Hello Stewart,

I didn't know how to answer your question, but I've found an
implementation of the same call. See the send of #listFamilies:count:
message in:
https://github.com/pharo-spec/gtk-bindings/blob/9cda0f563023c68714c6c54e6c5f77f3c57b6c90/src/Pango/PangoFontMap.class.st#L53

Cheers,
Mart��n

On Tue, Jan 25, 2022 at 7:36 AM Stewart MacLean <stewmaclean@gmail.com> wrote:
>
> Hi,
>
> I'm trying to figure out how to implement code to retrieve a list of font families using the Pango libraries. The key function definition is:
>
>�� https://docs.gtk.org/Pango/method.FontMap.list_families.html
>
> void
> pango_font_map_list_families (
>�� ��PangoFontMap* fontmap,
>�� ��PangoFontFamily*** families,
>�� ��int* n_families
> )
>
> I've found some C code, which is shown below. The tricky�� bit is the ***. I've managed to get this working in VisualWorks (code also below), but can't figure out how to do this using the Pharo FFI.
>
> I've managed to get the basic Pango functionality going, but I can't figure out how to use ExternalAddress to do this. Running on a MacMini M1.
>
> Any pointers (:)) appreciated!
>
> Thanks,
>
> Stew
>
> C Version
> ----------------
>�� #include <glib.h>
> #include <pango/pangocairo.h>
>
> static void
> list_fonts ()
> {
>�� �� ��int i;
>�� �� ��PangoFontFamily ** families;
>�� �� ��int n_families;
>�� �� ��PangoFontMap * fontmap;
>
>�� �� ��fontmap = pango_cairo_font_map_get_default();
>�� �� ��pango_font_map_list_families (fontmap, & families, & n_families);
>�� �� ��printf ("There are %d families\n", n_families);
>�� �� ��for (i = 0; i < n_families; i++) {
>�� �� �� �� ��PangoFontFamily * family = families[i];
>�� �� �� �� ��const char * family_name;
>
>�� �� �� �� ��family_name = pango_font_family_get_name (family);
>�� �� �� �� ��printf ("Family %d: %s\n", i, family_name);
>�� �� ��}
>�� �� ��g_free (families);
> }
>
> int main (int argc, char ** argv)
> {
>�� �� ��list_fonts ();
>�� �� ��return 0;
> }
>
> =================================
> VisualWorks Version
> ---------------------------
> availableFamilyNames
> "
> Transcript clear.
> (FontFamily availableFamilyNames asSortedCollection: [: a : b | a < b]) do: [: each | Transcript cr; show: each].
>
> NamedFontSelector open
> "
>
> "08/09/20 SIM. Modified to work on 64bit.
> Clues obtained from:
> XSurface class >>displaySurface:
> DisplaySurface>>cairoVisual
> PDFSurface class>>versions"
>
> | listPointer sizePointer ffPointers result |
>
> ObjectMemory is64Bit
>�� ��ifTrue:
>�� �� ��[listPointer := CIntegerType unsignedLongLong gcMalloc.
>�� �� ��sizePointer := listPointer sizeof gcCopyToHeap]
> ifFalse:
>�� �� [listPointer := 0 gcCopyToHeap.
>�� �� sizePointer := 0 gcCopyToHeap].
>
> LibPango default
> pango_font_map_list_families: LibPango default pango_cairo_font_map_get_default
> with: listPointer
> with: sizePointer.
>
> ffPointers :=
> (ObjectMemory is64Bit
>�� �� ifTrue: [CIntegerType unsignedLongLong]
>�� �� ifFalse: [ CIntegerType unsignedInt])
>�� �� �� �� ��newPointerToAddress: listPointer contents.
>
> result := OrderedCollection new: sizePointer contents.
> sizePointer contents timesRepeat:
>�� �� �� [result
>�� �� �� �� �� add: (LibPango default pango_font_family_get_name: ffPointers contents) utf8.
>�� �� �� ��ffPointers += 1].
> LibPango default g_free: listPointer contents.
> ^result
>
>