[cairo] PDF: Font size is rounded

[Kouhei Sutou]

Hi,

In <56FE6110.8070301 at redneon.com>
  "Re: [cairo] PDF: Font size is rounded" on Fri, 1 Apr 2016 22:22:48 +1030,
  Adrian Johnson <ajohnson at redneon.com> wrote:

>> The specified font size of scaled TrueType font is rounded
>> when PDF surface is used. Is it the expected behavior?
> 
> The PDF surface should turn off hinting metrics when generating PDF
> output. Have you tried checking the metrics returned by
> cairo_scaled_font_glyph_extents()?. Use cairo_set_font_options() to turn
> off hinting metrics when doing this.

I didn't tried it. Does the following code implement your
suggestion?

    cairo_select_font_face(cr,
                           "DejaVu Sans Mono",
                           CAIRO_FONT_SLANT_NORMAL,
                           CAIRO_FONT_WEIGHT_NORMAL);
    cairo_set_font_size(cr, font_size);
    {
      cairo_font_options_t *options;
      options = cairo_font_options_create();
      cairo_get_font_options(cr, options);
      cairo_font_options_set_hint_metrics(options, CAIRO_HINT_METRICS_OFF);
      cairo_set_font_options(cr, options);
    }
    {
      cairo_scaled_font_t *font;
      cairo_text_extents_t extents;
      font = cairo_get_scaled_font(cr);
      cairo_scaled_font_text_extents(font, "abcdefghijklm", &extents);
      printf("-------------\n"
             "font size: %10f\n"
             "x_bearing: %10f\n"
             "y_bearing: %10f\n"
             "    width: %10f\n"
             "   height: %10f\n"
             "x_advance: %10f\n"
             "y_advance: %10f\n",
             font_size,
             extents.x_bearing,
             extents.y_bearing,
             extents.width,
             extents.height,
             extents.x_advance,
             extents.y_advance);
    }

The test program with the above change outputs the
following:

-------------
font size:   8.000000
x_bearing:   0.515625
y_bearing:  -6.125000
    width:  61.718750
   height:   7.843750
x_advance:  62.613281
y_advance:   0.000000
-------------
font size:   8.125000
x_bearing:   0.515625
y_bearing:  -6.125000
    width:  61.718750
   height:   7.843750
x_advance:  62.613281
y_advance:   0.000000
-------------
font size:   8.250000
x_bearing:   0.515625
y_bearing:  -6.125000
    width:  61.718750
   height:   7.843750
x_advance:  62.613281
y_advance:   0.000000
(snip)

All of 8.0 font size, 8.125 font size and 8.25 font size
reports the same width and height.

It seems that

  cairo_font_options_set_hint_metrics(options, CAIRO_HINT_METRICS_OFF);

doesn't effect the result...

Full program: http://pub.cozmixng.org/~kou/tmp/truetype-size.c


Thanks,
--
kou