From 445dc0cc5770f9aa62264efb37c35d5964e41c0f Mon Sep 17 00:00:00 2001
From: Walter Bender <walter@sugarlabs.org>
Date: Wed, 11 Dec 2013 18:24:21 +0000
Subject: unpacking elements so as to be able to remove cjson dependency

---
(limited to 'elements/callbacks.py')

diff --git a/elements/callbacks.py b/elements/callbacks.py
new file mode 100644
index 0000000..01e9545
--- /dev/null
+++ b/elements/callbacks.py
@@ -0,0 +1,122 @@
+"""
+This file is part of the 'Elements' Project
+Elements is a 2D Physics API for Python (supporting Box2D2)
+
+Copyright (C) 2008, The Elements Team, <elements@linuxuser.at>
+
+Home:  http://elements.linuxuser.at
+IRC:   #elements on irc.freenode.org
+
+Code:  http://www.assembla.com/wiki/show/elements
+       svn co http://svn2.assembla.com/svn/elements                     
+
+License:  GPLv3 | See LICENSE for the full text
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.              
+"""
+from locals import *
+from elements import box2d
+
+class CallbackHandler:
+    # List of contact callbacks and shapes to start them - sorted by type for quicker access  
+    # Callbacks are saved as callbacks[callback_type][[function, parameters], ...]
+    callbacks = {}   
+    
+    def __init__(self, parent):
+        self.parent = parent
+        
+        # init callback dict to avoid those slow try 
+        # (especially for self.get, as it is called *often*)
+        for i in xrange(10):
+            self.callbacks[i] = []
+         
+    def add(self, callback_type, callback_handler, *args):
+            """ Users can add callbacks for certain (or all) collisions
+               
+               Parameters:
+                 callback_type ......... CALLBACK_CONTACT (nothing else for now)
+                 callback_handler ...... a callback function
+                 args (optional) ....... a list of parameters which can be used with callbacks.get
+               
+               Return:
+                 callback_id ... used to remove a callback later (int)
+            """
+            # Create contact listener if required
+            if callback_type in [CALLBACK_CONTACT_ADD, CALLBACK_CONTACT_PERSIST, CALLBACK_CONTACT_REMOVE]:
+                if self.parent.listener == None:
+                    self.parent.listener = kContactListener(self.get)
+                    self.parent.world.SetContactListener( self.parent.listener )
+                    print "* ContactListener added"
+            
+            # Get callback dict for this callback_type
+            c = self.callbacks[callback_type]
+                        
+            # Append to the Callback Dictionary
+            c.append([callback_handler, args])
+            self.callbacks[callback_type] = c
+            
+            # Return Callback ID
+            # ID = callback_type.callback_index (1...n)
+            return "%i.%i" % (callback_type, len(c))
+        
+    def get(self, callback_type):
+        return self.callbacks[callback_type]
+            
+    def start(self, callback_type, *args):
+        callbacks = self.get(callback_type)
+        for c in callbacks:
+            callback, params = c
+            callback()
+
+class kContactListener(box2d.b2ContactListener):
+    def __init__(self, get_callbacks): 
+        # Init the Box2D b2ContactListener
+        box2d.b2ContactListener.__init__(self)
+
+        # Function to get the current callbacks
+        self.get_callbacks = get_callbacks
+        
+    def check_contact(self, contact_type, point):
+        # Checks if a callback should be started with this contact point
+        contacts = self.get_callbacks(contact_type)
+
+        # Step through all callbacks for this type (eg ADD, PERSIST, REMOVE)
+        for c in contacts:
+            callback, bodylist = c
+            if len(bodylist) == 0:
+                # Without bodylist it's a universal callback (for all bodies) 
+                callback(point)
+                
+            else:
+                # This is a callback with specified bodies
+                # See if this contact involves one of the specified
+                b1 = str(point.shape1.GetBody())
+                b2 = str(point.shape2.GetBody())
+                for s in bodylist:
+                    s = str(s)
+                    if b1 == s or b2 == s: 
+                        # Yes, that's the one :)
+                        callback(point)
+         
+    def Add(self, point):
+        """Called when a contact point is created"""
+        self.check_contact(CALLBACK_CONTACT_ADD, point)
+        
+    def Persist(self, point):
+        """Called when a contact point persists for more than a time step"""
+        self.check_contact(CALLBACK_CONTACT_PERSIST, point)
+                        
+    def Remove(self, point):
+        """Called when a contact point is removed"""
+        self.check_contact(CALLBACK_CONTACT_REMOVE, point)
+        
--
cgit v0.9.1