1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License
15 */
16
17package com.android.systemui.statusbar.stack;
18
19/**
20 * A functor which can be queried for offset given the number of items before it.
21 */
22public abstract class StackIndentationFunctor {
23
24    protected int mTotalTransitionDistance;
25    protected int mDistanceToPeekStart;
26    protected int mMaxItemsInStack;
27    protected int mPeekSize;
28    protected boolean mStackStartsAtPeek;
29
30    /**
31     * @param maxItemsInStack The maximum number of items which should be visible at the same time,
32     *                        i.e the function returns totalTransitionDistance for the element with
33     *                        index maxItemsInStack
34     * @param peekSize The visual appearance of this is how far the cards in the stack peek
35     *                 out below the top card and it is measured in real pixels.
36     *                 Note that the visual appearance does not necessarily always correspond to
37     *                 the actual visual distance below the top card but is a maximum,
38     *                 achieved when the next card just starts transitioning into the stack and
39     *                 the stack is full.
40     *                 If distanceToPeekStart is 0, we directly start at the peek, otherwise the
41     *                 first element transitions between 0 and distanceToPeekStart.
42     *                 Visualization:
43     *           ---------------------------------------------------   ---
44     *          |                                                   |   |
45     *          |                  FIRST ITEM                       |   | <- distanceToPeekStart
46     *          |                                                   |   |
47     *          |---------------------------------------------------|  ---  ---
48     *          |__________________SECOND ITEM______________________|        |  <- peekSize
49     *          |===================================================|       _|_
50     *
51     * @param distanceToPeekStart The distance to the start of the peak.
52     */
53    StackIndentationFunctor(int maxItemsInStack, int peekSize, int distanceToPeekStart) {
54        mDistanceToPeekStart = distanceToPeekStart;
55        mStackStartsAtPeek = mDistanceToPeekStart == 0;
56        mMaxItemsInStack = maxItemsInStack;
57        mPeekSize = peekSize;
58        updateTotalTransitionDistance();
59
60    }
61
62    private void updateTotalTransitionDistance() {
63        mTotalTransitionDistance = mDistanceToPeekStart + mPeekSize;
64    }
65
66    public void setPeekSize(int mPeekSize) {
67        this.mPeekSize = mPeekSize;
68        updateTotalTransitionDistance();
69    }
70
71    public void setDistanceToPeekStart(int distanceToPeekStart) {
72        mDistanceToPeekStart = distanceToPeekStart;
73        mStackStartsAtPeek = mDistanceToPeekStart == 0;
74        updateTotalTransitionDistance();
75    }
76
77    /**
78     * Gets the offset of this Functor given a the quantity of items before it
79     *
80     * @param itemsBefore how many items are already in the stack before this element
81     * @return the offset
82     */
83    public abstract float getValue(float itemsBefore);
84}
85