Bug 1186004 - Add a pref to enable/disable APZ zooming behaviour. r=botond

b2g/app/b2g.js

@@ -1040,7 +1040,10 @@ pref("security.exthelperapp.disable_background_handling", true);
 pref("osfile.reset_worker_delay", 5000);
 
 // APZC preferences.
-//
+#ifdef MOZ_WIDGET_GONK
+pref("apz.allow_zooming", true);
+#endif
+
 // Gaia relies heavily on scroll events for now, so lets fire them
 // more often than the default value (100).
 pref("apz.asyncscroll.throttle", 40);

dom/base/nsDocument.cpp

@@ -7906,14 +7906,14 @@ nsDocument::GetViewportInfo(const ScreenIntSize& aDisplaySize)
     return nsViewportInfo(aDisplaySize,
                           defaultScale,
                           /*allowZoom*/false,
-                          /*allowDoubleTapZoom*/ true);
+                          /*allowDoubleTapZoom*/ false);
   }
 
   if (!gfxPrefs::MetaViewportEnabled()) {
     return nsViewportInfo(aDisplaySize,
                           defaultScale,
                           /*allowZoom*/ false,
-                          /*allowDoubleTapZoom*/ true);
+                          /*allowDoubleTapZoom*/ false);
   }
 
   // In cases where the width of the CSS viewport is less than or equal to the width

dom/base/nsViewportInfo.h

@@ -34,6 +34,9 @@ class MOZ_STACK_CLASS nsViewportInfo
       mAllowZoom(aAllowZoom),
       mAllowDoubleTapZoom(aAllowDoubleTapZoom)
     {
+        // Don't allow double-tap zooming unless zooming is also allowed
+        MOZ_ASSERT(mAllowZoom || !mAllowDoubleTapZoom);
+
         mSize = mozilla::ScreenSize(aDisplaySize) / mDefaultZoom;
         mozilla::CSSToLayoutDeviceScale pixelRatio(1.0f);
         mMinZoom = pixelRatio * kViewportMinScale;
@@ -56,6 +59,9 @@ class MOZ_STACK_CLASS nsViewportInfo
                      mAllowZoom(aAllowZoom),
                      mAllowDoubleTapZoom(aAllowDoubleTapZoom)
     {
+      // Don't allow double-tap zooming unless zooming is also allowed
+      MOZ_ASSERT(mAllowZoom || !mAllowDoubleTapZoom);
+
       ConstrainViewportValues();
     }
 

gfx/thebes/gfxPrefs.h

@@ -135,6 +135,7 @@ private:
 
   // The apz prefs are explained in AsyncPanZoomController.cpp
   DECL_GFX_PREF(Live, "apz.allow_checkerboarding",             APZAllowCheckerboarding, bool, true);
+  DECL_GFX_PREF(Live, "apz.allow_zooming",                     APZAllowZooming, bool, false);
   DECL_GFX_PREF(Live, "apz.asyncscroll.throttle",              APZAsyncScrollThrottleTime, int32_t, 100);
   DECL_GFX_PREF(Live, "apz.asyncscroll.timeout",               APZAsyncScrollTimeout, int32_t, 300);
   DECL_GFX_PREF(Live, "apz.axis_lock.breakout_angle",          APZAxisBreakoutAngle, float, float(M_PI / 8.0) /* 22.5 degrees */);

layout/base/MobileViewportManager.cpp

@@ -114,7 +114,11 @@ MobileViewportManager::UpdateResolution(const nsViewportInfo& aViewportInfo,
     / mPresShell->GetPresContext()->AppUnitsPerDevPixel());
   LayoutDeviceToLayerScale res(nsLayoutUtils::GetResolution(mPresShell));
 
-#if defined(MOZ_WIDGET_GONK) || defined(MOZ_WIDGET_ANDROID) || defined(MOZ_WIDGET_UIKIT)
+  if (!gfxPrefs::APZAllowZooming()) {
+    return ViewTargetAs<ScreenPixel>(cssToDev * res / ParentLayerToLayerScale(1),
+      PixelCastJustification::ScreenIsParentLayerForRoot);
+  }
+
   if (mIsFirstPaint) {
     CSSToScreenScale defaultZoom = aViewportInfo.GetDefaultZoom();
     MVM_LOG("%p: default zoom from viewport is %f\n", this, defaultZoom.scale);
@@ -173,7 +177,6 @@ MobileViewportManager::UpdateResolution(const nsViewportInfo& aViewportInfo,
     nsLayoutUtils::SetResolutionAndScaleTo(mPresShell, newRes.scale);
     res = newRes;
   }
-#endif
 
   return ViewTargetAs<ScreenPixel>(cssToDev * res / ParentLayerToLayerScale(1),
     PixelCastJustification::ScreenIsParentLayerForRoot);

layout/base/ZoomConstraintsClient.cpp

@@ -137,8 +137,8 @@ mozilla::layers::ZoomConstraints
 ComputeZoomConstraintsFromViewportInfo(const nsViewportInfo& aViewportInfo)
 {
   mozilla::layers::ZoomConstraints constraints;
-  constraints.mAllowZoom = aViewportInfo.IsZoomAllowed();
-  constraints.mAllowDoubleTapZoom = aViewportInfo.IsDoubleTapZoomAllowed();
+  constraints.mAllowZoom = aViewportInfo.IsZoomAllowed() && gfxPrefs::APZAllowZooming();
+  constraints.mAllowDoubleTapZoom = aViewportInfo.IsDoubleTapZoomAllowed() && gfxPrefs::APZAllowZooming();
   constraints.mMinZoom.scale = aViewportInfo.GetMinZoom().scale;
   constraints.mMaxZoom.scale = aViewportInfo.GetMaxZoom().scale;
   return constraints;

mobile/android/app/mobile.js

@@ -547,6 +547,7 @@ pref("layers.offmainthreadcomposition.enabled", true);
 pref("layers.async-video.enabled", true);
 #ifdef MOZ_ANDROID_APZ
 pref("layers.async-pan-zoom.enabled", true);
+pref("apz.allow_zooming", true);
 #endif
 pref("layers.progressive-paint", true);
 pref("layers.low-precision-buffer", true);

modules/libpref/init/all.js

@@ -516,6 +516,7 @@ pref("layout.event-regions.enabled", false);
 // APZ preferences. For documentation/details on what these prefs do, check
 // gfx/layers/apz/src/AsyncPanZoomController.cpp.
 pref("apz.allow_checkerboarding", true);
+pref("apz.allow_zooming", false);
 pref("apz.asyncscroll.throttle", 100);
 pref("apz.asyncscroll.timeout", 300);