Changeset 1397

Timestamp:

02/11/18 03:30:39 (2 months ago)

Author:

gogo

Message:

Improve the undo/redo handling considerably by preserving the caret position.

That is, each snapshot saves where the caret was, and undoing to a snapshot puts the caret back in that position.

So if you are typing along and hit ctrl-z to undo what you wrote, you don't get dumped back at the start (or end depending on browser) of the document but can carry on typing immediately where you left off.

Discussion in #360

File:

• trunk/XinhaCore.js (modified) (5 diffs)

trunk/XinhaCore.js

@@ -4805 +4805 @@
     --this._undoPos;
   }
-  // use the fasted method (getInnerHTML);
+  
+  var snapshotData = { 
+    'txt'        : null,
+    'caretInBody': false
+  };
+  
+  
+  // Caret preservation, when you hit undo, ideally put the caret back where it was.
+  // To accomplish this we figure out what NODE (Text Node typically) and offset into 
+  // it had the caret save this into the parent element of that node if it has one
+  // as an attribute, and attach a classname to be able to find it again
+  // then in the actual undo function we look for that class name after dropping 
+  // the HTML back into place, and reverse the process
+  
+  // Note that IE <11 does not support this, FF <3.6 won't either, 
+  // nor Safari <5.1, Chrome I dont' know it does currently I don't know how long ago
+  // Opera same, don't know how long but it works currently
+  // If a browser doesn't work with it, it won't cause a problem, it just won't 
+  // preserve the caret.
+  
+  try
+  {
+    // Insert a marker so we know where we are
+    var sel = this.getSelection();
+    var caretNode    = sel.focusNode;
+    if(caretNode)
+    {
+      var caretOffset  = sel.focusOffset
+      var rng = this.createRange(sel);
+      var caretParent   = this.getParentElement(sel);
+      
+      var caretRestorationData = false;
+      
+      switch(caretNode.nodeType)
+      {
+        case 3:  // TEXT
+        case 4:  // CDATA
+        case 8:  // COMMENT
+          // We need to record which child node the focus node is of the parent
+          //  default to the end
+          var whichChild = caretParent.childNodes.length-1;
+          for(var i = 0; i < caretParent.childNodes.length; i++)
+          {
+            if(caretParent.childNodes[i] == caretNode)
+            {
+              whichChild = i;
+            }
+          }
+          caretRestorationData = {
+            caretChild:   whichChild,
+            caretOffset:  caretOffset
+          };
+          break;
+        
+        case 1:
+          // Ehhhm, not sure.  This would be the case if the selection is an image, table whatever
+          //
+          // For example <p><img></p> with img selected you get caretNode = img, caretParent = p, 
+          // caretOffset = 0 (0th child of the p)
+          //
+          // I was going to make this handled so it would select the image again, but actually
+          // I think it works just fine without this, it feels natural-enough anyway.
+          break;
+      }
+      
+      if(caretRestorationData)
+      {
+        if(caretParent == this._doc.body)
+        {
+          // Body is tricky because it won't be included in the snapshot or restoration
+          // unless fullPage mode is being used, since there is only one body then we
+          // can record it in the snapshot data and we know where to put it in undo
+          snapshotData.caretInBody            = true;
+          snapshotData.caretRestorationData   = JSON.stringify(caretRestorationData);
+        }
+        else
+        {
+          // For other elements encode the caret data in the element itself
+          // so we can be sure we are looking at the right one when we find it
+          Xinha.addClass(caretParent, 'xinha-undo-caret');
+          caretParent.setAttribute('xinha-undo-caret', JSON.stringify(caretRestorationData));
+        }
+      }
+      
+      // Debug helper
+      //console.log({n: caretNode, p: caretOffset, r: rng, e: caretParent});
+    }
+  }
+  catch(e)
+  {
+    // Browser doesn't support something.  I'm not going to try and support
+    // very old browsers for this caret preservation feature
+    
+    // Old IE doesn't support
+    if(Xinha.is_gecko || Xinha.is_webkit)
+    {
+      Xinha.debugMsg('Caret preservation code for undo snapshot failed. If your browser is modern, developers need to check it out in XinhaCore.js (search for caret preservation).','warn');
+    }
+  }
+  
+  // use the faster method (getInnerHTML);
   var take = true;
-  var txt = this.getInnerHTML();
+  snapshotData.txt = this.getInnerHTML();
+  
+  // Find all carets we might have added (in theory, 0 or 1, but always a possibility of more)
+  var existingCarets = Xinha.getElementsByClassName(this._doc.body, 'xinha-undo-caret');
+  
+  // Remove them all
+  for(var i = 0; i < existingCarets.length; i++)
+  {
+    Xinha.removeClass(existingCarets[i], 'xinha-undo-caret');
+    existingCarets[i].removeAttribute('xinha-undo-caret');
+  }
+    
   if ( this._undoPos > 0 )
   {
-    take = (this._undoQueue[this._undoPos - 1] != txt);
+    take = (this._undoQueue[this._undoPos - 1].txt != snapshotData.txt);
   }
   if ( take )
   {
-    this._undoQueue[this._undoPos] = txt;
+    this._undoQueue[this._undoPos] = snapshotData;
   }
   else
@@ -4828 +4939 @@
   if ( this._undoPos > 0 )
   {
-    var txt = this._undoQueue[--this._undoPos];
-    if ( txt )
-    {
-      this.setHTML(txt);
-      
+    var snapshotData = this._undoQueue[--this._undoPos];
+    if ( snapshotData.txt )
+    {
+      this.setHTML(snapshotData.txt);
+      this._restoreCaretForUndoRedo(snapshotData);
     }
     else
@@ -4840 +4951 @@
   }
 };
+
 /** Custom implementation of redo functionality
  * @private
@@ -4847 +4959 @@
   if ( this._undoPos < this._undoQueue.length - 1 )
   {
-    var txt = this._undoQueue[++this._undoPos];
-    if ( txt )
-    {
-      this.setHTML(txt);
+    var snapshotData = this._undoQueue[++this._undoPos];
+    if ( snapshotData.txt )
+    {
+      this.setHTML(snapshotData.txt);
+      this._restoreCaretForUndoRedo(snapshotData);
     }
     else
@@ -4858 +4971 @@
   }
 };
+
+/** Used by undo and redo to restore a saved caret position.
+ * 
+ *  Undo and redo must have already set the html when they call this.
+ * 
+ * @private
+ * @param mixed snapshotData as recorded by _undoTakeSnapshot
+ */
+
+Xinha.prototype._restoreCaretForUndoRedo = function(snapshotData)
+{
+  // Caret restoration
+  try
+  {
+    // If the snapped caret was actually in the body as it's parent
+    //  (ie text with no containing element except body)
+    // push that data back into the body element so we can treat it as
+    // any other element
+    if(snapshotData.caretInBody)
+    {
+      Xinha.addClass(this._doc.body, 'xinha-undo-caret');
+      this._doc.body.setAttribute('xinha-undo-caret', snapshotData.caretRestorationData);
+    }
+    
+    // Find the caret data we might have recorded in the html
+    var caretParents = Xinha.getElementsByClassName(this._doc.body,'xinha-undo-caret');
+    
+    // Body itself may be the one
+    if(Xinha._hasClass(this._doc.body, 'xinha-undo-caret'))
+    {
+      caretParents[caretParents.length] = this._doc.body;
+    }
+            
+    // Just in case some bug happened and there was more than one caret saved
+    //  we will do them all to clear them, but there should only really be 0 or 1
+    for(var i = 0; i < caretParents.length; i++)
+    {
+      if(caretParents[i].getAttribute('xinha-undo-caret').length)
+      {
+        var caretRestorationData = JSON.parse(caretParents[i].getAttribute('xinha-undo-caret'));
+        
+        if(caretParents[i].childNodes.length > caretRestorationData.caretChild)
+        {
+          var rng = this.createRange();
+          rng.setStart(caretParents[i].childNodes[caretRestorationData.caretChild], caretRestorationData.caretOffset);
+          rng.collapse(true); // collapse to the start, although end would be ok I think, should be the same
+          
+          var sel = this.getSelection();
+          sel.removeAllRanges();
+          sel.addRange(rng);
+        }
+      }
+      
+      Xinha.removeClass(caretParents[i], 'xinha-undo-caret');
+      caretParents[i].removeAttribute('xinha-undo-caret');
+    }
+  }
+  catch(e)
+  {
+    // Browser doesn't support something, I'm not going to try and 
+    //  implement this on old browsers.
+    if(Xinha.is_gecko || Xinha.is_webkit)
+    {
+      Xinha.debugMsg('Caret restoration code for undo failed. If your browser is modern, developers should check it out in XinhaCore.js (search for caret restoration).','warn');
+    }
+  }
+}
+
 /** Disables (greys out) the buttons of the toolbar
  * @param {Array} except this array contains ids of toolbar objects that will not be disabled