Re: [gtkmm] how to display an image

[Paul Davis <paul linuxaudiosystems com>]

>I'm new to gtkmm (not to gtk+ though), and I have to write a simple gui
>that is supposed to display a pgm/ppm image and collect mouse clicks from
>the user. In gtk+ displaying the rgb image was done like so:
>
>gboolean on_darea_expose (GtkWidget *widget,
>                          GdkEventExpose *event,
>                          gpointer user_data)
>{
>  gdk_draw_rgb_image (widget->window,
>                      widget->style->fg_gc[GTK_STATE_NORMAL],
>                      0, 0, width, height,
>                      GDK_RGB_DITHER_MAX, rgbbuf, width * 3);
>  return 1;
>}
>
>How do I do this in gtkmm? Is there a function at a higher level than gdk,
>or do I derive my own Image from Gtk::Image with a member function which
>essentially digs for pointers to data, and wraps the gdk_draw_rgb_image
>call? Does anybody have an example of this?

there are several examples of many things in the examples directory
that comes with the source to gtkmm. a simple untested translation of
what you wrote above:

      gint
      MyWidget::on_expose_event (GdkEventExpose* event) 
      {
         get_window()->draw_rgb_image (get_style()->fg_gc (GTK_STATE_NORMAL),
				       0, 0, width, height,
				       GD_RGB_DITHER_MAX, rgbbuf, width*3);
         return TRUE;
      }				       

note that expose event handlers returns gint, not gboolean.

you'd define a MyWidget class something like this:

      class MyWidget : public Gtk::DrawingArea
      {
          public:
	     ...
	     
          protected:
	     gint on_expose_event (GdkEventExpose*);
	     ...
      };	     

i may have gotten the naming convention for virtual signal handling
methods wrong (i'm still stuck in the stone ages of gtkmm 1.2), but
the idea is that MyWidget::on_expose_event() will override
Gtk::DrawingArea::on_expose_event(), and so without any work on your
part it will be called whenever there is an expose event on the
widget.

--p