1 package com.android.launcher3.folder;
2 
3 public class ClippedFolderIconLayoutRule {
4 
5     public static final int MAX_NUM_ITEMS_IN_PREVIEW = 4;
6     private static final int MIN_NUM_ITEMS_IN_PREVIEW = 2;
7 
8     private static final float MIN_SCALE = 0.48f;
9     private static final float MAX_SCALE = 0.58f;
10     private static final float MAX_RADIUS_DILATION = 0.15f;
11     private static final float ITEM_RADIUS_SCALE_FACTOR = 1.33f;
12 
13     public static final int EXIT_INDEX = -2;
14     public static final int ENTER_INDEX = -3;
15 
16     private float[] mTmpPoint = new float[2];
17 
18     private float mAvailableSpace;
19     private float mRadius;
20     private float mIconSize;
21     private boolean mIsRtl;
22     private float mBaselineIconScale;
23 
init(int availableSpace, float intrinsicIconSize, boolean rtl)24     public void init(int availableSpace, float intrinsicIconSize, boolean rtl) {
25         mAvailableSpace = availableSpace;
26         mRadius = ITEM_RADIUS_SCALE_FACTOR * availableSpace / 2f;
27         mIconSize = intrinsicIconSize;
28         mIsRtl = rtl;
29         mBaselineIconScale = availableSpace / (intrinsicIconSize * 1f);
30     }
31 
computePreviewItemDrawingParams(int index, int curNumItems, PreviewItemDrawingParams params)32     public PreviewItemDrawingParams computePreviewItemDrawingParams(int index, int curNumItems,
33             PreviewItemDrawingParams params) {
34         float totalScale = scaleForItem(curNumItems);
35         float transX;
36         float transY;
37         float overlayAlpha = 0;
38 
39         if (index == EXIT_INDEX) {
40             // 0 1 * <-- Exit position (row 0, col 2)
41             // 2 3
42             getGridPosition(0, 2, mTmpPoint);
43         } else if (index == ENTER_INDEX) {
44             // 0 1
45             // 2 3 * <-- Enter position (row 1, col 2)
46             getGridPosition(1, 2, mTmpPoint);
47         } else if (index >= MAX_NUM_ITEMS_IN_PREVIEW) {
48             // Items beyond those displayed in the preview are animated to the center
49             mTmpPoint[0] = mTmpPoint[1] = mAvailableSpace / 2 - (mIconSize * totalScale) / 2;
50         } else {
51             getPosition(index, curNumItems, mTmpPoint);
52         }
53 
54         transX = mTmpPoint[0];
55         transY = mTmpPoint[1];
56 
57         if (params == null) {
58             params = new PreviewItemDrawingParams(transX, transY, totalScale, overlayAlpha);
59         } else {
60             params.update(transX, transY, totalScale);
61             params.overlayAlpha = overlayAlpha;
62         }
63         return params;
64     }
65 
66     /**
67      * Builds a grid based on the positioning of the items when there are
68      * {@link #MAX_NUM_ITEMS_IN_PREVIEW} in the preview.
69      *
70      * Positions in the grid: 0 1  // 0 is row 0, col 1
71      *                        2 3  // 3 is row 1, col 1
72      */
getGridPosition(int row, int col, float[] result)73     private void getGridPosition(int row, int col, float[] result) {
74         // We use position 0 and 3 to calculate the x and y distances between items.
75         getPosition(0, 4, result);
76         float left = result[0];
77         float top = result[1];
78 
79         getPosition(3, 4, result);
80         float dx = result[0] - left;
81         float dy = result[1] - top;
82 
83         result[0] = left + (col * dx);
84         result[1] = top + (row * dy);
85     }
86 
getPosition(int index, int curNumItems, float[] result)87     private void getPosition(int index, int curNumItems, float[] result) {
88         // The case of two items is homomorphic to the case of one.
89         curNumItems = Math.max(curNumItems, 2);
90 
91         // We model the preview as a circle of items starting in the appropriate piece of the
92         // upper left quadrant (to achieve horizontal and vertical symmetry).
93         double theta0 = mIsRtl ? 0 : Math.PI;
94 
95         // In RTL we go counterclockwise
96         int direction = mIsRtl ? 1 : -1;
97 
98         double thetaShift = 0;
99         if (curNumItems == 3) {
100             thetaShift = Math.PI / 6;
101         } else if (curNumItems == 4) {
102             thetaShift = Math.PI / 4;
103         }
104         theta0 += direction * thetaShift;
105 
106         // We want the items to appear in reading order. For the case of 1, 2 and 3 items, this
107         // is natural for the circular model. With 4 items, however, we need to swap the 3rd and
108         // 4th indices to achieve reading order.
109         if (curNumItems == 4 && index == 3) {
110             index = 2;
111         } else if (curNumItems == 4 && index == 2) {
112             index = 3;
113         }
114 
115         // We bump the radius up between 0 and MAX_RADIUS_DILATION % as the number of items increase
116         float radius = mRadius * (1 + MAX_RADIUS_DILATION * (curNumItems -
117                 MIN_NUM_ITEMS_IN_PREVIEW) / (MAX_NUM_ITEMS_IN_PREVIEW - MIN_NUM_ITEMS_IN_PREVIEW));
118         double theta = theta0 + index * (2 * Math.PI / curNumItems) * direction;
119 
120         float halfIconSize = (mIconSize * scaleForItem(curNumItems)) / 2;
121 
122         // Map the location along the circle, and offset the coordinates to represent the center
123         // of the icon, and to be based from the top / left of the preview area. The y component
124         // is inverted to match the coordinate system.
125         result[0] = mAvailableSpace / 2 + (float) (radius * Math.cos(theta) / 2) - halfIconSize;
126         result[1] = mAvailableSpace / 2 + (float) (- radius * Math.sin(theta) / 2) - halfIconSize;
127 
128     }
129 
scaleForItem(int numItems)130     public float scaleForItem(int numItems) {
131         // Scale is determined by the number of items in the preview.
132         final float scale;
133         if (numItems <= 2) {
134             scale = MAX_SCALE;
135         } else if (numItems == 3) {
136             scale = (MAX_SCALE + MIN_SCALE) / 2;
137         } else {
138             scale = MIN_SCALE;
139         }
140         return scale * mBaselineIconScale;
141     }
142 
getIconSize()143     public float getIconSize() {
144         return mIconSize;
145     }
146 }
147