[cairo] Using Pango and TrueType Fonts

Michael Gerbracht smartmails at arcor.de
Thu Feb 26 10:42:26 PST 2015

In article <54EE62FA.8020602 at behdad.org>, Behdad Esfahbod <behdad at behdad.org>
> > I would like to use Pango with Cairo to display data in graphs.[...] I am
> > using a pangocairo library for lua running on windows to generate the
> > graphics [...] First I noiced that I can display OpenType fonts but
> > TrueType fonts are not displayed (just a crossed out rectangle is shown
> > instead). I am using the pango_font_description_from_string method to set
> > the font. Do I have to convert TrueType fonts first?

> What do you mean by TrueType fonts/  Give us an example.

local outfile = "C:\\font_test.svg"
local surface = cairo.SvgSurface.create(outfile,744,526)
local cr = cairo.Context.create(surface)
cr:set_source_rgb(1, 1, 1)

local desc = pango.FontDescription.from_string("Wingdings regular 14")
local text = pangocairo.create_layout(cr)
text:set_text("Some Text", -1)
width, height = text:get_size()
cr:rotate(-alpha * math.pi / 180)
pangocairo.update_layout(cr, text)
pangocairo.show_layout(cr, text)
cr:rotate(alpha * math.pi / 180)


My problem is, that the resulting svg does not use the Wingdings font to
display the text. So I would expect the output to show some symbols from the
Wingdings font but instead it uses an standard font. I played around a little
bit and found out, that all OpenType fonts are shown correctly in the output
- also symbolic fonts. But all TrueType fonts are not shown - a default font
is used instead.

I guess I have to use pango_win32_font. But there is no
pango_win32_font_FontDescription_from_string methode so I expect that I need
to access the font in several steps but unfortunately I do not know how I can
do that. An simple example that shows the use of pango_win32_font would help.
I know the manual page but I don't understand how to combine the commands to
get what I want:

> > Is there a better way to get the dimension of a single character?
> An example would help.  Try get_extents(), which returns two different
> boxes, try both, see which one suits your need better.

Ok, thanks I will try whether this gives better results.

> > Finally I would like to be able to rotate the symbol. I can do this by
> > rotating the surface, drawing the character, and rotate back. But is this
> > the best way to do it or would you prefer another solution?

> cairo_rotate before calling into Pango should work.

Ok, so the above code is ok regarding rotation?

thank you very much!

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