Player-related code that should be improved

[litetex]

I and Stypox noticed some strange things while reviewing/refactoring the player #8170 (which were also there before the refactoring):

• When the playerservice is removed the complete app is killed (not gracefully terminated) by calling Runtime.getRuntime().halt(0): Refactor player and extract UI components #8170 (comment)
• Refactor player and extract UI components #8170 (comment) - here somehow a velocity is set to a position.

• NewPipe/app/src/main/java/org/schabi/newpipe/player/Player.java

  Line 2584 in d9af788

  //TODO check if this causes black screen when switching to fullscreen

  should be addressed (or removed) Refactor player and extract UI components #8170 (comment)

• NewPipe/app/src/main/java/org/schabi/newpipe/player/mediasession/MediaSessionPlayerUi.java

  Line 70 in e9e9e80

  // TODO decide whether to handle ACTION_HEADSET_PLUG or not

  should be addressed (or removed) Create media session UI and fix player notification #8678 (comment)

Other things to do:

• Add an UI that handles setting up a media session to send media information to the system, and try to fix the various issues with the player notification (e.g. wrong thumbnail, non-seekable current time, ...): Create media session UI and fix player notification #8678
• Properly implement a Picture In Picture popup: Use picture-in-picture (PIP) for the popup player on Android >= 8.0 #8750
• Make the playback parameters menu show up even when in popup mode
• Refactor player and extract UI components #8170 (comment)
• Refactor how the player is started or changed: Refactor how the player is started or changed #7673

[J-Stutzmann]

I think I have a decent explanation for what item 2 is/does:

• For a given velocityX and velocityY of a popup:
• if the Magnitude of either is greater than TOSS_FLING_VELOCITY:
• for each that is greater, set the axial position of the popup (playerUi.popupLayoutParams.*) to the rounded Value of its co-axial velocity (velocity*)
• clamp popup position into popupLayoutParams width/height

What this does, for a well chosen TOSS_FLING_VELOCITY that:

• As a velocity is high, but attainable
• As a position lies outside the popupLayoutParams width/height when either negative or positive

is to snap a flung popup to the edge of what popupLayoutParams says is the available space in the (approximate) direction it was sent.