Utils: Make it possible to change internal aspect updates

... without subclassing. This is useful in situations where there
are small modifications needed for simple aspects that are themselves
exposed as members of an aspect container in a header but we
don't want to create a subclass for it.

Change-Id: I058643137c38e564072af9a2f45b1576ea058651
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>

src/libs/utils/aspects.cpp

@@ -2739,5 +2739,4 @@ SettingsGroupNester::~SettingsGroupNester()
         theSettings->endGroup();
 }
 
-
 } // namespace Utils

src/libs/utils/aspects.h

@@ -222,7 +222,7 @@ protected:
 
 protected:
     template <class Value>
-    bool updateStorage(Value &target, const Value &val)
+    static bool updateStorage(Value &target, const Value &val)
     {
         if (target == val)
             return false;
@@ -354,6 +354,55 @@ protected:
     ValueType m_buffer{};
 };
 
+template <typename ValueType>
+class FlexibleTypedAspect : public TypedAspect<ValueType>
+{
+public:
+    using Base = TypedAspect<ValueType>;
+    using Updater = std::function<bool(ValueType &, const ValueType &)>;
+
+    using Base::Base;
+
+    void setInternalToBuffer(const Updater &updater) { m_internalToBuffer = updater; }
+    void setBufferToInternal(const Updater &updater) { m_bufferToInternal = updater; }
+    void setInternalToExternal(const Updater &updater) { m_internalToExternal = updater; }
+    void setExternalToInternal(const Updater &updater) { m_externalToInternal = updater; }
+
+protected:
+    bool internalToBuffer() override
+    {
+        if (m_internalToBuffer)
+            return m_internalToBuffer(Base::m_buffer, Base::m_internal);
+        return Base::internalToBuffer();
+    }
+
+    bool bufferToInternal() override
+    {
+        if (m_bufferToInternal)
+            return m_bufferToInternal(Base::m_internal, Base::m_buffer);
+        return Base::bufferToInternal();
+    }
+
+    bool internalToExternal() override
+    {
+        if (m_internalToExternal)
+            return m_internalToExternal(Base::m_external, Base::m_internal);
+        return Base::internalToExternal();
+    }
+
+    bool externalToInternal() override
+    {
+        if (m_externalToInternal)
+            return m_externalToInternal(Base::m_internal, Base::m_external);
+        return Base::externalToInternal();
+    }
+
+    Updater m_internalToBuffer;
+    Updater m_bufferToInternal;
+    Updater m_internalToExternal;
+    Updater m_externalToInternal;
+};
+
 class QTCREATOR_UTILS_EXPORT BoolAspect : public TypedAspect<bool>
 {
     Q_OBJECT