From a50ec42d674f37c74c8afa5ed38844fbf0da3088 Mon Sep 17 00:00:00 2001
From: Ian Storm Taylor <ian@ianstormtaylor.com>
Date: Mon, 18 Jul 2016 16:52:11 -0700
Subject: [PATCH] fix to not create snapshot history for selection changes,
 closes #94

---
 lib/models/transform.js | 133 ++++++++++++++++++++++++++--------------
 1 file changed, 87 insertions(+), 46 deletions(-)

diff --git a/lib/models/transform.js b/lib/models/transform.js
index bb63c1d03..8bc8f0913 100644
--- a/lib/models/transform.js
+++ b/lib/models/transform.js
@@ -68,25 +68,16 @@ const SELECTION_TRANSFORMS = [
 ]
 
 /**
- * State transforms, that act on both the document and selection.
+ * State-level document transforms.
  */
 
-const STATE_TRANSFORMS = [
-  'collapseToEndOfNextBlock',
-  'collapseToEndOfNextText',
-  'collapseToEndOfPreviousBlock',
-  'collapseToEndOfPreviousText',
-  'collapseToStartOfNextBlock',
-  'collapseToStartOfNextText',
-  'collapseToStartOfPreviousBlock',
-  'collapseToStartOfPreviousText',
+const STATE_DOCUMENT_TRANSFORMS = [
   'delete',
   'deleteBackward',
   'deleteForward',
   'insertFragment',
   'insertText',
   'addMark',
-  'moveTo',
   'setBlock',
   'setInline',
   'splitBlock',
@@ -98,6 +89,30 @@ const STATE_TRANSFORMS = [
   'wrapInline'
 ]
 
+/**
+ * State selection transforms.
+ */
+
+const STATE_SELECTION_TRANSFORMS = [
+  'collapseToEndOfNextBlock',
+  'collapseToEndOfNextText',
+  'collapseToEndOfPreviousBlock',
+  'collapseToEndOfPreviousText',
+  'collapseToStartOfNextBlock',
+  'collapseToStartOfNextText',
+  'collapseToStartOfPreviousBlock',
+  'collapseToStartOfPreviousText',
+  'moveTo',
+]
+
+/**
+ * All state-level transforms.
+ */
+
+const STATE_TRANSFORMS = []
+  .concat(STATE_DOCUMENT_TRANSFORMS)
+  .concat(STATE_SELECTION_TRANSFORMS)
+
 /**
  * All transforms.
  */
@@ -122,23 +137,12 @@ const DEFAULT_PROPERTIES = {
 
 class Transform extends new Record(DEFAULT_PROPERTIES) {
 
-  /**
-   * Create a history-ready snapshot of the current state.
-   *
-   * @return {Snapshot} snapshot
-   */
-
-  snapshot() {
-    let { state, steps } = this
-    let { document, selection } = state
-    return new Snapshot({ document, selection, steps })
-  }
-
   /**
    * Apply the transform and return the new state.
    *
    * @param {Object} options
    *   @property {Boolean} isNative
+   *   @property {Boolean} snapshot
    * @return {State} state
    */
 
@@ -149,29 +153,9 @@ class Transform extends new Record(DEFAULT_PROPERTIES) {
     let { undos, redos } = history
 
     // Determine whether we need to create a new snapshot.
-    let shouldSnapshot = false
-    const previous = undos.peek()
-
-    // If there isn't a previous state, snapshot.
-    if (!previous) shouldSnapshot = true
-
-    // If there is a previous state but the steps are different, snapshot.
-    if (!shouldSnapshot && previous) {
-      const types = steps.map(step => step.type)
-      const prevTypes = previous.steps.map(step => step.type)
-      const diff = xor(types.toArray(), prevTypes.toArray())
-      if (diff.length) shouldSnapshot = true
-    }
-
-    // If the current steps aren't one of the "combinale" types, snapshot.
-    if (!shouldSnapshot) {
-      const allCombinable = (
-        steps.every(step => step.type == 'insertText') ||
-        steps.every(step => step.type == 'deleteForward') ||
-        steps.every(step => step.type == 'deleteBackward')
-      )
-      if (!allCombinable) shouldSnapshot = true
-    }
+    const shouldSnapshot = options.snapshot == null
+      ? this.shouldSnapshot()
+      : options.snapshot
 
     // If we should, save a snapshot into the history before transforming.
     if (shouldSnapshot) {
@@ -237,6 +221,63 @@ class Transform extends new Record(DEFAULT_PROPERTIES) {
     }
   }
 
+  /**
+   * Check whether the current transform steps should create a snapshot.
+   *
+   * @return {Boolean}
+   */
+
+  shouldSnapshot() {
+    const transform = this
+    const { state, steps } = transform
+    const { cursorMarks, history, selection } = state
+    const { undos, redos } = history
+    const previous = undos.peek()
+
+    // If the only steps applied are selection transforms, don't snapshot.
+    const onlySelections = steps.every((step) => {
+      return (
+        includes(SELECTION_TRANSFORMS, step.type) ||
+        includes(STATE_SELECTION_TRANSFORMS, step.type)
+      )
+    })
+
+    if (onlySelections) return false
+
+    // If there isn't a previous state, snapshot.
+    if (!previous) return true
+
+    // If there is a previous state but the steps are different, snapshot.
+    const types = steps.map(step => step.type)
+    const prevTypes = previous.steps.map(step => step.type)
+    const diff = xor(types.toArray(), prevTypes.toArray())
+    if (diff.length) return true
+
+    // If the current steps aren't one of the "combinable" types, snapshot.
+    const allCombinable = (
+      steps.every(step => step.type == 'insertText') ||
+      steps.every(step => step.type == 'deleteForward') ||
+      steps.every(step => step.type == 'deleteBackward')
+    )
+
+    if (!allCombinable) return true
+
+    // Otherwise, don't snapshot.
+    return false
+  }
+
+  /**
+   * Create a history-ready snapshot of the current state.
+   *
+   * @return {Snapshot} snapshot
+   */
+
+  snapshot() {
+    let { state, steps } = this
+    let { document, selection } = state
+    return new Snapshot({ document, selection, steps })
+  }
+
   /**
    * Undo to the previous state in the history.
    *