Switch other backend code over to use transactions.

sub_crates/backend/src/buffer.rs

@@ -1,11 +1,8 @@
-use std::path::PathBuf;
+use std::{borrow::Cow, path::PathBuf};
 
 use ropey::Rope;
 
-use crate::{
+use crate::{history::History, marks::MarkSet, transaction::Transaction};
-    history::{Edit, History},
-    marks::MarkSet,
-};
 
 /// A path for an open text buffer.
 ///
@@ -21,7 +18,7 @@ pub enum BufferPath {
 #[derive(Debug, Clone)]
 pub struct Buffer {
     pub path: BufferPath,
-    pub is_dirty: bool,          // Is this buffer currently out of sync with disk.
+    pub edits_since_saved: i64, // Tracks whether this buffer is out of sync with the last save.
     pub text: Rope,             // The actual text content.
     pub mark_sets: Vec<MarkSet>, // MarkSets for cursors, view positions, etc.
     history: History,
@@ -31,19 +28,35 @@ impl Buffer {
     pub fn new(text: Rope, path: BufferPath) -> Buffer {
         Buffer {
             path: path,
-            is_dirty: false,
+            edits_since_saved: 0,
             text: text,
             mark_sets: Vec::new(),
             history: History::new(),
         }
     }
 
+    pub fn is_dirty(&self) -> bool {
+        self.edits_since_saved != 0
+    }
+
+    /// Saves the buffer to disk.
+    pub fn save(&mut self) {
+        self.edits_since_saved = 0;
+        todo!();
+    }
+
     /// Replaces the given range of chars with the given text.
     ///
     /// The range does not have to be ordered (i.e. the first component can be
     /// greater than the second).
     pub fn edit(&mut self, char_idx_range: (usize, usize), text: &str) {
-        self.is_dirty = true;
+        if self.edits_since_saved >= 0 {
+            self.edits_since_saved = self.edits_since_saved.wrapping_add(1);
+        } else {
+            // The undo state matching the last save is inaccessible, so
+            // set this to a similarly inaccessible number.
+            self.edits_since_saved = i64::MAX;
+        }
 
         // Get the range, properly ordered.
         let (start, end) = if char_idx_range.0 < char_idx_range.1 {
@@ -52,114 +65,69 @@ impl Buffer {
             (char_idx_range.1, char_idx_range.0)
         };
 
-        // Update undo stack.
+        // Build the transaction.
-        if char_idx_range.0 == char_idx_range.1 {
+        let trans = Transaction::from_edit(
-            // Fast-path for insertion-only edits.
+            self.text.char_to_byte(start),
-            self.history.push_edit(Edit {
+            &Cow::from(self.text.slice(start..end)),
-                char_idx: start,
+            text,
-                from: String::new(),
+        );
-                to: text.into(),
-            });
-        } else {
-            self.history.push_edit(Edit {
-                char_idx: start,
-                from: self.text.slice(start..end).into(),
-                to: text.into(),
-            });
-        }
 
         // Update mark sets.
-        let post_len = text.chars().count();
         for mark_set in self.mark_sets.iter_mut() {
-            for mark in mark_set.iter_mut() {
+            trans.apply_to_marks(mark_set);
-                *mark = mark.edit((start, end), post_len);
-            }
-
             mark_set.make_consistent();
         }
 
-        // Do removal if needed.
+        // Apply the edit to the document.
-        if start != end {
+        trans.apply(&mut self.text);
-            self.text.remove(start..end);
+
+        // Update undo stack.
+        self.history.push_edit(trans);
     }
 
-        // Do insertion if needed.
+    /// Un-does the last edit if there is one, and returns the
-        if !text.is_empty() {
+    /// Transaction that was inverse-applied, in case it's needed for
-            self.text.insert(start, text);
+    /// further processing.
-        }
-    }
-
-    /// Un-does the last edit if there is one, and returns the range of the
-    /// edited characters which can be used for e.g. placing a cursor or moving
-    /// the view.
     ///
     /// Returns None if there is no edit to undo.
-    pub fn undo(&mut self) -> Option<(usize, usize)> {
+    pub fn undo(&mut self) -> Option<&Transaction> {
-        if let Some(ed) = self.history.undo() {
+        if let Some(trans) = self.history.undo() {
-            self.is_dirty = true;
+            self.edits_since_saved = self.edits_since_saved.wrapping_sub(1);
-
-            let pre_len = ed.to.chars().count();
-            let post_len = ed.from.chars().count();
-            let (start, end) = (ed.char_idx, ed.char_idx + pre_len);
 
             // Update mark sets.
             for mark_set in self.mark_sets.iter_mut() {
-                for mark in mark_set.iter_mut() {
+                trans.apply_inverse_to_marks(mark_set);
-                    *mark = mark.edit((start, end), post_len);
-                }
-
                 mark_set.make_consistent();
             }
 
-            // Do removal if needed.
+            // Apply the edit to the document.
-            if start != end {
+            trans.apply_inverse(&mut self.text);
-                self.text.remove(start..end);
-            }
 
-            // Do insertion if needed.
+            return Some(trans);
-            if !ed.from.is_empty() {
-                self.text.insert(start, &ed.from);
-            }
-
-            return Some((start, start + post_len));
         } else {
             return None;
         }
     }
 
-    /// Re-does the last edit if there is one, and returns the range of the
+    /// Re-does the last edit if there is one, and returns the
-    /// edited characters which can be used for e.g. placing a cursor or moving
+    /// Transaction that was applied, in case it's needed for further
-    /// the view.
+    /// processing.
     ///
     /// Returns None if there is no edit to redo.
-    pub fn redo(&mut self) -> Option<(usize, usize)> {
+    pub fn redo(&mut self) -> Option<&Transaction> {
-        if let Some(ed) = self.history.redo() {
+        if let Some(trans) = self.history.redo() {
-            self.is_dirty = true;
+            self.edits_since_saved = self.edits_since_saved.wrapping_add(1);
-
-            let pre_len = ed.from.chars().count();
-            let post_len = ed.to.chars().count();
-            let (start, end) = (ed.char_idx, ed.char_idx + pre_len);
 
             // Update mark sets.
             for mark_set in self.mark_sets.iter_mut() {
-                for mark in mark_set.iter_mut() {
+                trans.apply_to_marks(mark_set);
-                    *mark = mark.edit((start, end), post_len);
-                }
-
                 mark_set.make_consistent();
             }
 
-            // Do removal if needed.
+            // Apply the edit to the document.
-            if start != end {
+            trans.apply(&mut self.text);
-                self.text.remove(start..end);
-            }
 
-            // Do insertion if needed.
+            return Some(trans);
-            if !ed.to.is_empty() {
-                self.text.insert(start, &ed.to);
-            }
-
-            return Some((start, start + post_len));
         } else {
             return None;
         }

sub_crates/backend/src/history.rs

@@ -1,6 +1,8 @@
+use crate::transaction::Transaction;
+
 #[derive(Debug, Clone)]
 pub struct History {
-    edits: Vec<Edit>,
+    edits: Vec<Transaction>,
     position: usize, // Where we are in the history.
 }
 
@@ -12,13 +14,13 @@ impl History {
         }
     }
 
-    pub fn push_edit(&mut self, edit: Edit) {
+    pub fn push_edit(&mut self, edit: Transaction) {
         self.edits.truncate(self.position);
         self.edits.push(edit);
         self.position += 1;
     }
 
-    pub fn undo(&mut self) -> Option<&Edit> {
+    pub fn undo(&mut self) -> Option<&Transaction> {
         if self.position > 0 {
             self.position -= 1;
             Some(&self.edits[self.position])
@@ -27,7 +29,7 @@ impl History {
         }
     }
 
-    pub fn redo(&mut self) -> Option<&Edit> {
+    pub fn redo(&mut self) -> Option<&Transaction> {
         if self.position < self.edits.len() {
             let edit = &self.edits[self.position];
             self.position += 1;
@@ -37,10 +39,3 @@ impl History {
         }
     }
 }
-
-#[derive(Debug, Clone)]
-pub struct Edit {
-    pub char_idx: usize,
-    pub from: String,
-    pub to: String,
-}

sub_crates/backend/src/transaction.rs

@@ -293,29 +293,6 @@ impl Transaction {
         trans
     }
 
-    /// Build a Transaction that is functionally identical to undoing
-    /// this Transaction.
-    ///
-    /// Note: the resulting Transaction will losslessly reverse the
-    /// original Transaction on text content, but will be lossy when
-    /// applied to Marks.
-    #[must_use]
-    pub fn invert(&self) -> Transaction {
-        let mut inverted = self.clone();
-        for op in inverted.ops.iter_mut() {
-            match *op {
-                Op::Retain(_) => {} // Do nothing.
-                Op::Replace {
-                    ref mut old,
-                    ref mut new,
-                } => {
-                    std::mem::swap(old, new);
-                }
-            }
-        }
-        inverted
-    }
-
     /// Applies the Transaction to a Rope.
     pub fn apply(&self, text: &mut Rope) {
         let mut i = 0;
@@ -327,8 +304,43 @@ impl Transaction {
                 Op::Replace { old, new } => {
                     let old = &self.buffer[old.0..old.1];
                     let new = &self.buffer[new.0..new.1];
-                    let char_i = text.byte_to_char(i);
 
+                    let char_i = text.byte_to_char(i);
+                    if !old.is_empty() {
+                        let old_char_len = old.chars().count();
+                        debug_assert_eq!(text.slice(char_i..(char_i + old_char_len)), old);
+                        text.remove(char_i..(char_i + old_char_len));
+                    }
+                    if !new.is_empty() {
+                        text.insert(char_i, new);
+                    }
+
+                    i = i + new.len();
+                }
+            }
+        }
+        debug_assert!(i <= text.len_bytes());
+    }
+
+    /// Applies the inverse of the Transaction to a Rope.
+    ///
+    /// This is an "undo" of the Transaction.
+    pub fn apply_inverse(&self, text: &mut Rope) {
+        let mut i = 0;
+        for op in self.ops.iter() {
+            match op {
+                Op::Retain(byte_count) => {
+                    i += byte_count;
+                }
+                Op::Replace {
+                    old: old_range,
+                    new: new_range,
+                } => {
+                    // Swap old and new, to do the inverse.
+                    let old = &self.buffer[new_range.0..new_range.1];
+                    let new = &self.buffer[old_range.0..old_range.1];
+
+                    let char_i = text.byte_to_char(i);
                     if !old.is_empty() {
                         let old_char_len = old.chars().count();
                         debug_assert_eq!(text.slice(char_i..(char_i + old_char_len)), old);
@@ -350,6 +362,15 @@ impl Transaction {
         todo!()
     }
 
+    /// Applies the inverse of the Transaction to a set of Marks.
+    ///
+    /// This is essentially an "undo" of the Transaction.  However, on
+    /// marks this is a lossy operation and is not guaranteed to return
+    /// the marks to their original count and position.
+    pub fn apply_inverse_to_marks(&self, _marks: &mut MarkSet) {
+        todo!()
+    }
+
     //---------------------------------------------------------
 
     /// Pushes a retain op onto the transaction operations.