Since C++11 when enum class (also named scoped enum) is introduced, it is preferred to plain enum which is inherited from C programming languages. The task here is to convert the old enum instances to enum class.
Rationale
enum class has many benefits when compared to plain enum, as it provides better type safety among other things. Implicit conversion to integers, lack of ability to define the underlying data type and compatibility issues were some of the problems with plain enum that enum class solved in C++11. Although since then enum has improved and one can specify underlying type in the scoped enumerations.
Plain enums pollute namespace, and you have to pick names that are too long, and have to carry the context inside their names. For example: INETMSG_RFC822_BEGIN inside enum _ImplINetRFC822MessageHeaderState. With an enum class, it is simply written as HeaderState::BEGIN. When placed inside a file/class/namespace that makes it relevant, it is much easier to use: it is more readable, and causes no issues for other identifiers with possible similar names.,
See this change:
You can read more about that in:
Finding Instances
You may find some of the instances with:
$ git grep -w enum *.cxx *.hxx|grep -v "enum class"
When you count it with wc -l, it shows something more than 2k instances.
Examples Commits
You can see some of the previous conversions here, which is around 1k changes:
$ git log --oneline -i -E --grep="convert enum|scoped enum"
This is a good, but lengthy example of such a conversion:
Implementation
First of all, please choose good names for the new enum class and values. For example, you may convert APPLICATION_WINDOW_TITLE into Application::WindowTitle. Therefore, do not use the old names as they were.
Converting enum to enum class is not always straightforward. You should try to understand the code using the enum, and then try to replace it with enum class. You may need to add extra state/values for situations where 0 or -1 or some default value was used. There are cases where a numerical value is used for different conflicting purposes, and then you have to do some sort of conflict resolution to separate those cases.
You may end up modifying more and more files, and a few static_casts where they are absolutely necessary because you are interpreting some integer value read from input. These are the places where you should check the values yourself in the code. You have to make sure that the numerical value is appropriate before casting it to the enum class.
If you want to do bitwise operations, you should use o3tl::typed_flags, for example:
enum class FileViewFlags
{
None = 0x00,
MultiSelection = 0x02,
ShowType = 0x04,
ShowNone = 0x20,
};
template<> struct o3tl::typed_flags : o3tl::is_typed_flags<FileViewFlags, 0x26> {}
Then, you may use it like this:
if (nFlags & FileViewFlags::MULTISELECTION)
mxTreeView->set_selection_mode(SelectionMode::Multiple …
Code span: baseline
Code span: old result
Code span: new result
Lists: baseline
Lists: old result
Lists: new result
Image: baseline
Image: old result
Image: new result
Table: baseline
Table: old result
Table: new result
Quote: baseline
Quote: old result
Quote: new result
Interdependent tracked change: improved format, after document load
Interdependent tracked change: old reject, lost character style / direct format
Interdependent tracked change: new reject, handled character style / direct format
Floating table, followed by heading: new Writer render
Floating table, followed by heading: old Writer render
Floating table, followed by heading: reference render
Interdependent tracked change: just insert
Interdependent tracked change: old, format is not tracked separately
Interdependent tracked change: new, format is tracked separately
Interdependent tracked change: UI dialog now showing multiple redlines 
Interdependent tracked change: insert, then delete
Interdependent tracked change: insert, then format
Interdependent tracked change: delete, then format
Reinstate: an insert
Reinstate: a reinstated insert
Reinstate: a delete
Reinstate: a reinstated delete
Per-view tracked changes recording
