DisplayMetrics.java revision d96e3dfa02b203b1fc826e80d6f9aa074ba9c250 
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.os.SystemProperties;
20
21
22/**
23 * A structure describing general information about a display, such as its
24 * size, density, and font scaling.
25 * <p>To access the DisplayMetrics members, initialize an object like this:</p>
26 * <pre> DisplayMetrics metrics = new DisplayMetrics();
27 * getWindowManager().getDefaultDisplay().getMetrics(metrics);</pre>
28 */
29public class DisplayMetrics {
30    /**
31     * Standard quantized DPI for low-density screens.
32     */
33    public static final int DENSITY_LOW = 120;
34
35    /**
36     * Standard quantized DPI for medium-density screens.
37     */
38    public static final int DENSITY_MEDIUM = 160;
39
40    /**
41     * Standard quantized DPI for 720p TV screens.  Applications should
42     * generally not worry about this density, instead targeting
43     * {@link #DENSITY_XHIGH} for 1080p TV screens.  For situations where
44     * output is needed for a 720p screen, the UI elements can be scaled
45     * automatically by the platform.
46     */
47    public static final int DENSITY_TV = 213;
48
49    /**
50     * Standard quantized DPI for high-density screens.
51     */
52    public static final int DENSITY_HIGH = 240;
53
54    /**
55     * Standard quantized DPI for extra-high-density screens.
56     */
57    public static final int DENSITY_XHIGH = 320;
58
59    /**
60     * Standard quantized DPI for extra-extra-high-density screens.  Applications
61     * should not generally worry about this density; relying on XHIGH graphics
62     * being scaled up to it should be sufficient for almost all cases.
63     */
64    public static final int DENSITY_XXHIGH = 480;
65
66    /**
67     * The reference density used throughout the system.
68     */
69    public static final int DENSITY_DEFAULT = DENSITY_MEDIUM;
70
71    /**
72     * The device's density.
73     * @hide becase eventually this should be able to change while
74     * running, so shouldn't be a constant.
75     */
76    public static final int DENSITY_DEVICE = getDeviceDensity();
77
78    /**
79     * The absolute width of the display in pixels.
80     */
81    public int widthPixels;
82    /**
83     * The absolute height of the display in pixels.
84     */
85    public int heightPixels;
86    /**
87     * The logical density of the display.  This is a scaling factor for the
88     * Density Independent Pixel unit, where one DIP is one pixel on an
89     * approximately 160 dpi screen (for example a 240x320, 1.5"x2" screen),
90     * providing the baseline of the system's display. Thus on a 160dpi screen
91     * this density value will be 1; on a 120 dpi screen it would be .75; etc.
92     *
93     * <p>This value does not exactly follow the real screen size (as given by
94     * {@link #xdpi} and {@link #ydpi}, but rather is used to scale the size of
95     * the overall UI in steps based on gross changes in the display dpi.  For
96     * example, a 240x320 screen will have a density of 1 even if its width is
97     * 1.8", 1.3", etc. However, if the screen resolution is increased to
98     * 320x480 but the screen size remained 1.5"x2" then the density would be
99     * increased (probably to 1.5).
100     *
101     * @see #DENSITY_DEFAULT
102     */
103    public float density;
104    /**
105     * The screen density expressed as dots-per-inch.  May be either
106     * {@link #DENSITY_LOW}, {@link #DENSITY_MEDIUM}, or {@link #DENSITY_HIGH}.
107     */
108    public int densityDpi;
109    /**
110     * A scaling factor for fonts displayed on the display.  This is the same
111     * as {@link #density}, except that it may be adjusted in smaller
112     * increments at runtime based on a user preference for the font size.
113     */
114    public float scaledDensity;
115    /**
116     * The exact physical pixels per inch of the screen in the X dimension.
117     */
118    public float xdpi;
119    /**
120     * The exact physical pixels per inch of the screen in the Y dimension.
121     */
122    public float ydpi;
123
124    /**
125     * The reported display width prior to any compatibility mode scaling
126     * being applied.
127     * @hide
128     */
129    public int noncompatWidthPixels;
130    /**
131     * The reported display height prior to any compatibility mode scaling
132     * being applied.
133     * @hide
134     */
135    public int noncompatHeightPixels;
136    /**
137     * The reported display density prior to any compatibility mode scaling
138     * being applied.
139     * @hide
140     */
141    public float noncompatDensity;
142    /**
143     * The reported scaled density prior to any compatibility mode scaling
144     * being applied.
145     * @hide
146     */
147    public float noncompatScaledDensity;
148    /**
149     * The reported display xdpi prior to any compatibility mode scaling
150     * being applied.
151     * @hide
152     */
153    public float noncompatXdpi;
154    /**
155     * The reported display ydpi prior to any compatibility mode scaling
156     * being applied.
157     * @hide
158     */
159    public float noncompatYdpi;
160
161    public DisplayMetrics() {
162    }
163
164    public void setTo(DisplayMetrics o) {
165        widthPixels = o.widthPixels;
166        heightPixels = o.heightPixels;
167        density = o.density;
168        densityDpi = o.densityDpi;
169        scaledDensity = o.scaledDensity;
170        xdpi = o.xdpi;
171        ydpi = o.ydpi;
172        noncompatWidthPixels = o.noncompatWidthPixels;
173        noncompatHeightPixels = o.noncompatHeightPixels;
174        noncompatDensity = o.noncompatDensity;
175        noncompatScaledDensity = o.noncompatScaledDensity;
176        noncompatXdpi = o.noncompatXdpi;
177        noncompatYdpi = o.noncompatYdpi;
178    }
179
180    public void setToDefaults() {
181        widthPixels = 0;
182        heightPixels = 0;
183        density = DENSITY_DEVICE / (float) DENSITY_DEFAULT;
184        densityDpi = DENSITY_DEVICE;
185        scaledDensity = density;
186        xdpi = DENSITY_DEVICE;
187        ydpi = DENSITY_DEVICE;
188        noncompatWidthPixels = 0;
189        noncompatHeightPixels = 0;
190    }
191
192    @Override
193    public String toString() {
194        return "DisplayMetrics{density=" + density + ", width=" + widthPixels +
195            ", height=" + heightPixels + ", scaledDensity=" + scaledDensity +
196            ", xdpi=" + xdpi + ", ydpi=" + ydpi + "}";
197    }
198
199    private static int getDeviceDensity() {
200        // qemu.sf.lcd_density can be used to override ro.sf.lcd_density
201        // when running in the emulator, allowing for dynamic configurations.
202        // The reason for this is that ro.sf.lcd_density is write-once and is
203        // set by the init process when it parses build.prop before anything else.
204        return SystemProperties.getInt("qemu.sf.lcd_density",
205                SystemProperties.getInt("ro.sf.lcd_density", DENSITY_DEFAULT));
206    }
207}
208