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/EditorBase.cpp

@@ -1248,7 +1248,7 @@ NS_IMETHODIMP EditorBase::CanCut(bool* aCanCut) {
   if (NS_WARN_IF(!aCanCut)) {
     return NS_ERROR_INVALID_ARG;
   }
-  *aCanCut = AsTextEditor()->IsCutCommandEnabled();
+  *aCanCut = MOZ_KnownLive(AsTextEditor())->IsCutCommandEnabled();
   return NS_OK;
 }
 
@@ -1258,7 +1258,7 @@ NS_IMETHODIMP EditorBase::CanCopy(bool* aCanCopy) {
   if (NS_WARN_IF(!aCanCopy)) {
     return NS_ERROR_INVALID_ARG;
   }
-  *aCanCopy = AsTextEditor()->IsCopyCommandEnabled();
+  *aCanCopy = MOZ_KnownLive(AsTextEditor())->IsCopyCommandEnabled();
   return NS_OK;
 }
 

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 +1217,64 @@ bool TextEditor::AreClipboardCommandsUnconditionallyEnabled() const {
   return document && document->AreClipboardCommandsUnconditionallyEnabled();
 }
 
+bool TextEditor::CheckForClipboardCommandListener(
+    nsAtom* aCommand, EventMessage aEventMessage) const {
+  RefPtr<Document> document = GetDocument();
+  if (!document) {
+    return false;
+  }
+
+  // We exclude XUL and chrome docs here to maintain current behavior where
+  // in these cases the editor element alone is expected to handle clipboard
+  // command availability.
+  if (!document->AreClipboardCommandsUnconditionallyEnabled()) {
+    return false;
+  }
+
+  // So in web content documents, "unconditionally" enabled Cut/Copy are not
+  // really unconditional; they're enabled if there is a listener that wants
+  // to handle them. What they're not conditional on here is whether there is
+  // currently a selection in the editor.
+  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 +1296,12 @@ 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 {

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;
 

editor/nsIEditor.idl

@@ -328,6 +328,7 @@ interface nsIEditor  : nsISupports
    * HTML/XHTML document.
    * FYI: Current user in script is only BlueGriffon.
    */
+  [can_run_script]
   boolean canCut();
 
   /** copy the currently selected text, putting it into the OS clipboard
@@ -344,6 +345,7 @@ interface nsIEditor  : nsISupports
    * HTML/XHTML document.
    * FYI: Current user in script is only BlueGriffon.
    */
+  [can_run_script]
   boolean canCopy();
 
   /** paste the text in the OS clipboard at the cursor position, replacing