Pango+Cario : proper font rendering under Win32

Dear Pango/Cairo enthusiast,

I have written a terminal to gnuplot ( which draws thanks to cairo, and handles text via pango... and I have some questions about font rendering.

I use a generic cairo "image" surface, and create my text layouts with pango_cairo_create_layout(cairo_t*) or pango_cairo_font_map_get_default() plus other calls.
I choose my font with :

desc = pango_font_description_new ();
pango_font_description_set_family (desc, (const char*) plot->fontname);
pango_font_description_set_size (desc, (int) (plot->fontsize*PANGO_SCALE) );

where plot->fontname is a char* containing the desired font name, usually Sans, Verdana or other usual fonts.

Under Linux, the result is good, the fonts are properly antialiased.
However, under MS-Windows (with binary snapshots of cairo1.0.2/pango1.10.1 distributed at, the same code gives uglier results, with black text "over-antialiased" with a subpixel method.

Here are screenshots : (linux, various fonts, result satisfying) (windows, using font "Sans", size 15)

I have tried to modify manually the way antialiasing is set. I use :

   PangoFontMap* fontmap = pango_cairo_font_map_get_default();
PangoContext* context = pango_cairo_font_map_create_context(PANGO_CAIRO_FONT_MAP(fontmap));

   desc = pango_font_description_new ();
   pango_font_description_set_family (desc, (const char*) plot->fontname);
pango_font_description_set_size (desc, (int) (plot->fontsize*PANGO_SCALE) );
   pango_context_set_font_description (context, desc);
   pango_font_description_free (desc);
cairo_font_options_t* options = cairo_font_options_create();
   pango_cairo_context_set_font_options(context, options);
layout = pango_layout_new (context);

With this code, my settings (cairo_font_options_set_...) are not taken into account unless I hardcode the font in the file with, for example :
   pango_font_description_set_family (desc, "Sans");
I think it is a bug...

If I use a description_from_string, the settings are taken into account properly :
   desc = pango_font_description_from_string ("Sans 20");
   pango_context_set_font_description (context, desc);
   pango_font_description_free (desc);

So that's a first point : how to make the font options taken into account with pango_font_description_set_family (desc, (const char*) plot->fontname)) ??? (note that plot->fontname contains exactly "Sans" or other font names, so the problem is not in it)

Then, even when hardcoding the fontfamily and trying to tweak the font options, I did not manage to get perfect results. With CAIRO_ANTIALIAS_GRAY, I observed that there's no antialiasing below font size = 14, for "Sans". With CAIRO_ANTIALIAS_SUBPIXEL, I get the same unsatisfying results as reported above and illustrated in the screenshot. Other settings (hint_style and hint_metrics) don't give noticeable changes to my eyes.

So here's the second point : how to get correct antialiasing, such as gray antialiasing even at low font sizes, or subpixel antialiasing but more accurate compared to the general appearance of fonts under Windows ?

To give you a whole idea, here is a screenshot of the whole screen, where you can compare the fonts drawn under cairo/pango with subpixel_antialiasing, hint_style=full, and fonts in Thunderbird, which are also drawn with subpixel antialiasing, but really more readable :

I hope some of you may be able to give me advice.

Thanks for your consideration and time, and thanks for the great work already done on pango and cairo !

Timothée Lecomte

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