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66fa801e74
The computation of length on screen depend in particular of the computation of the size of an em. Many places of the code used to rely on the width of the M character, which is not really correct: http://en.wikipedia.org/wiki/Em_%28typography%29 In digital typography, the best value to use is the point size of the font. * Implement FontMetrics::em(), which returns the value in pixels of the EM unit. Convert code to use it. * Introduce Length::inPixel(MetricsBase const &), which takes the textwidth and em information from the MetricsBase object. Convert code to use it. * Fix several places where Length::inPixel is used without a proper em value. * add mathed_font_em() helper function. It should eventually be removed like some other functions in MathSupport. * Add dummy implementation of FontMetrics to tex2lyx for linking purposes.
140 lines
4.2 KiB
C++
140 lines
4.2 KiB
C++
// -*- C++ -*-
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/**
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* \file FontMetrics.h
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* This file is part of LyX, the document processor.
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* Licence details can be found in the file COPYING.
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*
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* \author unknown
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* \author John Levon
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* \author Abdelrazak Younes
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*
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* Full author contact details are available in file CREDITS.
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*/
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#ifndef FONT_METRICS_H
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#define FONT_METRICS_H
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#include "support/strfwd.h"
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/**
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* A class holding helper functions for determining
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* the screen dimensions of fonts.
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*
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* The geometry is the standard typographical geometry,
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* as follows :
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*
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* --------------+------------------<maxAscent
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* | |
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* <-------> (right bearing)
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* <-> (left bearing)
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* char ascent>___ |
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* ^ oooo | oooo
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* origin>____ | oo oo | oo oo
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* \| oo oo | oo oo
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* --------------+---ooooo--|--oooo-<baseline
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* | oo |
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* char | oo oo |
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* descent>______| oooo |
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* <- width ->
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* --------------+----------+-------<maxDescent
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*
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* Caution: All char_type and docstring arguments of any method of this class
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* are no UCS4 chars or strings if the font is a symbol font. They simply
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* denote the code points of the font instead. You have to keep this in mind
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* when you implement the methods in a frontend. You must not pass these
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* parameters to a unicode conversion function in particular.
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*/
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namespace lyx {
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class Dimension;
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namespace frontend {
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class FontMetrics
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{
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public:
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virtual ~FontMetrics() {}
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/// return the maximum ascent of the font
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virtual int maxAscent() const = 0;
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/// return the maximum descent of the font
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virtual int maxDescent() const = 0;
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/// return default dimension of the font.
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/// \warning \c width is set to zero.
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virtual Dimension const defaultDimension() const = 0;
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/// return the em size
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virtual int em() const = 0;
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/// return the width of the char in the font
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virtual int width(char_type c) const = 0;
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/// return the ascent of the char in the font
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virtual int ascent(char_type c) const = 0;
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/// return the descent of the char in the font
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virtual int descent(char_type c) const = 0;
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/// return the left bearing of the char in the font
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virtual int lbearing(char_type c) const = 0;
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/// return the right bearing of the char in the font
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virtual int rbearing(char_type c) const = 0;
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/// return the width of the string in the font
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virtual int width(docstring const & s) const = 0;
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/// FIXME ??
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virtual int signedWidth(docstring const & s) const = 0;
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/**
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* return the x offset of a position in the string. The
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* direction of the string is forced, and the returned value
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* is from the left edge of the word, not from the start of the string.
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*/
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virtual int pos2x(docstring const & s, int pos, bool rtl) const = 0;
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/**
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* return the position in the string for a given x offset. The
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* direction of the string is forced, and the returned value
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* is from the left edge of the word, not from the start of the string.
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* the offset x is updated to match the closest position in the string.
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*/
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virtual int x2pos(docstring const & s, int & x, bool rtl) const = 0;
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/// return char dimension for the font.
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virtual Dimension const dimension(char_type c) const = 0;
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/**
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* fill in width,ascent,descent with the values for the
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* given string in the font.
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*/
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virtual void rectText(docstring const & str,
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int & width,
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int & ascent,
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int & descent) const = 0;
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/**
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* fill in width,ascent,descent with the values for the
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* given string in the font for a button.
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*/
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virtual void buttonText(docstring const & str,
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int & width,
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int & ascent,
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int & descent) const = 0;
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/// return the maximum descent of the font
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inline int maxHeight() const { return maxAscent() + maxDescent(); }
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/// return the descent of the char in the font
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inline int height(char_type c) const { return ascent(c) + descent(c); }
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/// return the inner width of the char in the font
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inline int center(char_type c) const {
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return (rbearing(c) - lbearing(c)) / 2;
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}
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};
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} // namespace frontend
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class Font;
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class FontInfo;
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/// Implementation is in Application.cpp
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frontend::FontMetrics const & theFontMetrics(Font const & f);
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frontend::FontMetrics const & theFontMetrics(FontInfo const & fi);
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} // namespace lyx
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#endif // FONT_METRICS_H
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