Scintilla 'Before change' notification

Question

I need to do certain processing when a Scintilla editor first becomes 'dirty' before the document actually changes.

The SCN_SAVEPOINTLEFT notification seems like the obvious candidate, but unfortunately this is fired after the change that made the document dirty has occurred.

Looking through the other available notifications, SCN_MODIFIED also is fired after the change has happened (and the same is true of SCEN_CHANGE of course).

The best I can think of is to start macro recording in response to SCN_SAVEPOINTREACHED (i.e. when the document is saved or all changes are undone). Then when I detect the first change with SCN_MODIFIED, I stop recording, undo all changes until I get back to the save point, perform my custom processing (which happens to be modifying a date field in the document), then replay the recorded macros to restore the undone changes.

This seems horribly convoluted. Is there an easier way? (Maybe it would be simpler to create my own custom version of Scintilla with a SCN_BEFORECHANGE notification, but I'd prefer to avoid creating a fork. And a cursory glance through the source suggests that there are a great many points from where this notification would have to be sent, making it easy to miss some.)

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Update: The real requirement was that when the user executes 'Undo' after first modifying the document, the 'automatic' edit and the user's first edit are not in the wrong order in the undo buffer. The simplest solution turned out to be, not to force the automatic update to be first, but to coalesce these two actions into a single undo action using SCI_BEGINUNDOACTION/SCI_ENDUNDOACTION. See my comment below on how I did this.

Answer 1

The SCN_MODIFIED notification does seem to fit your spec. The modificationType field provides information about what has been done, including:

SC_MOD_BEFOREINSERT 0x400 Text is about to be inserted into the document.
SC_MOD_BEFOREDELETE 0x800 Text is about to be deleted from the document.