define message methods for SharedBuffer instead of Buffer

[matthias314]

AddMessage and the like are defined for Buffer although they only use the SharedBuffer part. This PR defines them for SharedBuffer. As a consequence, these methods can now be used from within the onBeforeTextEvent callback, which receives a SharedBuffer as argument.

[usfbih8u]

As a consequence, these methods can now be used from within the onBeforeTextEvent callback, which receives a SharedBuffer as argument

With this PR, how a plugin can differentiate between a text event in the buffer and a message added?

[matthias314]

What exactly do you mean? Everything that a plugin could do without this PR is still possible with it.

OK, now I believe I know what you mean. The idea is that text events can trigger messages. For example, the bookmark plugin uses messages to define bookmarks. Currently, it needs a lot of code to adjust the position of those bookmarks when text is added or deleted. With onBeforeTextEvent, this becomes much simpler in my opinion. See the proof of concept here.

[usfbih8u]

I misread your first message.

What I was asking was whether adding a Message, etc., now triggers the onBeforeTextEvent() callback.

Now I see that what you are doing is checking if the text events are affecting your bookmarks (by moving them through removing/inserting lines, etc.).