Use pango_cairo_show_glyph_item() or cairo_show_text_glyphs()

[BehdadEsfahbod]

Currently Inkscape uses cairo_show_glyphs() to render text to PS/PDF. This is suboptimal. By using any of the two APIs listed in Summary [1] will result in better text extraction from the resulting PS/PDF.

Those two APIs are newer than cairo_show_glyphs() though. And the code needs some change to push the text down to the drawing layer as well as the glyphs.

[1] references:
pango_cairo_show_glyph_item() -- new in pango 1.22
<http://library.gnome.org/devel/pango/stable/pango-Cairo-Rendering.html#pango-cairo-show-glyph-item>
cairo_show_text_glyphs() -- new in cairo 1.8
<http://cairographics.org/manual/cairo-text.html#cairo-show-text-glyphs>

[jazzynico (jazzynico)]

According to <http://wiki.inkscape.org/wiki/index.php/Tracking_Dependencies> all the targeted distros have pango>1.28 and cairo>1.10. That would somewhat ease the migration.

The only occurrence of cairo_show_glyphs() is in src/extension/internal/cairo-render-context.cpp:1517 (trunk revision 12886).