Add a view to show magnified link preview on Andrdoid.

content/public/android/java/src/org/chromium/content/browser/PopupZoomer.java

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.content.browser;
+
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.graphics.Path;
+import android.graphics.Path.Direction;
+import android.graphics.PointF;
+import android.graphics.PorterDuff.Mode;
+import android.graphics.PorterDuffXfermode;
+import android.graphics.Rect;
+import android.graphics.RectF;
+import android.graphics.Region.Op;
+import android.graphics.drawable.Drawable;
+import android.os.SystemClock;
+import android.view.GestureDetector;
+import android.view.MotionEvent;
+import android.view.View;
+import android.view.animation.Interpolator;
+import android.view.animation.OvershootInterpolator;
+
+import org.chromium.content.app.AppResource;
+
+/**
+ * PopupZoomer is used to show the on-demand link zooming popup. It handles manipulation of the
+ * canvas and touch events to display the on-demand zoom magnifier.
+ */
+class PopupZoomer extends View {
+    // The padding between the edges of the view and the popup. Note that there is a mirror
+    // constant in content/renderer/render_view_impl.cc which should be kept in sync if
+    // this is changed.
+    private static final int ZOOM_BOUNDS_MARGIN = 25;
+    // Time it takes for the animation to finish in ms.
+    private static final long ANIMATION_DURATION = 300;
+
+    /**
+     * Interface to be implemented to listen for touch events inside the zoomed area.
+     * The MotionEvent coordinates correspond to original unzoomed view.
+     */
+    public static interface OnTapListener {
+        public boolean onSingleTap(View v, MotionEvent event);
+        public boolean onLongPress(View v, MotionEvent event);
+    }
+
+    private OnTapListener mOnTapListener = null;
+
+    // Cached drawable used to frame the zooming popup.
+    // TODO(tonyg): This should be marked purgeable so that if the system wants to recover this
+    // memory, we can just reload it from the resource ID next time it is needed.
+    // See android.graphics.BitmapFactory.Options#inPurgeable
+    private static Drawable sOverlayDrawable;
+    // The padding used for drawing the overlay around the content, instead of directly above it.
+    private static Rect sOverlayPadding;
+    // The radius of the overlay bubble, used for rounding the bitmap to draw underneath it.
+    private static float sOverlayCornerRadius;
+
+    private Interpolator mShowInterpolator = new OvershootInterpolator();
+    private Interpolator mHideInterpolator = new ReverseInterpolator(mShowInterpolator);
+
+    private boolean mAnimating = false;
+    private boolean mShowing = false;
+    private long mAnimationStartTime = 0;
+
+    // The time that was left for the outwards animation to finish.
+    // This is used in the case that the zoomer is cancelled while it is still animating outwards,
+    // to avoid having it jump to full size then animate closed.
+    private long mTimeLeft = 0;
+
+    // Available view area after accounting for ZOOM_BOUNDS_MARGIN.
+    private RectF mViewClipRect;
+
+    // The target rect to be zoomed.
+    private Rect mTargetBounds;
+
+    // The bitmap to hold the zoomed view.
+    private Bitmap mZoomedBitmap;
+
+    // How far to shift the canvas after all zooming is done, to keep it inside the bounds of the
+    // view (including margin).
+    private float mShiftX = 0, mShiftY = 0;
+    // The magnification factor of the popup. It is recomputed once we have mTargetBounds and
+    // mZoomedBitmap.
+    private float mScale = 1.0f;
+    // The bounds representing the actual zoomed popup.
+    private RectF mClipRect;
+    // The extrusion values are how far the zoomed area (mClipRect) extends from the touch point.
+    // These values to used to animate the popup.
+    private float mLeftExtrusion, mTopExtrusion, mRightExtrusion, mBottomExtrusion;
+    // The last touch point, where the animation will start from.
+    private PointF mTouch = new PointF();
+
+    // Since we sometimes overflow the bounds of the mViewClipRect, we need to allow scrolling.
+    // Current scroll position.
+    private float mPopupScrollX, mPopupScrollY;
+    // Scroll bounds.
+    private float mMinScrollX, mMaxScrollX;
+    private float mMinScrollY, mMaxScrollY;
+
+    private GestureDetector mGestureDetector;
+
+    /**
+     * Gets the drawable that should be used to frame the zooming popup, loading
+     * it from the resource bundle if not already cached.
+     */
+    protected Drawable getOverlayDrawable() {
+        if (sOverlayDrawable == null) {
+            sOverlayDrawable = loadOverlayDrawable();
+            sOverlayPadding = new Rect();
+            sOverlayDrawable.getPadding(sOverlayPadding);
+        }
+        return sOverlayDrawable;
+    }
+
+    /**
+     * Loads the overlay drawable from the resource bundle.
+     *
+     * @VisibleForTesting
+     */
+    protected Drawable loadOverlayDrawable() {
+        assert AppResource.DRAWABLE_LINK_PREVIEW_POPUP_OVERLAY != 0;
+        return getContext().getResources().getDrawable(
+                AppResource.DRAWABLE_LINK_PREVIEW_POPUP_OVERLAY);
+    }
+
+    private static float constrain(float amount, float low, float high) {
+        return amount < low ? low : (amount > high ? high : amount);
+    }
+
+    private static int constrain(int amount, int low, int high) {
+        return amount < low ? low : (amount > high ? high : amount);
+    }
+
+    /**
+     * Creates Popupzoomer.
+     * @param context Context to be used.
+     * @param overlayRadiusDimensoinResId Resource to be used to get overlay corner radius.
+     */
+    public PopupZoomer(Context context, int overlayRadiusDimensoinResId) {
+        super(context);
+
+        if (overlayRadiusDimensoinResId != 0) {
+            sOverlayCornerRadius = context.getResources().getDimension(overlayRadiusDimensoinResId);
+        } else {
+            sOverlayCornerRadius = 0;
+        }
+
+        setVisibility(INVISIBLE);
+        setFocusable(true);
+        setFocusableInTouchMode(true);
+
+        GestureDetector.SimpleOnGestureListener listener =
+            new GestureDetector.SimpleOnGestureListener() {
+                @Override
+                public boolean onScroll(MotionEvent e1, MotionEvent e2,
+                        float distanceX, float distanceY) {
+                    if (mAnimating) return true;
+
+                    if (isTouchOutsideArea(e1.getX(), e1.getY())) {
+                        hide(true);
+                    } else {
+                        scroll(distanceX, distanceY);
+                    }
+                    return true;
+                }
+
+                @Override
+                public boolean onSingleTapUp(MotionEvent e) {
+                    return handleTapOrPress(e, false);
+                }
+
+                @Override
+                public void onLongPress(MotionEvent e) {
+                    handleTapOrPress(e, true);
+                }
+
+                private boolean handleTapOrPress(MotionEvent e, boolean isLongPress) {
+                    if (mAnimating) return true;
+
+                    float x = e.getX();
+                    float y = e.getY();
+                    if (isTouchOutsideArea(x, y)) {
+                        // User clicked on area outside the popup.
+                        hide(true);
+                    } else if (mOnTapListener != null) {
+                        PointF converted = convertTouchPoint(x, y);
+                        MotionEvent event = MotionEvent.obtainNoHistory(e);
+                        event.setLocation(converted.x, converted.y);
+                        if (isLongPress) {
+                            mOnTapListener.onLongPress(PopupZoomer.this, event);
+                        } else {
+                            mOnTapListener.onSingleTap(PopupZoomer.this, event);
+                        }
+                        hide(true);
+                    }
+                    return true;
+                }
+        };
+        mGestureDetector = new GestureDetector(context, listener);
+    }
+
+    /**
+     * Sets the OnTapListener.
+     */
+    public void setOnTapListener(OnTapListener listener) {
+        mOnTapListener = listener;
+    }
+
+    /**
+     * Sets the bitmap to be used for the zoomed view.
+     */
+    public void setBitmap(Bitmap bitmap) {
+        if (mZoomedBitmap != null) {
+            mZoomedBitmap.recycle();
+            mZoomedBitmap = null;
+        }
+        mZoomedBitmap = bitmap;
+        // Round the corners of the bitmap so it doesn't stick out around the overlay.
+        Canvas canvas = new Canvas(mZoomedBitmap);
+        Path path = new Path();
+        RectF canvasRect = new RectF(0, 0, canvas.getWidth(), canvas.getHeight());
+        path.addRoundRect(canvasRect, sOverlayCornerRadius, sOverlayCornerRadius, Direction.CCW);
+        canvas.clipPath(path, Op.XOR);
+        Paint clearPaint = new Paint();
+        clearPaint.setXfermode(new PorterDuffXfermode(Mode.SRC));
+        clearPaint.setColor(Color.TRANSPARENT);
+        canvas.drawPaint(clearPaint);
+    }
+
+    private void scroll(float x, float y) {
+        mPopupScrollX = constrain(mPopupScrollX - x, mMinScrollX, mMaxScrollX);
+        mPopupScrollY = constrain(mPopupScrollY - y, mMinScrollY, mMaxScrollY);
+        invalidate();
+    }
+
+    private void startAnimation(boolean show) {
+        mAnimating = true;
+        mShowing = show;
+        mTimeLeft = 0;
+        if (show) {
+            setVisibility(VISIBLE);
+            initDimensions();
+        } else {
+            long endTime = mAnimationStartTime + ANIMATION_DURATION;
+            mTimeLeft = endTime - SystemClock.uptimeMillis();
+            if (mTimeLeft < 0) mTimeLeft = 0;
+        }
+        mAnimationStartTime = SystemClock.uptimeMillis();
+        invalidate();
+    }
+
+    private void hideImmediately() {
+        mAnimating = false;
+        mShowing = false;
+        mTimeLeft = 0;
+        setVisibility(INVISIBLE);
+        mZoomedBitmap.recycle();
+        mZoomedBitmap = null;
+    }
+
+    /**
+     * Returns true if the view is currently being shown (or is animating).
+     */
+    public boolean isShowing() {
+        return mShowing || mAnimating;
+    }
+
+    /**
+     * Sets the last touch point (on the unzoomed view).
+     */
+    public void setLastTouch(float x, float y) {
+        mTouch.x = x;
+        mTouch.y = y;
+    }
+
+    private void setTargetBounds(Rect rect) {
+        mViewClipRect = new RectF(ZOOM_BOUNDS_MARGIN,
+                ZOOM_BOUNDS_MARGIN,
+                getWidth() - ZOOM_BOUNDS_MARGIN,
+                getHeight() - ZOOM_BOUNDS_MARGIN);
+        mTargetBounds = rect;
+    }
+
+    private void initDimensions() {
+        if (mTargetBounds == null || mTouch == null) return;
+
+        // Compute the final zoom scale.
+        mScale = (float) mZoomedBitmap.getWidth() / mTargetBounds.width();
+
+        float l = mTouch.x - mScale * (mTouch.x - mTargetBounds.left);
+        float t = mTouch.y - mScale * (mTouch.y - mTargetBounds.top);
+        float r = l + mZoomedBitmap.getWidth();
+        float b = t + mZoomedBitmap.getHeight();
+        mClipRect = new RectF(l, t, r, b);
+        int width = getWidth();
+        int height = getHeight();
+
+        // Ensure it stays inside the bounds of the view.  First shift it around to see if it
+        // can fully fit in the view, then clip it to the padding section of the view to
+        // ensure no overflow.
+        mShiftX = 0;
+        mShiftY = 0;
+
+        // Right now this has the happy coincidence of showing the leftmost portion
+        // of a scaled up bitmap, which usually has the text in it.  When we want to support
+        // RTL languages, we can conditionally switch the order of this check to push it
+        // to the left instead of right.
+        if (mClipRect.left < ZOOM_BOUNDS_MARGIN) {
+            mShiftX = ZOOM_BOUNDS_MARGIN - mClipRect.left;
+            mClipRect.left += mShiftX;
+            mClipRect.right += mShiftX;
+        } else if (mClipRect.right > width - ZOOM_BOUNDS_MARGIN) {
+            mShiftX = (width - ZOOM_BOUNDS_MARGIN - mClipRect.right);
+            mClipRect.right += mShiftX;
+            mClipRect.left += mShiftX;
+        }
+        if (mClipRect.top < ZOOM_BOUNDS_MARGIN) {
+            mShiftY = ZOOM_BOUNDS_MARGIN - mClipRect.top;
+            mClipRect.top += mShiftY;
+            mClipRect.bottom += mShiftY;
+        } else if (mClipRect.bottom > height - ZOOM_BOUNDS_MARGIN) {
+            mShiftY = height - ZOOM_BOUNDS_MARGIN - mClipRect.bottom;
+            mClipRect.bottom += mShiftY;
+            mClipRect.top += mShiftY;
+        }
+
+        // Allow enough scrolling to get to the entire bitmap that may be clipped inside the
+        // bounds of the view.
+        mMinScrollX = mMaxScrollX = mMinScrollY = mMaxScrollY = 0;
+        if (mViewClipRect.right + mShiftX < mClipRect.right) {
+            mMinScrollX = mViewClipRect.right - mClipRect.right;
+        }
+        if (mViewClipRect.left + mShiftX > mClipRect.left) {
+            mMaxScrollX = mViewClipRect.left - mClipRect.left;
+        }
+        if (mViewClipRect.top + mShiftY > mClipRect.top) {
+            mMaxScrollY = mViewClipRect.top - mClipRect.top;
+        }
+        if (mViewClipRect.bottom + mShiftY < mClipRect.bottom) {
+            mMinScrollY = mViewClipRect.bottom - mClipRect.bottom;
+        }
+        // Now that we know how much we need to scroll, we can intersect with mViewClipRect.
+        mClipRect.intersect(mViewClipRect);
+
+        mLeftExtrusion = mTouch.x - mClipRect.left;
+        mRightExtrusion = mClipRect.right - mTouch.x;
+        mTopExtrusion = mTouch.y - mClipRect.top;
+        mBottomExtrusion = mClipRect.bottom - mTouch.y;
+
+        // Set an initial scroll position to take touch point into account.
+        float percentX =
+                (mTouch.x - mTargetBounds.centerX()) / (mTargetBounds.width() / 2.f) + .5f;
+        float percentY =
+                (mTouch.y - mTargetBounds.centerY()) / (mTargetBounds.height() / 2.f) + .5f;
+
+        float scrollWidth = mMaxScrollX - mMinScrollX;
+        float scrollHeight = mMaxScrollY - mMinScrollY;
+        mPopupScrollX = scrollWidth * percentX * -1f;
+        mPopupScrollY = scrollHeight * percentY * -1f;
+        // Constrain initial scroll position within allowed bounds.
+        mPopupScrollX = constrain(mPopupScrollX, mMinScrollX, mMaxScrollX);
+        mPopupScrollY = constrain(mPopupScrollY, mMinScrollY, mMaxScrollY);
+    }
+
+    @Override
+    protected void onDraw(Canvas canvas) {
+        if (!isShowing() || mZoomedBitmap == null) return;
+        canvas.save();
+        // Calculate the elapsed fraction of animation.
+        float time = (SystemClock.uptimeMillis() - mAnimationStartTime + mTimeLeft) /
+                ((float) ANIMATION_DURATION);
+        time = constrain(time, 0, 1);
+        if (time >= 1) {
+            mAnimating = false;
+            if (!isShowing()) {
+                hideImmediately();
+                return;
+            }
+        } else {
+            invalidate();
+        }
+
+        // Fraction of the animation to actally show.
+        float fractionAnimation;
+        if (mShowing) {
+            fractionAnimation = mShowInterpolator.getInterpolation(time);
+        } else {
+            fractionAnimation = mHideInterpolator.getInterpolation(time);
+        }
+
+        // Draw a faded color over the entire view to fade out the original content, increasing
+        // the alpha value as fractionAnimation increases.
+        // TODO(nileshagrawal): We should use time here instead of fractionAnimation
+        // as fractionAnimaton is interpolated and can go over 1.
+        canvas.drawARGB((int) (80 * fractionAnimation), 0, 0, 0);
+        canvas.save();
+
+        // Since we want the content to appear directly above its counterpart we need to make
+        // sure that it starts out at exactly the same size as it appears in the page,
+        // i.e. scale grows from 1/mScale to 1. Note that extrusion values are already zoomed
+        // with mScale.
+        float scale = fractionAnimation * (mScale - 1.0f) / mScale + 1.0f / mScale;
+
+        // Since we want the content to appear directly above its counterpart on the
+        // page, we need to remove the mShiftX/Y effect at the beginning of the animation.
+        // The unshifting decreases with the animation.
+        float unshiftX = - mShiftX * (1.0f - fractionAnimation) / mScale;
+        float unshiftY = - mShiftY * (1.0f - fractionAnimation) / mScale;
+
+        // Compute the rect to show.
+        RectF rect = new RectF();
+        rect.left = mTouch.x - mLeftExtrusion * scale + unshiftX;
+        rect.top = mTouch.y - mTopExtrusion * scale + unshiftY;
+        rect.right = mTouch.x + mRightExtrusion * scale + unshiftX;
+        rect.bottom = mTouch.y + mBottomExtrusion * scale + unshiftY;
+        canvas.clipRect(rect);
+
+        // Since the canvas transform APIs all pre-concat the transformations, this is done in
+        // reverse order. The canvas is first scaled up, then shifted the appropriate amount of
+        // pixels.
+        canvas.scale(scale, scale, rect.left, rect.top);
+        canvas.translate(mPopupScrollX, mPopupScrollY);
+        canvas.drawBitmap(mZoomedBitmap, rect.left, rect.top, null);
+        canvas.restore();
+        Drawable overlayNineTile = getOverlayDrawable();
+        overlayNineTile.setBounds((int) rect.left - sOverlayPadding.left,
+                (int) rect.top - sOverlayPadding.top,
+                (int) rect.right + sOverlayPadding.right,
+                (int) rect.bottom + sOverlayPadding.bottom);
+        // TODO(nileshagrawal): We should use time here instead of fractionAnimation
+        // as fractionAnimaton is interpolated and can go over 1.
+        int alpha = constrain((int) (fractionAnimation * 255), 0, 255);
+        overlayNineTile.setAlpha(alpha);
+        overlayNineTile.draw(canvas);
+        canvas.restore();
+    }
+
+    /**
+     * Show the PopupZoomer view with given target bounds.
+     */
+    public void show(Rect rect){
+        if (mShowing || mZoomedBitmap == null) return;
+
+        setTargetBounds(rect);
+        startAnimation(true);
+    }
+
+    /**
+     * Hide the PopupZoomer view.
+     * @param animation true if hide with animation.
+     */
+    public void hide(boolean animation){
+        if (!mShowing) return;
+
+        if (animation) {
+            startAnimation(false);
+        } else {
+            hideImmediately();
+        }
+    }
+
+    /**
+     * Converts the coordinates to a point on the original un-zoomed view.
+     */
+    private PointF convertTouchPoint(float x, float y) {
+        x -= mShiftX;
+        y -= mShiftY;
+        x = mTouch.x + (x - mTouch.x - mPopupScrollX) / mScale;
+        y = mTouch.y + (y - mTouch.y - mPopupScrollY) / mScale;
+        return new PointF(x, y);
+    }
+
+    /**
+     * Returns true if the point is inside the final drawable area for this popup zoomer.
+     */
+    private boolean isTouchOutsideArea(float x, float y) {
+        return !mClipRect.contains(x, y);
+    }
+
+    @Override
+    public boolean onTouchEvent(MotionEvent event) {
+        mGestureDetector.onTouchEvent(event);
+        return true;
+    }
+
+    private static class ReverseInterpolator implements Interpolator {
+        private Interpolator mInterpolator;
+
+        public ReverseInterpolator(Interpolator i) {
+            mInterpolator = i;
+        }
+
+        @Override
+        public float getInterpolation(float input) {
+            input = 1.0f - input;
+            if (mInterpolator == null) return input;
+            return mInterpolator.getInterpolation(input);
+        }
+    }
+}