pythonnet/src/runtime/eventobject.cs at v2.5.1 · pythonnet/pythonnet · GitHub

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using System;

using System.Collections;

using System.Reflection;

namespace Python.Runtime

{

/// <summary>

/// Implements a Python descriptor type that provides access to CLR events.

/// </summary>

internal class EventObject : ExtensionType

{

internal string name;

internal EventBinding unbound;

internal EventInfo info;

internal Hashtable reg;

public EventObject(EventInfo info)

{

this.name = info.Name;

this.info = info;

}

/// <summary>

/// Register a new Python object event handler with the event.

/// </summary>

internal bool AddEventHandler(IntPtr target, IntPtr handler)

{

object obj = null;

if (target != IntPtr.Zero)

{

var co = (CLRObject)GetManagedObject(target);

obj = co.inst;

}

// Create a true delegate instance of the appropriate type to

// wrap the Python handler. Note that wrapper delegate creation

// always succeeds, though calling the wrapper may fail.

Type type = info.EventHandlerType;

Delegate d = PythonEngine.DelegateManager.GetDelegate(type, handler);

// Now register the handler in a mapping from instance to pairs

// of (handler hash, delegate) so we can lookup to remove later.

// All this is done lazily to avoid overhead until an event is

// actually subscribed to by a Python event handler.

if (reg == null)

{

reg = new Hashtable();

}

object key = obj ?? info.ReflectedType;

var list = reg[key] as ArrayList;

if (list == null)

{

list = new ArrayList();

reg[key] = list;

}

list.Add(new Handler(Runtime.PyObject_Hash(handler), d));

// Note that AddEventHandler helper only works for public events,

// so we have to get the underlying add method explicitly.

object[] args = { d };

MethodInfo mi = info.GetAddMethod(true);

mi.Invoke(obj, BindingFlags.Default, null, args, null);

return true;

}

/// <summary>

/// Remove the given Python object event handler.

/// </summary>

internal bool RemoveEventHandler(IntPtr target, IntPtr handler)

{

object obj = null;

if (target != IntPtr.Zero)

{

var co = (CLRObject)GetManagedObject(target);

obj = co.inst;

}

IntPtr hash = Runtime.PyObject_Hash(handler);

if (Exceptions.ErrorOccurred() || reg == null)

{

Exceptions.SetError(Exceptions.ValueError, "unknown event handler");

return false;

}

object key = obj ?? info.ReflectedType;

var list = reg[key] as ArrayList;

if (list == null)

{

Exceptions.SetError(Exceptions.ValueError, "unknown event handler");

return false;

}

object[] args = { null };

MethodInfo mi = info.GetRemoveMethod(true);

for (var i = 0; i < list.Count; i++)

{

var item = (Handler)list[i];

if (item.hash != hash)

{

continue;

}

args[0] = item.del;

try

{

mi.Invoke(obj, BindingFlags.Default, null, args, null);

}

catch

{

continue;

}

list.RemoveAt(i);

return true;

}

Exceptions.SetError(Exceptions.ValueError, "unknown event handler");

return false;

}

/// <summary>

/// Descriptor __get__ implementation. A getattr on an event returns

/// a "bound" event that keeps a reference to the object instance.

/// </summary>

public static IntPtr tp_descr_get(IntPtr ds, IntPtr ob, IntPtr tp)

{

var self = GetManagedObject(ds) as EventObject;

EventBinding binding;

if (self == null)

{

return Exceptions.RaiseTypeError("invalid argument");

}

// If the event is accessed through its type (rather than via

// an instance) we return an 'unbound' EventBinding that will

// be cached for future accesses through the type.

if (ob == IntPtr.Zero)

{

if (self.unbound == null)

{

self.unbound = new EventBinding(self, IntPtr.Zero);

}

binding = self.unbound;

Runtime.XIncref(binding.pyHandle);

return binding.pyHandle;

}

if (Runtime.PyObject_IsInstance(ob, tp) < 1)

{

return Exceptions.RaiseTypeError("invalid argument");

}

binding = new EventBinding(self, ob);

return binding.pyHandle;

}

/// <summary>

/// Descriptor __set__ implementation. This actually never allows you

/// to set anything; it exists solely to support the '+=' spelling of

/// event handler registration. The reason is that given code like:

/// 'ob.SomeEvent += method', Python will attempt to set the attribute

/// SomeEvent on ob to the result of the '+=' operation.

/// </summary>

public new static int tp_descr_set(IntPtr ds, IntPtr ob, IntPtr val)

{

var e = GetManagedObject(val) as EventBinding;

if (e != null)

{

return 0;

}

Exceptions.RaiseTypeError("cannot set event attributes");

return -1;

}

/// <summary>

/// Descriptor __repr__ implementation.

/// </summary>

public static IntPtr tp_repr(IntPtr ob)

{

var self = (EventObject)GetManagedObject(ob);

return Runtime.PyString_FromString($"<event '{self.name}'>");

}

/// <summary>

/// Descriptor dealloc implementation.

/// </summary>

public new static void tp_dealloc(IntPtr ob)

{

var self = (EventObject)GetManagedObject(ob);

if (self.unbound != null)

{

Runtime.XDecref(self.unbound.pyHandle);

}

FinalizeObject(self);

}

internal class Handler

{

public IntPtr hash;

public Delegate del;

public Handler(IntPtr hash, Delegate d)

{

this.hash = hash;

this.del = d;

}

pythonnet/src/runtime/eventobject.cs at v2.5.1 · pythonnet/pythonnet · GitHub

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