src/com/android/gallery3d/ui/PositionController.java

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.gallery3d.ui;

import com.android.gallery3d.R;
import com.android.gallery3d.app.GalleryActivity;
import com.android.gallery3d.common.Utils;
import com.android.gallery3d.data.Path;
import com.android.gallery3d.ui.PositionRepository.Position;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Color;
import android.graphics.RectF;
import android.os.Message;
import android.os.SystemClock;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;

class PositionController {
    private long mAnimationStartTime = NO_ANIMATION;
    private static final long NO_ANIMATION = -1;
    private static final long LAST_ANIMATION = -2;

    private int mAnimationKind;
    private final static int ANIM_KIND_SCROLL = 0;
    private final static int ANIM_KIND_SCALE = 1;
    private final static int ANIM_KIND_SNAPBACK = 2;
    private final static int ANIM_KIND_SLIDE = 3;
    private final static int ANIM_KIND_ZOOM = 4;

    // Animation time in milliseconds. The order must match ANIM_KIND_* above.
    private final static int ANIM_TIME[] = {
        0,    // ANIM_KIND_SCROLL
        50,   // ANIM_KIND_SCALE
        600,  // ANIM_KIND_SNAPBACK
        400,  // ANIM_KIND_SLIDE
        300,  // ANIM_KIND_ZOOM
    };

    // We try to scale up the image to fill the screen. But in order not to
    // scale too much for small icons, we limit the max up-scaling factor here.
    private static final float SCALE_LIMIT = 4;

    private PhotoView mViewer;
    private int mImageW, mImageH;
    private int mViewW, mViewH;

    // The X, Y are the coordinate on bitmap which shows on the center of
    // the view. We always keep the mCurrent{X,Y,Scale} sync with the actual
    // values used currently.
    private int mCurrentX, mFromX, mToX;
    private int mCurrentY, mFromY, mToY;
    private float mCurrentScale, mFromScale, mToScale;

    // The focus point of the scaling gesture (in bitmap coordinates).
    private float mFocusBitmapX;
    private float mFocusBitmapY;
    private boolean mInScale;

    // The minimum and maximum scale we allow.
    private float mScaleMin, mScaleMax = SCALE_LIMIT;

    // Assume the image size is the same as view size before we know the actual
    // size of image.
    private boolean mUseViewSize = true;

    private RectF mTempRect = new RectF();
    private float[] mTempPoints = new float[8];

    public PositionController(PhotoView viewer) {
        mViewer = viewer;
    }

    public void setImageSize(int width, int height) {

        // If no image available, use view size.
        if (width == 0 || height == 0) {
            mUseViewSize = true;
            mImageW = mViewW;
            mImageH = mViewH;
            mCurrentX = mImageW / 2;
            mCurrentY = mImageH / 2;
            mCurrentScale = 1;
            mScaleMin = 1;
            mViewer.setPosition(mCurrentX, mCurrentY, mCurrentScale);
            return;
        }

        mUseViewSize = false;

        float ratio = Math.min(
                (float) mImageW / width, (float) mImageH / height);

        // See the comment above translate() for details.
        mCurrentX = translate(mCurrentX, mImageW, width, ratio);
        mCurrentY = translate(mCurrentY, mImageH, height, ratio);
        mCurrentScale = mCurrentScale * ratio;

        mFromX = translate(mFromX, mImageW, width, ratio);
        mFromY = translate(mFromY, mImageH, height, ratio);
        mFromScale = mFromScale * ratio;

        mToX = translate(mToX, mImageW, width, ratio);
        mToY = translate(mToY, mImageH, height, ratio);
        mToScale = mToScale * ratio;

        mImageW = width;
        mImageH = height;

        mScaleMin = getMinimalScale(mImageW, mImageH);

        // Start animation from the saved position if we have one.
        Position position = mViewer.retrieveSavedPosition();
        if (position != null) {
            // The animation starts from 240 pixels and centers at the image
            // at the saved position.
            float scale = 240f / Math.min(width, height);
            mCurrentX = Math.round((mViewW / 2f - position.x) / scale) + mImageW / 2;
            mCurrentY = Math.round((mViewH / 2f - position.y) / scale) + mImageH / 2;
            mCurrentScale = scale;
            mViewer.openAnimationStarted();
            startSnapback();
        } else if (mAnimationStartTime == NO_ANIMATION) {
            mCurrentScale = Utils.clamp(mCurrentScale, mScaleMin, mScaleMax);
        }
        mViewer.setPosition(mCurrentX, mCurrentY, mCurrentScale);
    }

    public void zoomIn(float tapX, float tapY, float targetScale) {
        if (targetScale > mScaleMax) targetScale = mScaleMax;
        float scale = mCurrentScale;

        // Convert the tap position to image coordinate
        float tempX = (tapX - mViewW / 2) / mCurrentScale + mCurrentX;
        float tempY = (tapY - mViewH / 2) / mCurrentScale + mCurrentY;

        // We want to make sure that after zoom-in, we don't see black regions
        // because we zoom too close to the border. The conditions are:
        //
        //  (mViewW / 2) / targetScale + mCurrentX < mImageW
        // -(mViewW / 2) / targetScale + mCurrentX > 0
        float min = mViewW / 2.0f / targetScale;
        float max = mImageW - mViewW / 2.0f / targetScale;
        int targetX = (int) Utils.clamp(tempX, min, max);

        min = mViewH / 2.0f / targetScale;
        max = mImageH - mViewH / 2.0f / targetScale;
        int targetY = (int) Utils.clamp(tempY, min, max);

        // If the width of the image is less then the view, center the image
        if (mImageW * targetScale < mViewW) targetX = mImageW / 2;
        if (mImageH * targetScale < mViewH) targetY = mImageH / 2;

        startAnimation(targetX, targetY, targetScale, ANIM_KIND_ZOOM);
    }

    public void resetToFullView() {
        startAnimation(mImageW / 2, mImageH / 2, mScaleMin, ANIM_KIND_ZOOM);
    }

    public float getMinimalScale(int w, int h) {
        return Math.min(SCALE_LIMIT,
                Math.min((float) mViewW / w, (float) mViewH / h));
    }

    // Translate the coordinate if the aspect ratio of the image changes.
    // When the user slides a image before it's loaded, we don't know the
    // actual aspect ratio, so we will assume one. When we receive the actual
    // aspect ratio, we need to translate the coordinate from the old (assumed)
    // bitmap into the new (actual) bitmap.
    //
    // +-------------------------+  "o" is where center of the view
    // |          +--------+     |  is. mCurrent{X,Y} is the coordinate of
    // |          |        |     |  "o" relative to the old bitmap. Assume
    // |          | o      |     |  the old bitmap size is (w, h).  The new
    // |          +--------+     |  bitmap size is (w', h'). First we adjust
    // |                         |  mCurrentScale by factor r = min(w/w',
    // +-------------------------+  h/h'), so one of the sides matches the old
    //              |               bitmap (w'*r == w or h'*r == h).
    //              v
    // +-------------------------+  Then we put the new scaled bitmap to the
    // |  +--+    ..........     |  center of the original bitmap's bounding
    // |  |  |    .        .     |  box. The center of the old bitmap and the
    // |  |  |    . o      .     |  new bitmap must match in view coordinate:
    // |  +--+    ..........     |
    // |                         |  (w/2 - mCurrentX) * mCurrentScale =
    // +-------------------------+  (w'/2 - mCurrentX') * mCurrentScale * r
    //              |
    //              v               Solve for mCurrentX' we have:
    // +-------------------------+
    // |          ...+--+...     |  mCurrentX' = w'/2 + (mCurrentX - w/2) / r
    // |          .  |  |  .     |
    // |          . o|  |  .     |
    // |          ...+--+...     |
    // |                         |
    // +-------------------------+
    private static int translate(int value, int size, int newSize, float ratio) {
        return Math.round(newSize / 2f + (value - size / 2f) / ratio);
    }

    public void setViewSize(int viewW, int viewH) {
        boolean needLayout = mViewW == 0 || mViewH == 0;

        mViewW = viewW;
        mViewH = viewH;

        if (mUseViewSize) {
            mImageW = viewW;
            mImageH = viewH;
            mCurrentX = mImageW / 2;
            mCurrentY = mImageH / 2;
            mCurrentScale = 1;
            mScaleMin = 1;
            mViewer.setPosition(mCurrentX, mCurrentY, mCurrentScale);
            return;
        }

        // In most cases we want to keep the scaling factor intact when the
        // view size changes. The cases we want to reset the scaling factor
        // (to fit the view if possible) are (1) the scaling factor is too
        // small for the new view size (2) the scaling factor has not been
        // changed by the user.
        boolean wasMinScale = (mCurrentScale == mScaleMin);
        mScaleMin = getMinimalScale(mImageW, mImageH);

        if (needLayout || mCurrentScale < mScaleMin || wasMinScale) {
            mCurrentX = mImageW / 2;
            mCurrentY = mImageH / 2;
            mCurrentScale = mScaleMin;
            mViewer.setPosition(mCurrentX, mCurrentY, mCurrentScale);
        }
    }

    public void stopAnimation() {
        mAnimationStartTime = NO_ANIMATION;
    }

    public void skipAnimation() {
        if (mAnimationStartTime == NO_ANIMATION) return;
        mAnimationStartTime = NO_ANIMATION;
        mCurrentX = mToX;
        mCurrentY = mToY;
        mCurrentScale = mToScale;
    }

    public void beginScale(float focusX, float focusY) {
        mInScale = true;
        mFocusBitmapX = mCurrentX + (focusX - mViewW / 2f) / mCurrentScale;
        mFocusBitmapY = mCurrentY + (focusY - mViewH / 2f) / mCurrentScale;
    }

    public void scaleBy(float s, float focusX, float focusY) {

        // We want to keep the focus point (on the bitmap) the same as when
        // we begin the scale guesture, that is,
        //
        // mCurrentX' + (focusX - mViewW / 2f) / scale = mFocusBitmapX
        //
        s *= getTargetScale();
        int x = Math.round(mFocusBitmapX - (focusX - mViewW / 2f) / s);
        int y = Math.round(mFocusBitmapY - (focusY - mViewH / 2f) / s);

        startAnimation(x, y, s, ANIM_KIND_SCALE);
    }

    public void endScale() {
        mInScale = false;
        startSnapbackIfNeeded();
    }

    public float getCurrentScale() {
        return mCurrentScale;
    }

    public boolean isAtMinimalScale() {
        return isAlmostEquals(mCurrentScale, mScaleMin);
    }

    private static boolean isAlmostEquals(float a, float b) {
        float diff = a - b;
        return (diff < 0 ? -diff : diff) < 0.02f;
    }

    public void up() {
        startSnapback();
    }

    //             |<--| (1/2) * mImageW
    // +-------+-------+-------+
    // |       |       |       |
    // |       |   o   |       |
    // |       |       |       |
    // +-------+-------+-------+
    // |<----------| (3/2) * mImageW
    // Slide in the image from left or right.
    // Precondition: mCurrentScale = 1 (mView{W|H} == mImage{W|H}).
    // Sliding from left:  mCurrentX = (1/2) * mImageW
    //              right: mCurrentX = (3/2) * mImageW
    public void startSlideInAnimation(int direction) {
        int fromX = (direction == PhotoView.TRANS_SLIDE_IN_LEFT) ?
                mImageW / 2 : 3 * mImageW / 2;
        mFromX = Math.round(fromX);
        mFromY = Math.round(mImageH / 2f);
        mCurrentX = mFromX;
        mCurrentY = mFromY;
        startAnimation(
                mImageW / 2, mImageH / 2, mCurrentScale, ANIM_KIND_SLIDE);
    }

    public void startHorizontalSlide(int distance) {
        scrollBy(distance, 0, ANIM_KIND_SLIDE);
    }

    public void startScroll(float dx, float dy) {
        scrollBy(dx, dy, ANIM_KIND_SCROLL);
    }

    private void scrollBy(float dx, float dy, int type) {
        startAnimation(getTargetX() + Math.round(dx / mCurrentScale),
                getTargetY() + Math.round(dy / mCurrentScale),
                mCurrentScale, type);
    }

    private void startAnimation(
            int centerX, int centerY, float scale, int kind) {
        if (centerX == mCurrentX && centerY == mCurrentY
                && scale == mCurrentScale) return;

        mFromX = mCurrentX;
        mFromY = mCurrentY;
        mFromScale = mCurrentScale;

        mToX = centerX;
        mToY = centerY;
        mToScale = Utils.clamp(scale, 0.6f * mScaleMin, 1.4f * mScaleMax);

        // If the scaled dimension is smaller than the view,
        // force it to be in the center.
        if (Math.floor(mImageH * mToScale) <= mViewH) {
            mToY = mImageH / 2;
        }

        mAnimationStartTime = SystemClock.uptimeMillis();
        mAnimationKind = kind;
        if (advanceAnimation()) mViewer.invalidate();
    }

    // Returns true if redraw is needed.
    public boolean advanceAnimation() {
        if (mAnimationStartTime == NO_ANIMATION) {
            return false;
        } else if (mAnimationStartTime == LAST_ANIMATION) {
            mAnimationStartTime = NO_ANIMATION;
            if (mViewer.isInTransition()) {
                mViewer.notifyTransitionComplete();
                return false;
            } else {
                return startSnapbackIfNeeded();
            }
        }

        float animationTime = ANIM_TIME[mAnimationKind];
        float progress;
        if (animationTime == 0) {
            progress = 1;
        } else {
            long now = SystemClock.uptimeMillis();
            progress = (now - mAnimationStartTime) / animationTime;
        }

        if (progress >= 1) {
            progress = 1;
            mCurrentX = mToX;
            mCurrentY = mToY;
            mCurrentScale = mToScale;
            mAnimationStartTime = LAST_ANIMATION;
        } else {
            float f = 1 - progress;
            switch (mAnimationKind) {
                case ANIM_KIND_SCROLL:
                    progress = 1 - f;  // linear
                    break;
                case ANIM_KIND_SCALE:
                    progress = 1 - f * f;  // quadratic
                    break;
                case ANIM_KIND_SNAPBACK:
                case ANIM_KIND_ZOOM:
                case ANIM_KIND_SLIDE:
                    progress = 1 - f * f * f * f * f; // x^5
                    break;
            }
            linearInterpolate(progress);
        }
        mViewer.setPosition(mCurrentX, mCurrentY, mCurrentScale);
        return true;
    }

    // Interpolates mCurrent{X,Y,Scale} given the progress in [0, 1].
    private void linearInterpolate(float progress) {
        // To linearly interpolate the position on view coordinates, we do the
        // following steps:
        // (1) convert a bitmap position (x, y) to view coordinates:
        //     from: (x - mFromX) * mFromScale + mViewW / 2
        //     to: (x - mToX) * mToScale + mViewW / 2
        // (2) interpolate between the "from" and "to" coordinates:
        //     (x - mFromX) * mFromScale * (1 - p) + (x - mToX) * mToScale * p
        //     + mViewW / 2
        //     should be equal to
        //     (x - mCurrentX) * mCurrentScale + mViewW / 2
        // (3) The x-related terms in the above equation can be removed because
        //     mFromScale * (1 - p) + ToScale * p = mCurrentScale
        // (4) Solve for mCurrentX, we have mCurrentX =
        // (mFromX * mFromScale * (1 - p) + mToX * mToScale * p) / mCurrentScale
        float fromX = mFromX * mFromScale;
        float toX = mToX * mToScale;
        float currentX = fromX + progress * (toX - fromX);

        float fromY = mFromY * mFromScale;
        float toY = mToY * mToScale;
        float currentY = fromY + progress * (toY - fromY);

        mCurrentScale = mFromScale + progress * (mToScale - mFromScale);
        mCurrentX = Math.round(currentX / mCurrentScale);
        mCurrentY = Math.round(currentY / mCurrentScale);
    }

    // Returns true if redraw is needed.
    private boolean startSnapbackIfNeeded() {
        if (mAnimationStartTime != NO_ANIMATION) return false;
        if (mInScale) return false;
        if (mAnimationKind == ANIM_KIND_SCROLL && mViewer.isDown()) {
            return false;
        }
        return startSnapback();
    }

    public boolean startSnapback() {
        boolean needAnimation = false;
        int x = mCurrentX;
        int y = mCurrentY;
        float scale = mCurrentScale;

        if (mCurrentScale < mScaleMin || mCurrentScale > mScaleMax) {
            needAnimation = true;
            scale = Utils.clamp(mCurrentScale, mScaleMin, mScaleMax);
        }

        // The number of pixels between the center of the view
        // and the edge when the edge is aligned.
        int left = (int) Math.ceil(mViewW / (2 * scale));
        int right = mImageW - left;
        int top = (int) Math.ceil(mViewH / (2 * scale));
        int bottom = mImageH - top;

        if (mImageW * scale > mViewW) {
            if (mCurrentX < left) {
                needAnimation = true;
                x = left;
            } else if (mCurrentX > right) {
                needAnimation = true;
                x = right;
            }
        } else if (mCurrentX != mImageW / 2) {
            needAnimation = true;
            x = mImageW / 2;
        }

        if (mImageH * scale > mViewH) {
            if (mCurrentY < top) {
                needAnimation = true;
                y = top;
            } else if (mCurrentY > bottom) {
                needAnimation = true;
                y = bottom;
            }
        } else if (mCurrentY != mImageH / 2) {
            needAnimation = true;
            y = mImageH / 2;
        }

        if (needAnimation) {
            startAnimation(x, y, scale, ANIM_KIND_SNAPBACK);
        }

        return needAnimation;
    }

    private float getTargetScale() {
        if (mAnimationStartTime == NO_ANIMATION
                || mAnimationKind == ANIM_KIND_SNAPBACK) return mCurrentScale;
        return mToScale;
    }

    private int getTargetX() {
        if (mAnimationStartTime == NO_ANIMATION
                || mAnimationKind == ANIM_KIND_SNAPBACK) return mCurrentX;
        return mToX;
    }

    private int getTargetY() {
        if (mAnimationStartTime == NO_ANIMATION
                || mAnimationKind == ANIM_KIND_SNAPBACK) return mCurrentY;
        return mToY;
    }

    public RectF getImageBounds() {
        float points[] = mTempPoints;

        /*
         * (p0,p1)----------(p2,p3)
         *   |                  |
         *   |                  |
         * (p4,p5)----------(p6,p7)
         */
        points[0] = points[4] = -mCurrentX;
        points[1] = points[3] = -mCurrentY;
        points[2] = points[6] = mImageW - mCurrentX;
        points[5] = points[7] = mImageH - mCurrentY;

        RectF rect = mTempRect;
        rect.set(Float.POSITIVE_INFINITY, Float.POSITIVE_INFINITY,
                Float.NEGATIVE_INFINITY, Float.NEGATIVE_INFINITY);

        float scale = mCurrentScale;
        float offsetX = mViewW / 2;
        float offsetY = mViewH / 2;
        for (int i = 0; i < 4; ++i) {
            float x = points[i + i] * scale + offsetX;
            float y = points[i + i + 1] * scale + offsetY;
            if (x < rect.left) rect.left = x;
            if (x > rect.right) rect.right = x;
            if (y < rect.top) rect.top = y;
            if (y > rect.bottom) rect.bottom = y;
        }
        return rect;
    }

    public int getImageWidth() {
        return mImageW;
    }

    public int getImageHeight() {
        return mImageH;
    }
}