Receiving dbus signals using low-level C API

Havoc Pennington hp at
Wed Jan 24 13:27:22 PST 2007

Krishna R wrote:
> 4. In my filter function, i read the message using 
> dbus_message_get_args() and return DBUS_HANDLER_RESULT_HANDLED.

It usually makes more sense to return NOT_YET_HANDLED from a signal 
handler, since other handlers may also be interested. Though if your app 
isn't using any libraries that may also be interested, it doesn't matter.

> 1. Is this a correct way to recv signals? Do i have to do 
> dbus_message_unref(message) in the filter function after handling it 
> before i return?

I don't believe so, I could misremember, but it would be documented if 
you did have to probably.

> 2. I also see that as soon as i call the match rule api, the filter 
> function gets called. I further found that the message has a argument 
> which a string, which is 2. Is this expected? I had assumed that the 
> filter function will only be called when i send a signal and not before 
> that. Why is this?

The filter function will be called for any kind of message.

> Seperate point: Also in the tutorial the send signal function closes the 
> dbus connection and the dbus version 1.0.2 complains about this. Can 
> someone pls fix the tutorial for this. I assume from the error message 
> we dont close the connection anymore?

Yes, if it's a shared connection you should unref but not close. (The 
documentation goes into more detail.)


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