android: add FixedZoomTileLayer as a low-res layer

Change-Id: I20d6fb3117ac46c8de63708a122253444bca1671

android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/FixedZoomTileLayer.java

+package org.mozilla.gecko.gfx;
+
+public class FixedZoomTileLayer extends ComposedTileLayer {
+    @Override
+    protected float getZoom(ImmutableViewportMetrics viewportMetrics) {
+        return 0.5f;
+    }
+
+    @Override
+    public void addTile(SubTile tile) {
+
+    }
+}

android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/GeckoLayerClient.java

@@ -33,6 +33,7 @@ public class GeckoLayerClient implements PanZoomTarget, LayerView.Listener {
     private boolean mRecordDrawTimes;
     private final DrawTimingQueue mDrawTimingQueue;
 
+    private ComposedTileLayer mLowResLayer;
     private ComposedTileLayer mRootLayer;
 
     /* The Gecko viewport as per the UI thread. Must be touched only on the UI thread.
@@ -111,6 +112,8 @@ public class GeckoLayerClient implements PanZoomTarget, LayerView.Listener {
         mGeckoIsReady = true;
 
         mRootLayer = new DynamicTileLayer();
+        mLowResLayer = new FixedZoomTileLayer();
+
         mLayerRenderer = new LayerRenderer(mView);
 
         mView.setListener(this);
@@ -139,6 +142,10 @@ public class GeckoLayerClient implements PanZoomTarget, LayerView.Listener {
         return mGeckoIsReady ? mRootLayer : null;
     }
 
+    Layer getLowResLayer() {
+        return mGeckoIsReady ? mLowResLayer : null;
+    }
+
     public LayerView getView() {
         return mView;
     }
@@ -281,8 +288,8 @@ public class GeckoLayerClient implements PanZoomTarget, LayerView.Listener {
     }
 
     public void beginDrawing() {
+        mLowResLayer.beginTransaction();
         mRootLayer.beginTransaction();
-
     }
 
     public void endDrawing(ImmutableViewportMetrics viewportMetrics) {
@@ -290,8 +297,10 @@ public class GeckoLayerClient implements PanZoomTarget, LayerView.Listener {
             try {
                 mNewGeckoViewport = viewportMetrics;
                 updateViewport(true);
+                mLowResLayer.invalidate();
                 mRootLayer.invalidate();
             } finally {
+                mLowResLayer.endTransaction();
                 mRootLayer.endTransaction();
             }
         }
@@ -309,6 +318,9 @@ public class GeckoLayerClient implements PanZoomTarget, LayerView.Listener {
         mRootLayer.setPosition(RectUtils.round(position));
         mRootLayer.setResolution(mGeckoViewport.zoomFactor);
 
+        mLowResLayer.setPosition(RectUtils.round(position));
+        mLowResLayer.setResolution(mGeckoViewport.zoomFactor);
+
         if (onlyUpdatePageSize) {
             // Don't adjust page size when zooming unless zoom levels are
             // approximately equal.
@@ -471,10 +483,12 @@ public class GeckoLayerClient implements PanZoomTarget, LayerView.Listener {
 
     /* Root Layer Access */
     public void reevaluateTiles() {
+        mLowResLayer.reevaluateTiles(getViewportMetrics());
         mRootLayer.reevaluateTiles(getViewportMetrics());
     }
 
     public void clearAndResetlayers() {
+        mLowResLayer.clearAndReset();
         mRootLayer.clearAndReset();
     }
 }
\ No newline at end of file

android/experimental/LOAndroid3/src/java/org/mozilla/gecko/gfx/LayerRenderer.java

@@ -497,6 +497,7 @@ public class LayerRenderer implements GLSurfaceView.Renderer {
             mUpdated = true;
 
             Layer rootLayer = mView.getLayerClient().getRoot();
+            Layer lowResLayer = mView.getLayerClient().getLowResLayer();
 
             if (!mPageContext.fuzzyEquals(mLastPageContext)) {
                 // the viewport or page changed, so show the scrollbars again
@@ -514,6 +515,7 @@ public class LayerRenderer implements GLSurfaceView.Renderer {
 
             /* Update layers. */
             if (rootLayer != null) mUpdated &= rootLayer.update(mPageContext);  // called on compositor thread
+            if (lowResLayer != null) mUpdated &= lowResLayer.update(mPageContext);  // called on compositor thread
             mUpdated &= mBackgroundLayer.update(mScreenContext);    // called on compositor thread
             mUpdated &= mShadowLayer.update(mPageContext);  // called on compositor thread
             mUpdated &= mScreenshotLayer.update(mPageContext);   // called on compositor thread
@@ -609,6 +611,12 @@ public class LayerRenderer implements GLSurfaceView.Renderer {
 
         // Draws the layer the client added to us.
         void drawRootLayer() {
+            Layer lowResLayer = mView.getLayerClient().getLowResLayer();
+            if (lowResLayer == null) {
+                return;
+            }
+            lowResLayer.draw(mPageContext);
+
             Layer rootLayer = mView.getLayerClient().getRoot();
             if (rootLayer == null) {
                 return;