From afdb6ee2958319e98fd3b696ed4cbb45b98ca621 Mon Sep 17 00:00:00 2001
From: Kartikaya Gupta <kgupta@mozilla.com>
Date: Wed, 26 Aug 2015 14:41:12 -0400
Subject: [PATCH] Bug 1194811 Part 1 - Recompute the zoom constraints if the
 available screen area changes. r=botond

---
 layout/base/ZoomConstraintsClient.cpp | 7 +++++++
 layout/base/ZoomConstraintsClient.h   | 1 +
 layout/base/nsPresShell.cpp           | 6 ++++++
 3 files changed, 14 insertions(+)

diff --git a/layout/base/ZoomConstraintsClient.cpp b/layout/base/ZoomConstraintsClient.cpp
index 648129fb3ca..61f896b467f 100644
--- a/layout/base/ZoomConstraintsClient.cpp
+++ b/layout/base/ZoomConstraintsClient.cpp
@@ -133,6 +133,13 @@ ZoomConstraintsClient::Observe(nsISupports* aSubject, const char* aTopic, const
   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)
 {
diff --git a/layout/base/ZoomConstraintsClient.h b/layout/base/ZoomConstraintsClient.h
index 87be1162697..4a2da9114e2 100644
--- a/layout/base/ZoomConstraintsClient.h
+++ b/layout/base/ZoomConstraintsClient.h
@@ -33,6 +33,7 @@ private:
 public:
   void Init(nsIPresShell* aPresShell, nsIDocument *aDocument);
   void Destroy();
+  void ScreenSizeChanged();
 
 private:
   void RefreshZoomConstraints();
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index c596d76aa98..30c0b2075c4 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -1795,6 +1795,12 @@ PresShell::ResizeReflow(nscoord aWidth, nscoord aHeight)
     return NS_OK;
   }
 
+  if (mZoomConstraintsClient) {
+    // If we have a ZoomConstraintsClient and the available screen area
+    // changed, then we might need to disable double-tap-to-zoom, so notify
+    // the ZCC to update itself.
+    mZoomConstraintsClient->ScreenSizeChanged();
+  }
   if (mMobileViewportManager) {
     // If we have a mobile viewport manager, request a reflow from it. It can
     // recompute the final CSS viewport and trigger a call to