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| author | Ryan Chipman <rchipman@mit.edu> | 2015-06-27 13:47:44 -0400 |
|---|---|---|
| committer | Ryan Chipman <rchipman@mit.edu> | 2015-06-27 13:58:51 -0400 |
| commit | be1fc07077f8fe3e18fdfbe48042d5a75e326de6 (patch) | |
| tree | d5ad0e1b827a36fb2d21e7144ecdd317b458b874 | |
| parent | af43549eb3a6add4c9ae5ac86f30fc2bd0325ac6 (diff) | |
| download | vis-be1fc07077f8fe3e18fdfbe48042d5a75e326de6.tar.gz vis-be1fc07077f8fe3e18fdfbe48042d5a75e326de6.tar.xz | |
Add more thorough description of history to README
| -rw-r--r-- | README.md | 27 |
1 files changed, 16 insertions, 11 deletions
@@ -135,17 +135,22 @@ As illustrated above, each change to the text is recorded by an old and a new span. An action consists of multiple changes which logically belong to each other and should thus also be reverted together. For example a search and replace operation is one action with possibly many changes -all over the text. Actions are saved in a tree structure. - -A state of the text can be marked by means of a snapshotting operation. -Snapshotting saves a new node to the history tree and creates a fresh Action -to which future changes will be appended until the next snapshot. -The undo/redo functionality operates on such marked states and switches -between them by traversing adjacent nodes in the tree. - -Undo and Redo move the state of the document up and down on a single branch -of the history tree, but other branches can be accessed with the Earlier -and Later commands, which iterate through snapshotted states chronologically. +all over the text. + +The text states can be marked by means of a snapshotting operation. +Snapshotting saves a new node to the history graph and creates a fresh +Action to which future changes will be appended until the next snapshot. + +Actions make up the nodes of a connected digraph, each representing a state +of the file at some time during the current editing session. The edges of the +digraph represent state transitions that are supported by the editor. The edges +are implemented as four Action pointers (`prev`, `next`, `earlier`, and `later`). + +The editor operations that execute the four aforementioned transitions +are `undo`, `redo`,`earlier`, and `later`, respectively. Undo and +redo behave in the traditional manner, changing the state one Action +at a time. Earlier and later, however, traverse the states in chronological +order, which may occasionally involve undoing and redoing many Actions at once. Properties ---------- |