[Kde-hardware-devel] Data format for RemoteControl events

[Michael Zanetti]

Hi all,

As some of you may know I'm currently working on a remote control integration 
for solid with a lirc backend. Now I have a problem regarding the api.

Until now, lirc remote control keypresses are represented as a free-form 
string containing the button name. The button names are defined in lircd.conf 
and for this they vary from remote to remote and from system to system.

As you can immagine this makes it really hard for application developers to 
work with remotes because you need a place where you can map those free form 
strings to functions.

It would be very nice to have a set of defined buttons an app developer can 
work with. For example a slideshow tool could just connect to the 
buttonPressed(event) signal and process it like:

switch(event->id()){
	case Left:
		showPrevious();
		break;
	case Right:
		showNext();
		break;
}

Well, the lirc and ubuntu guys have also recognized this problem and have 
created something called "namespace". This is a defined set of button names 
that tries to stay as near as possible to linux/input.h. [1] Currently about 
60% of lirc remotes are converted and work is going on.

In my opinion it would be a good idea to adapt this. On the other hand, I 
would like to stay compatible to backends not having defined button names.

This means I'd need something like the following:

class RemoteControlEvent
{
public:
  enum ButtonID {Play, Pause ... Stop, Invalid};

  RemoteControlEvent(const QString &buttonName);
  RemoteControlEvent(ButtonID);

  ButtonID id();
  QString name();
  QString translatedName();
};

If the event is created using the QString c'tor it would set the ID to 
ButtonID::Invalid and indicating the app developer that this isn't a button 
defined in the namespace. He can use the free-form string or just ignore it.

If the event is created using the ButtonID c'tor, the id would be set 
accordingly and the name would be set to a nice human readable name of the 
button. Also, the perhas a translated name would be of interest if the 
developer would like to show it in a ui.

However, the lirc namespace contains already about 400 button ids... This is 
quite a lot and im in daubt if my approach is really the best in this 
situation. It would require a 400-entries containing enum and some 400 entries 
containing switch statement for the names and translations... Also, this 
wouldn't be very nice to maintain...

Is there a better way or perhaps already a KDE way of dealing with such 
problems?

What do you think about the situation? Thanks for all your input.

Cheers,
Michael

[1] https://wiki.ubuntu.com/RemoteControls (Section Lirc Signal Naming)