Circuit python 7 absolute mouse example

boot.py

import usb_hid

# https://stackoverflow.com/questions/36750287/two-byte-report-count-for-hid-report-descriptor
absolute_mouse = usb_hid.Device(
    report_descriptor=bytes(
        # Absolute mouse
        (0x05, 0x01)    # Usage Page (Generic Desktop)
        + (0x09, 0x02)  # Usage (Mouse)
        + (0xA1, 0x01)  # Collection (Application)
        + (0x09, 0x01)  # Usage (Pointer)
        + (0xA1, 0x00)  # Collection (Physical)
        + (0x85, 0x0B)  # Report ID  [11 is SET at RUNTIME]
        # Buttons
        + (0x05, 0x09)  # Usage Page (Button)
        + (0x19, 0x01)  # Usage Minimum (0x01)
        + (0x29, 0x05)  # Usage Maximum (0x05)
        + (0x15, 0x00)  # Logical Minimum (0)
        + (0x25, 0x01)  # Logical Maximum (1)
        + (0x95, 0x05)  # Report Count (5)
        + (0x75, 0x01)  # Report Size (1)
        + (0x81, 0x02)  # Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
        + (0x75, 0x03)  # Report Size (3)
        + (0x95, 0x01)  # Report Count (1)
        + (0x81, 0x03)  # Input (Const,Array,Abs,No Wrap,Linear,Preferred State,No Null Position)
        # Movement
        + (0x05, 0x01)        # Usage Page (Generic Desktop Ctrls)
        + (0x09, 0x30)        # Usage (X)
        + (0x09, 0x31)        # Usage (Y)  
        + (0x15, 0x00)        # LOGICAL_MINIMUM (0)       ; Note: 0x15 = 1 Byte; 0x16 = 2 Byte; 0x17 = 4 Byte
        + (0x26, 0xFF, 0x7F)  # LOGICAL_MAXIMUM (32767)   ; Note: 0x25 = 1 Byte, 0x26 = 2 Byte; 0x27 = 4 Byte Report
        #+ (0x35, 0x00)        # Physical Minimum (0)
        #+ (0x46, 0xff, 0x7f)  # Physical Maximum (32767)
        + (0x75, 0x10)        # REPORT_SIZE (16)
        + (0x95, 0x02)        # REPORT_COUNT (2)
        + (0x81, 0x02)        # Input (Data,Var,Rel,No Wrap,Linear,Preferred State,No Null Position)
        # Wheel
        + (0x09, 0x38)   # Usage (Wheel)
        + (0x15, 0x81)   # Logical Minimum (-127)
        + (0x25, 0x7F)   # Logical Maximum (127)
        #+ (0x35, 0x81)   # Physical Minimum (same as logical)
        #+ (0x45, 0x7f)   # Physical Maximum (same as logical)
        + (0x75, 0x08)   # Report Size (8)
        + (0x95, 0x01)   # Report Count (1)
        + (0x81, 0x06)   # Input (Data,Var,Rel,No Wrap,Linear,Preferred State,No Null Position)
        + (0xC0,)  #   End Collection  
        + (0xC0,) # End Collection
    ),
    usage_page=1,
    usage=2,
    in_report_lengths=(6,), # Number of bytes in the send report = 1 byte for buttons, 2 bytes for x, 2 bytes for y, 1 byte for wheel
    out_report_lengths=(0,),
    report_ids=(11,),
)

usb_hid.enable((usb_hid.Device.KEYBOARD,), boot_device=1)
usb_hid.enable((absolute_mouse,), boot_device=0)

mouse_abs.py

# SPDX-FileCopyrightText: 2017 Dan Halbert for Adafruit Industries
#
# SPDX-License-Identifier: MIT

"""
`adafruit_hid.mouse.Mouse`
====================================================

* Author(s): Dan Halbert, Bitboy
"""
import time

from . import find_device


class Mouse:
    """Send USB HID mouse reports."""

    LEFT_BUTTON = 1
    """Left mouse button."""
    RIGHT_BUTTON = 2
    """Right mouse button."""
    MIDDLE_BUTTON = 4
    """Middle mouse button."""

    def __init__(self, devices):
        """Create a Mouse object that will send USB mouse HID reports.

        Devices can be a list of devices that includes a keyboard device or a keyboard device
        itself. A device is any object that implements ``send_report()``, ``usage_page`` and
        ``usage``.
        """
        self._mouse_device = find_device(devices, usage_page=0x1, usage=0x02)
        #print(dir(devices))
        # Reuse this bytearray to send mouse reports.
        # report[0] buttons pressed (LEFT, MIDDLE, RIGHT)
        # report[1] x1 movement
        # report[2] x2 movement
        # report[3] y1 movement
        # report[4] y2 movement
        # report[5] wheel movement
        self.report = bytearray(6)

        # Do a no-op to test if HID device is ready.
        # If not, wait a bit and try once more.
        try:
            self._send_no_move()
        except OSError:
            time.sleep(1)
            self._send_no_move()

    def press(self, buttons):
        """Press the given mouse buttons.

        :param buttons: a bitwise-or'd combination of ``LEFT_BUTTON``,
            ``MIDDLE_BUTTON``, and ``RIGHT_BUTTON``.

        Examples::

            # Press the left button.
            m.press(Mouse.LEFT_BUTTON)

            # Press the left and right buttons simultaneously.
            m.press(Mouse.LEFT_BUTTON | Mouse.RIGHT_BUTTON)
        """
        self.report[0] |= buttons
        self._send_no_move()

    def release(self, buttons):
        """Release the given mouse buttons.

        :param buttons: a bitwise-or'd combination of ``LEFT_BUTTON``,
            ``MIDDLE_BUTTON``, and ``RIGHT_BUTTON``.
        """
        self.report[0] &= ~buttons
        self._send_no_move()

    def release_all(self):
        """Release all the mouse buttons."""
        self.report[0] = 0
        self._send_no_move()

    def click(self, buttons):
        """Press and release the given mouse buttons.

        :param buttons: a bitwise-or'd combination of ``LEFT_BUTTON``,
            ``MIDDLE_BUTTON``, and ``RIGHT_BUTTON``.

        Examples::

            # Click the left button.
            m.click(Mouse.LEFT_BUTTON)

            # Double-click the left button.
            m.click(Mouse.LEFT_BUTTON)
            m.click(Mouse.LEFT_BUTTON)
        """
        self.press(buttons)
        self.release(buttons)

    def move(self, x=0, y=0, wheel=0):
        """Move the mouse and turn the wheel as directed.

        :param x: Set pointer on x axis. 32767 = 100% to the right
        :param y: Set pointer on y axis. 32767 = 100% to the bottom
        :param wheel: Rotate the wheel this amount. Negative is toward the user, positive
            is away from the user. The scrolling effect depends on the host.

        Examples::

            # Move 100 to the left. Do not move up and down. Do not roll the scroll wheel.
            m.move(1000, 3000, 0)
            # Same, with keyword arguments.
            m.move(x=1000, y=3000, wheel=0)


            # Roll the mouse wheel away from the user.
            m.move(wheel=1)
        """

        # Wheel
        while wheel != 0:
            partial_wheel = self._limit(wheel)
            print(wheel)
            self.report[5] = partial_wheel & 0xFF
            self._mouse_device.send_report(self.report)
            wheel -= partial_wheel

        # Coordinates
        x = self._limit_coord(x)
        y = self._limit_coord(y)
        # HID reports use little endian
        x1, x2 = (x & 0xFFFFFFFF).to_bytes(2, 'little')
        y1, y2 = (y & 0xFFFFFFFF).to_bytes(2, 'little')
        #print(x1)
        #print(x2)
        #print(y1)
        #print(y2)
        self.report[1] = x1
        self.report[2] = x2
        self.report[3] = y1
        self.report[4] = y2
        self._mouse_device.send_report(self.report)

    def _send_no_move(self):
        """Send a button-only report."""
        self.report[1] = 0
        self.report[2] = 0
        self.report[3] = 0
        self.report[4] = 0
        self._mouse_device.send_report(self.report)

    @staticmethod
    def _limit(dist):
        return min(127, max(-127, dist))

    @staticmethod
    def _limit_coord(coord):
        return min(32767, max(0, coord))

sample.py

import usb_hid
from adafruit_hid.mouse_abs import Mouse

mouse = Mouse(usb_hid.devices)
# Note: Values are NOT pixels! 32767 = 100% (to right or to bottom) 
mouse.move(x=20000, y=2000)

I would like to confirm that this "Buffer incorrect size." is occuring when you change the boot.py without powercycling the board.
You need the board to re-negotiate with the host at USB level... unplugging and replugging is the best way to garantee that.

Also I have used your code for this demo: https://github.com/dglaude/CircuitPython_udraw_Absolute_Mouse

A fork of my library is now accepted in CircuitPython Community Bundle and can be found here: https://github.com/Neradoc/CircuitPython_Absolute_Mouse
There is a nice very simple example code there.

Nice! Thanks for mentioning my example :)