feat(#1289): Adds music reading mode and configuration

[KorigamiK]

This shows how it can be used with the following config in user keys:

toggle_music_reading_mode <A-m>
music_reading_speed_up <A-.>
music_reading_speed_down <A-,>

music.mp4

[KorigamiK]

@ahrm could you please help review this? 😊

[ahrm]

Hi! Thanks, I am impressed by your ability to implement this, I will look at this hopefully in the next few days. However, since this is a very niche yet sizeable feature, I would prefer if it was implemented as an extension (in python or JS), since I don't know much about music and probably can't do a good job of maintaining this feature. The current extension system might not be powerful enough that it can handle such a complex feature, but I am willing to implement the features needed to implement this (off the top of my head, you probably need some way to periodically execute a custom script) so other use cases can also benefit from this.

[ahrm]

Added a periodic_commands config and a new set_fixed_velocity command in 62a0b84, which should help your use-caes. Here is an example of using it, this script moves the page every two seconds some amount.

prefs_user.config (the periodic_commands is probably set dynamically using setconfig commands, I just set it by default here as an example):

new_async_js_command _periodic /path/to/periodic.js
periodic_commands _periodic

periodic.js:

let lastMoveTime = sioyek_api.get_variable('korigamik.last_move_time');

let currentTime = new Date();
const moveEveryMiliseconds = 2000;

if ((lastMoveTime === undefined) || ((currentTime - lastMoveTime) > moveEveryMiliseconds)){

    sioyek.set_fixed_velocity("10000 500");
    sioyek_api.set_variable('korigamik.last_move_time', currentTime);
}

set_fixed_velocity takes two arguments, the first is the velocity and the second is how much to move. In the javascript you can call any sioyek command like this: sioyek.toggle_dark_mode() and there are some special api-specific functions that do not have a sioyek command equivalent (e.g. set_variable). You can call these like so: sioyek_api.set_variable. You can see a list of such commands by searching for Q_INVOKABLE in main_widget.h.

Let me know if there are any more functionality required to implement your use-cases.