4 * This file is part of LyX, the document processor.
5 * Licence details can be found in the file COPYING.
9 * \author Abdelrazak Younes
11 * Full author contact details are available in file CREDITS.
14 #ifndef FONT_METRICS_H
15 #define FONT_METRICS_H
17 #include "support/strfwd.h"
22 * A class holding helper functions for determining
23 * the screen dimensions of fonts.
25 * The geometry is the standard typographical geometry,
28 * --------------+------------------<maxAscent
30 * <-------> (right bearing)
34 * origin>____ | oo oo | oo oo
36 * --------------+---ooooo--|--oooo-<baseline
39 * descent>______| oooo |
41 * --------------+----------+-------<maxDescent
43 * Caution: All char_type and docstring arguments of any method of this class
44 * are no UCS4 chars or strings if the font is a symbol font. They simply
45 * denote the code points of the font instead. You have to keep this in mind
46 * when you implement the methods in a frontend. You must not pass these
47 * parameters to a unicode conversion function in particular.
59 virtual ~FontMetrics() {}
61 /// return the maximum ascent of the font
62 virtual int maxAscent() const = 0;
63 /// return the maximum descent of the font
64 virtual int maxDescent() const = 0;
65 /// return default dimension of the font.
66 /// \warning \c width is set to zero.
67 virtual Dimension const defaultDimension() const = 0;
68 /// return the em size
69 virtual int em() const = 0;
70 /// return the x height
71 virtual int xHeight() const = 0;
72 /// return the width of a line for underlining
73 virtual int lineWidth() const = 0;
74 /// return the distance from the base line to where an underline
76 virtual int underlinePos() const = 0;
77 /// return the distance from the base line to where the strike out line
79 virtual int strikeoutPos() const = 0;
80 /// return true if font is not upright (italic or oblique)
81 virtual bool italic() const = 0;
82 /// return slope for italic font
83 virtual double italicSlope() const = 0;
85 /// return the ascent of the char in the font
86 virtual int ascent(char_type c) const = 0;
87 /// return the descent of the char in the font
88 virtual int descent(char_type c) const = 0;
89 /// return the maximum height of the font
90 inline int maxHeight() const { return maxAscent() + maxDescent(); }
91 /// return the height of the char in the font
92 inline int height(char_type c) const { return ascent(c) + descent(c); }
94 /// return the left bearing of the char in the font
95 virtual int lbearing(char_type c) const = 0;
96 /// return the right bearing of the char in the font
97 virtual int rbearing(char_type c) const = 0;
98 /// return the width of the char in the font
99 virtual int width(char_type c) const = 0;
100 /// return the width of the string in the font
101 virtual int width(docstring const & s) const = 0;
103 virtual int signedWidth(docstring const & s) const = 0;
104 /// return the inner width of the char in the font
105 inline int center(char_type c) const {
106 return (rbearing(c) - lbearing(c)) / 2;
110 * return the x offset of a position in the string. The
111 * direction of the string is forced, and the returned value
112 * is from the left edge of the word, not from the start of the string.
113 * \param rtl is true for right-to-left layout
114 * \param ws is the amount of extra inter-word space applied text justification.
116 virtual int pos2x(docstring const & s, int pos, bool rtl, double ws) const = 0;
118 * return the position in the string for a given x offset. The
119 * direction of the string is forced, and the returned value
120 * is from the left edge of the word, not from the start of the string.
121 * the offset x is updated to match the closest position in the string.
122 * \param rtl is true for right-to-left layout
123 * \param ws is the amount of extra inter-word space applied text justification.
125 virtual int x2pos(docstring const & s, int & x, bool rtl, double ws) const = 0;
127 // The places where to break a string and the width of the resulting lines.
129 Break(int l, int w) : len(l), wid(w) {}
133 typedef std::vector<Break> Breaks;
135 * Break a string in multiple fragments according to width limits.
136 * \return a sequence of Break elements.
137 * \param s is the string to break.
138 * \param first_wid is the available width for first line.
139 * \param wid is the available width for the next lines.
140 * \param rtl is true for right-to-left layout.
141 * \param force is false for breaking at word separator, true for
142 * arbitrary position.
145 breakString(docstring const & s, int first_wid, int wid, bool rtl, bool force) const = 0;
147 /// return char dimension for the font.
148 virtual Dimension const dimension(char_type c) const = 0;
150 * fill in width,ascent,descent with the values for the
151 * given string in the font.
153 virtual void rectText(docstring const & str,
156 int & descent) const = 0;
158 * fill in width,ascent,descent with the values for the
159 * given string in the font for a button with given offset.
161 virtual void buttonText(docstring const & str,
165 int & descent) const = 0;
167 /// return the number of expanding characters taken into account for
168 /// increased inter-word spacing during justification
169 virtual int countExpanders(docstring const & str) const = 0;
173 } // namespace frontend
178 /// Implementation is in Application.cpp
179 frontend::FontMetrics const & theFontMetrics(Font const & f);
180 frontend::FontMetrics const & theFontMetrics(FontInfo const & fi);
184 #endif // FONT_METRICS_H