Undo breaks speed-type session

[lordnik22]

Currently speed-type doesn't do anything directly to handle undos C-x u.

It doesn't try to make it work, nor does it hinder the user using it.

Undoing things...

• can break the speed-type session.
• make the state-variables go inconsistent
• can result in "no action" (it can't jump back for some reason)
• undo and than correcting the mistyped character doesn't count as corrections (probably intended)

[lordnik22]

Undo also has an effect on related buffers like the preview-buffer and the content-buffer.

[lordnik22]

When undo is called our change-hook should probably be deactivated, or detect that it was an undo action. Maybe checking the var last-command could be a "fix".
if last-command is undo, then only sync vars but don't do a diff.
Maybe exclude fill-paragraph the same way. This way the user can use it but dosn't explode the buffer.

[lordnik22]

point movement in content-buffer can't be tracked by undo. That's why before adding word the point should be moved in the content-buffer by extracting the last point by extracting orig-pos of the last character.
just wrap the hooks with undo-in-progress and atomic-change-group.

[lordnik22]

undo works quite well for correctly typed content.
For errors things get out of sync. "excluded commands" also create strange behaviour.

overlays aren't affected by undo, if we set the face as text-property it would work but then we would need to use the content-buffer for replay because the face may have changed in case prog-mode was active.

adding words should be excluded if undo-in-progress