Limit the undo stack size

Add an undo configuration.
If the document is larger than the configured threshold, then limit the
number of undo states that can be saved to the configured amount.
Defaults to no limit.

build/squire-raw.js

@@ -2435,6 +2435,10 @@ proto.setConfig = function ( config ) {
             ol: null,
             li: null,
             a: null
+        },
+        undo: {
+            documentSizeThreshold: -1, // -1 means no threshold
+            undoLimit: -1 // -1 means no limit
         }
     }, config );
 
@@ -2531,6 +2535,7 @@ proto.destroy = function () {
     var l = instances.length;
     var events = this._events;
     var type;
+
     for ( type in events ) {
         this.removeEventListener( type );
     }
@@ -2542,6 +2547,11 @@ proto.destroy = function () {
             instances.splice( l, 1 );
         }
     }
+
+    // Destroy undo stack
+    this._undoIndex = -1;
+    this._undoStack = [];
+    this._undoStackLength = 0;
 };
 
 proto.handleEvent = function ( event ) {
@@ -2969,6 +2979,12 @@ proto._docWasChanged = function () {
     this.fireEvent( 'input' );
 };
 
+// Gets the size of the document in bytes.
+var documentSizeInBytes = function () {
+    // Javascript uses 2 bytes per character
+    return this._getHTML().length * 2;
+};
+
 // Leaves bookmark
 proto._recordUndoState = function ( range ) {
     // Don't record if we're already in an undo state
@@ -2982,6 +2998,20 @@ proto._recordUndoState = function ( range ) {
             undoStack.length = this._undoStackLength = undoIndex;
         }
 
+        var undoThreshold = this._config.undo.documentSizeThreshold,
+            undoLimit = this._config.undo.undoLimit;
+
+        // If this document is above the configured size threshold, limit the number
+        // of saved undo states.
+        if( undoThreshold > -1 && undoThreshold <= documentSizeInBytes.call( this ) ) {
+            if( undoLimit > -1 && undoLimit < undoIndex ) {
+                undoStack.splice( 0, undoIndex - undoLimit );
+
+                undoIndex = this._undoIndex = undoLimit;
+                this._undoStackLength = undoStack.length;
+            }
+        }
+
         // Write out data
         if ( range ) {
             this._saveRangeToBookmark( range );

source/Editor.js

@@ -167,6 +167,10 @@ proto.setConfig = function ( config ) {
             ol: null,
             li: null,
             a: null
+        },
+        undo: {
+            documentSizeThreshold: -1, // -1 means no threshold
+            undoLimit: -1 // -1 means no limit
         }
     }, config );
 
@@ -263,6 +267,7 @@ proto.destroy = function () {
     var l = instances.length;
     var events = this._events;
     var type;
+
     for ( type in events ) {
         this.removeEventListener( type );
     }
@@ -274,6 +279,11 @@ proto.destroy = function () {
             instances.splice( l, 1 );
         }
     }
+
+    // Destroy undo stack
+    this._undoIndex = -1;
+    this._undoStack = [];
+    this._undoStackLength = 0;
 };
 
 proto.handleEvent = function ( event ) {
@@ -701,6 +711,12 @@ proto._docWasChanged = function () {
     this.fireEvent( 'input' );
 };
 
+// Gets the size of the document in bytes.
+var documentSizeInBytes = function () {
+    // Javascript uses 2 bytes per character
+    return this._getHTML().length * 2;
+};
+
 // Leaves bookmark
 proto._recordUndoState = function ( range ) {
     // Don't record if we're already in an undo state
@@ -714,6 +730,20 @@ proto._recordUndoState = function ( range ) {
             undoStack.length = this._undoStackLength = undoIndex;
         }
 
+        var undoThreshold = this._config.undo.documentSizeThreshold,
+            undoLimit = this._config.undo.undoLimit;
+
+        // If this document is above the configured size threshold, limit the number
+        // of saved undo states.
+        if( undoThreshold > -1 && undoThreshold <= documentSizeInBytes.call( this ) ) {
+            if( undoLimit > -1 && undoLimit < undoIndex ) {
+                undoStack.splice( 0, undoIndex - undoLimit );
+
+                undoIndex = this._undoIndex = undoLimit;
+                this._undoStackLength = undoStack.length;
+            }
+        }
+
         // Write out data
         if ( range ) {
             this._saveRangeToBookmark( range );