Bees…

When I was looking for new ink cartridges last night, I found the website INKredible.co.uk and they had a really good price against a very promising looking set of replacement cartridges. Unfortunately, when I got to the checkout stage, my SSL-Blacklist Extension in Firefox warned me about a connection based on md5 which is not deemed secure any more. I dropped them a ticket explaining the situation and within less than 24 hours they had re-issued their certificate and notified me of the changes. Since I had been unwilling tto spend more money on a similar product somewhere else, I promptly went and bought the set of cartridges I had had in mind before. I love good customer service, I am sure we all do, and so I thought I put this little praise out there. Maybe it will help other people make a more informed decision, who knows.

Ok, so this wasn’t too hard, but there was a little hiccup and so I thought I’d briefly note down the solution.

The first step is to find the actual driver because the iP4500 model not listed in the standard set of drivers (at least not in mine). Choosing one of the other PIXMA drivers (like the 4100) will only result in blanc pages.

1) Find the drivers on the Canon website (google search for it. I would post the link but the page is currently not working for me, it did so a minute ago though).
There are two files, one is a common driver (file name: cnijfilter-common-2.80-1.i386.rpm) and the other one is the model specific driver (file name: cnijfilter-ip4500series-2.80-1.i386.rpm). They need to be installed in order, so I suggest you also download the instructions, a file called: guideip4500series-pd-2.80-1.tar.tar
The instructions are very clear and come in flavours for Fedora 7, openSUSE 10.3 and Ubuntu 7.04 (all the same file).

2) After the installation I tried to print but without success. Looking at the printer properties (Control Center - Printer - <printer name> (right click) -> Properties) I found the error message /usr/lib64/cups/backend/cnij_usb failed. I did a google search, and the solution is the following (as found on Linuxuser LigLog).

Open a terminal and as root, type the following two commands:

ln /usr/lib/cups/backend/cnij_usb /usr/lib64/cups/backend/cnij_usb
ln /usr/lib/cups/filter/pstocanonij /usr/lib64/cups/filter/pstocanonij

Restart CUPS ( /etc/init.d/cups restart) and it should work.

See my former post on “How to access two GTK+ widgets from a single callback function (using libglade)” for a different way of achieving the same thing. However, the method described below is the official way of doing things and thus to be preferred.

GtkWidgets are derived from GObjects. They can be cast back and forth using the G_OBJECT() and GTK_WIDGET() macros. Use g_object_set_data() to attach a gpointer and its key to a GObject of your choice (find the definition at library.gnome.org). The pointers can then be retrieved wherever the GObject that they have been attached to, is available. This is done using g_object_get_data(). Attaching two pointers to two different GtkWidgets to the main window widget, will enable you to call on them from any callback function you use.

I hope the code below may be useful to some people. I am new to GTK+ myself so I am not sure whether this is the best solution, but it is certainly on of the better ones. Other solutions would be to use globals or possibly structs.

What the function does:
It is a simple callback function that has been connected to the GladeXML file by the following line:
glade_xml_signal_connect(gxml, "on_execute_recording_button_clicked", G_CALLBACK(on_execute_recording_button_clicked));
where gxml is the main GladeXML file that was created using Glade-3. Look on Micah Carrick’s blog for information and tutorials on Glade.

Using glade_get_widget_tree() we can get hold of the GladeXML file inside the callback function without using globals. From there is it easy, we simply use the glade_xml_get_widget() function to create the widgets we want.

Here is the code:

/*
 * Function aquires a handle on the GtkProgressBar and the GtkTreeView widget
 * then calls a function that works on both widgets.
 *
*/
void on_execute_recording_button_clicked  (GtkButton *button, GtkWidget *window, gpointer gptr)
{
	GladeXML *gxml;
	GtkWidget  *pbarWidget, *data_viewWidget;
	GtkProgressBar *pbar;
	GtkTreeView *data_view;

	gxml = glade_get_widget_tree(GTK_WIDGET(button));

	pbarWidget = glade_xml_get_widget (gxml, "record_progressbar");
	pbar =  GTK_PROGRESS_BAR(pbarWidget);

	data_viewWidget = glade_xml_get_widget (gxml, "data_view");
	data_view = GTK_TREE_VIEW(data_viewWidget);

	get_data(pbar, data_view);
}

Check out the Processing project!
The website describes it as “[...] an open source programming language and environment for people who want to program images, animation, and interactions.” The things that have been done with it are truly amazing! Check out the exhibition or look at Daniel Shiffman’s projects!