DisplayMetrics.java revision 64f59342d41849bd365cb43fad7505d5e3daa417 
1/*
2 * Copyright (C) 2006 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 android.util;
18
19import android.content.res.CompatibilityInfo;
20import android.content.res.Configuration;
21import android.os.*;
22
23
24/**
25 * A structure describing general information about a display, such as its
26 * size, density, and font scaling.
27 */
28public class DisplayMetrics {
29    /**
30     * The reference density used throughout the system.
31     *
32     * @hide Pending API council approval
33     */
34    public static final int DEFAULT_DENSITY = 160;
35
36    /**
37     * The device's density.
38     * @hide
39     */
40    public static final int DEVICE_DENSITY = getDeviceDensity();
41
42    /**
43     * The absolute width of the display in pixels.
44     */
45    public int widthPixels;
46    /**
47     * The absolute height of the display in pixels.
48     */
49    public int heightPixels;
50    /**
51     * The logical density of the display.  This is a scaling factor for the
52     * Density Independent Pixel unit, where one DIP is one pixel on an
53     * approximately 160 dpi screen (for example a 240x320, 1.5"x2" screen),
54     * providing the baseline of the system's display. Thus on a 160dpi screen
55     * this density value will be 1; on a 106 dpi screen it would be .75; etc.
56     *
57     * <p>This value does not exactly follow the real screen size (as given by
58     * {@link #xdpi} and {@link #ydpi}, but rather is used to scale the size of
59     * the overall UI in steps based on gross changes in the display dpi.  For
60     * example, a 240x320 screen will have a density of 1 even if its width is
61     * 1.8", 1.3", etc. However, if the screen resolution is increased to
62     * 320x480 but the screen size remained 1.5"x2" then the density would be
63     * increased (probably to 1.5).
64     *
65     * @see #DEFAULT_DENSITY
66     */
67    public float density;
68    /**
69     * A scaling factor for fonts displayed on the display.  This is the same
70     * as {@link #density}, except that it may be adjusted in smaller
71     * increments at runtime based on a user preference for the font size.
72     */
73    public float scaledDensity;
74    /**
75     * The exact physical pixels per inch of the screen in the X dimension.
76     */
77    public float xdpi;
78    /**
79     * The exact physical pixels per inch of the screen in the Y dimension.
80     */
81    public float ydpi;
82
83    public DisplayMetrics() {
84    }
85
86    public void setTo(DisplayMetrics o) {
87        widthPixels = o.widthPixels;
88        heightPixels = o.heightPixels;
89        density = o.density;
90        scaledDensity = o.scaledDensity;
91        xdpi = o.xdpi;
92        ydpi = o.ydpi;
93    }
94
95    public void setToDefaults() {
96        widthPixels = 0;
97        heightPixels = 0;
98        density = DEVICE_DENSITY / (float) DEFAULT_DENSITY;
99        scaledDensity = density;
100        xdpi = DEVICE_DENSITY;
101        ydpi = DEVICE_DENSITY;
102    }
103
104    /**
105     * Update the display metrics based on the compatibility info and orientation
106     * {@hide}
107     */
108    public void updateMetrics(CompatibilityInfo compatibilityInfo, int orientation) {
109        int xOffset = 0;
110        if (!compatibilityInfo.isConfiguredExpandable()) {
111            // Note: this assume that configuration is updated before calling
112            // updateMetrics method.
113            int defaultWidth;
114            int defaultHeight;
115            switch (orientation) {
116                case Configuration.ORIENTATION_LANDSCAPE: {
117                    defaultWidth = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_HEIGHT * density);
118                    defaultHeight = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_WIDTH * density);
119                    break;
120                }
121                case Configuration.ORIENTATION_PORTRAIT:
122                case Configuration.ORIENTATION_SQUARE:
123                default: {
124                    defaultWidth = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_WIDTH * density);
125                    defaultHeight = (int)(CompatibilityInfo.DEFAULT_PORTRAIT_HEIGHT * density);
126                    break;
127                }
128                case Configuration.ORIENTATION_UNDEFINED: {
129                    // don't change
130                    return;
131                }
132            }
133
134            if (defaultWidth == widthPixels && defaultHeight == heightPixels) {
135                // the screen size is same as expected size. make it expandable
136                compatibilityInfo.setExpandable(true);
137            } else {
138                compatibilityInfo.setExpandable(false);
139                // adjust the size only when the device's screen is bigger.
140                if (defaultWidth < widthPixels) {
141                    // content/window's x offset in original pixels
142                    xOffset = ((widthPixels - defaultWidth) / 2);
143                    widthPixels = defaultWidth;
144                }
145                if (defaultHeight < heightPixels) {
146                    heightPixels = defaultHeight;
147                }
148            }
149        }
150        compatibilityInfo.setVisibleRect(xOffset, widthPixels, heightPixels);
151        if (compatibilityInfo.isScalingRequired()) {
152            float invertedRatio = compatibilityInfo.applicationInvertedScale;
153            density *= invertedRatio;
154            scaledDensity *= invertedRatio;
155            xdpi *= invertedRatio;
156            ydpi *= invertedRatio;
157            widthPixels *= invertedRatio;
158            heightPixels *= invertedRatio;
159        }
160    }
161
162    @Override
163    public String toString() {
164        return "DisplayMetrics{density=" + density + ", width=" + widthPixels +
165            ", height=" + heightPixels + ", scaledDensity=" + scaledDensity +
166            ", xdpi=" + xdpi + ", ydpi=" + ydpi + "}";
167    }
168
169    private static int getDeviceDensity() {
170        // qemu.sf.lcd_density can be used to override ro.sf.lcd_density
171        // when running in the emulator, allowing for dynamic configurations.
172        // The reason for this is that ro.sf.lcd_density is write-once and is
173        // set by the init process when it parses build.prop before anything else.
174        return SystemProperties.getInt("qemu.sf.lcd_density",
175                SystemProperties.getInt("ro.sf.lcd_density", DEFAULT_DENSITY));
176    }
177}
178