gergelypolonkai-web-jekyll/_posts/2016-01-13-emacs-implement-a-gobject-s-virtual-function.md

54 lines
1.9 KiB
Markdown
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

---
layout: post
title: "Emacs: Implement a GObjects virtual function"
date: 2016-01-13 13:31:12
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 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`.