diff --git a/widget/gtk/nsGtkIMModule.cpp b/widget/gtk/nsGtkIMModule.cpp
index 9dc2eeec9957..b0f42db8e3da 100644
--- a/widget/gtk/nsGtkIMModule.cpp
+++ b/widget/gtk/nsGtkIMModule.cpp
@@ -306,7 +306,8 @@ nsGtkIMModule::OnKeyEvent(nsWindow* aCaller, GdkEventKey* aEvent,
 {
     NS_PRECONDITION(aEvent, "aEvent must be non-null");
 
-    if (!IsEditable() || MOZ_UNLIKELY(IsDestroyed())) {
+    if (!mInputContext.mIMEState.MaybeEditable() ||
+        MOZ_UNLIKELY(IsDestroyed())) {
         return false;
     }
 
@@ -495,7 +496,7 @@ nsGtkIMModule::SetInputContext(nsWindow* aCaller,
         aContext->mHTMLInputType != mInputContext.mHTMLInputType;
 
     // Release current IME focus if IME is enabled.
-    if (changingEnabledState && IsEditable()) {
+    if (changingEnabledState && mInputContext.mIMEState.MaybeEditable()) {
         EndIMEComposition(mLastFocusedWindow);
         Blur();
     }
@@ -505,7 +506,7 @@ nsGtkIMModule::SetInputContext(nsWindow* aCaller,
     if (changingEnabledState) {
 #if (MOZ_WIDGET_GTK == 3)
         static bool sInputPurposeSupported = !gtk_check_version(3, 6, 0);
-        if (sInputPurposeSupported && IsEditable()) {
+        if (sInputPurposeSupported && mInputContext.mIMEState.MaybeEditable()) {
             GtkIMContext* context = GetContext();
             if (context) {
                 GtkInputPurpose purpose = GTK_INPUT_PURPOSE_FREE_FORM;
@@ -602,14 +603,6 @@ nsGtkIMModule::IsEnabled()
             mInputContext.mIMEState.mEnabled == IMEState::PASSWORD);
 }
 
-bool
-nsGtkIMModule::IsEditable()
-{
-    return mInputContext.mIMEState.mEnabled == IMEState::ENABLED ||
-           mInputContext.mIMEState.mEnabled == IMEState::PLUGIN ||
-           mInputContext.mIMEState.mEnabled == IMEState::PASSWORD;
-}
-
 void
 nsGtkIMModule::Focus()
 {
diff --git a/widget/gtk/nsGtkIMModule.h b/widget/gtk/nsGtkIMModule.h
index e9678365e207..36f3b01cd478 100644
--- a/widget/gtk/nsGtkIMModule.h
+++ b/widget/gtk/nsGtkIMModule.h
@@ -251,12 +251,6 @@ protected:
     // state.  So, this means *current* IM context.
     GtkIMContext* GetContext();
 
-    // "Editable" means the users can input characters. They may be not able to
-    // use IMEs but they can use dead keys.
-    // I.e., the focus is in the normal editors or the password editors or
-    // the |ime-mode: disabled;| editors.
-    bool IsEditable();
-
     // If the owner window and IM context have been destroyed, returns TRUE.
     bool IsDestroyed() { return !mOwnerWindow; }
 
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index a7b44247a0d5..71e01395768c 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -384,10 +384,21 @@ struct IMEState {
   {
   }
 
+  // Returns true if the user can input characters.
+  // This means that a plain text editor, an HTML editor, a password editor or
+  // a plain text editor whose ime-mode is "disabled".
   bool IsEditable() const
   {
     return mEnabled == ENABLED || mEnabled == PASSWORD;
   }
+  // Returns true if the user might be able to input characters.
+  // This means that a plain text editor, an HTML editor, a password editor,
+  // a plain text editor whose ime-mode is "disabled" or a windowless plugin
+  // has focus.
+  bool MaybeEditable() const
+  {
+    return IsEditable() || mEnabled == PLUGIN;
+  }
 };
 
 struct InputContext {