src/frontends/FontMetrics.h

   1 // -*- C++ -*-
   2 /**
   3  * \file FontMetrics.h
   4  * This file is part of LyX, the document processor.
   5  * Licence details can be found in the file COPYING.
   6  *
   7  * \author unknown
   8  * \author John Levon
   9  * \author Abdelrazak Younes
  10  *
  11  * Full author contact details are available in file CREDITS.
  12  */
  13
  14 #ifndef FONT_METRICS_H
  15 #define FONT_METRICS_H
  16
  17 #include "support/docstring.h"
  18
  19 /**
  20  * A class holding helper functions for determining
  21  * the screen dimensions of fonts.
  22  *
  23  * The geometry is the standard typographical geometry,
  24  * as follows :
  25  *
  26  * --------------+------------------<maxAscent
  27  *               |          |
  28  *               <-------> (right bearing)
  29  *               <-> (left bearing)
  30  * char ascent>___          |
  31  *               ^   oooo   |  oooo
  32  *   origin>____ |  oo  oo  | oo  oo
  33  *              \|  oo  oo  | oo  oo
  34  * --------------+---ooooo--|--oooo-<baseline
  35  *               |      oo  |
  36  * char          |  oo  oo  |
  37  * descent>______|   oooo   |
  38  *               <-  width ->
  39  * --------------+----------+-------<maxDescent
  40  *
  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.
  46  */
  47
  48 namespace lyx {
  49
  50 class Dimension;
  51
  52 namespace frontend {
  53
  54 class FontMetrics
  55 {
  56 public:
  57         virtual ~FontMetrics() {}
  58
  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 width of the char in the font
  67         virtual int width(char_type c) const = 0;
  68         /// return the ascent of the char in the font
  69         virtual int ascent(char_type c) const = 0;
  70         /// return the descent of the char in the font
  71         virtual int descent(char_type c) const = 0;
  72         /// return the left bearing of the char in the font
  73         virtual int lbearing(char_type c) const = 0;
  74         /// return the right bearing of the char in the font
  75         virtual int rbearing(char_type c) const = 0;
  76         /// return the width of the string in the font
  77         virtual int width(docstring const & s) const = 0;
  78         /// FIXME ??
  79         virtual int signedWidth(docstring const & s) const = 0;
  80         /// return char dimension for the font.
  81         virtual Dimension const dimension(char_type c) const = 0;
  82         /**
  83          * fill in width,ascent,descent with the values for the
  84          * given string in the font.
  85          */
  86         virtual void rectText(docstring const & str,
  87                 int & width,
  88                 int & ascent,
  89                 int & descent) const = 0;
  90         /**
  91          * fill in width,ascent,descent with the values for the
  92          * given string in the font for a button.
  93          */
  94         virtual void buttonText(docstring const & str,
  95                 int & width,
  96                 int & ascent,
  97                 int & descent) const = 0;
  98
  99         /// return the maximum descent of the font
 100         inline int maxHeight() const {
 101                 return maxAscent() + maxDescent();
 102         }
 103
 104         /// return the descent of the char in the font
 105         inline int height(char_type c) const
 106         {
 107                 return ascent(c) + descent(c);
 108         }
 109
 110         /// return the inner width of the char in the font
 111         inline int center(char_type c) const {
 112                 return (rbearing(c) - lbearing(c)) / 2;
 113         }
 114 };
 115
 116
 117 } // namespace frontend
 118
 119 class Font;
 120
 121 /// Implementation is in Application.cpp
 122 frontend::FontMetrics const & theFontMetrics(Font const & f);
 123
 124 } // namespace lyx
 125
 126 #endif // FONT_METRICS_H