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Diffstat (limited to 'content/handlers/css/utils.c')
| -rw-r--r-- | content/handlers/css/utils.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/content/handlers/css/utils.c b/content/handlers/css/utils.c new file mode 100644 index 000000000..59ad41216 --- /dev/null +++ b/content/handlers/css/utils.c @@ -0,0 +1,127 @@ +/* + * 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 "utils/nsoption.h" +#include "utils/log.h" + +#include "utils.h" + +/** Screen DPI in fixed point units: defaults to 90, which RISC OS uses */ +css_fixed nscss_screen_dpi = F_90; + +/* exported interface documented in content/handlers/css/utils.h */ +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; +} + + +/* exported interface documented in content/handlers/css/utils.h */ +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)); +} |