netsurf/css/utils.c

143 lines
4.0 KiB
C

/*
* Copyright 2004 James Bursa <james@netsurf-browser.org>
* Copyright 2009 John-Mark Bell <jmb@netsurf-browser.org>
*
* This file is part of NetSurf, http://www.netsurf-browser.org/
*
* NetSurf is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* NetSurf is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <assert.h>
#include "css/utils.h"
#include "utils/nsoption.h"
#include "utils/log.h"
/** Screen DPI in fixed point units: defaults to 90, which RISC OS uses */
css_fixed nscss_screen_dpi = F_90;
/**
* Convert an absolute CSS length to points.
*
* \param length Length to convert
* \param unit Corresponding unit
* \return length in points
*/
css_fixed nscss_len2pt(css_fixed length, css_unit unit)
{
/* Length must not be relative */
assert(unit != CSS_UNIT_EM && unit != CSS_UNIT_EX);
switch (unit) {
/* We assume the screen and any other output has the same dpi */
/* 1in = DPIpx => 1px = (72/DPI)pt */
case CSS_UNIT_PX: return FDIV(FMUL(length, F_72), nscss_screen_dpi);
/* 1in = 72pt */
case CSS_UNIT_IN: return FMUL(length, F_72);
/* 1in = 2.54cm => 1cm = (72/2.54)pt */
case CSS_UNIT_CM: return FMUL(length,
FDIV(F_72, FLTTOFIX(2.54)));
/* 1in = 25.4mm => 1mm = (72/25.4)pt */
case CSS_UNIT_MM: return FMUL(length,
FDIV(F_72, FLTTOFIX(25.4)));
case CSS_UNIT_PT: return length;
/* 1pc = 12pt */
case CSS_UNIT_PC: return FMUL(length, INTTOFIX(12));
default: break;
}
return 0;
}
/**
* Convert a CSS length to pixels.
*
* \param length Length to convert
* \param unit Corresponding unit
* \param style Computed style applying to length. May be NULL if unit is
* neither em nor ex
* \return length in pixels
*/
css_fixed nscss_len2px(css_fixed length, css_unit unit,
const css_computed_style *style)
{
/* We assume the screen and any other output has the same dpi */
css_fixed px_per_unit;
assert(style != NULL || (unit != CSS_UNIT_EM && unit != CSS_UNIT_EX));
switch (unit) {
case CSS_UNIT_EM:
case CSS_UNIT_EX:
{
css_fixed font_size = 0;
css_unit font_unit = CSS_UNIT_PT;
css_computed_font_size(style, &font_size, &font_unit);
/* Convert to points */
font_size = nscss_len2pt(font_size, font_unit);
/* Clamp to configured minimum */
if (font_size < FDIV(INTTOFIX(nsoption_int(font_min_size)), F_10)) {
font_size = FDIV(INTTOFIX(nsoption_int(font_min_size)), F_10);
}
/* Convert to pixels (manually, to maximise precision)
* 1in = 72pt => 1pt = (DPI/72)px */
px_per_unit = FDIV(FMUL(font_size, nscss_screen_dpi), F_72);
/* Scale ex units: we use a fixed ratio of 1ex = 0.6em */
if (unit == CSS_UNIT_EX)
px_per_unit = FMUL(px_per_unit, FLTTOFIX(0.6));
}
break;
case CSS_UNIT_PX:
px_per_unit = F_1;
break;
/* 1in = DPIpx */
case CSS_UNIT_IN:
px_per_unit = nscss_screen_dpi;
break;
/* 1in = 2.54cm => 1cm = (DPI/2.54)px */
case CSS_UNIT_CM:
px_per_unit = FDIV(nscss_screen_dpi, FLTTOFIX(2.54));
break;
/* 1in = 25.4mm => 1mm = (DPI/25.4)px */
case CSS_UNIT_MM:
px_per_unit = FDIV(nscss_screen_dpi, FLTTOFIX(25.4));
break;
/* 1in = 72pt => 1pt = (DPI/72)px */
case CSS_UNIT_PT:
px_per_unit = FDIV(nscss_screen_dpi, F_72);
break;
/* 1pc = 12pt => 1in = 6pc => 1pc = (DPI/6)px */
case CSS_UNIT_PC:
px_per_unit = FDIV(nscss_screen_dpi, INTTOFIX(6));
break;
default:
px_per_unit = 0;
break;
}
/* Ensure we round px_per_unit to the nearest whole number of pixels:
* the use of FIXTOINT() below will truncate. */
px_per_unit += F_0_5;
/* Calculate total number of pixels */
return FMUL(length, TRUNCATEFIX(px_per_unit));
}