1 files changed, 253 insertions, 0 deletions
diff --git a/layout/base/ZoomConstraintsClient.cpp b/layout/base/ZoomConstraintsClient.cpp
new file mode 100644
index 000000000..2391a116d
--- /dev/null
+++ b/layout/base/ZoomConstraintsClient.cpp
@@ -0,0 +1,253 @@
+/* -*- Mode: C++; 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/. */
+
+#include "ZoomConstraintsClient.h"
+
+#include <inttypes.h>
+#include "FrameMetrics.h"
+#include "gfxPrefs.h"
+#include "LayersLogging.h"
+#include "mozilla/layers/APZCCallbackHelper.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/Event.h"
+#include "nsDocument.h"
+#include "nsIFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsPoint.h"
+#include "nsPresShell.h"
+#include "nsView.h"
+#include "nsViewportInfo.h"
+#include "Units.h"
+#include "UnitTransforms.h"
+
+#define ZCC_LOG(...)
+// #define ZCC_LOG(...) printf_stderr("ZCC: " __VA_ARGS__)
+
+NS_IMPL_ISUPPORTS(ZoomConstraintsClient, nsIDOMEventListener, nsIObserver)
+
+static const nsLiteralString DOM_META_ADDED = NS_LITERAL_STRING("DOMMetaAdded");
+static const nsLiteralString DOM_META_CHANGED = NS_LITERAL_STRING("DOMMetaChanged");
+static const nsLiteralString FULLSCREEN_CHANGED = NS_LITERAL_STRING("fullscreenchange");
+static const nsLiteralCString BEFORE_FIRST_PAINT = NS_LITERAL_CSTRING("before-first-paint");
+static const nsLiteralCString NS_PREF_CHANGED = NS_LITERAL_CSTRING("nsPref:changed");
+
+using namespace mozilla;
+using namespace mozilla::layers;
+
+ZoomConstraintsClient::ZoomConstraintsClient() :
+  mDocument(nullptr),
+  mPresShell(nullptr)
+{
+}
+
+ZoomConstraintsClient::~ZoomConstraintsClient()
+{
+}
+
+static nsIWidget*
+GetWidget(nsIPresShell* aShell)
+{
+  if (!aShell) {
+    return nullptr;
+  }
+  if (nsIFrame* rootFrame = aShell->GetRootFrame()) {
+#if defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
+    return rootFrame->GetNearestWidget();
+#else
+    if (nsView* view = rootFrame->GetView()) {
+      return view->GetWidget();
+    }
+#endif
+  }
+  return nullptr;
+}
+
+void
+ZoomConstraintsClient::Destroy()
+{
+  if (!(mPresShell && mDocument)) {
+    return;
+  }
+
+  ZCC_LOG("Destroying %p\n", this);
+
+  if (mEventTarget) {
+    mEventTarget->RemoveEventListener(DOM_META_ADDED, this, false);
+    mEventTarget->RemoveEventListener(DOM_META_CHANGED, this, false);
+    mEventTarget->RemoveSystemEventListener(FULLSCREEN_CHANGED, this, false);
+    mEventTarget = nullptr;
+  }
+
+  nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
+  if (observerService) {
+    observerService->RemoveObserver(this, BEFORE_FIRST_PAINT.Data());
+  }
+
+  Preferences::RemoveObserver(this, "browser.ui.zoom.force-user-scalable");
+
+  if (mGuid) {
+    if (nsIWidget* widget = GetWidget(mPresShell)) {
+      ZCC_LOG("Sending null constraints in %p for { %u, %" PRIu64 " }\n",
+        this, mGuid->mPresShellId, mGuid->mScrollId);
+      widget->UpdateZoomConstraints(mGuid->mPresShellId, mGuid->mScrollId, Nothing());
+      mGuid = Nothing();
+    }
+  }
+
+  mDocument = nullptr;
+  mPresShell = nullptr;
+}
+
+void
+ZoomConstraintsClient::Init(nsIPresShell* aPresShell, nsIDocument* aDocument)
+{
+  if (!(aPresShell && aDocument)) {
+    return;
+  }
+
+  mPresShell = aPresShell;
+  mDocument = aDocument;
+
+  if (nsCOMPtr<nsPIDOMWindowOuter> window = mDocument->GetWindow()) {
+    mEventTarget = window->GetParentTarget();
+  }
+  if (mEventTarget) {
+    mEventTarget->AddEventListener(DOM_META_ADDED, this, false);
+    mEventTarget->AddEventListener(DOM_META_CHANGED, this, false);
+    mEventTarget->AddSystemEventListener(FULLSCREEN_CHANGED, this, false);
+  }
+
+  nsCOMPtr<nsIObserverService> observerService = mozilla::services::GetObserverService();
+  if (observerService) {
+    observerService->AddObserver(this, BEFORE_FIRST_PAINT.Data(), false);
+  }
+
+  Preferences::AddStrongObserver(this, "browser.ui.zoom.force-user-scalable");
+}
+
+NS_IMETHODIMP
+ZoomConstraintsClient::HandleEvent(nsIDOMEvent* event)
+{
+  nsAutoString type;
+  event->GetType(type);
+
+  if (type.Equals(DOM_META_ADDED)) {
+    ZCC_LOG("Got a dom-meta-added event in %p\n", this);
+    RefreshZoomConstraints();
+  } else if (type.Equals(DOM_META_CHANGED)) {
+    ZCC_LOG("Got a dom-meta-changed event in %p\n", this);
+    RefreshZoomConstraints();
+  } else if (type.Equals(FULLSCREEN_CHANGED)) {
+    ZCC_LOG("Got a fullscreen-change event in %p\n", this);
+    RefreshZoomConstraints();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ZoomConstraintsClient::Observe(nsISupports* aSubject, const char* aTopic, const char16_t* aData)
+{
+  if (SameCOMIdentity(aSubject, mDocument) && BEFORE_FIRST_PAINT.EqualsASCII(aTopic)) {
+    ZCC_LOG("Got a before-first-paint event in %p\n", this);
+    RefreshZoomConstraints();
+  } else if (NS_PREF_CHANGED.EqualsASCII(aTopic)) {
+    ZCC_LOG("Got a pref-change event in %p\n", this);
+    // We need to run this later because all the pref change listeners need
+    // to execute before we can be guaranteed that gfxPrefs::ForceUserScalable()
+    // returns the updated value.
+    NS_DispatchToMainThread(NewRunnableMethod(
+      this, &ZoomConstraintsClient::RefreshZoomConstraints));
+  }
+  return NS_OK;
+}
+
+void
+ZoomConstraintsClient::ScreenSizeChanged()
+{
+  ZCC_LOG("Got a screen-size change notification in %p\n", this);
+  RefreshZoomConstraints();
+}
+
+mozilla::layers::ZoomConstraints
+ComputeZoomConstraintsFromViewportInfo(const nsViewportInfo& aViewportInfo)
+{
+  mozilla::layers::ZoomConstraints constraints;
+  constraints.mAllowZoom = aViewportInfo.IsZoomAllowed() && gfxPrefs::APZAllowZooming();
+  constraints.mAllowDoubleTapZoom = constraints.mAllowZoom;
+  if (constraints.mAllowZoom) {
+    constraints.mMinZoom.scale = aViewportInfo.GetMinZoom().scale;
+    constraints.mMaxZoom.scale = aViewportInfo.GetMaxZoom().scale;
+  } else {
+    constraints.mMinZoom.scale = aViewportInfo.GetDefaultZoom().scale;
+    constraints.mMaxZoom.scale = aViewportInfo.GetDefaultZoom().scale;
+  }
+  return constraints;
+}
+
+void
+ZoomConstraintsClient::RefreshZoomConstraints()
+{
+  nsIWidget* widget = GetWidget(mPresShell);
+  if (!widget) {
+    return;
+  }
+
+  uint32_t presShellId = 0;
+  FrameMetrics::ViewID viewId = FrameMetrics::NULL_SCROLL_ID;
+  bool scrollIdentifiersValid = APZCCallbackHelper::GetOrCreateScrollIdentifiers(
+        mDocument->GetDocumentElement(),
+        &presShellId, &viewId);
+  if (!scrollIdentifiersValid) {
+    return;
+  }
+
+  LayoutDeviceIntSize screenSize;
+  if (!nsLayoutUtils::GetContentViewerSize(mPresShell->GetPresContext(), screenSize)) {
+    return;
+  }
+
+  nsViewportInfo viewportInfo = mDocument->GetViewportInfo(
+    ViewAs<ScreenPixel>(screenSize, PixelCastJustification::LayoutDeviceIsScreenForBounds));
+
+  mozilla::layers::ZoomConstraints zoomConstraints =
+    ComputeZoomConstraintsFromViewportInfo(viewportInfo);
+
+  if (mDocument->Fullscreen()) {
+    ZCC_LOG("%p is in fullscreen, disallowing zooming\n", this);
+    zoomConstraints.mAllowZoom = false;
+    zoomConstraints.mAllowDoubleTapZoom = false;
+  }
+
+  if (zoomConstraints.mAllowDoubleTapZoom) {
+    // If the CSS viewport is narrower than the screen (i.e. width <= device-width)
+    // then we disable double-tap-to-zoom behaviour.
+    CSSToLayoutDeviceScale scale =
+        mPresShell->GetPresContext()->CSSToDevPixelScale();
+    if ((viewportInfo.GetSize() * scale).width <= screenSize.width) {
+      zoomConstraints.mAllowDoubleTapZoom = false;
+    }
+  }
+
+  // We only ever create a ZoomConstraintsClient for an RCD, so the RSF of
+  // the presShell must be the RCD-RSF (if it exists).
+  MOZ_ASSERT(mPresShell->GetPresContext()->IsRootContentDocument());
+  if (nsIScrollableFrame* rcdrsf = mPresShell->GetRootScrollFrameAsScrollable()) {
+    ZCC_LOG("Notifying RCD-RSF that it is zoomable: %d\n", zoomConstraints.mAllowZoom);
+    rcdrsf->SetZoomableByAPZ(zoomConstraints.mAllowZoom);
+  }
+
+  ScrollableLayerGuid newGuid(0, presShellId, viewId);
+  if (mGuid && mGuid.value() != newGuid) {
+    ZCC_LOG("Clearing old constraints in %p for { %u, %" PRIu64 " }\n",
+      this, mGuid->mPresShellId, mGuid->mScrollId);
+    // If the guid changes, send a message to clear the old one
+    widget->UpdateZoomConstraints(mGuid->mPresShellId, mGuid->mScrollId, Nothing());
+  }
+  mGuid = Some(newGuid);
+  ZCC_LOG("Sending constraints %s in %p for { %u, %" PRIu64 " }\n",
+    Stringify(zoomConstraints).c_str(), this, presShellId, viewId);
+  widget->UpdateZoomConstraints(presShellId, viewId, Some(zoomConstraints));
+}