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"
20 * A class holding helper functions for determining
21 * the screen dimensions of fonts.
23 * The geometry is the standard typographical geometry,
26 * --------------+------------------<maxAscent
28 * <-------> (right bearing)
32 * origin>____ | oo oo | oo oo
34 * --------------+---ooooo--|--oooo-<baseline
37 * descent>______| oooo |
39 * --------------+----------+-------<maxDescent
41 * Caution: All char_type and docstring arguments of any method of this class
42 * are no UCS4 chars or strings if the font is a symbol font. They simply
43 * denote the code points of the font instead. You have to keep this in mind
44 * when you implement the methods in a frontend. You must not pass these
45 * parameters to a unicode conversion function in particular.
57 virtual ~FontMetrics() {}
59 /// return the maximum ascent of the font
60 virtual int maxAscent() const = 0;
61 /// return the maximum descent of the font
62 virtual int maxDescent() const = 0;
63 /// return default dimension of the font.
64 /// \warning \c width is set to zero.
65 virtual Dimension const defaultDimension() const = 0;
66 /// return the em size
67 virtual int em() const = 0;
68 /// return the x height
69 virtual int xHeight() const = 0;
70 /// return the width of a line for underlining
71 virtual int lineWidth() const = 0;
72 /// return the distance from the base line to where an underline
74 virtual int underlinePos() const = 0;
75 /// return the distance from the base line to where the strike out line
77 virtual int strikeoutPos() const = 0;
79 /// return the width of the char in the font
80 virtual int width(char_type c) const = 0;
81 /// return the ascent of the char in the font
82 virtual int ascent(char_type c) const = 0;
83 /// return the descent of the char in the font
84 virtual int descent(char_type c) const = 0;
85 /// return the left bearing of the char in the font
86 virtual int lbearing(char_type c) const = 0;
87 /// return the right bearing of the char in the font
88 virtual int rbearing(char_type c) const = 0;
89 /// return the width of the string in the font
90 virtual int width(docstring const & s) const = 0;
92 virtual int signedWidth(docstring const & s) const = 0;
94 * return the x offset of a position in the string. The
95 * direction of the string is forced, and the returned value
96 * is from the left edge of the word, not from the start of the string.
97 * \param rtl is true for right-to-left layout
98 * \param ws is the amount of extra inter-word space applied text justication.
100 virtual int pos2x(docstring const & s, int pos, bool rtl, double ws) const = 0;
102 * return the position in the string for a given x offset. The
103 * direction of the string is forced, and the returned value
104 * is from the left edge of the word, not from the start of the string.
105 * the offset x is updated to match the closest position in the string.
106 * \param rtl is true for right-to-left layout
107 * \param ws is the amount of extra inter-word space applied text justication.
109 virtual int x2pos(docstring const & s, int & x, bool rtl, double ws) const = 0;
111 * Break string at width at most x.
112 * \return true if successful
113 * \param rtl is true for right-to-left layout
114 * \param force is false for breaking at word separator, true for
115 * arbitrary position.
117 virtual bool breakAt(docstring & s, int & x, bool rtl, bool force) const = 0;
118 /// return char dimension for the font.
119 virtual Dimension const dimension(char_type c) const = 0;
121 * fill in width,ascent,descent with the values for the
122 * given string in the font.
124 virtual void rectText(docstring const & str,
127 int & descent) const = 0;
129 * fill in width,ascent,descent with the values for the
130 * given string in the font for a button with given offset.
132 virtual void buttonText(docstring const & str,
136 int & descent) const = 0;
138 /// return the maximum descent of the font
139 inline int maxHeight() const { return maxAscent() + maxDescent(); }
141 /// return the descent of the char in the font
142 inline int height(char_type c) const { return ascent(c) + descent(c); }
144 /// return the inner width of the char in the font
145 inline int center(char_type c) const {
146 return (rbearing(c) - lbearing(c)) / 2;
149 /// return the number of expanding characters taken into account for
150 /// increased inter-word spacing during justification
151 virtual int countExpanders(docstring const & str) const = 0;
155 } // namespace frontend
160 /// Implementation is in Application.cpp
161 frontend::FontMetrics const & theFontMetrics(Font const & f);
162 frontend::FontMetrics const & theFontMetrics(FontInfo const & fi);
166 #endif // FONT_METRICS_H