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 the default leading of the font (often 0)
64 virtual int leading() 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;
81 /// return the width of the char in the font
82 virtual int width(char_type c) const = 0;
83 /// return the ascent of the char in the font
84 virtual int ascent(char_type c) const = 0;
85 /// return the descent of the char in the font
86 virtual int descent(char_type c) const = 0;
87 /// return the left bearing of the char in the font
88 virtual int lbearing(char_type c) const = 0;
89 /// return the right bearing of the char in the font
90 virtual int rbearing(char_type c) const = 0;
91 /// return the width of the string in the font
92 virtual int width(docstring const & s) const = 0;
94 virtual int signedWidth(docstring const & s) const = 0;
96 * return the x offset of a position in the string. The
97 * direction of the string is forced, and the returned value
98 * is from the left edge of the word, not from the start of the string.
99 * \param rtl is true for right-to-left layout
100 * \param ws is the amount of extra inter-word space applied text justication.
102 virtual int pos2x(docstring const & s, int pos, bool rtl, double ws) const = 0;
104 * return the position in the string for a given x offset. The
105 * direction of the string is forced, and the returned value
106 * is from the left edge of the word, not from the start of the string.
107 * the offset x is updated to match the closest position in the string.
108 * \param rtl is true for right-to-left layout
109 * \param ws is the amount of extra inter-word space applied text justication.
111 virtual int x2pos(docstring const & s, int & x, bool rtl, double ws) const = 0;
113 * Break string at width at most x.
114 * \return true if successful
115 * \param rtl is true for right-to-left layout
116 * \param force is false for breaking at word separator, true for
117 * arbitrary position.
119 virtual bool breakAt(docstring & s, int & x, bool rtl, bool force) const = 0;
120 /// return char dimension for the font.
121 virtual Dimension const dimension(char_type c) const = 0;
123 * fill in width,ascent,descent with the values for the
124 * given string in the font.
126 virtual void rectText(docstring const & str,
129 int & descent) const = 0;
131 * fill in width,ascent,descent with the values for the
132 * given string in the font for a button with given offset.
134 virtual void buttonText(docstring const & str,
138 int & descent) const = 0;
140 /// return the maximum descent of the font
141 inline int maxHeight() const { return maxAscent() + maxDescent(); }
143 /// return the descent of the char in the font
144 inline int height(char_type c) const { return ascent(c) + descent(c); }
146 /// return the inner width of the char in the font
147 inline int center(char_type c) const {
148 return (rbearing(c) - lbearing(c)) / 2;
151 /// return the number of expanding characters taken into account for
152 /// increased inter-word spacing during justification
153 virtual int countExpanders(docstring const & str) const = 0;
157 } // namespace frontend
162 /// Implementation is in Application.cpp
163 frontend::FontMetrics const & theFontMetrics(Font const & f);
164 frontend::FontMetrics const & theFontMetrics(FontInfo const & fi);
168 #endif // FONT_METRICS_H