymbol(Symbol, object):
         ''' Return all the items's sibling symbols '''
         try:
             return (item for item in self.parent.childItems()
-                    if item is not self and type(item) is type(self))
+                    if item is not self and (isinstance(self, type(item)) or
+                        isinstance(item, type(self)))) # is type(self))
         except:
             return ()
 
@@ -1508,7 +1525,7 @@ class VerticalSymbol(Symbol, object):
             x=None, y=None, hyperlink=None):
         super(VerticalSymbol, self).__init__(parent)
         self.connection = None
-        if self.editable:
+        if self.has_text_area:
             self.text = EditableText(parent=self,
                                      text=text,
                                      hyperlink=hyperlink)

icons/connect.svg

+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="48px"
+   height="48px"
+   id="svg3021"
+   version="1.1"
+   inkscape:version="0.48.4 r9939"
+   sodipodi:docname="connect.svg"
+   inkscape:export-filename="/home/maxime/taste/tool-src/misc/opengeode/icons/connect.png"
+   inkscape:export-xdpi="90"
+   inkscape:export-ydpi="90">
+  <defs
+     id="defs3023">
+    <marker
+       inkscape:stockid="Arrow2Mend"
+       orient="auto"
+       refY="0.0"
+       refX="0.0"
+       id="Arrow2Mend"
+       style="overflow:visible;">
+      <path
+         id="path3838"
+         style="fill-rule:evenodd;stroke-width:0.62500000;stroke-linejoin:round;"
+         d="M 8.7185878,4.0337352 L -2.2072895,0.016013256 L 8.7185884,-4.0017078 C 6.9730900,-1.6296469 6.9831476,1.6157441 8.7185878,4.0337352 z "
+         transform="scale(0.6) rotate(180) translate(0,0)" />
+    </marker>
+    <marker
+       inkscape:stockid="Arrow1Mstart"
+       orient="auto"
+       refY="0.0"
+       refX="0.0"
+       id="Arrow1Mstart"
+       style="overflow:visible">
+      <path
+         id="path3817"
+         d="M 0.0,0.0 L 5.0,-5.0 L -12.5,0.0 L 5.0,5.0 L 0.0,0.0 z "
+         style="fill-rule:evenodd;stroke:#000000;stroke-width:1.0pt"
+         transform="scale(0.4) translate(10,0)" />
+    </marker>
+    <marker
+       inkscape:stockid="Arrow2Lend"
+       orient="auto"
+       refY="0.0"
+       refX="0.0"
+       id="Arrow2Lend"
+       style="overflow:visible;">
+      <path
+         id="path3832"
+         style="fill-rule:evenodd;stroke-width:0.62500000;stroke-linejoin:round;"
+         d="M 8.7185878,4.0337352 L -2.2072895,0.016013256 L 8.7185884,-4.0017078 C 6.9730900,-1.6296469 6.9831476,1.6157441 8.7185878,4.0337352 z "
+         transform="scale(1.1) rotate(180) translate(1,0)" />
+    </marker>
+  </defs>
+  <sodipodi:namedview
+     id="base"
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1.0"
+     inkscape:pageopacity="0.0"
+     inkscape:pageshadow="2"
+     inkscape:zoom="7"
+     inkscape:cx="24"
+     inkscape:cy="24"
+     inkscape:current-layer="layer1"
+     showgrid="true"
+     inkscape:grid-bbox="true"
+     inkscape:document-units="px"
+     inkscape:window-width="894"
+     inkscape:window-height="688"
+     inkscape:window-x="960"
+     inkscape:window-y="134"
+     inkscape:window-maximized="0" />
+  <metadata
+     id="metadata3026">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+        <dc:title />
+      </cc:Work>
+    </rdf:RDF>
+  </metadata>
+  <g
+     id="layer1"
+     inkscape:label="Layer 1"
+     inkscape:groupmode="layer">
+    <rect
+       style="opacity:0.98999999;fill:#ffdab9;stroke:#000000;stroke-width:0.99311829;stroke-opacity:1"
+       id="rect3029"
+       width="46.720268"
+       height="27.150137"
+       x="0.85415173"
+       y="0.56778735"
+       rx="10.993615"
+       ry="13.575068" />
+    <rect
+       style="opacity:0.98999999;fill:#ffdab9;stroke:#000000;stroke-width:0.79259622;stroke-opacity:1"
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+       width="39.206127"
+       height="20.607506"
+       x="4.7540388"
+       y="3.6228223"
+       rx="9.2254829"
+       ry="10.303753" />
+    <path
+       style="fill:none;stroke:#000000;stroke-width:1.23133481;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-opacity:1;stroke-dasharray:none;marker-end:url(#Arrow2Mend)"
+       d="M 24.271272,27.713533 24.436688,46.625446 24.171719,27.65284 24.436688,45.496976"
+       id="path3019"
+       inkscape:connector-curvature="0"
+       sodipodi:nodetypes="cccc" />
+  </g>
+</svg>

ogAST.py

@@ -391,7 +391,10 @@ class Terminator(object):
         # Return expression
         self.return_expr = None
         # via clause, used for entering nested state with an entry point
+        # 'via' is the string for the renderer (e.g. "via foo")
         self.via = None
+        # 'entrypoint' is the string of the entry point (e.g. "foo")
+        self.entrypoint = None
         # some transitions can be chained, when entering/leaving nested states
         self.next_id = -1
 
@@ -508,6 +511,21 @@ class Input(object):
                 l=self.line, c=self.charPositionInLine)
 
 
+class Connect(Input):
+    ''' AST Entry for the CONNECT part (transition below a nested state) '''
+    def __init__(self):
+        ''' Only one difference with INPUT: the connect_list attribute '''
+        super(Connect, self).__init__()
+        # List of strings
+        self.connect_list = []
+        self.width = 1
+
+    def __repr__(self):
+        ''' Debug output for a CONNECT symbol '''
+        return 'CONNECT {exp} ({l},{c})'.format(exp=self.inputString,
+                l=self.line, c=self.charPositionInLine)
+
+
 class Start(object):
     ''' AST Entry for the START symbol '''
     def __init__(self):
@@ -578,6 +596,8 @@ class State(object):
         self.height = 35
         # list of type Input
         self.inputs = []
+        # list of type Connect (connection below a nested state)
+        self.connects = []
         # optional comment symbol
         self.comment = None
         # optional hyperlink

ogParser.py

@@ -1777,7 +1777,6 @@ def process_definition(root, parent=None):
             errors.extend(err)
             warnings.extend(warn)
             process.composite_states.append(comp)
-            warnings.append('Composite state detected but not supported yet')
         elif child.type == lexer.REFERENCED:
             process.referenced = True
         else:
@@ -1788,8 +1787,7 @@ def process_definition(root, parent=None):
 def input_part(root, parent, context):
     ''' Parse an INPUT - set of TASTE provided interfaces '''
     i = ogAST.Input()
-    warnings = []
-    errors = []
+    warnings, errors = [], []
     coord = False
     # Keep track of the number of terminator statements follow the input
     # useful if we want to render graphs from the SDL model
@@ -1946,7 +1944,8 @@ def state(root, parent, context):
                               'be followed by a connect statement'
                               .format(state_def.statelist[0]))
             else:
-                err, warn = connect_part(child, state_def, context)
+                conn_part, err, warn = connect_part(child, state_def, context)
+                state_def.connects.append(conn_part)
                 warnings.extend(warn)
                 errors.extend(err)
         elif child.type == lexer.COMMENT:
@@ -1976,31 +1975,59 @@ def state(root, parent, context):
 
 
 def connect_part(root, parent, context):
-    ''' Connection of a nested state exit point with a transition '''
+    ''' Connection of a nested state exit point with a transition
+        Very similar to INPUT '''
     errors, warnings = [], []
-    connect_list = []
+    coord = False
+    conn = ogAST.Connect()
     statename = parent.statelist[0].lower()
+    id_token = []
+    # Keep track of the number of terminator statements follow the input
+    # useful if we want to render graphs from the SDL model
+    terms = len(context.terminators)
     # Retrieve composite state
     nested, = (comp for comp in context.composite_states
                if comp.statename == statename)
 
     for child in root.getChildren():
-        if child.type == lexer.ID:
-            connect_list.append(child.toString().lower())
+        if child.type == lexer.CIF:
+            # Get symbol coordinates
+            conn.pos_x, conn.pos_y, conn.width, conn.height = cif(child)
+            coord = True
+        elif child.type == lexer.ID:
+            id_token.append(child)
+            conn.connect_list.append(child.toString().lower())
         elif child.type == lexer.ASTERISK:
-            connect_list = nested.state_exitpoints
+            id_token.append(child)
+            conn.connect_list = nested.state_exitpoints
         elif child.type == lexer.TRANSITION:
-            trans, err, warn = transition(child, parent, context=context)
+            trans, err, warn = transition(child, parent=conn, context=context)
             errors.extend(err)
             warnings.extend(warn)
             context.transitions.append(trans)
             trans_id = len(context.transitions) - 1
+            conn.transition_id = trans_id
+            conn.transition = trans
+        elif child.type == lexer.HYPERLINK:
+            conn.hyperlink = child.getChild(0).toString()[1:-1]
+        elif child.type == lexer.COMMENT:
+            conn.comment, _, ___ = end(child)
         else:
             warnings.append('Unsupported CONNECT PART child type: ' +
-                            str(child.type))
-    if not connect_list:
-        connect_list.append('')
-    for exitp in connect_list:
+                            sdl92Parser.tokenNames[child.type])
+    if not conn.connect_list:
+        conn.connect_list.append('')
+    if not id_token:
+        conn.inputString = ''
+        conn.line = root.getLine()
+        conn.charPositionInLine = root.getCharPositionInLine()
+    else:
+        conn.line = id_token[0].getLine()
+        conn.charPositionInLine = id_token[0].getCharPositionInLine()
+        conn.inputString = token_stream(id_token[0]).toString(
+                                        id_token[0].getTokenStartIndex(),
+                                        id_token[-1].getTokenStopIndex())
+    for exitp in conn.connect_list:
         if exitp != '' and not exitp in nested.state_exitpoints:
             errors.append('Exit point {ep} not defined in state {st}'
                           .format(ep=exitp, st=statename))
@@ -2013,7 +2040,13 @@ def connect_part(root, parent, context):
         for each in terminators:
             # Set transition ID, referencing process.transitions
             each.next_id = trans_id
-    return errors, warnings
+    # Set list of terminators
+    conn.terminators = list(context.terminators[terms:])
+    # Report errors with symbol coordinates
+    if coord:
+        errors = [[e, [conn.pos_x, conn.pos_y]] for e in errors]
+        warnings = [[w, [conn.pos_x, conn.pos_y]] for w in warnings]
+    return conn, errors, warnings
 
 
 def cif(root):
@@ -2303,38 +2336,41 @@ def decision(root, parent, context):
 
 def nextstate(root, context):
     ''' Parse a NEXTSTATE [VIA State_Entry_Point] '''
-    next_state_id, via = '', None
+    next_state_id, via, entrypoint = '', None, None
     for child in root.getChildren():
         if child.type == lexer.ID:
-            next_state_id = child.text.lower()
+            next_state_id = child.text
         elif child.type == lexer.DASH:
             next_state_id = '-'
         elif child.type == lexer.VIA:
             if next_state_id.strip() != '-':
-                via = child.getChild(0).text.lower()
+                via = get_input_string(root).replace(
+                                                'NEXTSTATE', '', 1).strip()
+                entrypoint = child.getChild(0).text
                 try:
                     composite, = (comp for comp in context.composite_states
-                                  if comp.statename == next_state_id)
+                                  if comp.statename.lower()
+                                                == next_state_id.lower())
                 except ValueError:
                     raise TypeError('State {} is not a composite state'
                                     .format(next_state_id))
                 else:
-                    if via not in composite.state_entrypoints:
+                    if entrypoint.lower() not in composite.state_entrypoints:
                         raise TypeError('State {s} has no "{p}" entrypoint'
-                                        .format(s=next_state_id, p=via))
+                                        .format(s=next_state_id, p=entrypoint))
                     for each in composite.content.named_start:
-                        if each.inputString == via + '_START':
+                        if each.inputString == entrypoint.lower() + '_START':
                             break
                     else:
                         raise TypeError('Entrypoint {p} in state {s} is '
                                         'declared but not defined'.format
-                                        (s=next_state_id, p=via))
+                                        (s=next_state_id, p=entrypoint))
             else:
                 raise TypeError('"History" NEXTSTATE'
                                  ' cannot have a "via" clause')
         else:
             raise TypeError('NEXTSTATE undefined construct')
-    return next_state_id, via
+    return next_state_id, via, entrypoint
 
 
 def terminator_statement(root, parent, context):
@@ -2357,7 +2393,7 @@ def terminator_statement(root, parent, context):
         elif term.type == lexer.NEXTSTATE:
             t.kind = 'next_state'
             try:
-                t.inputString, t.via = nextstate(term, context)
+                t.inputString, t.via, t.entrypoint = nextstate(term, context)
             except TypeError as err:
                 errors.append(str(err))
             t.line = term.getChild(0).getLine()
@@ -2839,7 +2875,7 @@ def parseSingleElement(elem='', string=''):
             'terminator_statement', 'label', 'task', 'procedure_call', 'end',
             'text_area', 'state', 'start', 'procedure', 'floating_label',
             'connect_part'))
-    LOG.debug('Parsing string: ' + string)
+    LOG.debug('Parsing string: ' + string + 'with elem ' + elem)
     parser = parser_init(string=string)
     parser_ptr = getattr(parser, elem)
     assert(parser_ptr is not None)

opengeode.py

@@ -24,6 +24,8 @@ import re
 import code
 import pprint
 from functools import partial
+from collections import deque
+from itertools import chain
 
 # Added to please py2exe - NOQA makes flake8 ignore the following lines:
 # pylint: disable=W0611
@@ -50,10 +52,11 @@ from PySide.QtCore import Qt, QSize, QFile, QIODevice, QRectF, QTimer
 from PySide.QtUiTools import QUiLoader
 from PySide import QtSvg
 
-from genericSymbols import Symbol, Comment, EditableText, Cornergrabber
+from genericSymbols import(Symbol, Comment, EditableText, Cornergrabber,
+                           Connection)
 from sdlSymbols import(Input, Output, Decision, DecisionAnswer, Task,
         ProcedureCall, TextSymbol, State, Start, Join, Label, Procedure,
-        ProcedureStart, ProcedureStop, StateStart)
+        ProcedureStart, ProcedureStop, StateStart, Connect)
 
 # Icons and png files generated from the resource file:
 import icons  # NOQA
@@ -122,14 +125,15 @@ G_SYMBOLS = set()
 
 # Lookup table used to configure the context-dependent toolbars
 ACTIONS = {
-    'process': [Start, State, Input, Task, Decision, DecisionAnswer,
+    'process': [Start, State, Input, Connect, 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, Task, Decision, DecisionAnswer, Output,
+    'state': [StateStart, State, Input, Connect, Task, Decision,
+              DecisionAnswer, Output,
               ProcedureCall, TextSymbol, Comment, Label, Join, ProcedureStop]
 }
 
@@ -231,9 +235,9 @@ class Sdl_toolbar(QtGui.QToolBar, object):
 
             # Check for singletons (e.g. START symbol)
             try:
-                for item in scene.items():
+                for item in scene.visible_symb:
                     try:
-                        if item.is_singleton and item.isVisible():
+                        if item.is_singleton: # and item.isVisible():
                             self.actions[
                                     item.__class__.__name__].setEnabled(False)
                     except (AttributeError, KeyError) as error:
@@ -289,10 +293,63 @@ class SDL_Scene(QtGui.QGraphicsScene, object):
         # Selection rectangle when user clicks on the scene and moves mouse
         self.select_rect = None
 
+
+    @property
+    def visible_symb(self):
+        ''' Return the visible items of a scene '''