On Sunday, November 8, 2020 at 8:08:19 AM UTC-6, Edward K. Ream wrote:
> Work has gone surprisingly well. PR 1725
<https://github.com/leo-editor/leo-editor/pull/1725> gives the full details.
Yesterday was a very good day for Leo...
*Breakthrough: Tracking headline changes for undo*
qtree.endEditLabel now just closes the headline editor calling
w.closeEditor! This in turn fires a callback, editingFinished_callback.
This callback is very similar to the old qtree.onHeadChanged method, which
no longer exists!
Why did I never think of this before? Probably because I was fixated on the
base LeoTree.onHeadChanged method. But when using the qt gui there is never
any need ever to call qtree.onHeadChanged directly!
Aside: I'm dithering about whether to *prevent* scripts from calling
qtree.onHeadChanged. If a script called g.app.gui.onHeadChanged, it would
in fact be calling LeoTree.onHeadChanged. But I doubt that would matter.
*Simplifying undo*
> The key to eliminating kwargs was to create new
u.before/afterChangeHeadline methods. These are specialized to headlines,
thereby reducing the complexity of u.before/afterChangeNodeContents.
These methods simplified editingFinished_callback. Furthermore, they
simplified my thought processes, which probably was an essential
precondition for the breakthrough.
Today I'll add similar u.before/afterChangeBody methods. It *might* be
possible to simplify some of Leo's existing commands using those methods,
but that remains to be seen.
Nevertheless, it would be perfectly fine to leave Leo's body-changing code
unchanged. In other words, u.before/afterChangeBody will primarily be for
the use of scripts.
*Ahas re undo granularity*
Many of Leo's body-changing commands eventually call u.setUndoTypingParams.
This is clumsy, and the calling sequenced pretty much require lots of ugly
kwargs. However, in most cases (eventually) calling u.setUndoTypingParams
is not required. Calling the upcoming u.before/afterChangeBody methods
would suffice!
Indeed, u.setUndoTypingParams contains complex logic to handle the
so-called "granularity" of changes to body text. This is *extremely*
important when handling the endless changes created as the user types in
the body pane. But Aha:
*undo granularity does not matter for commands that change body text!*
In other words, Leo can, and should, create a new undo "bead" for each
text-altering command, *regardless* of undo granularity. In other words,
commands should just call u.before/afterChangeBody, not (circuitously)
u.setUndoTypingParams. In other words:
*u.setUndoTypingParams is really a callback for onTextChanged events!*
This Aha will guide me if I do decide to refactor or eliminate ugly methods
such as c.updateBodyPane and LeoBody.onBodyChanged. u.setUndoTypingParams
is now deprecated for new commands, and in scripts. But to repeat, there is
no real need to *avoid* u.setUndoTypingParams. Existing code is fine as it
is.
*Summary*
Leo's headline code has collapsed. From now on, the new
u.before/afterChangeHeadline methods are the recommended way of handling
undo/redo (in headline text) in scripts, and in Leo's core.
Similarly, the upcoming u.before/afterChangeHeadline methods will be the
recommended way of handling undo/redo (in body text) in scripts, and in
Leo's core.
u.setUndoTypingParams is deprecated for commands involving body text. It is
really a too-visible callback for qt onTextChanged events. But there is *no*
need to change Leo's existing body-changing commands.
Leo's undo documentation
<http://leoeditor.com/scripting-miscellany.html#making-operations-undoable>
will be revised to discuss the new undoer methods. This section needs
examples, and the new methods will make the examples much simpler and
easier to understand.
Edward
P.S. None of this work would have been possible 10 years ago. It would have
been out of the question without Leo's clone-find and git-diff commands,
git branches, and pylint. Focusing on eliminating kwargs was also an
essential part of the discovery process.
*Many *clone-find commands were needed to reveal the Aha's discussed above.
Even more clone-find commands were needed to untangle the relationships
between c.updateBodyPane, LeoBody.onBodyChanged, and u.setUndoTypingParams.
I'll discuss a new pattern involving clone-find in another thread.
EKR
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