These files are used for Apple's EFI boot selector to show the
Qubes OS text and icon during Apple's Boot Selection process 
(hold down OPTION KEY at startup).  

These files are installed at the following location:

    /usr/share/pixmaps/bootloader/apple/*

A basic description of the files are as follows:

* qubes, qubes-install, qubes-rescue
  These directories hold a list of three files each pre-rendered
  for macOS machines.

    disk_label
    disk_label_2x
    disk_label.contentDetails

  The first two files, disk_label and disk_label_2x, are special
  image bitmaps of 12px high and various widths saved in macOS
  proprietary "label" format.  The _2x version are high DPI 
  Retina versions.

  By default, macOS shows bootable partitions as "EFI Boot" with
  a generic USB drive icon.  These files rename the text.

  The EFI installer copies it to the correct locations, typically:
  
    /boot/efi/EFI/qubes/
    /boot/efi/System/Library/CoreServices/
  
  You can generate these by properly setting the 
  SystemVersion.plist for your target boot partition and then 
  running on macOS:

    sudo bless --folder <path-to-partition>/System/Library/CoreServices \
      --label "<matching label name>"
  
  Where <matching label name> must match the product Version
  listed in the SystemVersion.plist file.  The result will be 
  the three files listed above, but as hidden files with the 
  "." prefix.

  To keep it simple for installation of artwork, the files were
  renamed to non-hidden files and placed into three directories.

  There are three sets of disk_labels in this folder, used for 
  different installations of Qubes OS:

    qubes/ :
    These are labelled "Qubes OS" and used during macOS installs.

    qubes-install/ :
    These are labelled "Install Qubes OS" and may be used for the
    installer image to present a nice "Q" logo and text.

    qubes-rescue/ :
    These are labelled "Qubes OS (rescue)" and may be used to
    indicate special Rescue EFI partitions during Apple's Boot Camp
    selection screen.

* qubes.icns
  This file is a collection of Apple ICNS formatted bitmap images.

  By default, macOS shows bootable partitions as "EFI Boot" with
  a generic USB drive icon.  This file replaces the generic icon
  with the official "Q" Qubes OS logo.

  The EFI installer copies and renames this file to:
  
    /boot/efi/.VolumeIcon.icns

  It was originally sourced from the file located at:

    ../../icons/512x512/apps/qubes-logo-icon.png
  
  The most reliable Linux utility to create ICNS was a large NodeJS
  installation and did not produce Retina high-resolution images.
  Therefore, macOS was used to create this file using:

    $ iconutil -c icns <name>.iconset
  
  Where <name>.iconset is the name of the folder with the collection
  of sizes starting with 512x512 and smaller following a specific
  naming convention.
