android: replace with ImmutableViewportMetrics (Fennec import)

Change-Id: I46509f8be4dc49dac45eb98059dad25e150988dd

10 files changed, 227 insertions, 193 deletions

diff --git a/android/experimental/LOAndroid3/src/java/org/libreoffice/LOEvent.java b/android/experimental/LOAndroid3/src/java/org/libreoffice/LOEvent.java
index f16b2da237bc..80210a7e45a8 100644
--- a/android/experimental/LOAndroid3/src/java/org/libreoffice/LOEvent.java
+++ b/android/experimental/LOAndroid3/src/java/org/libreoffice/LOEvent.java
@@ -2,8 +2,8 @@ package org.libreoffice;
 
 import android.graphics.Rect;
 
+import org.mozilla.gecko.gfx.ImmutableViewportMetrics;
 import org.mozilla.gecko.gfx.IntSize;
-import org.mozilla.gecko.gfx.ViewportMetrics;
 
 public class LOEvent {
 
@@ -15,7 +15,7 @@ public class LOEvent {
     public static final int LOAD = 6;
 
     public int mType;
-    private ViewportMetrics mViewportMetrics;
+    private ImmutableViewportMetrics mViewportMetrics;
     private String mTypeString;
     private int mPartIndex;
     private String mFilename;
@@ -35,7 +35,7 @@ public class LOEvent {
         mTypeString = "Tile size";
     }
 
-    public LOEvent(int type, ViewportMetrics viewportMetrics) {
+    public LOEvent(int type, ImmutableViewportMetrics viewportMetrics) {
         mType = type;
         mTypeString = "Viewport";
         mViewportMetrics = viewportMetrics;
@@ -64,7 +64,7 @@ public class LOEvent {
         return new LOEvent(TILE_SIZE, tileSize);
     }
 
-    public static LOEvent viewport(ViewportMetrics viewportMetrics) {
+    public static LOEvent viewport(ImmutableViewportMetrics viewportMetrics) {
         return new LOEvent(VIEWPORT, viewportMetrics);
     }
 
@@ -80,7 +80,7 @@ public class LOEvent {
         return mTypeString;
     }
 
-    public ViewportMetrics getViewport() {
+    public ImmutableViewportMetrics getViewport() {
         return mViewportMetrics;
     }
 
diff --git a/android/experimental/LOAndroid3/src/java/org/libreoffice/LOKitThread.java b/android/experimental/LOAndroid3/src/java/org/libreoffice/LOKitThread.java
index ddc18d4eb885..f808f57b4bbe 100644
--- a/android/experimental/LOAndroid3/src/java/org/libreoffice/LOKitThread.java
+++ b/android/experimental/LOAndroid3/src/java/org/libreoffice/LOKitThread.java
@@ -7,8 +7,8 @@ import android.util.DisplayMetrics;
 import android.util.Log;
 
 import org.mozilla.gecko.gfx.GeckoLayerClient;
+import org.mozilla.gecko.gfx.ImmutableViewportMetrics;
 import org.mozilla.gecko.gfx.LayerController;
-import org.mozilla.gecko.gfx.ViewportMetrics;
 
 import java.util.concurrent.LinkedBlockingQueue;
 
@@ -18,7 +18,7 @@ public class LOKitThread extends Thread {
     public LinkedBlockingQueue<LOEvent> mEventQueue = new LinkedBlockingQueue<LOEvent>();
     private LibreOfficeMainActivity mApplication;
     private TileProvider mTileProvider;
-    private ViewportMetrics mViewportMetrics;
+    private ImmutableViewportMetrics mViewportMetrics;
     private boolean mCheckboardImageSet = false;
     private GeckoLayerClient mLayerClient;
     private LayerController mController;
@@ -33,8 +33,8 @@ public class LOKitThread extends Thread {
 
         RectF rect = new RectF(0, 0, pageWidth, pageHeight);
         DisplayMetrics displayMetrics = LibreOfficeMainActivity.mAppContext.getResources().getDisplayMetrics();
-        mViewportMetrics = new ViewportMetrics(displayMetrics);
-        mViewportMetrics.setPageRect(rect, rect);
+        mViewportMetrics = new ImmutableViewportMetrics(displayMetrics);
+        mViewportMetrics = mViewportMetrics.setPageRect(rect, rect);
 
         GeckoLayerClient layerClient = mApplication.getLayerClient();
 
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/GeckoLayerClient.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/GeckoLayerClient.java
index e3f57933ff67..e847c01c9139 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/GeckoLayerClient.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/GeckoLayerClient.java
@@ -65,10 +65,10 @@ public class GeckoLayerClient implements LayerView.Listener {
     private MultiTileLayer mRootLayer;
 
     /* The viewport that Gecko is currently displaying. */
-    private ViewportMetrics mGeckoViewport;
+    private ImmutableViewportMetrics mGeckoViewport;
 
     /* The viewport that Gecko will display when drawing is finished */
-    private ViewportMetrics mNewGeckoViewport;
+    private ImmutableViewportMetrics mNewGeckoViewport;
     private Context mContext;
     private boolean mPendingViewportAdjust;
     private boolean mViewportSizeChanged;
@@ -109,7 +109,7 @@ public class GeckoLayerClient implements LayerView.Listener {
 
     }
 
-    public void endDrawing(ViewportMetrics viewportMetrics) {
+    public void endDrawing(ImmutableViewportMetrics viewportMetrics) {
         synchronized (mLayerController) {
             try {
                 mNewGeckoViewport = viewportMetrics;
@@ -128,19 +128,18 @@ public class GeckoLayerClient implements LayerView.Listener {
         // java is the One True Source of this information, and allowing JS
         // to override can lead to race conditions where this data gets clobbered.
         FloatSize viewportSize = mLayerController.getViewportSize();
-        mGeckoViewport = mNewGeckoViewport;
-        mGeckoViewport.setSize(viewportSize);
+        mGeckoViewport = mNewGeckoViewport.setViewportSize(viewportSize.width, viewportSize.height);
 
         RectF position = mGeckoViewport.getViewport();
         mRootLayer.setPosition(RectUtils.round(position));
-        mRootLayer.setResolution(mGeckoViewport.getZoomFactor());
+        mRootLayer.setResolution(mGeckoViewport.zoomFactor);
 
         Log.e(LOGTAG, "### updateViewport onlyUpdatePageSize=" + onlyUpdatePageSize + " getTileViewport " + mGeckoViewport);
 
         if (onlyUpdatePageSize) {
             // Don't adjust page size when zooming unless zoom levels are
             // approximately equal.
-            if (FloatUtils.fuzzyEquals(mLayerController.getViewportMetrics().zoomFactor, mGeckoViewport.getZoomFactor())) {
+            if (FloatUtils.fuzzyEquals(mLayerController.getViewportMetrics().zoomFactor, mGeckoViewport.zoomFactor)) {
                 mLayerController.setPageRect(mGeckoViewport.getPageRect(), mGeckoViewport.getCssPageRect());
             }
         } else {
@@ -193,8 +192,7 @@ public class GeckoLayerClient implements LayerView.Listener {
     void adjustViewport(DisplayPortMetrics displayPort) {
         ImmutableViewportMetrics metrics = mLayerController.getViewportMetrics();
 
-        ViewportMetrics clampedMetrics = new ViewportMetrics(metrics);
-        clampedMetrics.setViewport(clampedMetrics.getClampedViewport());
+        ImmutableViewportMetrics clampedMetrics = metrics.clamp();
 
         if (displayPort == null) {
             displayPort = DisplayPortCalculator.calculate(metrics,
@@ -244,7 +242,7 @@ public class GeckoLayerClient implements LayerView.Listener {
         }
     }
 
-    public ViewportMetrics getGeckoViewportMetrics() {
+    public ImmutableViewportMetrics getGeckoViewportMetrics() {
         return mGeckoViewport;
     }
 
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ImmutableViewportMetrics.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ImmutableViewportMetrics.java
index 5403c80ff42d..35b417593acf 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ImmutableViewportMetrics.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ImmutableViewportMetrics.java
@@ -7,6 +7,9 @@ package org.mozilla.gecko.gfx;
 
 import android.graphics.PointF;
 import android.graphics.RectF;
+import android.util.DisplayMetrics;
+
+import org.mozilla.gecko.util.FloatUtils;
 
 /**
  * ImmutableViewportMetrics are used to store the viewport metrics
@@ -31,26 +34,33 @@ public class ImmutableViewportMetrics {
     public final float viewportRectBottom;
     public final float zoomFactor;
 
-    public ImmutableViewportMetrics(ViewportMetrics m) {
-        RectF viewportRect = m.getViewport();
-        viewportRectLeft = viewportRect.left;
-        viewportRectTop = viewportRect.top;
-        viewportRectRight = viewportRect.right;
-        viewportRectBottom = viewportRect.bottom;
-
-        RectF pageRect = m.getPageRect();
-        pageRectLeft = pageRect.left;
-        pageRectTop = pageRect.top;
-        pageRectRight = pageRect.right;
-        pageRectBottom = pageRect.bottom;
-
-        RectF cssPageRect = m.getCssPageRect();
-        cssPageRectLeft = cssPageRect.left;
-        cssPageRectTop = cssPageRect.top;
-        cssPageRectRight = cssPageRect.right;
-        cssPageRectBottom = cssPageRect.bottom;
+    public ImmutableViewportMetrics(DisplayMetrics metrics) {
+        viewportRectLeft   = pageRectLeft   = cssPageRectLeft   = 0;
+        viewportRectTop    = pageRectTop    = cssPageRectTop    = 0;
+        viewportRectRight  = pageRectRight  = cssPageRectRight  = metrics.widthPixels;
+        viewportRectBottom = pageRectBottom = cssPageRectBottom = metrics.heightPixels;
+        zoomFactor = 1.0f;
+    }
 
-        zoomFactor = m.getZoomFactor();
+    private ImmutableViewportMetrics(float aPageRectLeft, float aPageRectTop,
+        float aPageRectRight, float aPageRectBottom, float aCssPageRectLeft,
+        float aCssPageRectTop, float aCssPageRectRight, float aCssPageRectBottom,
+        float aViewportRectLeft, float aViewportRectTop, float aViewportRectRight,
+        float aViewportRectBottom, float aZoomFactor)
+    {
+        pageRectLeft = aPageRectLeft;
+        pageRectTop = aPageRectTop;
+        pageRectRight = aPageRectRight;
+        pageRectBottom = aPageRectBottom;
+        cssPageRectLeft = aCssPageRectLeft;
+        cssPageRectTop = aCssPageRectTop;
+        cssPageRectRight = aCssPageRectRight;
+        cssPageRectBottom = aCssPageRectBottom;
+        viewportRectLeft = aViewportRectLeft;
+        viewportRectTop = aViewportRectTop;
+        viewportRectRight = aViewportRectRight;
+        viewportRectBottom = aViewportRectBottom;
+        zoomFactor = aZoomFactor;
     }
 
     public float getWidth() {
@@ -61,8 +71,6 @@ public class ImmutableViewportMetrics {
         return viewportRectBottom - viewportRectTop;
     }
 
-    // some helpers to make ImmutableViewportMetrics act more like ViewportMetrics
-
     public PointF getOrigin() {
         return new PointF(viewportRectLeft, viewportRectTop);
     }
@@ -98,6 +106,126 @@ public class ImmutableViewportMetrics {
         return new RectF(cssPageRectLeft, cssPageRectTop, cssPageRectRight, cssPageRectBottom);
     }
 
+    /*
+     * Returns the viewport metrics that represent a linear transition between "this" and "to" at
+     * time "t", which is on the scale [0, 1). This function interpolates all values stored in
+     * the viewport metrics.
+     */
+    public ImmutableViewportMetrics interpolate(ImmutableViewportMetrics to, float t) {
+        return new ImmutableViewportMetrics(
+            FloatUtils.interpolate(pageRectLeft, to.pageRectLeft, t),
+            FloatUtils.interpolate(pageRectTop, to.pageRectTop, t),
+            FloatUtils.interpolate(pageRectRight, to.pageRectRight, t),
+            FloatUtils.interpolate(pageRectBottom, to.pageRectBottom, t),
+            FloatUtils.interpolate(cssPageRectLeft, to.cssPageRectLeft, t),
+            FloatUtils.interpolate(cssPageRectTop, to.cssPageRectTop, t),
+            FloatUtils.interpolate(cssPageRectRight, to.cssPageRectRight, t),
+            FloatUtils.interpolate(cssPageRectBottom, to.cssPageRectBottom, t),
+            FloatUtils.interpolate(viewportRectLeft, to.viewportRectLeft, t),
+            FloatUtils.interpolate(viewportRectTop, to.viewportRectTop, t),
+            FloatUtils.interpolate(viewportRectRight, to.viewportRectRight, t),
+            FloatUtils.interpolate(viewportRectBottom, to.viewportRectBottom, t),
+            FloatUtils.interpolate(zoomFactor, to.zoomFactor, t));
+    }
+
+    public ImmutableViewportMetrics setViewportSize(float width, float height) {
+        return new ImmutableViewportMetrics(
+            pageRectLeft, pageRectTop, pageRectRight, pageRectBottom,
+            cssPageRectLeft, cssPageRectTop, cssPageRectRight, cssPageRectBottom,
+            viewportRectLeft, viewportRectTop, viewportRectLeft + width, viewportRectTop + height,
+            zoomFactor);
+    }
+
+    public ImmutableViewportMetrics setViewportOrigin(float newOriginX, float newOriginY) {
+        return new ImmutableViewportMetrics(
+            pageRectLeft, pageRectTop, pageRectRight, pageRectBottom,
+            cssPageRectLeft, cssPageRectTop, cssPageRectRight, cssPageRectBottom,
+            newOriginX, newOriginY, newOriginX + getWidth(), newOriginY + getHeight(),
+            zoomFactor);
+    }
+
+    public ImmutableViewportMetrics setZoomFactor(float newZoomFactor) {
+        return new ImmutableViewportMetrics(
+            pageRectLeft, pageRectTop, pageRectRight, pageRectBottom,
+            cssPageRectLeft, cssPageRectTop, cssPageRectRight, cssPageRectBottom,
+            viewportRectLeft, viewportRectTop, viewportRectRight, viewportRectBottom,
+            newZoomFactor);
+    }
+
+    public ImmutableViewportMetrics offsetViewportBy(float dx, float dy) {
+        return setViewportOrigin(viewportRectLeft + dx, viewportRectTop + dy);
+    }
+
+    public ImmutableViewportMetrics setPageRect(RectF pageRect, RectF cssPageRect) {
+        return new ImmutableViewportMetrics(
+            pageRect.left, pageRect.top, pageRect.right, pageRect.bottom,
+            cssPageRect.left, cssPageRect.top, cssPageRect.right, cssPageRect.bottom,
+            viewportRectLeft, viewportRectTop, viewportRectRight, viewportRectBottom,
+            zoomFactor);
+    }
+
+    /* This will set the zoom factor and re-scale page-size and viewport offset
+     * accordingly. The given focus will remain at the same point on the screen
+     * after scaling.
+     */
+    public ImmutableViewportMetrics scaleTo(float newZoomFactor, PointF focus) {
+        // cssPageRect* is invariant, since we're setting the scale factor
+        // here. The page rect is based on the CSS page rect.
+        float newPageRectLeft = cssPageRectLeft * newZoomFactor;
+        float newPageRectTop = cssPageRectTop * newZoomFactor;
+        float newPageRectRight = cssPageRectLeft + ((cssPageRectRight - cssPageRectLeft) * newZoomFactor);
+        float newPageRectBottom = cssPageRectTop + ((cssPageRectBottom - cssPageRectTop) * newZoomFactor);
+
+        PointF origin = getOrigin();
+        origin.offset(focus.x, focus.y);
+        origin = PointUtils.scale(origin, newZoomFactor / zoomFactor);
+        origin.offset(-focus.x, -focus.y);
+
+        return new ImmutableViewportMetrics(
+            newPageRectLeft, newPageRectTop, newPageRectRight, newPageRectBottom,
+            cssPageRectLeft, cssPageRectTop, cssPageRectRight, cssPageRectBottom,
+            origin.x, origin.y, origin.x + getWidth(), origin.y + getHeight(),
+            newZoomFactor);
+    }
+
+    /** Clamps the viewport to remain within the page rect. */
+    public ImmutableViewportMetrics clamp() {
+        RectF newViewport = getViewport();
+
+        // The viewport bounds ought to never exceed the page bounds.
+        if (newViewport.right > pageRectRight)
+            newViewport.offset(pageRectRight - newViewport.right, 0);
+        if (newViewport.left < pageRectLeft)
+            newViewport.offset(pageRectLeft - newViewport.left, 0);
+
+        if (newViewport.bottom > pageRectBottom)
+            newViewport.offset(0, pageRectBottom - newViewport.bottom);
+        if (newViewport.top < pageRectTop)
+            newViewport.offset(0, pageRectTop - newViewport.top);
+
+        return new ImmutableViewportMetrics(
+            pageRectLeft, pageRectTop, pageRectRight, pageRectBottom,
+            cssPageRectLeft, cssPageRectTop, cssPageRectRight, cssPageRectBottom,
+            newViewport.left, newViewport.top, newViewport.right, newViewport.bottom,
+            zoomFactor);
+    }
+
+    public boolean fuzzyEquals(ImmutableViewportMetrics other) {
+        return FloatUtils.fuzzyEquals(pageRectLeft, other.pageRectLeft)
+            && FloatUtils.fuzzyEquals(pageRectTop, other.pageRectTop)
+            && FloatUtils.fuzzyEquals(pageRectRight, other.pageRectRight)
+            && FloatUtils.fuzzyEquals(pageRectBottom, other.pageRectBottom)
+            && FloatUtils.fuzzyEquals(cssPageRectLeft, other.cssPageRectLeft)
+            && FloatUtils.fuzzyEquals(cssPageRectTop, other.cssPageRectTop)
+            && FloatUtils.fuzzyEquals(cssPageRectRight, other.cssPageRectRight)
+            && FloatUtils.fuzzyEquals(cssPageRectBottom, other.cssPageRectBottom)
+            && FloatUtils.fuzzyEquals(viewportRectLeft, other.viewportRectLeft)
+            && FloatUtils.fuzzyEquals(viewportRectTop, other.viewportRectTop)
+            && FloatUtils.fuzzyEquals(viewportRectRight, other.viewportRectRight)
+            && FloatUtils.fuzzyEquals(viewportRectBottom, other.viewportRectBottom)
+            && FloatUtils.fuzzyEquals(zoomFactor, other.zoomFactor);
+    }
+
     @Override
     public String toString() {
         return "ImmutableViewportMetrics v=(" + viewportRectLeft + "," + viewportRectTop + ","
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/LayerController.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/LayerController.java
index ca02e1c784d4..2e6a4a0f20df 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/LayerController.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/LayerController.java
@@ -67,7 +67,7 @@ public class LayerController implements PanZoomTarget {
         mContext = context;
         mForceRedraw = true;
         DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
-        mViewportMetrics = new ImmutableViewportMetrics(new ViewportMetrics(displayMetrics));
+        mViewportMetrics = new ImmutableViewportMetrics(displayMetrics);
         mPanZoomController = new PanZoomController(this);
         mView = new LayerView(context, this);
         mCheckerboardShouldShowChecks = true;
@@ -127,9 +127,7 @@ public class LayerController implements PanZoomTarget {
      * result in an infinite loop.
      */
     public void setViewportSize(FloatSize size) {
-        ViewportMetrics viewportMetrics = new ViewportMetrics(mViewportMetrics);
-        viewportMetrics.setSize(size);
-        mViewportMetrics = new ImmutableViewportMetrics(viewportMetrics);
+        mViewportMetrics = mViewportMetrics.setViewportSize(size.width, size.height);
 
         if (mLayerClient != null) {
             mLayerClient.viewportSizeChanged();
@@ -144,9 +142,7 @@ public class LayerController implements PanZoomTarget {
         if (mViewportMetrics.getCssPageRect().equals(cssRect))
             return;
 
-        ViewportMetrics viewportMetrics = new ViewportMetrics(mViewportMetrics);
-        viewportMetrics.setPageRect(rect, cssRect);
-        mViewportMetrics = new ImmutableViewportMetrics(viewportMetrics);
+        mViewportMetrics = mViewportMetrics.setPageRect(rect, cssRect);
 
         // Page size is owned by the layer client, so no need to notify it of
         // this change.
@@ -163,20 +159,19 @@ public class LayerController implements PanZoomTarget {
      * Sets the entire viewport metrics at once.
      * You must hold the monitor while calling this.
      */
-    public void setViewportMetrics(ViewportMetrics viewport) {
-        mViewportMetrics = new ImmutableViewportMetrics(viewport);
+    public void setViewportMetrics(ImmutableViewportMetrics viewport) {
+        mViewportMetrics = viewport;
         mView.requestRender();
         notifyLayerClientOfGeometryChange();
     }
 
-    public void setAnimationTarget(ViewportMetrics viewport) {
+    public void setAnimationTarget(ImmutableViewportMetrics viewport) {
         if (mLayerClient != null) {
             // We know what the final viewport of the animation is going to be, so
             // immediately request a draw of that area by setting the display port
             // accordingly. This way we should have the content pre-rendered by the
             // time the animation is done.
-            ImmutableViewportMetrics metrics = new ImmutableViewportMetrics(viewport);
-            DisplayPortMetrics displayPort = DisplayPortCalculator.calculate(metrics, null);
+            DisplayPortMetrics displayPort = DisplayPortCalculator.calculate(viewport, null);
             mLayerClient.adjustViewport(displayPort);
         }
     }
@@ -232,9 +227,9 @@ public class LayerController implements PanZoomTarget {
         ImmutableViewportMetrics viewportMetrics = mViewportMetrics;
         PointF origin = viewportMetrics.getOrigin();
         float zoom = viewportMetrics.zoomFactor;
-        ViewportMetrics geckoViewport = mLayerClient.getGeckoViewportMetrics();
+        ImmutableViewportMetrics geckoViewport = mLayerClient.getGeckoViewportMetrics();
         PointF geckoOrigin = geckoViewport.getOrigin();
-        float geckoZoom = geckoViewport.getZoomFactor();
+        float geckoZoom = geckoViewport.zoomFactor;
 
         // viewPoint + origin gives the coordinate in device pixels from the top-left corner of the page.
         // Divided by zoom, this gives us the coordinate in CSS pixels from the top-left corner of the page.
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/PointUtils.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/PointUtils.java
index cdacc317ee13..4eb07a31f147 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/PointUtils.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/PointUtils.java
@@ -10,7 +10,6 @@ import android.graphics.PointF;
 
 import org.json.JSONException;
 import org.json.JSONObject;
-import org.mozilla.gecko.util.FloatUtils;
 
 public final class PointUtils {
     public static PointF add(PointF one, PointF two) {
@@ -29,19 +28,10 @@ public final class PointUtils {
         return new Point(Math.round(point.x), Math.round(point.y));
     }
 
-    /* Returns a new point that is a linear interpolation between start and end points. weight conrols the weighting
-     * of each of the original points (weight = 1 returns endPoint, weight = 0 returns startPoint)
-     */
-    public static PointF interpolate(PointF startPoint, PointF endPoint, float weight) {
-        float x = FloatUtils.interpolate(startPoint.x, endPoint.x, weight);
-        float y = FloatUtils.interpolate(startPoint.y, endPoint.y, weight);
-        return new PointF(x, y);
-    }
-
-    /* Computes the magnitude of the given vector. */
-    public static float distance(PointF point) {
+   /* Computes the magnitude of the given vector. */
+   public static float distance(PointF point) {
         return (float)Math.sqrt(point.x * point.x + point.y * point.y);
-    }
+   }
 
     /** Computes the scalar distance between two points. */
     public static float distance(PointF one, PointF two) {
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/RectUtils.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/RectUtils.java
index 92ea78f8a177..1608e91ad062 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/RectUtils.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/RectUtils.java
@@ -10,22 +10,10 @@ import android.graphics.PointF;
 import android.graphics.Rect;
 import android.graphics.RectF;
 
-import org.json.JSONException;
-import org.json.JSONObject;
 import org.mozilla.gecko.util.FloatUtils;
 
 public final class RectUtils {
-    public static Rect create(JSONObject json) {
-        try {
-            int x = json.getInt("x");
-            int y = json.getInt("y");
-            int width = json.getInt("width");
-            int height = json.getInt("height");
-            return new Rect(x, y, x + width, y + height);
-        } catch (JSONException e) {
-            throw new RuntimeException(e);
-        }
-    }
+    private RectUtils() {}
 
     public static RectF expand(RectF rect, float moreWidth, float moreHeight) {
         float halfMoreWidth = moreWidth / 2;
@@ -63,8 +51,14 @@ public final class RectUtils {
 
     /** Returns the nearest integer rect of the given rect. */
     public static Rect round(RectF rect) {
-        return new Rect(Math.round(rect.left), Math.round(rect.top),
-                        Math.round(rect.right), Math.round(rect.bottom));
+        Rect r = new Rect();
+        round(rect, r);
+        return r;
+    }
+
+    public static void round(RectF rect, Rect dest) {
+        dest.set(Math.round(rect.left), Math.round(rect.top),
+                 Math.round(rect.right), Math.round(rect.bottom));
     }
 
     public static Rect roundIn(RectF rect) {
@@ -84,17 +78,6 @@ public final class RectUtils {
         return new PointF(rect.left, rect.top);
     }
 
-    /*
-     * Returns the rect that represents a linear transition between `from` and `to` at time `t`,
-     * which is on the scale [0, 1).
-     */
-    public static RectF interpolate(RectF from, RectF to, float t) {
-        return new RectF(FloatUtils.interpolate(from.left, to.left, t),
-                         FloatUtils.interpolate(from.top, to.top, t),
-                         FloatUtils.interpolate(from.right, to.right, t),
-                         FloatUtils.interpolate(from.bottom, to.bottom, t));
-    }
-
     public static boolean fuzzyEquals(RectF a, RectF b) {
         if (a == null && b == null)
             return true;
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ViewportMetrics.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ViewportMetrics.java
index 789bb0bff0b5..f8b5c2e055dc 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ViewportMetrics.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/ViewportMetrics.java
@@ -11,7 +11,6 @@ import android.util.DisplayMetrics;
 
 import org.json.JSONException;
 import org.json.JSONObject;
-import org.mozilla.gecko.util.FloatUtils;
 
 /**
  * ViewportMetrics manages state and contains some utility functions related to
@@ -76,6 +75,16 @@ public class ViewportMetrics {
         mZoomFactor = zoom;
     }
 
+    public ViewportMetrics(float x, float y, float width, float height,
+                           float pageLeft, float pageTop, float pageRight, float pageBottom,
+                           float cssPageLeft, float cssPageTop, float cssPageRight, float cssPageBottom,
+                           float zoom) {
+        mPageRect = new RectF(pageLeft, pageTop, pageRight, pageBottom);
+        mCssPageRect = new RectF(cssPageLeft, cssPageTop, cssPageRight, cssPageBottom);
+        mViewportRect = new RectF(x, y, x + width, y + height);
+        mZoomFactor = zoom;
+    }
+
     public PointF getOrigin() {
         return new PointF(mViewportRect.left, mViewportRect.top);
     }
@@ -92,24 +101,6 @@ public class ViewportMetrics {
         return RectUtils.scale(mViewportRect, 1/mZoomFactor);
     }
 
-    /** Returns the viewport rectangle, clamped within the page-size. */
-    public RectF getClampedViewport() {
-        RectF clampedViewport = new RectF(mViewportRect);
-
-        // The viewport bounds ought to never exceed the page bounds.
-        if (clampedViewport.right > mPageRect.right)
-            clampedViewport.offset(mPageRect.right - clampedViewport.right, 0);
-        if (clampedViewport.left < mPageRect.left)
-            clampedViewport.offset(mPageRect.left - clampedViewport.left, 0);
-
-        if (clampedViewport.bottom > mPageRect.bottom)
-            clampedViewport.offset(0, mPageRect.bottom - clampedViewport.bottom);
-        if (clampedViewport.top < mPageRect.top)
-            clampedViewport.offset(0, mPageRect.top - clampedViewport.top);
-
-        return clampedViewport;
-    }
-
     public RectF getPageRect() {
         return mPageRect;
     }
@@ -146,48 +137,6 @@ public class ViewportMetrics {
         mZoomFactor = zoomFactor;
     }
 
-    /* This will set the zoom factor and re-scale page-size and viewport offset
-     * accordingly. The given focus will remain at the same point on the screen
-     * after scaling.
-     */
-    public void scaleTo(float newZoomFactor, PointF focus) {
-        // mCssPageRect is invariant, since we're setting the scale factor
-        // here. The page rect is based on the CSS page rect.
-        mPageRect = RectUtils.scale(mCssPageRect, newZoomFactor);
-
-        float scaleFactor = newZoomFactor / mZoomFactor;
-        PointF origin = getOrigin();
-
-        origin.offset(focus.x, focus.y);
-        origin = PointUtils.scale(origin, scaleFactor);
-        origin.offset(-focus.x, -focus.y);
-
-        setOrigin(origin);
-
-        mZoomFactor = newZoomFactor;
-    }
-
-    /*
-     * Returns the viewport metrics that represent a linear transition between `from` and `to` at
-     * time `t`, which is on the scale [0, 1). This function interpolates the viewport rect, the
-     * page size, the offset, and the zoom factor.
-     */
-    public ViewportMetrics interpolate(ViewportMetrics to, float t) {
-        ViewportMetrics result = new ViewportMetrics(this);
-        result.mPageRect = RectUtils.interpolate(mPageRect, to.mPageRect, t);
-        result.mCssPageRect = RectUtils.interpolate(mCssPageRect, to.mCssPageRect, t);
-        result.mZoomFactor = FloatUtils.interpolate(mZoomFactor, to.mZoomFactor, t);
-        result.mViewportRect = RectUtils.interpolate(mViewportRect, to.mViewportRect, t);
-        return result;
-    }
-
-    public boolean fuzzyEquals(ViewportMetrics other) {
-        return RectUtils.fuzzyEquals(mPageRect, other.mPageRect)
-            && RectUtils.fuzzyEquals(mCssPageRect, other.mCssPageRect)
-            && RectUtils.fuzzyEquals(mViewportRect, other.mViewportRect)
-            && FloatUtils.fuzzyEquals(mZoomFactor, other.mZoomFactor);
-    }
-
     public String toJSON() {
         // Round off height and width. Since the height and width are the size of the screen, it
         // makes no sense to send non-integer coordinates to Gecko.
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomController.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomController.java
index 02e45daf3a15..555c7ebe60fa 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomController.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomController.java
@@ -16,7 +16,6 @@ import org.libreoffice.LOKitShell;
 import org.libreoffice.LibreOfficeMainActivity;
 import org.mozilla.gecko.ZoomConstraints;
 import org.mozilla.gecko.gfx.ImmutableViewportMetrics;
-import org.mozilla.gecko.gfx.ViewportMetrics;
 import org.mozilla.gecko.util.FloatUtils;
 
 import java.util.Timer;
@@ -118,10 +117,6 @@ public class PanZoomController
         return mTarget.getViewportMetrics();
     }
 
-    private ViewportMetrics getMutableMetrics() {
-        return new ViewportMetrics(getMetrics());
-    }
-
     // for debugging bug 713011; it can be taken out once that is resolved.
     private void checkMainThread() {
         if (mMainThread != Thread.currentThread()) {
@@ -195,8 +190,8 @@ public class PanZoomController
     public void pageRectUpdated() {
         if (mState == PanZoomState.NOTHING) {
             synchronized (mTarget.getLock()) {
-                ViewportMetrics validated = getValidViewportMetrics();
-                if (! getMutableMetrics().fuzzyEquals(validated)) {
+                ImmutableViewportMetrics validated = getValidViewportMetrics();
+                if (!getMetrics().fuzzyEquals(validated)) {
                     // page size changed such that we are now in overscroll. snap to the
                     // the nearest valid viewport
                     mTarget.setViewportMetrics(validated);
@@ -421,13 +416,9 @@ public class PanZoomController
         updatePosition();
     }
 
-    private void scrollBy(PointF point) {
-        ViewportMetrics viewportMetrics = getMutableMetrics();
-        PointF origin = viewportMetrics.getOrigin();
-        origin.offset(point.x, point.y);
-        viewportMetrics.setOrigin(origin);
-
-        mTarget.setViewportMetrics(viewportMetrics);
+    private void scrollBy(float dx, float dy) {
+        ImmutableViewportMetrics scrolled = getMetrics().offsetViewportBy(dx, dy);
+        mTarget.setViewportMetrics(scrolled);
     }
 
     private void fling() {
@@ -443,10 +434,10 @@ public class PanZoomController
     }
 
     /* Performs a bounce-back animation to the given viewport metrics. */
-    private void bounce(ViewportMetrics metrics) {
+    private void bounce(ImmutableViewportMetrics metrics) {
         stopAnimationTimer();
 
-        ViewportMetrics bounceStartMetrics = getMutableMetrics();
+        ImmutableViewportMetrics bounceStartMetrics = getMetrics();
         if (bounceStartMetrics.fuzzyEquals(metrics)) {
             setState(PanZoomState.NOTHING);
             return;
@@ -520,7 +511,7 @@ public class PanZoomController
         }
         if (! mSubscroller.scrollBy(displacement)) {
             synchronized (mTarget.getLock()) {
-                scrollBy(displacement);
+                scrollBy(displacement.x, displacement.y);
             }
         }
     }
@@ -558,10 +549,10 @@ public class PanZoomController
          * The viewport metrics that represent the start and end of the bounce-back animation,
          * respectively.
          */
-        private ViewportMetrics mBounceStartMetrics;
-        private ViewportMetrics mBounceEndMetrics;
+        private ImmutableViewportMetrics mBounceStartMetrics;
+        private ImmutableViewportMetrics mBounceEndMetrics;
 
-        BounceRunnable(ViewportMetrics startMetrics, ViewportMetrics endMetrics) {
+        BounceRunnable(ImmutableViewportMetrics startMetrics, ImmutableViewportMetrics endMetrics) {
             mBounceStartMetrics = startMetrics;
             mBounceEndMetrics = endMetrics;
         }
@@ -593,7 +584,7 @@ public class PanZoomController
         private void advanceBounce() {
             synchronized (mTarget.getLock()) {
                 float t = easeOut(mBounceFrame * Axis.MS_PER_FRAME / 256f);
-                ViewportMetrics newMetrics = mBounceStartMetrics.interpolate(mBounceEndMetrics, t);
+                ImmutableViewportMetrics newMetrics = mBounceStartMetrics.interpolate(mBounceEndMetrics, t);
                 mTarget.setViewportMetrics(newMetrics);
                 mBounceFrame++;
             }
@@ -667,13 +658,13 @@ public class PanZoomController
     }
 
     /* Returns the nearest viewport metrics with no overscroll visible. */
-    private ViewportMetrics getValidViewportMetrics() {
-        return getValidViewportMetrics(getMutableMetrics());
+    private ImmutableViewportMetrics getValidViewportMetrics() {
+        return getValidViewportMetrics(getMetrics());
     }
 
-    private ViewportMetrics getValidViewportMetrics(ViewportMetrics viewportMetrics) {
+    private ImmutableViewportMetrics getValidViewportMetrics(ImmutableViewportMetrics viewportMetrics) {
         /* First, we adjust the zoom factor so that we can make no overscrolled area visible. */
-        float zoomFactor = viewportMetrics.getZoomFactor();
+        float zoomFactor = viewportMetrics.zoomFactor;
         RectF pageRect = viewportMetrics.getPageRect();
         RectF viewport = viewportMetrics.getViewport();
 
@@ -718,14 +709,14 @@ public class PanZoomController
             // by different scale factors, we end up scrolled to the end on one axis
             // after applying the scale
             PointF center = new PointF(focusX, focusY);
-            viewportMetrics.scaleTo(minZoomFactor, center);
+            viewportMetrics = viewportMetrics.scaleTo(minZoomFactor, center);
         } else if (zoomFactor > maxZoomFactor) {
             PointF center = new PointF(viewport.width() / 2.0f, viewport.height() / 2.0f);
-            viewportMetrics.scaleTo(maxZoomFactor, center);
+            viewportMetrics = viewportMetrics.scaleTo(maxZoomFactor, center);
         }
 
         /* Now we pan to the right origin. */
-        viewportMetrics.setViewport(viewportMetrics.getClampedViewport());
+        viewportMetrics = viewportMetrics.clamp();
 
         return viewportMetrics;
     }
@@ -826,8 +817,8 @@ public class PanZoomController
                 newZoomFactor = maxZoomFactor + excessZoom;
             }
 
-            scrollBy(new PointF(mLastZoomFocus.x - detector.getFocusX(),
-                    mLastZoomFocus.y - detector.getFocusY()));
+            scrollBy(mLastZoomFocus.x - detector.getFocusX(),
+                     mLastZoomFocus.y - detector.getFocusY());
             PointF focus = new PointF(detector.getFocusX(), detector.getFocusY());
             scaleWithFocus(newZoomFactor, focus);
         }
@@ -854,8 +845,8 @@ public class PanZoomController
      * scale operation. You must hold the monitor while calling this.
      */
     private void scaleWithFocus(float zoomFactor, PointF focus) {
-        ViewportMetrics viewportMetrics = getMutableMetrics();
-        viewportMetrics.scaleTo(zoomFactor, focus);
+        ImmutableViewportMetrics viewportMetrics = getMetrics();
+        viewportMetrics = viewportMetrics.scaleTo(zoomFactor, focus);
         mTarget.setViewportMetrics(viewportMetrics);
     }
 
@@ -931,10 +922,11 @@ public class PanZoomController
 
         float finalZoom = viewport.width() / zoomToRect.width();
 
-        ViewportMetrics finalMetrics = getMutableMetrics();
-        finalMetrics.setOrigin(new PointF(zoomToRect.left * finalMetrics.getZoomFactor(),
-                                          zoomToRect.top * finalMetrics.getZoomFactor()));
-        finalMetrics.scaleTo(finalZoom, new PointF(0.0f, 0.0f));
+        ImmutableViewportMetrics finalMetrics = getMetrics();
+        finalMetrics = finalMetrics.setViewportOrigin(
+            zoomToRect.left * finalMetrics.zoomFactor,
+            zoomToRect.top * finalMetrics.zoomFactor);
+        finalMetrics = finalMetrics.scaleTo(finalZoom, new PointF(0.0f, 0.0f));
 
         // 2. now run getValidViewportMetrics on it, so that the target viewport is
         // clamped down to prevent overscroll, over-zoom, and other bad conditions.
diff --git a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomTarget.java b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomTarget.java
index 3ebc4f1bb392..fdac874ee6f9 100644
--- a/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomTarget.java
+++ b/android/experimental/LOAndroid3/src/java/org/mozilla/gecko/ui/PanZoomTarget.java
@@ -9,14 +9,13 @@ import android.graphics.PointF;
 
 import org.mozilla.gecko.ZoomConstraints;
 import org.mozilla.gecko.gfx.ImmutableViewportMetrics;
-import org.mozilla.gecko.gfx.ViewportMetrics;
 
 public interface PanZoomTarget {
     public ImmutableViewportMetrics getViewportMetrics();
     public ZoomConstraints getZoomConstraints();
 
-    public void setAnimationTarget(ViewportMetrics viewport);
-    public void setViewportMetrics(ViewportMetrics viewport);
+    public void setAnimationTarget(ImmutableViewportMetrics viewport);
+    public void setViewportMetrics(ImmutableViewportMetrics viewport);
     public void setForceRedraw();
 
     public boolean post(Runnable action);