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ttext: tweaks to rendering, especially on Windows

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This restores some code that wasn't being used on Windows to strip pre-multiplied alpha
from the text render before passing it to SDL_CreateRGBSurfaceFrom. Despite the code comment
to the contrary, enabling this code doesn't seem to mutilate the text output unless
pango_cairo_show_layout is called *after* stripping.

Unless I'm misunderstanding, pango_cairo_show_layout would get called 4 times on Windows.
Removing 3 of those calls meant the use of CAIRO_ANTIALIAS_GRAY as a fix for bug #21648
now resulted in horrible-looking text. Changing the AA method to CAIRO_ANTIALIAS_GRAY now
seems to produce acceptable results.

The resulting text is only slightly different from that produced before this change, though
very slightly more anti-aliased and a little grayer.
This commit is contained in:
Charles Dang 2016-08-07 20:56:19 +11:00
parent 40bc508f7f
commit c91b200b7a
1 changed files with 3 additions and 21 deletions
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24
src/text.cpp
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@ -136,15 +136,8 @@ ttext::ttext() :
cairo_font_options_t *fo = cairo_font_options_create();
cairo_font_options_set_hint_style(fo, CAIRO_HINT_STYLE_FULL);
cairo_font_options_set_hint_metrics(fo, CAIRO_HINT_METRICS_ON);
#ifdef _WIN32
// Cairo on Windows (at least the latest available version from gtk.org
// as of 2014-02-22, version 1.10.2) has issues with ClearType resulting
// in glitchy anti-aliasing with CAIRO_ANTIALIAS_SUBPIXEL or
// CAIRO_ANTIALIAS_DEFAULT, but not CAIRO_ANTIALIAS_GRAY, so we use that
// as a workaround until the Windows package is updated to use a newer
// version of Cairo (see Wesnoth bug #21648).
cairo_font_options_set_antialias(fo, CAIRO_ANTIALIAS_GRAY);
#endif
cairo_font_options_set_antialias(fo, CAIRO_ANTIALIAS_DEFAULT);
pango_cairo_context_set_font_options(context_, fo);
cairo_font_options_destroy(fo);
}
@ -706,7 +699,6 @@ struct decode_table
static struct decode_table decode_table;
#ifndef _WIN32
/**
* Converts from premultiplied alpha to plain alpha.
* @param p pointer to a 4-byte endian-dependent color.
@ -739,7 +731,6 @@ static void decode_pixel(unsigned char *p)
DECODE(1);
DECODE(2);
}
#endif
void ttext::rerender(const bool force) const
@ -771,8 +762,6 @@ void ttext::rerender(const bool force) const
pango_cairo_show_layout(cr, layout_);
#ifndef _WIN32
// The cairo surface is in CAIRO_FORMAT_ARGB32 which uses
// pre-multiplied alpha. SDL doesn't use that so the pixels need to be
// decoded again.
@ -783,13 +772,7 @@ void ttext::rerender(const bool force) const
decode_pixel(pixel);
}
}
#else
// The solution code above doesn't seem to work properly on windows so
// use the old trick of drawing the same text a few times.
pango_cairo_show_layout(cr, layout_);
pango_cairo_show_layout(cr, layout_);
pango_cairo_show_layout(cr, layout_);
#endif
surface_.assign(SDL_CreateRGBSurfaceFrom(
surface_buffer_, width, height, 32, stride,
0x00FF0000, 0x0000FF00, 0x000000FF, 0xFF000000));
@ -908,4 +891,3 @@ bool ttext::set_markup_helper(const std::string& text)
}
} // namespace font