Bug 1551882. Refactor the print preview listener code to make its purpose clear. r=bobowen

Differential Revision: https://phabricator.services.mozilla.com/D31252

--HG--
rename : layout/printing/nsPrintPreviewListener.cpp => layout/printing/PrintPreviewUserEventSuppressor.cpp
rename : layout/printing/nsPrintPreviewListener.h => layout/printing/PrintPreviewUserEventSuppressor.h
extra : rebase_source : a2bfc2635d8cb98ee7c93597c6f805122e99111f
extra : amend_source : 2d3c11cbc8e07fa90b1960c4e1a4422c12f2761b

layout/printing/PrintPreviewUserEventSuppressor.cpp

@@ -4,7 +4,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "nsPrintPreviewListener.h"
+#include "PrintPreviewUserEventSuppressor.h"
 
 #include "mozilla/TextEvents.h"
 #include "mozilla/dom/Element.h"
@@ -17,28 +17,19 @@
 #include "nsFocusManager.h"
 #include "nsLiteralString.h"
 
-using namespace mozilla;
 using namespace mozilla::dom;
 
-NS_IMPL_ISUPPORTS(nsPrintPreviewListener, nsIDOMEventListener)
+namespace mozilla {
 
-//
-// nsPrintPreviewListener ctor
-//
-nsPrintPreviewListener::nsPrintPreviewListener(EventTarget* aTarget)
+PrintPreviewUserEventSuppressor::PrintPreviewUserEventSuppressor(
+    EventTarget* aTarget)
     : mEventTarget(aTarget) {
-  NS_ADDREF_THIS();
-}  // ctor
+  AddListeners();
+}
 
-nsPrintPreviewListener::~nsPrintPreviewListener() {}
+NS_IMPL_ISUPPORTS(PrintPreviewUserEventSuppressor, nsIDOMEventListener)
 
-//-------------------------------------------------------
-//
-// AddListeners
-//
-// Subscribe to the events that will allow us to track various events.
-//
-nsresult nsPrintPreviewListener::AddListeners() {
+void PrintPreviewUserEventSuppressor::AddListeners() {
   if (mEventTarget) {
     mEventTarget->AddEventListener(NS_LITERAL_STRING("click"), this, true);
     mEventTarget->AddEventListener(NS_LITERAL_STRING("contextmenu"), this,
@@ -55,17 +46,9 @@ nsresult nsPrintPreviewListener::AddListeners() {
     mEventTarget->AddSystemEventListener(NS_LITERAL_STRING("keydown"), this,
                                          true);
   }
-
-  return NS_OK;
 }
 
-//-------------------------------------------------------
-//
-// RemoveListeners
-//
-// Unsubscribe from all the various events that we were listening to.
-//
-nsresult nsPrintPreviewListener::RemoveListeners() {
+void PrintPreviewUserEventSuppressor::RemoveListeners() {
   if (mEventTarget) {
     mEventTarget->RemoveEventListener(NS_LITERAL_STRING("click"), this, true);
     mEventTarget->RemoveEventListener(NS_LITERAL_STRING("contextmenu"), this,
@@ -87,16 +70,8 @@ nsresult nsPrintPreviewListener::RemoveListeners() {
     mEventTarget->RemoveSystemEventListener(NS_LITERAL_STRING("keydown"), this,
                                             true);
   }
-
-  return NS_OK;
 }
 
-//-------------------------------------------------------
-//
-// GetActionForEvent
-//
-// Helper function to let certain key events through
-//
 enum eEventAction {
   eEventAction_Tab,
   eEventAction_ShiftTab,
@@ -105,6 +80,7 @@ enum eEventAction {
   eEventAction_StopPropagation
 };
 
+// Helper function to let certain key events through
 static eEventAction GetActionForEvent(Event* aEvent) {
   WidgetKeyboardEvent* keyEvent = aEvent->WidgetEventPtr()->AsKeyboardEvent();
   if (!keyEvent) {
@@ -150,11 +126,11 @@ static eEventAction GetActionForEvent(Event* aEvent) {
 }
 
 NS_IMETHODIMP
-nsPrintPreviewListener::HandleEvent(Event* aEvent) {
+PrintPreviewUserEventSuppressor::HandleEvent(Event* aEvent) {
   nsCOMPtr<nsIContent> content =
       do_QueryInterface(aEvent ? aEvent->GetOriginalTarget() : nullptr);
   if (content && !content->IsXULElement()) {
-    eEventAction action = ::GetActionForEvent(aEvent);
+    eEventAction action = GetActionForEvent(aEvent);
     switch (action) {
       case eEventAction_Tab:
       case eEventAction_ShiftTab: {
@@ -173,10 +149,9 @@ nsPrintPreviewListener::HandleEvent(Event* aEvent) {
 
           nsIFocusManager* fm = nsFocusManager::GetFocusManager();
           if (fm && win) {
-            dom::Element* fromElement =
-                parentDoc->FindContentForSubDocument(doc);
+            Element* fromElement = parentDoc->FindContentForSubDocument(doc);
             bool forward = (action == eEventAction_Tab);
-            RefPtr<dom::Element> result;
+            RefPtr<Element> result;
             fm->MoveFocus(win, fromElement,
                           forward ? nsIFocusManager::MOVEFOCUS_FORWARD
                                   : nsIFocusManager::MOVEFOCUS_BACKWARD,
@@ -199,3 +174,5 @@ nsPrintPreviewListener::HandleEvent(Event* aEvent) {
   }
   return NS_OK;
 }
+
+}  // namespace mozilla

layout/printing/PrintPreviewUserEventSuppressor.h

@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_PrintPreviewUserEventSuppressor_h
+#define mozilla_PrintPreviewUserEventSuppressor_h
+
+#include "nsCOMPtr.h"
+#include "nsIDOMEventListener.h"
+#include "mozilla/Attributes.h"
+
+namespace mozilla {
+
+namespace dom {
+class EventTarget;
+}  // namespace dom
+
+/**
+ * A class that filters out certain user events targeted at the given event
+ * target (a document).  Intended for use with the Print Preview document to
+ * stop users from doing anything that would break printing invariants.  (For
+ * example, blocks opening of the context menu, interaction with form controls,
+ * content selection, etc.)
+ */
+class PrintPreviewUserEventSuppressor final : public nsIDOMEventListener {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOMEVENTLISTENER
+
+  explicit PrintPreviewUserEventSuppressor(dom::EventTarget* aTarget);
+
+  /**
+   * Must be called before releasing this object in order to break the strong
+   * reference cycle between ourselves and the document we're listening to,
+   * or else the objects in the cylce will be leaked (since this class does
+   * not participate in cycle collection).
+   */
+  void StopSuppressing() { RemoveListeners(); }
+
+ private:
+  ~PrintPreviewUserEventSuppressor() { RemoveListeners(); }
+
+  void AddListeners();
+  void RemoveListeners();
+
+  nsCOMPtr<mozilla::dom::EventTarget> mEventTarget;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_PrintPreviewUserEventSuppressor_h

layout/printing/moz.build

@@ -28,7 +28,7 @@ UNIFIED_SOURCES += [
     'nsPrintData.cpp',
     'nsPrintJob.cpp',
     'nsPrintObject.cpp',
-    'nsPrintPreviewListener.cpp',
+    'PrintPreviewUserEventSuppressor.cpp',
     'PrintTranslator.cpp',
 ]
 

layout/printing/nsPrintData.cpp

@@ -10,9 +10,9 @@
 #include "nsIServiceManager.h"
 #include "nsIWidget.h"
 #include "nsPrintObject.h"
-#include "nsPrintPreviewListener.h"
 #include "nsIWebProgressListener.h"
 #include "mozilla/Services.h"
+#include "PrintPreviewUserEventSuppressor.h"
 
 //-----------------------------------------------------
 // PR LOGGING
@@ -38,8 +38,7 @@ nsPrintData::nsPrintData(ePrintDataType aType)
       mPrintFrameType(nsIPrintSettings::kFramesAsIs),
       mNumPrintablePages(0),
       mNumPagesPrinted(0),
-      mShrinkRatio(1.0),
-      mPPEventListeners(nullptr) {
+      mShrinkRatio(1.0) {
   nsCOMPtr<nsIStringBundle> brandBundle;
   nsCOMPtr<nsIStringBundleService> svc =
       mozilla::services::GetStringBundleService();
@@ -57,10 +56,9 @@ nsPrintData::nsPrintData(ePrintDataType aType)
 }
 
 nsPrintData::~nsPrintData() {
-  // remove the event listeners
-  if (mPPEventListeners) {
-    mPPEventListeners->RemoveListeners();
-    NS_RELEASE(mPPEventListeners);
+  if (mPPEventSuppressor) {
+    mPPEventSuppressor->StopSuppressing();
+    mPPEventSuppressor = nullptr;
   }
 
   // Only Send an OnEndPrinting if we have started printing

layout/printing/nsPrintData.h

@@ -18,11 +18,13 @@
 #include "nsTArray.h"
 #include "nsCOMArray.h"
 
-// Classes
 class nsPrintObject;
-class nsPrintPreviewListener;
 class nsIWebProgressListener;
 
+namespace mozilla {
+class PrintPreviewUserEventSuppressor;
+}  // namespace mozilla
+
 //------------------------------------------------------------------------
 // nsPrintData Class
 //
@@ -38,6 +40,9 @@ class nsIWebProgressListener;
 //
 //------------------------------------------------------------------------
 class nsPrintData {
+  typedef mozilla::PrintPreviewUserEventSuppressor
+      PrintPreviewUserEventSuppressor;
+
  public:
   typedef enum { eIsPrinting, eIsPrintPreview } ePrintDataType;
 
@@ -82,7 +87,7 @@ class nsPrintData {
   float mShrinkRatio;
 
   nsCOMPtr<nsIPrintSettings> mPrintSettings;
-  nsPrintPreviewListener* mPPEventListeners;
+  RefPtr<PrintPreviewUserEventSuppressor> mPPEventSuppressor;
 
   nsString mBrandName;  //  needed as a substitute name for a document
 

layout/printing/nsPrintJob.cpp

@@ -38,8 +38,6 @@
 static const char sPrintSettingsServiceContractID[] =
     "@mozilla.org/gfx/printsettings-service;1";
 
-// Printing Events
-#include "nsPrintPreviewListener.h"
 #include "nsThreadUtils.h"
 
 // Printing
@@ -116,6 +114,7 @@ static const char kPrintingPromptService[] =
 #include "mozilla/dom/HTMLFrameElement.h"
 #include "nsContentList.h"
 #include "nsIChannel.h"
+#include "PrintPreviewUserEventSuppressor.h"
 #include "xpcpublic.h"
 #include "nsVariant.h"
 #include "mozilla/ServoStyleSet.h"
@@ -571,8 +570,8 @@ nsresult nsPrintJob::Cancelled() {
 // some events from being processed while in PrintPreview
 //
 // No return code - if this fails, there isn't much we can do
-void nsPrintJob::InstallPrintPreviewListener() {
-  if (!mPrt->mPPEventListeners) {
+void nsPrintJob::SuppressPrintPreviewUserEvents() {
+  if (!mPrt->mPPEventSuppressor) {
     nsCOMPtr<nsIDocShell> docShell = do_QueryReferent(mContainer);
     if (!docShell) {
       return;
@@ -580,8 +579,7 @@ void nsPrintJob::InstallPrintPreviewListener() {
 
     if (nsPIDOMWindowOuter* win = docShell->GetWindow()) {
       nsCOMPtr<EventTarget> target = win->GetFrameElementInternal();
-      mPrt->mPPEventListeners = new nsPrintPreviewListener(target);
-      mPrt->mPPEventListeners->AddListeners();
+      mPrt->mPPEventSuppressor = new PrintPreviewUserEventSuppressor(target);
     }
   }
 }
@@ -1007,7 +1005,7 @@ nsresult nsPrintJob::DoCommonPrint(bool aIsPrintPreview,
     TurnScriptingOn(false);
 
     if (!notifyOnInit) {
-      InstallPrintPreviewListener();
+      SuppressPrintPreviewUserEvents();
       rv = InitPrintDocConstruction(false);
     } else {
       rv = NS_OK;

layout/printing/nsPrintJob.h

@@ -109,7 +109,13 @@ class nsPrintJob final : public nsIObserver,
 
   void TurnScriptingOn(bool aDoTurnOn);
   bool CheckDocumentForPPCaching();
-  void InstallPrintPreviewListener();
+
+  /**
+   * Filters out certain user events while Print Preview is open to prevent
+   * the user from interacting with the Print Preview document and breaking
+   * printing invariants.
+   */
+  void SuppressPrintPreviewUserEvents();
 
   // nsIDocumentViewerPrint Printing Methods
   bool HasPrintCallbackCanvas();

layout/printing/nsPrintPreviewListener.h

@@ -1,51 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef nsPrintPreviewListener_h__
-#define nsPrintPreviewListener_h__
-
-// Interfaces needed to be included
-#include "nsIDOMEventListener.h"
-// Helper Classes
-#include "nsCOMPtr.h"
-#include "mozilla/Attributes.h"
-
-namespace mozilla {
-namespace dom {
-class EventTarget;
-}  // namespace dom
-}  // namespace mozilla
-
-//
-// class nsPrintPreviewListener
-//
-// The class that listens to the chrome events and tells the embedding
-// chrome to show context menus, as appropriate. Handles registering itself
-// with the DOM with AddChromeListeners() and removing itself with
-// RemoveChromeListeners().
-//
-class nsPrintPreviewListener final : public nsIDOMEventListener
-
-{
- public:
-  NS_DECL_ISUPPORTS
-  NS_DECL_NSIDOMEVENTLISTENER
-
-  explicit nsPrintPreviewListener(mozilla::dom::EventTarget* aTarget);
-
-  // Add/remove the relevant listeners, based on what interfaces
-  // the embedding chrome implements.
-  nsresult AddListeners();
-  nsresult RemoveListeners();
-
- private:
-  ~nsPrintPreviewListener();
-
-  nsCOMPtr<mozilla::dom::EventTarget> mEventTarget;
-
-};  // class nsPrintPreviewListener
-
-#endif /* nsPrintPreviewListener_h__ */