Re: [gtkmm] problems using pangomm to render text on a drawable (1.3.21)

[MHL Schulze t-online de (Martin Schulze)]

Am 03.09.2002 22:12 schrieb(en) Martin Schulze:
> Am 03.09.2002 21:05 schrieb(en) Patrick Crosby:
> > in converting one of my apps to gtkmm2 (using v1.3.21), i've been
> > trying to use pango for font rendering but haven't had much luck.  the
> > following program:
> >
> > #include <gtkmm/main.h>
> > #include <gtkmm/window.h>
> > #include <pangomm/layout.h>
> >
> > int
> > main(int argc, char* argv[])
> > {
> >     Gtk::Main kit(argc, argv);
> >
> >     Gtk::Window win(Gtk::WINDOW_TOPLEVEL);
> >
> >     win.set_default_size(500, 100);
> >     win.show_all();
> > 	     Glib::RefPtr<Pango::Context> pContext = 
> > Pango::Context::create();
> >     pContext->set_font_description(Pango::FontDescription("fixed"));
> >     Glib::RefPtr<Pango::Layout> pLayout =
> > Pango::Layout::create(pContext);
> >     pLayout->set_text("Pango Test Application");
> >
> >     Glib::RefPtr<Gdk::GC> gc = win.get_style()->get_black_gc();
> >     win.get_window()->draw_layout(gc, 10, 10, pLayout);
> > 	     kit.run();
> > }
>
> I guess you should try:
>
> Glib::RefPtr<Pango::Context> pContext = win.get_pango_context();
>
> or
>
> Glib::RefPtr<Pango::Layout> pLayout = win.create_pango_layout("Pango 
> Test Application");
>
> The output sounds as if some fields of the context were not set.

Further investigations lead to the result that Pango::Context::create()
is malfunctioning. It doesn't initialize the Context object correctly.
This is due to the fact that the generation of PangoContext structures
in pango is only provided by backend specific c functions,
e.g. pango_x_get_context(). These functions are currently not wrapped.

I don't find them very user friendly either because a program aiming
to be platform independant can't know which backend to use. So until
the pango people learn how to write a proper backend infrastructure
(like the one the ggi people use: http://www.ggi-project.org) I
propose to just get rid of Pango::Context::create() and not to
wrap the backend specific stuff. If you want to create a pango
Context, you have to use:

Gtk::Widget::create_pango_context() or Gtk::Widget::get_pango::context()

which automatically chooses the right backend or you must create the
context with an unwrapped c function like:

Glib::wrap(pango_x_get_context())

Regards,

  Martin