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