020c598c18
This class doesn't have to be used with wxWindow or similar as object type, so use a more neutral "Object" instead of "Window".
85 lines
2.9 KiB
C++
85 lines
2.9 KiB
C++
///////////////////////////////////////////////////////////////////////////////
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// Name: wx/private/extfield.h
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// Purpose: Declare wxExternalField helper
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// Author: Vadim Zeitlin
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// Created: 2017-11-21
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// Copyright: (c) 2017 Vadim Zeitlin <vadim@wxwidgets.org>
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// Licence: wxWindows licence
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///////////////////////////////////////////////////////////////////////////////
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#ifndef _WX_PRIVATE_EXTFIELD_H_
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#define _WX_PRIVATE_EXTFIELD_H_
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// ----------------------------------------------------------------------------
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// wxExternalField: store object data outside of it
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// ----------------------------------------------------------------------------
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// This class allows to store some data without consuming space for the objects
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// that don't need it and can be useful for avoiding to add rarely used fields
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// to the classes that are used by many objects, e.g. wxWindow.
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//
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// Note that using this class costs in speed and convenience of access to the
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// field, which requires a hash lookup instead of accessing it directly. It
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// also only currently works for heap-allocated fields as it's probably never
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// worth using it for fields of simple types.
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//
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// Template parameter Object is the class that "contains" the field, Field is
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// the type of the field itself and FieldMap is the hash map, defined
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// separately using WX_DECLARE_HASH_MAP(), with Object* as the key and Field*
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// as the value type.
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template <typename Object, typename Field, typename FieldMap>
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class wxExternalField
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{
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public:
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typedef Object ObjectType;
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typedef Field FieldType;
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typedef FieldMap MapType;
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// Store the field object to be used for the given object, replacing the
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// existing one, if any.
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//
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// This method takes ownership of the field pointer which will be destroyed
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// by EraseForObject().
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static void StoreForObject(ObjectType* obj, FieldType* field)
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{
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const typename MapType::iterator it = ms_map.find(obj);
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if ( it != ms_map.end() )
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{
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delete it->second;
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it->second = field;
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}
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else
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{
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ms_map.insert(typename MapType::value_type(obj, field));
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}
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}
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// Find the object for the corresponding window.
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static FieldType* FromObject(ObjectType* obj)
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{
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const typename MapType::const_iterator it = ms_map.find(obj);
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return it == ms_map.end() ? NULL : it->second;
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}
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// Erase the object used for the corresponding window, return true if there
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// was one or false otherwise.
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static bool EraseForObject(ObjectType* obj)
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{
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const typename MapType::iterator it = ms_map.find(obj);
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if ( it == ms_map.end() )
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return false;
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delete it->second;
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ms_map.erase(it);
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return true;
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}
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private:
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static FieldMap ms_map;
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};
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template <typename O, typename F, typename M>
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M wxExternalField<O, F, M>::ms_map;
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#endif // _WX_PRIVATE_EXTFIELD_H_
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