Here is how gnome-terminal (libvte9) determines the width of an
xft font with pango in vtepangocairo.c:
367 static void
368 font_info_measure_font (struct font_info *info)
369 {
370 PangoRectangle logical;
371
372 /* Estimate for ASCII characters. */
373 pango_layout_set_text (info->layout,
VTE_DRAW_SINGLE_WIDE_CHARACTERS, -1);
374 pango_layout_get_extents (info->layout, NULL, &logical);
375 /* We don't do CEIL for width since we are averaging;
376 * rounding is more accurate */
377 info->width = PANGO_PIXELS (howmany (logical.width,
strlen(VTE_DRAW_SINGLE_WIDE_CHARACTERS)));
378 info->height = PANGO_PIXELS_CEIL (logical.height);
379 info->ascent = PANGO_PIXELS_CEIL (pango_layout_get_baseline
(info->layout));
Here is the definition of VTE_DRAW_SINGLE_WIDE_CHARACTERS in
vtedraw.h:
33 #define VTE_DRAW_SINGLE_WIDE_CHARACTERS \
34 " !\"#$%&'()*+,-./" \
35 "0123456789" \
36 ":;<=>?@" \
37 "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
38 "[\\]^_`" \
39 "abcdefghijklmnopqrstuvwxyz" \
40 "{|}~" \
41 ""
and here is the definition of PANGO_PIXELS from
/usr/include/pango-1.0/pango/pango-types.h:
48 #define PANGO_PIXELS(d) (((int)(d) + 512) >> 10)
49 #define PANGO_PIXELS_FLOOR(d) (((int)(d)) >> 10)
50 #define PANGO_PIXELS_CEIL(d) (((int)(d) + 1023) >> 10)
Note this is different from rxvt-unicode which includes
double-width fonts in the rendering test, despite the comment in
rxvtfont.C:
152 // these characters are used to guess the font height and width
153 // pango uses a similar algorithm and doesn't trust the font either.
154 static uint16_t extent_test_chars[] = {
155 '0', '1', '8', 'a', 'd', 'x', 'm', 'y', 'g', 'W', 'X', '\'', '_',
156 0x00cd, 0x00d5, 0x0114, 0x0177, 0x0643, // ÍÕĔŷﻙ
157 0x304c, 0x672c, // が本
158 };
I would test changing this but frankly, it's already working
properly on my one system (Debian). On my other system (Ubuntu
Jaunty) I can't figure out the correspondance between the font
sizes I request in gnome-terminal and the font sizes I request
with size= or pixelsize= in urxvt. :-(
Aron
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