From 24a5b45445c1d3ffa0a7c683d3695919af282668 Mon Sep 17 00:00:00 2001
From: Jonathan Kew <jkew@mozilla.com>
Date: Thu, 11 Mar 2021 10:27:04 +0000
Subject: [PATCH] Bug 1692673 - Avoid enabling Cut/Copy menu commands in text
 editor context when there's no selection, unless a listener is present.
 r=masayuki

Differential Revision: https://phabricator.services.mozilla.com/D107480
---
 editor/libeditor/TextEditor.cpp | 47 ++++++++++++++++++++++++++++++---
 editor/libeditor/TextEditor.h   | 11 ++++++--
 2 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/editor/libeditor/TextEditor.cpp b/editor/libeditor/TextEditor.cpp
index 4cac42a23938..86cd733ae1e4 100644
--- a/editor/libeditor/TextEditor.cpp
+++ b/editor/libeditor/TextEditor.cpp
@@ -13,9 +13,11 @@
 #include "PlaceholderTransaction.h"
 #include "gfxFontUtils.h"
 #include "mozilla/Assertions.h"
+#include "mozilla/ContentEvents.h"
 #include "mozilla/ContentIterator.h"
 #include "mozilla/EditAction.h"
 #include "mozilla/EditorDOMPoint.h"
+#include "mozilla/EventDispatcher.h"
 #include "mozilla/HTMLEditor.h"
 #include "mozilla/IMEStateManager.h"
 #include "mozilla/LookAndFeel.h"
@@ -54,6 +56,7 @@
 #include "nsIWeakReferenceUtils.h"
 #include "nsNameSpaceManager.h"
 #include "nsLiteralString.h"
+#include "nsPresContext.h"
 #include "nsReadableUtils.h"
 #include "nsServiceManagerUtils.h"
 #include "nsString.h"
@@ -1214,17 +1217,52 @@ bool TextEditor::AreClipboardCommandsUnconditionallyEnabled() const {
   return document && document->AreClipboardCommandsUnconditionallyEnabled();
 }
 
+bool TextEditor::CheckForClipboardCommandListener(
+    nsAtom* aCommand, EventMessage aEventMessage) const {
+  RefPtr<Document> document = GetDocument();
+  if (!document) {
+    return false;
+  }
+  RefPtr<PresShell> presShell = document->GetObservingPresShell();
+  if (!presShell) {
+    return false;
+  }
+  RefPtr<nsPresContext> presContext = presShell->GetPresContext();
+  if (!presContext) {
+    return false;
+  }
+
+  RefPtr<EventTarget> et = GetDOMEventTarget();
+  while (et) {
+    EventListenerManager* elm = et->GetOrCreateListenerManager();
+    if (elm && elm->HasListenersFor(aCommand)) {
+      return true;
+    }
+    InternalClipboardEvent event(true, aEventMessage);
+    EventChainPreVisitor visitor(presContext, &event, nullptr,
+                                 nsEventStatus_eIgnore, false, et);
+    et->GetEventTargetParent(visitor);
+    et = visitor.GetParentTarget();
+  }
+
+  return false;
+}
+
 bool TextEditor::IsCutCommandEnabled() const {
   AutoEditActionDataSetter editActionData(*this, EditAction::eNotEditing);
   if (NS_WARN_IF(!editActionData.CanHandle())) {
     return false;
   }
 
-  if (AreClipboardCommandsUnconditionallyEnabled()) {
+  if (IsModifiable() && IsCopyToClipboardAllowedInternal()) {
     return true;
   }
 
-  return IsModifiable() && IsCopyToClipboardAllowedInternal();
+  // If there's an event listener for "cut", we always enable the command
+  // as we don't really know what the listener may want to do in response.
+  // We look up the event target chain for a possible listener on a parent
+  // in addition to checking the immediate target.
+  return CheckForClipboardCommandListener(nsGkAtoms::oncut, eCut);
 }
 
 NS_IMETHODIMP TextEditor::Copy() {
@@ -1246,11 +1284,12 @@ bool TextEditor::IsCopyCommandEnabled() const {
     return false;
   }
 
-  if (AreClipboardCommandsUnconditionallyEnabled()) {
+  if (IsCopyToClipboardAllowedInternal()) {
     return true;
   }
 
-  return IsCopyToClipboardAllowedInternal();
+  // Like "cut", always enable "copy" if there's a listener.
+  return CheckForClipboardCommandListener(nsGkAtoms::oncopy, eCopy);
 }
 
 bool TextEditor::CanDeleteSelection() const {
diff --git a/editor/libeditor/TextEditor.h b/editor/libeditor/TextEditor.h
index a08f57952cdd..14c93eac6d0e 100644
--- a/editor/libeditor/TextEditor.h
+++ b/editor/libeditor/TextEditor.h
@@ -96,7 +96,7 @@ class TextEditor : public EditorBase, public nsITimerCallback, public nsINamed {
    * disabled.  This always returns true if we're in non-chrome HTML/XHTML
    * document.  Otherwise, same as the result of `IsCopyToClipboardAllowed()`.
    */
-  bool IsCutCommandEnabled() const;
+  MOZ_CAN_RUN_SCRIPT bool IsCutCommandEnabled() const;
 
   NS_IMETHOD Copy() override;
 
@@ -105,7 +105,7 @@ class TextEditor : public EditorBase, public nsITimerCallback, public nsINamed {
    * This always returns true if we're in non-chrome HTML/XHTML document.
    * Otherwise, same as the result of `IsCopyToClipboardAllowed()`.
    */
-  bool IsCopyCommandEnabled() const;
+  MOZ_CAN_RUN_SCRIPT bool IsCopyCommandEnabled() const;
 
   /**
    * IsCopyToClipboardAllowed() returns true if the selected content can
@@ -786,6 +786,13 @@ class TextEditor : public EditorBase, public nsITimerCallback, public nsINamed {
                                                      bool aNotify,
                                                      bool aForceStartMasking);
 
+  /**
+   * Helper for Is{Cut|Copy}CommandEnabled.
+   * Look for a listener for the given command, including up the target chain.
+   */
+  MOZ_CAN_RUN_SCRIPT bool CheckForClipboardCommandListener(
+      nsAtom* aCommand, EventMessage aEventMessage) const;
+
  protected:
   mutable nsCOMPtr<nsIDocumentEncoder> mCachedDocumentEncoder;