1 /*
2 * Copyright (c) 1998, 2020, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.awt.font;
27
28 /**
29 * The {@code LineMetrics} class allows access to the
30 * metrics needed to layout characters along a line
31 * and to layout of a set of lines. A {@code LineMetrics}
32 * object encapsulates the measurement information associated
33 * with a run of text.
34 * <p>
35 * Fonts can have different metrics for different ranges of
36 * characters. The {@code getLineMetrics} methods of
37 * {@link java.awt.Font Font} take some text as an argument
38 * and return a {@code LineMetrics} object describing the
39 * metrics of the initial number of characters in that text, as
40 * returned by {@link #getNumChars}.
41 */
42
43
44 public abstract class LineMetrics {
45
46 /**
47 * Constructor for subclasses to call.
48 */
49 protected LineMetrics() {}
50
51 /**
52 * Returns the number of characters ({@code char} values) in the text whose
53 * metrics are encapsulated by this {@code LineMetrics}
54 * object.
55 * @return the number of characters ({@code char} values) in the text with which
56 * this {@code LineMetrics} was created.
57 */
58 public abstract int getNumChars();
59
60 /**
61 * Returns the ascent of the text. The ascent
62 * is the distance from the baseline
63 * to the ascender line. The ascent usually represents the
64 * the height of the capital letters of the text. Some characters
65 * can extend above the ascender line.
66 * @return the ascent of the text.
67 */
68 public abstract float getAscent();
69
70 /**
71 * Returns the descent of the text. The descent
72 * is the distance from the baseline
73 * to the descender line. The descent usually represents
74 * the distance to the bottom of lower case letters like
75 * 'p'. Some characters can extend below the descender
76 * line.
77 * @return the descent of the text.
78 */
79 public abstract float getDescent();
80
81 /**
82 * Returns the leading of the text. The
83 * leading is the recommended
84 * distance from the bottom of the descender line to the
85 * top of the next line.
86 * @return the leading of the text.
87 */
88 public abstract float getLeading();
89
90 /**
91 * Returns the height of the text. The
92 * height is equal to the sum of the ascent, the
93 * descent and the leading.
94 * @return the height of the text.
95 */
96 public abstract float getHeight();
97
98 /**
99 * Returns the baseline index of the text.
100 * The index is one of
101 * {@link java.awt.Font#ROMAN_BASELINE ROMAN_BASELINE},
102 * {@link java.awt.Font#CENTER_BASELINE CENTER_BASELINE},
103 * {@link java.awt.Font#HANGING_BASELINE HANGING_BASELINE}.
104 * @return the baseline of the text.
105 */
106 public abstract int getBaselineIndex();
107
108 /**
109 * Returns the baseline offsets of the text,
110 * relative to the baseline of the text. The
111 * offsets are indexed by baseline index. For
112 * example, if the baseline index is
113 * {@code CENTER_BASELINE} then
114 * {@code offsets[HANGING_BASELINE]} is usually
115 * negative, {@code offsets[CENTER_BASELINE]}
116 * is zero, and {@code offsets[ROMAN_BASELINE]}
117 * is usually positive.
118 * @return the baseline offsets of the text.
119 */
120 public abstract float[] getBaselineOffsets();
121
122 /**
123 * Returns the position of the strike-through line
124 * relative to the baseline.
125 * @return the position of the strike-through line.
126 */
127 public abstract float getStrikethroughOffset();
128
129 /**
130 * Returns the thickness of the strike-through line.
131 * @return the thickness of the strike-through line.
132 */
133 public abstract float getStrikethroughThickness();
134
135 /**
136 * Returns the position of the underline relative to
137 * the baseline.
138 * @return the position of the underline.
139 */
140 public abstract float getUnderlineOffset();
141
142 /**
143 * Returns the thickness of the underline.
144 * @return the thickness of the underline.
145 */
146 public abstract float getUnderlineThickness();
147 }