gtknode

Yet Another GUI framework for Erlang

DESIGN GOALS

• GUI separated from application by message passing
• distributed (application and GUI can run on different machines)
• centered around a GUI builder
• small volume of (hand-written) code
• pre-documented

ARCHITECTURE

A c-node (a daemon that implements the Erlang distribution protocol) that instantiates the GUI from a configuration file. The c-node sends messages to the Erlang node when the user interacts with the GUI; the Erlang application changes the state of the GUI by sending messages to widgets in the c-node. The widgets should look like Erlang processes with registered names. The protocol should look something like this:

CnodePid ! {aWidget,dosomething,Args}       % erlang->cNode
ApplicationPid ! {reply, Val}               % cNode->erlang
ApplicationPid ! {signal,aWidget,eventType} % cNode->erlang

In this example aWidget is the name given to a widget in the configration file. It can also be thought of as the registered name of the process implementing the widget in the c-node.

The c-node is responsible for garbage-collecting all temporary data.

IMPLEMENTATION

REFERENCE

The c-node is started thus;

gtknode node host regname cookie cnode-name otp-version

When started, gtknode will connect to it's application by sending a handshake message to {node@host, regname}.

The messsage looks like this;

{{GtkPid,handshake}, []}

The Erlang application sends messages to the gtknode using GtkPid. messages look like this:

list({'Gtk_function', [Args]})

E.g., if we have a GtkButton widget, named b1, and we want to use these functions:

const gchar* gtk_button_get_label (GtkButton *button);
void         gtk_button_set_label (GtkButton *button, const gchar *label);

we could send this:

GtkPid ! [{'Gtk_button_set_label',[b1,"foo"]},{'Gtk_button_get_label',[b1]}].

and we would receive this:

{{GtkPid,reply}, [{ok,void},{ok,"foo"}]}

Signals are sent from gtknode if the signal handler for a specified signal-widget combination is set to gn_sighandler. The signals look like this:

{{GtkPid, signal}, {atom(WidgetName),atom(SignalName)}}

E.g., if we delete the GtkWindow named window1 we'll get this signal:

{{GtkPid, signal},{window1,'GDK_DELETE'}}

Given that we've requested it, of course.

EXAMPLES

The file src/gtknode.erl implements a controller/middleman for the gtknode, it's quite instructive. It is recommended to use this instead of working directly against the c-node.

The priv/examples directory contains a few examples.

GETTING IT

http://github.com/massemanet/gtknode/

STATUS

Stable since 2008