root/ROOT/RAttrValue.hxx

0001 /*************************************************************************
0002  * Copyright (C) 1995-2021, Rene Brun and Fons Rademakers.               *
0003  * All rights reserved.                                                  *
0004  *                                                                       *
0005  * For the licensing terms see $ROOTSYS/LICENSE.                         *
0006  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
0007  *************************************************************************/
0008
0009 #ifndef ROOT7_RAttrValue
0010 #define ROOT7_RAttrValue
0011
0012 #include <ROOT/RAttrBase.hxx>
0013
0014 namespace ROOT {
0015 namespace Experimental {
0016
0017 /** \class RAttrValue
0018 \ingroup GpadROOT7
0019 \author Sergey Linev <s.linev@gsi.de>
0020 \date 2020-06-24
0021 \brief Template class to access single value from drawable or other attributes
0022 \warning This is part of the ROOT 7 prototype! It will change without notice. It might trigger earthquakes. Feedback is welcome!
0023 */
0024
0025 template<typename T>
0026 class RAttrValue : public RAttrBase {
0027
0028    template <typename Q, bool = std::is_enum<Q>::value>
0029    struct ValueExtractor {
0030       Q Get(const RAttrMap::Value_t *value)
0031       {
0032          return (Q) RAttrMap::Value_t::GetValue<int>(value);
0033       }
0034    };
0035
0036    template <typename Q>
0037    struct ValueExtractor<Q, false> {
0038       Q Get(const RAttrMap::Value_t *value) {
0039          return RAttrMap::Value_t::GetValue<Q>(value);
0040       }
0041    };
0042
0043 protected:
0044
0045    T fDefault{};          ///<!    default value
0046
0047    RAttrMap CollectDefaults() const override
0048    {
0049       return RAttrMap().AddValue(GetName(), fDefault);
0050    }
0051
0052 public:
0053
0054    RAttrValue() : RAttrBase("") {}
0055
0056    RAttrValue(const T& dflt) : RAttrBase(""), fDefault(dflt) {}
0057
0058    RAttrValue(RDrawable *drawable, const char *name, const T &dflt = T()) : RAttrBase(drawable, name ? name : ""), fDefault(dflt) { }
0059
0060    RAttrValue(RAttrBase *parent, const char *name, const T &dflt = T()) : RAttrBase(parent, name ? name : ""), fDefault(dflt) { }
0061
0062    RAttrValue(const RAttrValue& src) : RAttrBase("")
0063    {
0064       Set(src.Get());
0065       fDefault = src.GetDefault();
0066    }
0067
0068    T GetDefault() const { return fDefault; }
0069
0070    void Set(const T &v)
0071    {
0072       if (auto access = EnsureAttr(GetName()))
0073          access.attr->AddValue(access.fullname, v);
0074    }
0075
0076    T Get() const
0077    {
0078       if (auto v = AccessValue(GetName(), true))
0079          return ValueExtractor<T>().Get(v.value);
0080       return fDefault;
0081    }
0082
0083    const char *GetName() const { return GetPrefix(); }
0084
0085    void Clear() override { ClearValue(GetName()); }
0086
0087    bool Has() const
0088    {
0089       if (auto v = AccessValue(GetName(), true)) {
0090          auto res = RAttrMap::Value_t::GetValue<const RAttrMap::Value_t *,T>(v.value);
0091          return res ? (res->Kind() != RAttrMap::kNoValue) : false;
0092       }
0093
0094       return false;
0095    }
0096
0097    RAttrValue &operator=(const T &v) { Set(v); return *this; }
0098
0099    RAttrValue &operator=(const RAttrValue &v) { Set(v.Get()); return *this; }
0100
0101    operator T() const { return Get(); }
0102
0103    friend bool operator==(const RAttrValue& lhs, const RAttrValue& rhs) { return lhs.Get() == rhs.Get(); }
0104    friend bool operator!=(const RAttrValue& lhs, const RAttrValue& rhs) { return lhs.Get() != rhs.Get(); }
0105
0106    friend bool operator==(const RAttrValue& lhs, const T& rhs) { return lhs.Get() == rhs; }
0107    friend bool operator!=(const RAttrValue& lhs, const T& rhs) { return lhs.Get() != rhs; }
0108
0109 };
0110
0111 } // namespace Experimental
0112 } // namespace ROOT
0113
0114 #endif // ROOT7_RAttrValue