gecko/embedding/android/gfx/LayerController.java

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package org.mozilla.gecko.gfx;

import org.mozilla.gecko.gfx.IntSize;
import org.mozilla.gecko.gfx.Layer;
import org.mozilla.gecko.gfx.LayerClient;
import org.mozilla.gecko.gfx.LayerView;
import org.mozilla.gecko.ui.PanZoomController;
import org.mozilla.gecko.GeckoApp;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.PointF;
import android.graphics.Rect;
import android.graphics.RectF;
import android.util.Log;
import android.view.MotionEvent;
import android.view.GestureDetector;
import android.view.ScaleGestureDetector;
import android.view.View.OnTouchListener;
import java.util.ArrayList;

/**
 * The layer controller manages a tile that represents the visible page. It does panning and
 * zooming natively by delegating to a panning/zooming controller. Touch events can be dispatched
 * to a higher-level view.
 */
public class LayerController {
    private Layer mRootLayer;                   /* The root layer. */
    private LayerView mView;                    /* The main rendering view. */
    private Context mContext;                   /* The current context. */
    private RectF mVisibleRect;                 /* The current visible region. */
    private IntSize mScreenSize;                /* The screen size of the viewport. */
    private IntSize mPageSize;                  /* The current page size. */

    private PanZoomController mPanZoomController;
    /*
     * The panning and zooming controller, which interprets pan and zoom gestures for us and
     * updates our visible rect appropriately.
     */

    private OnTouchListener mOnTouchListener;   /* The touch listener. */
    private LayerClient mLayerClient;           /* The layer client. */

    public static final int TILE_WIDTH = 1024;
    public static final int TILE_HEIGHT = 2048;
    /* NB: These must be powers of two due to the OpenGL ES 1.x restriction on NPOT textures. */

    private static final int DANGER_ZONE_X = 150;
    private static final int DANGER_ZONE_Y = 300;
    /* If the visible rect is within the danger zone (measured in pixels from each edge of a tile),
     * we start aggressively redrawing to minimize checkerboarding. */

    public LayerController(Context context) {
        mContext = context;

        mVisibleRect = new RectF(0.0f, 0.0f, 1.0f, 1.0f);
        /* Gets filled in when the surface changes. */

        mScreenSize = new IntSize(1, 1);
        mPageSize = new IntSize(LayerController.TILE_WIDTH, LayerController.TILE_HEIGHT);

        mPanZoomController = new PanZoomController(this);
        mView = new LayerView(context, this);
    }

    public void setRoot(Layer layer) { mRootLayer = layer; }

    public void setLayerClient(LayerClient layerClient) {
        mLayerClient = layerClient;
        mPageSize = layerClient.getPageSize();
        layerClient.setLayerController(this);
        layerClient.init();
    }

    public Layer getRoot()              { return mRootLayer; }
    public LayerView getView()          { return mView; }
    public Context getContext()         { return mContext; }
    public RectF getVisibleRect()       { return mVisibleRect; }
    public IntSize getScreenSize()      { return mScreenSize; }
    public IntSize getPageSize()        { return mPageSize; }

    public Bitmap getCheckerboardPattern()  { return getDrawable("checkerboard"); }
    public Bitmap getShadowPattern()        { return getDrawable("shadow"); }

    public GestureDetector.OnGestureListener getGestureListener()                   { return mPanZoomController; }
    public ScaleGestureDetector.OnScaleGestureListener getScaleGestureListener()    { return mPanZoomController; }

    private Bitmap getDrawable(String name) {
        Resources resources = mContext.getResources();
        int resourceID = resources.getIdentifier(name, "drawable", mContext.getPackageName());
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inScaled = false;
        return BitmapFactory.decodeResource(mContext.getResources(), resourceID, options);
    }

    /*
     * Note that the zoom factor of the layer controller differs from the zoom factor of the layer
     * client (i.e. the page).
     */
    public float getZoomFactor() { return (float)mScreenSize.width / mVisibleRect.width(); }

    /**
     * The view calls this to indicate that the screen changed size.
     *
     * TODO: Refactor this to use an interface. Expose that interface only to the view and not
     * to the layer client. That way, the layer client won't be tempted to call this, which might
     * result in an infinite loop.
     */
    public void setScreenSize(int width, int height) {
        float zoomFactor = getZoomFactor();     /* Must come first. */

        mScreenSize = new IntSize(width, height);
        setVisibleRect(mVisibleRect.left, mVisibleRect.top, width / zoomFactor,
                       height / zoomFactor);

        notifyLayerClientOfGeometryChange();
    }

    public void setNeedsDisplay() {
        // TODO
    }

    public void scrollTo(float x, float y) {
        setVisibleRect(x, y, mVisibleRect.width(), mVisibleRect.height());
    }

    public void setVisibleRect(float x, float y, float width, float height) {
        mVisibleRect = new RectF(x, y, x + width, y + height);
        setNeedsDisplay();
        GeckoApp.mAppContext.repositionPluginViews(false);
    }

    /**
     * Sets the zoom factor to 1, adjusting the visible rect accordingly. The Gecko layer client
     * calls this function after a zoom has completed and Gecko is done rendering the new visible
     * region.
     */
    public void unzoom() {
        float zoomFactor = getZoomFactor();
        float x = Math.round(mVisibleRect.left * zoomFactor);
        float y = Math.round(mVisibleRect.top * zoomFactor);
        mVisibleRect = new RectF(x, y, x + mScreenSize.width, y + mScreenSize.height);
        mPageSize = mPageSize.scale(zoomFactor);
        setNeedsDisplay();
    }

    public void setPageSize(IntSize size) {
        mPageSize = size.scale(getZoomFactor());
        mView.notifyRendererOfPageSizeChange();
    }

    public boolean post(Runnable action) { return mView.post(action); }

    public void setOnTouchListener(OnTouchListener onTouchListener) {
        mOnTouchListener = onTouchListener;
    }

    /**
     * The view as well as the controller itself use this method to notify the layer client that
     * the geometry changed.
     */
    public void notifyLayerClientOfGeometryChange() {
        if (mLayerClient != null)
            mLayerClient.geometryChanged();
    }

    // Informs the view and the panning and zooming controller that the geometry changed.
    public void notifyViewOfGeometryChange() {
        mView.geometryChanged();
        mPanZoomController.geometryChanged();
    }

    /**
     * Returns true if this controller is fine with performing a redraw operation or false if it
     * would prefer that the action didn't take place.
     */
    public boolean getRedrawHint() {
        return aboutToCheckerboard();
    }

    private RectF getTileRect() {
        float x = mRootLayer.origin.x, y = mRootLayer.origin.y;
        return new RectF(x, y, x + TILE_WIDTH, y + TILE_HEIGHT);
    }

    // Returns true if a checkerboard is about to be visible.
    private boolean aboutToCheckerboard() {
        Rect pageRect = new Rect(0, 0, mPageSize.width, mPageSize.height);
        Rect adjustedPageRect = RectUtils.contract(pageRect, DANGER_ZONE_X, DANGER_ZONE_Y);
        RectF visiblePageRect = RectUtils.intersect(mVisibleRect, new RectF(adjustedPageRect));
        RectF adjustedTileRect = RectUtils.contract(getTileRect(), DANGER_ZONE_X, DANGER_ZONE_Y);
        return !adjustedTileRect.contains(visiblePageRect);
    }

    /** Returns the given rect, clamped to the boundaries of a tile. */
    public RectF clampRect(RectF rect) {
        float x = clamp(0, rect.left, mPageSize.width - LayerController.TILE_WIDTH);
        float y = clamp(0, rect.top, mPageSize.height - LayerController.TILE_HEIGHT);
        return new RectF(x, y, x + rect.width(), y + rect.height());
    }

    private float clamp(float min, float value, float max) {
        if (max < min)
            return min;
        return (value < min) ? min : (value > max) ? max : value;
    }

    // Returns the coordinates of a tile, scaled by the given factor, centered on the given rect.
    private static RectF widenRect(RectF rect, float scaleFactor) {
        PointF center = new PointF(rect.centerX(), rect.centerY());
        float halfTileWidth = TILE_WIDTH * scaleFactor / 2.0f;
        float halfTileHeight = TILE_HEIGHT * scaleFactor / 2.0f;
        return new RectF(rect.centerX() - halfTileWidth, rect.centerY() - halfTileHeight,
                         rect.centerX() + halfTileWidth, rect.centerY() + halfTileHeight);
    }

    /** Returns the coordinates of a tile centered on the given rect. */
    public static RectF widenRect(RectF rect) {
        return widenRect(rect, 1.0f);
    }

    /**
     * Converts a point from layer view coordinates to layer coordinates. In other words, given a
     * point measured in pixels from the top left corner of the layer view, returns the point in
     * pixels measured from the top left corner of the root layer, in the coordinate system of the
     * layer itself. This method is used by the viewport controller as part of the process of
     * translating touch events to Gecko's coordinate system.
     */
    public PointF convertViewPointToLayerPoint(PointF viewPoint) {
        if (mRootLayer == null)
            return null;

        // Undo the transforms.
        PointF scaledPoint = PointUtils.scale(viewPoint, 1.0f / getZoomFactor());
        return PointUtils.subtract(PointUtils.add(new PointF(mVisibleRect.left, mVisibleRect.top),
                                                  scaledPoint),
                                   mRootLayer.origin);
    }

    /*
     * Gesture detection. This is handled only at a high level in this class; we dispatch to the
     * pan/zoom controller to do the dirty work.
     */

    public boolean onTouchEvent(MotionEvent event) {
        if (mPanZoomController.onTouchEvent(event))
            return true;
        if (mOnTouchListener != null)
            return mOnTouchListener.onTouch(mView, event);
        return false;
    }
}