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+/*
+ * 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 "desktop/options.h"
+#include "utils/log.h"
+
+/** Screen DPI in fixed point units: defaults to 90, which RISC OS uses */
+css_fixed nscss_screen_dpi = INTTOFIX(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(FMULI(length, 72), nscss_screen_dpi);
+ /* 1in = 72pt */
+ case CSS_UNIT_IN: return FMULI(length, 72);
+ /* 1in = 2.54cm => 1cm = (72/2.54)pt */
+ case CSS_UNIT_CM: return FMUL(length,
+ FDIV(INTTOFIX(72), FLTTOFIX(2.54)));
+ /* 1in = 25.4mm => 1mm = (72/25.4)pt */
+ case CSS_UNIT_MM: return FMUL(length,
+ FDIV(INTTOFIX(72), FLTTOFIX(25.4)));
+ case CSS_UNIT_PT: return length;
+ /* 1pc = 12pt */
+ case CSS_UNIT_PC: return FMULI(length, 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 */
+ const css_fixed lendpi = FMUL(length, nscss_screen_dpi);
+
+ 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 < FDIVI(INTTOFIX(option_font_min_size), 10)) {
+ font_size = FDIVI(INTTOFIX(option_font_min_size), 10);
+ }
+
+ /* Expand relative length */
+ length = FMUL(length,
+ nscss_len2px(font_size, CSS_UNIT_PT, style));
+
+ /* Scale ex units: we use a fixed ratio of 1ex = 0.6em */
+ if (unit == CSS_UNIT_EX)
+ length = FMUL(length, FLTTOFIX(0.6));
+
+ return length;
+ }
+ case CSS_UNIT_PX: return length;
+ /* 1in = DPIpx */
+ case CSS_UNIT_IN: return lendpi;
+ /* 1in = 2.54cm => 1cm = (DPI/2.54)px */
+ case CSS_UNIT_CM: return FDIV(lendpi, FLTTOFIX(2.54));
+ /* 1in = 25.4mm => 1mm = (DPI/25.4)px */
+ case CSS_UNIT_MM: return FDIV(lendpi, FLTTOFIX(25.4));
+ /* 1in = 72pt => 1pt = (DPI/72)px */
+ case CSS_UNIT_PT: return FDIV(lendpi, INTTOFIX(72));
+ /* 1pc = 12pt => 1in = 6pc => 1pc = (DPI/6)px */
+ case CSS_UNIT_PC: return FDIV(lendpi, INTTOFIX(6));
+ default: break;
+ }
+
+ return 0;
+}
+