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2016-01-13 14:35:03 +00:00
---
layout: post
title: "Emacs: Implement a GObjects virtual function"
date: 2016-01-13 15:31:12+02:00
tags: [c, development, emacs]
published: true
author:
name: "Gergely Polonkai"
email: "gergely@polonkai.eu"
---
I have recently started creating a GLib implementation of the
Matrix.org API. For that, I have created a GObject interface,
MatrixAPI, which has as many virtual functions as API calls (which is
a lot, and expanding). This way I ended up with the following scenario.
In `matrix-api.h` I had a struct like this, with a lot more elements:
typedef struct {
void (*initial_sync)(MatrixAPI *api,
MatrixAPICallback callback,
gpointer user_data,
GError **error);
void (*sync)(MatrixAPI *api,
MatrixAPICallback callback,
gpointer user_data,
GError **error);
And in `matrix-http-api.c`, which implements `MatrixAPI`, I have a
function like this (again, with a lot more elements):
static void
matrix_http_api_matrix_api_init(GObjectInterface *iface)
{
iface->initial_sync = i_initial_sync;
iface->sync = i_sync;
}
And every time I wanted to implement a new function from the vtable, I
had to copy the prototype, and add an `iface->foo_bar = i_foo_bar`
line and an actual function header for `i_foo_bar` with the same
parameters. Thats a cumbersome job for more than 40 function
headers. But emacs comes to the rescue!
{% gist gergelypolonkai/bfd36be8b515edced3d2 implement-gobject-vfunc.el %}
Now all I have to do is to copy the whole vtable entry into
`matrix_http_api_matrix_api_init()`, execute `M-x
implement-gobject-vfunc`, then put the same vtable entry somewhere
before the interface init function, and execute `M-x
implement-gobject-vfunc-prototype`.