Issue #2714 - Implement the Visual Viewport API

This DOM/Web API is entirely irrelevant for desktop use.
We give back the width/height of the root scrollframe of content and
for scale we pass forward our dpp resolution (usually 1.0).
Since we have no "no touch" zones in our content on desktop,. the rest
(origin and offset) is hard-coded to (0,0).

dom/base/VisualViewport.cpp

@@ -0,0 +1,144 @@
+/* -*- 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/. */
+
+#include "VisualViewport.h"
+#include "nsIScrollableFrame.h"
+#include "nsIDocShell.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+VisualViewport::VisualViewport(nsPIDOMWindowInner* aWindow)
+  : DOMEventTargetHelper(aWindow)
+{
+}
+
+VisualViewport::VisualViewport(nsIGlobalObject* aGlobal)
+  : DOMEventTargetHelper(aGlobal)
+{
+}
+
+VisualViewport::~VisualViewport()
+{
+}
+
+/* virtual */
+JSObject*
+VisualViewport::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
+{
+  return VisualViewportBinding::Wrap(aCx, this, aGivenProto);
+}
+
+/* XXXMC: We are effectively getting the size from the root scrollframe of the content
+ * and the scale from our DPP resolution.
+ * Since we are only on desktop, by definition have full view size (no "notch" or
+ * other mobile "don't touch" areas), we are hard-coding:
+ * - VisualViewportOffset = (0,0)
+ * - PageLeft/PageTop = 0.0
+ * - OffsetLeft/OffsetTop = 0.0
+ */
+ 
+CSSSize
+VisualViewport::VisualViewportSize() const
+{
+  CSSSize size = CSSSize(0,0);
+
+  nsIPresShell* presShell = GetPresShell();
+  if (presShell) {
+    nsIScrollableFrame* sf = presShell->GetRootScrollFrameAsScrollable();
+    if (sf) {
+      size = CSSRect::FromAppUnits(sf->GetScrollPortRect().Size());
+    }
+  }
+  return size;
+}
+
+double
+VisualViewport::Width() const
+{
+  CSSSize size = VisualViewportSize();
+  return size.width;
+}
+
+double
+VisualViewport::Height() const
+{
+  CSSSize size = VisualViewportSize();
+  return size.height;
+}
+
+double
+VisualViewport::Scale() const
+{
+  double scale = 1;
+  nsIPresShell* presShell = GetPresShell();
+  if (presShell) {
+    scale = presShell->GetResolution();
+  }
+  return scale;
+}
+
+CSSPoint
+VisualViewport::VisualViewportOffset() const
+{
+  CSSPoint offset = CSSPoint(0,0);
+  return offset;
+}
+
+CSSPoint
+VisualViewport::LayoutViewportOffset() const
+{
+  CSSPoint offset = CSSPoint(0,0);
+
+  nsIPresShell* presShell = GetPresShell();
+  if (presShell) {
+    nsIScrollableFrame* sf = presShell->GetRootScrollFrameAsScrollable();
+    if (sf) {
+      offset = CSSPoint::FromAppUnits(sf->GetScrollPosition());
+    }
+  }
+  return offset;
+}
+
+double
+VisualViewport::PageLeft() const
+{
+  return 0.0;
+}
+
+double
+VisualViewport::PageTop() const
+{
+  return 0.0;
+}
+
+double
+VisualViewport::OffsetLeft() const
+{
+  return 0.0;
+}
+
+double
+VisualViewport::OffsetTop() const
+{
+  return 0.0;
+}
+
+nsIPresShell*
+VisualViewport::GetPresShell() const
+{
+  nsCOMPtr<nsPIDOMWindowInner> window = GetOwner();
+  if (!window) {
+    return nullptr;
+  }
+
+  nsIDocShell* docShell = window->GetDocShell();
+  if (!docShell) {
+    return nullptr;
+  }
+
+  return docShell->GetPresShell();
+}

dom/base/VisualViewport.h

@@ -0,0 +1,49 @@
+/* -*- 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_dom_VisualViewport_h
+#define mozilla_dom_VisualViewport_h
+
+#include "mozilla/DOMEventTargetHelper.h"
+#include "mozilla/dom/VisualViewportBinding.h"
+#include "Units.h"
+#include "nsIPresShell.h"
+
+namespace mozilla {
+namespace dom {
+
+/* Visual Viewport API spec:  https://wicg.github.io/visual-viewport/#the-visualviewport-interface */
+class VisualViewport final: public mozilla::DOMEventTargetHelper
+{
+
+public:
+  explicit VisualViewport(nsPIDOMWindowInner* aWindow);
+  explicit VisualViewport(nsIGlobalObject* aGlobal);
+
+  double OffsetLeft() const;
+  double OffsetTop() const;
+  double PageLeft() const;
+  double PageTop() const;
+  double Width() const;
+  double Height() const;
+  double Scale() const;
+
+  virtual JSObject* WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
+
+private:
+  virtual ~VisualViewport();
+
+  CSSSize VisualViewportSize() const;
+  CSSPoint VisualViewportOffset() const;
+  CSSPoint LayoutViewportOffset() const;
+  nsIPresShell* GetPresShell() const;
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_VisualViewport_h

dom/base/moz.build

@@ -217,6 +217,7 @@ EXPORTS.mozilla.dom += [
     'Timeout.h',
     'TimeoutHandler.h',
     'TreeWalker.h',
+    'VisualViewport.h',
     'WebKitCSSMatrix.h',
     'WebSocket.h',
     'WindowOrientationObserver.h',
@@ -365,6 +366,7 @@ UNIFIED_SOURCES += [
     'TimeoutHandler.cpp',
     'TimerClamping.cpp',
     'TreeWalker.cpp',
+    'VisualViewport.cpp',
     'WebKitCSSMatrix.cpp',
     'WebSocket.cpp',
     'WindowNamedPropertiesHandler.cpp',

dom/base/nsGlobalWindow.cpp

@@ -23,6 +23,7 @@
 #include "mozilla/dom/StorageEventBinding.h"
 #include "mozilla/dom/Timeout.h"
 #include "mozilla/dom/TimeoutHandler.h"
+#include "mozilla/dom/VisualViewport.h"
 #include "mozilla/IntegerPrintfMacros.h"
 #include "nsDOMOfflineResourceList.h"
 #include "nsError.h"
@@ -4156,6 +4157,16 @@ nsGlobalWindow::GetNavigator()
   return navigator;
 }
 
+VisualViewport*
+nsGlobalWindow::VisualViewport()
+{
+  if (!mVisualViewport) {
+    mVisualViewport = new mozilla::dom::VisualViewport(this);
+  }
+
+  return mVisualViewport;
+}
+
 nsScreen*
 nsGlobalWindow::GetScreen(ErrorResult& aError)
 {

dom/base/nsGlobalWindow.h

@@ -134,6 +134,7 @@ class SpeechSynthesis;
 class TabGroup;
 class Timeout;
 class U2F;
+class VisualViewport;
 class WakeLock;
 struct WindowPostMessageOptions;
 class Worklet;
@@ -974,6 +975,7 @@ public:
   already_AddRefed<nsICSSDeclaration>
     GetComputedStyle(mozilla::dom::Element& aElt, const nsAString& aPseudoElt,
                      mozilla::ErrorResult& aError) override;
+  mozilla::dom::VisualViewport* VisualViewport();
   already_AddRefed<mozilla::dom::MediaQueryList> MatchMediaOuter(const nsAString& aQuery);
   already_AddRefed<mozilla::dom::MediaQueryList> MatchMedia(const nsAString& aQuery,
                                                             mozilla::ErrorResult& aError);
@@ -1854,6 +1856,8 @@ protected:
   RefPtr<nsHistory>           mHistory;
   RefPtr<mozilla::dom::CustomElementRegistry> mCustomElements;
 
+  RefPtr<mozilla::dom::VisualViewport> mVisualViewport;
+
   // These member variables are used on both inner and the outer windows.
   nsCOMPtr<nsIPrincipal> mDocumentPrincipal;
 

dom/bindings/Bindings.conf

@@ -1162,6 +1162,10 @@ DOMInterfaces = {
     'wrapperCache': False,
 },
 
+'VisualViewport': {
+    'nativeType': 'mozilla::dom::VisualViewport',
+},
+
 'VTTCue': {
     'nativeType': 'mozilla::dom::TextTrackCue'
 },

dom/webidl/VisualViewport.webidl

@@ -0,0 +1,21 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/.
+ *
+ * The origin of this IDL file is:
+ * https://wicg.github.io/visual-viewport/#the-visualviewport-interface
+ */
+
+interface VisualViewport : EventTarget {
+  readonly attribute double offsetLeft;
+  readonly attribute double offsetTop;
+
+  readonly attribute double pageLeft;
+  readonly attribute double pageTop;
+
+  readonly attribute double width;
+  readonly attribute double height;
+
+  readonly attribute double scale;
+};

dom/webidl/Window.webidl

@@ -15,6 +15,7 @@
  * http://dvcs.w3.org/hg/speech-api/raw-file/tip/speechapi.html
  * https://w3c.github.io/webappsec-secure-contexts/#monkey-patching-global-object
  * https://w3c.github.io/requestidlecallback/
+ * https://wicg.github.io/visual-viewport/#the-visualviewport-interface
  */
 
 interface ApplicationCache;
@@ -492,3 +493,8 @@ partial interface Window {
 dictionary WindowPostMessageOptions : StructuredSerializeOptions {
   USVString targetOrigin = "/";
 };
+
+partial interface Window {
+  [SameObject, Pref="dom.visualviewport.enabled", Replaceable]
+  readonly attribute VisualViewport visualViewport;
+};

dom/webidl/moz.build

@@ -557,6 +557,7 @@ WEBIDL_FILES = [
     'VideoStreamTrack.webidl',
     'VideoTrack.webidl',
     'VideoTrackList.webidl',
+    'VisualViewport.webidl',
     'VTTCue.webidl',
     'VTTRegion.webidl',
     'WaveShaperNode.webidl',

gfx/thebes/gfxPrefs.h

@@ -317,6 +317,7 @@ private:
 
   DECL_GFX_PREF(Live, "dom.ipc.plugins.asyncdrawing.enabled",  PluginAsyncDrawingEnabled, bool, false);
   DECL_GFX_PREF(Live, "dom.meta-viewport.enabled",             MetaViewportEnabled, bool, false);
+  DECL_GFX_PREF(Live, "dom.visualviewport.enabled",            VisualViewportEnabled, bool, false);
   DECL_GFX_PREF(Once, "dom.vr.enabled",                        VREnabled, bool, false);
   DECL_GFX_PREF(Once, "dom.vr.oculus.enabled",                 VROculusEnabled, bool, true);
   DECL_GFX_PREF(Once, "dom.vr.openvr.enabled",                 VROpenVREnabled, bool, false);

modules/libpref/init/all.js

@@ -5045,6 +5045,9 @@ pref("intl.allow-insecure-text-input", false);
 // Enable meta-viewport support in remote APZ-enabled frames.
 pref("dom.meta-viewport.enabled", false);
 
+// Disable the Visual Viewport API
+pref("dom.visualviewport.enabled", false);
+
 // Disable <meta http-equiv=set-cookie> support. See m-c bug 1457503 / UXP #1102.
 pref("dom.meta-set-cookie.enabled", false);