INPUT/TEXTAREA elements: Fix incorrect selectionStart/selectionEnd values after blur.

third_party/WebKit/Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
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  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 200 matching lines @@
   // TODO(yosin): We should move to call |TypingCommand::closeTyping()| to
   // |Editor| class.
   if (close_typing)
     TypingCommand::CloseTyping(frame_);
 
   if (should_clear_typing_style)
     frame_->GetEditor().ClearTypingStyle();
 
   const SelectionInDOMTree old_selection_in_dom_tree =
       selection_editor_->GetSelectionInDOMTree();
-  if (old_selection_in_dom_tree == new_selection)
+  if (old_selection_in_dom_tree == new_selection) {
+    // Even if DOM representation of text selection is not changed,
+    // selectionStart / selectionEnd IDL attributes of a text control can be
+    // changed.

[yoichio, 2017/05/12 01:54:00]

Could you explain why?

[tkent, 2017/05/12 02:01:01]

e.g.

DIV id=inner-editor
  #text "line-1\n"
  #text "line-2\n"

The caret is on offset=0 of the second Text node, and type Backspace will make
the DOM:

DIV id=inner-editor
  #text "line-1"
  #text "line-2\n"

but the caret position is still offset=0 of the second Text node.

Patch Set 3 has a comment on this.

+    NotifyTextControlOfSelectionChange(

[yosin_UTC9, 2017/05/12 01:37:00]

Can we update cached selection in "webkitEditableContentChanged" event handler
in
TextControlElement::DefaultEventHandler()?

void TextControlElement::DefaultEventHandler(Event* event) {
  if (event->type() == EventTypeNames::webkitEditableContentChanged &&
      GetLayoutObject() && GetLayoutObject()->IsTextControl()) {
    last_change_was_user_edit_ = !GetDocument().IsRunningExecCommand();
    SubtreeHasChanged();
    return;
  }
  ...

It seems SubtreeHasChange() is the right place to sync cached selection.

[tkent, 2017/05/12 02:01:01]

Patch Set 3 follows it.

Yes, handling in TextControl is better than adding notification to the
no-selection-change path.

+        SelectionOptionsToUserTriggered(options));
     return false;
+  }
   selection_editor_->SetSelection(new_selection);
   ScheduleVisualUpdateForPaintInvalidationIfNeeded();
 
   const Document& current_document = GetDocument();
   // TODO(yosin): We should get rid of unsued |options| for
   // |Editor::respondToChangedSelection()|.
   // Note: Since, setting focus can modify DOM tree, we should use
   // |oldSelection| before setting focus
   frame_->GetEditor().RespondToChangedSelection(
       old_selection_in_dom_tree.ComputeStartPosition(), options);
@@ skipping 29 matching lines @@
     SelectFrameElementInParentIfFullySelected();
     if (!IsAvailable() || GetDocument() != current_document) {
       // editing/selection/selectallchildren-crash.html and
       // editing/selection/longpress-selection-in-iframe-removed-crash.html
       // reach here.
       return;
     }
   }
 
   EUserTriggered user_triggered = SelectionOptionsToUserTriggered(options);
-  NotifyLayoutObjectOfSelectionChange(user_triggered);
+  NotifyTextControlOfSelectionChange(user_triggered);
   if (user_triggered == kUserTriggered) {
     ScrollAlignment alignment;
 
     if (frame_->GetEditor()
             .Behavior()
             .ShouldCenterAlignWhenSelectionIsRevealed())
       alignment = (align == CursorAlignOnScroll::kAlways)
                       ? ScrollAlignment::kAlignCenterAlways
                       : ScrollAlignment::kAlignCenterIfNeeded;
     else
@@ skipping 418 matching lines @@
     // |root| may be detached due to selectstart event.
     if (!root->isConnected() || expected_document != root->GetDocument())
       return;
   }
 
   SetSelection(SelectionInDOMTree::Builder()
                    .SelectAllChildren(*root)
                    .SetIsHandleVisible(IsHandleVisible())
                    .Build());
   SelectFrameElementInParentIfFullySelected();
-  NotifyLayoutObjectOfSelectionChange(kUserTriggered);
+  NotifyTextControlOfSelectionChange(kUserTriggered);
 }
 
 bool FrameSelection::SetSelectedRange(const EphemeralRange& range,
                                       TextAffinity affinity,
                                       SelectionDirectionalMode directional,
                                       SetSelectionOptions options) {
   if (range.IsNull())
     return false;
   SetSelection(SelectionInDOMTree::Builder()
                    .SetBaseAndExtent(range)
@@ skipping 111 matching lines @@
 void FrameSelection::DidLayout() {
   UpdateAppearance();
 }
 
 void FrameSelection::UpdateAppearance() {
   DCHECK(!frame_->ContentLayoutItem().IsNull());
   frame_caret_->ScheduleVisualUpdateForPaintInvalidationIfNeeded();
   layout_selection_->SetHasPendingSelection();
 }
 
-void FrameSelection::NotifyLayoutObjectOfSelectionChange(
+void FrameSelection::NotifyTextControlOfSelectionChange(
     EUserTriggered user_triggered) {
   TextControlElement* text_control =
       EnclosingTextControl(GetSelectionInDOMTree().Base());
   if (!text_control)
     return;
   text_control->SelectionChanged(user_triggered == kUserTriggered);
 }
 
 // Helper function that tells whether a particular node is an element that has
 // an entire LocalFrame and FrameView, a <frame>, <iframe>, or <object>.
@@ skipping 364 matching lines @@
 }
 
 void showTree(const blink::FrameSelection* sel) {
   if (sel)
     sel->ShowTreeForThis();
   else
     LOG(INFO) << "Cannot showTree for <null> FrameSelection.";
 }
 
 #endif