"Professional CMake" book suggest the following:
"Targets should build successfully with or without compiler support for precompiled headers. It
should be considered an optimization, not a requirement. In particular, do not explicitly include a
precompile header (e.g. stdafx.h) in the source code, let CMake force-include an automatically
generated precompile header on the compiler command line instead. This is more portable across
the major compilers and is likely to be easier to maintain. It will also avoid warnings being
generated from certain code checking tools like iwyu (include what you use)."
Therefore, removed the "#include <PreCompiled.h>" from sources, also
there is no need for the "#ifdef _PreComp_" anymore
This adds isNullOrEmpty string helper that cheks if string is... well
null or empty. It is done to improve readability of the code and better
express intent.
In order to make getNameInDocument() always return a valid string,
we implement a getDagKey() method that shall be used instead of getNameInDocument()
when we want to use the pointer value as a "key" to identify the DocumentObject.
This patch substitutes by isAttachedToDocument() (almost) everywhere where
getNameInDocument() is used for this purpose.
The very few places not touched by this patch demand a (just a little) less trivial change.
When we change the returning type of getNameInDocument() to std::string,
those places will be easily found, because they shall generate a compiler error
(converting std::string to bool).
Rationale:
The fact that getNameInDocument() return nullptr to indicate
that the object is not attached to a document is responsible for lots of bugs
where the developer does not check for "nullptr".
The idea is to eliminate all those uses of getNameInDocument() and, in the near future,
make getNameInDocument() return always a valid std::string.
New property status bit 'CopyOnChange' is added for any document object
to publish any property as a 'Configuration' option. When Link is
linked to any object with such property, it will duplicate those
properties and added it Link itself as dynamic properties. If the user
changes any of these dynamic properties, the Link will auto copy the
linked to object and apply the new configuration to it.
The Link has a new property 'LinkCopyOnChange' to allow user to
enable/disable this feature.
Spreadsheet's 'Configuration Table' feature will publish its
configuration property with 'CopyOnChange'.
Currently, once the linked object is copied, it will be independent with
the original object. There is no mechanism to auto sync changes back to
the copy.
