Re: Fatal IO error 104 when using Gtk::Context::show_text

["Jake Brownson" <jbrownson gmail com>]

Yup you're exactly right... I've filed a bug on Cairo for this...
maybe Cairo needs to be checking the font size before using it, or
handing the error from X, or maybe it's in X. Hadn't noticed my
move_to problem since it kept crashing before I got there :).

Thanks!

On Nov 16, 2007 9:13 AM, Jonathon Jongsma <jonathon quotidian org> wrote:
>
> On Wed, 2007-11-14 at 01:48 -0800, Jake Brownson wrote:
> > See below for a small program to recreate the problem.
> >
> > The window just flashes up and then I quickly get:
> > "Fatal IO error 104 (Connection reset by peer) on X server :0.0."
> >
> > If I use a debugger the crash happens on the line with the show_text
> > call, but I don't seem to get a signal, the app just crashes.
> >
> > I tried going through pango to draw text and see the same problem. I
> > sent this to a friend (who runs the same distro and version I do) and
> > he had the same problem. I also tried setting up all the font settings
> > like in example code that comes with libcairomm, but that didn't seem
> > to help.
> >
> > Am I doing something wrong? or is this a bug?
> >
> > I'm using Ubuntu 7.10, gtkmm 2.12.0, gtk 2.12.0, pango 1.18.3
> >
> > #include <gtkmm.h>
> > #include <cairomm/cairomm.h>
> >
> > class CairoDrawer : public Gtk::DrawingArea
> > {
> > public:
> >       virtual bool on_expose_event(GdkEventExpose*)
> >       {
> >               Cairo::RefPtr<Cairo::Context> c = get_window()->create_cairo_context();
> >               Gtk::Allocation allocation = get_allocation();
> >               c->scale(allocation.get_width(), allocation.get_height());
> >               c->move_to(0, 0);
> >               c->show_text("Crash Here");
> >               return true;
> >       }
> > };
> >
> > int main(int argc, char *argv[])
> > {
> >       Gtk::Main kit(argc, argv);
> >       Gtk::Window window;
> >       CairoDrawer cairo_drawer;
> >       cairo_drawer.show();
> >       window.add(cairo_drawer);
>
> As far as I can tell this is because when you call Cairo::scale(), it
> doesn't seem to affect the font scale, so it is trying to draw a huge
> font (e.g. the default font size of 10 or 12 multiplied by the size of
> the window (~200), so it's trying to draw a font size of approximately
> 2000, and I guess X has problems with that).  So you must explicitly set
> the font size after scaling the context.  But even with that, it
> wouldn't show anything, because your move_to() sets the current point to
> the top left corner of the window, and the call to show_text() will make
> the text extend right and up, which will be outside of the boundary of
> the window, so you need to change the move_to() so that the text gets
> drawn within the window.  The following code should work.
>
> #include <gtkmm.h>
> #include <cairomm/cairomm.h>
>
> class CairoDrawer : public Gtk::DrawingArea
> {
> public:
>        virtual bool on_expose_event(GdkEventExpose*)
>        {
>                Cairo::RefPtr<Cairo::Context> c =
> get_window()->create_cairo_context();
>                Gtk::Allocation allocation = get_allocation();
>                c->scale(allocation.get_width(),
> allocation.get_height());
>                const double font_size = 0.05;
>                c->move_to(0, font_size);
>                c->set_font_size(font_size);
>                c->show_text("No Crash Here");
>
>                return true;
>        }
> };
>
> int main(int argc, char *argv[])
> {
>        Gtk::Main kit(argc, argv);
>        Gtk::Window window;
>        CairoDrawer cairo_drawer;
>        cairo_drawer.show();
>        window.add(cairo_drawer);
>        kit.run(window);
> }
>
>
> --
> Jonner
>
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