add support for mpv internal mp.input function

[dyphire]

ref #111

[CogentRedTester]

Call input.terminate() before this to ensure there is not another input already active. If another input is active, then console.lua will abort the input.get request without any feedback. That means our coroutine would never be resumed, causing a memory leak.

[CogentRedTester]

Alternatively, you could use the new coroutine.callback() behaviour I'm adding in #113:

    input.get({
        prompt = text .. "\n>",
        id = "find",
        opened = fb.coroutine.callback(1.5),
        submit = fb.coroutine.callback(),
    })

    local console_opened = coroutine.yield()
    if not console_opened then return msg.warn('failed to open mp.input') end
    local query = coroutine.yield()
    input.terminate()

[CogentRedTester]

Upon inspecting the mp.input code it appears that mp.input discards all the old callbacks when a new input.get request is created. This should discard the callback, which should discard the reference to the coroutine, and hence mean no memory leak. But you may still want to add a timeout to opened to provide a useful error message.

[CogentRedTester]

This breaks the keybind expressions that use the input field because they won't know which module is being used. The run-statement example would break for instance. I'm happy for you to replace input in the expressions with the new mpv.input for future compatibility, but mpv-user-input still needs to be provided, perhaps through a user_input variable instead (here). The documentation will also need to be updated.

[dyphire]

Didn't notice this usage before, undo change.