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