Adafruit_CircuitPython_HID/adafruit_hid/keyboard.py

# The MIT License (MIT)
#
# Copyright (c) 2017 Dan Halbert
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"""
`adafruit_hid.keyboard.Keyboard`
====================================================

* Author(s): Scott Shawcroft, Dan Halbert
"""

import time
from micropython import const

from .keycode import Keycode

from . import find_device

_MAX_KEYPRESSES = const(6)


class Keyboard:
    """Send HID keyboard reports."""

    # No more than _MAX_KEYPRESSES regular keys may be pressed at once.

    def __init__(self, devices):
        """Create a Keyboard object that will send keyboard 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._keyboard_device = find_device(devices, usage_page=0x1, usage=0x06)

        # Reuse this bytearray to send keyboard reports.
        self.report = bytearray(8)

        # report[0] modifiers
        # report[1] unused
        # report[2:8] regular key presses

        # View onto byte 0 in report.
        self.report_modifier = memoryview(self.report)[0:1]

        # List of regular keys currently pressed.
        # View onto bytes 2-7 in report.
        self.report_keys = memoryview(self.report)[2:]

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

    def press(self, *keycodes):
        """Send a report indicating that the given keys have been pressed.

        :param keycodes: Press these keycodes all at once.
        :raises ValueError: if more than six regular keys are pressed.

        Keycodes may be modifiers or regular keys.
        No more than six regular keys may be pressed simultaneously.

        Examples::

            from adafruit_hid.keycode import Keycode

            # Press ctrl-x.
            kbd.press(Keycode.LEFT_CONTROL, Keycode.X)

            # Or, more conveniently, use the CONTROL alias for LEFT_CONTROL:
            kbd.press(Keycode.CONTROL, Keycode.X)

            # Press a, b, c keys all at once.
            kbd.press(Keycode.A, Keycode.B, Keycode.C)
        """
        for keycode in keycodes:
            self._add_keycode_to_report(keycode)
        self._keyboard_device.send_report(self.report)

    def release(self, *keycodes):
        """Send a USB HID report indicating that the given keys have been released.

        :param keycodes: Release these keycodes all at once.

        If a keycode to be released was not pressed, it is ignored.

        Example::

            # release SHIFT key
            kbd.release(Keycode.SHIFT)
        """
        for keycode in keycodes:
            self._remove_keycode_from_report(keycode)
        self._keyboard_device.send_report(self.report)

    def release_all(self):
        """Release all pressed keys."""
        for i in range(8):
            self.report[i] = 0
        self._keyboard_device.send_report(self.report)

    def send(self, *keycodes):
        """Press the given keycodes and then release all pressed keys.

        :param keycodes: keycodes to send together
        """
        self.press(*keycodes)
        self.release_all()

    def _add_keycode_to_report(self, keycode):
        """Add a single keycode to the USB HID report."""
        modifier = Keycode.modifier_bit(keycode)
        if modifier:
            # Set bit for this modifier.
            self.report_modifier[0] |= modifier
        else:
            # Don't press twice.
            # (I'd like to use 'not in self.report_keys' here, but that's not implemented.)
            for i in range(_MAX_KEYPRESSES):
                if self.report_keys[i] == keycode:
                    # Already pressed.
                    return
            # Put keycode in first empty slot.
            for i in range(_MAX_KEYPRESSES):
                if self.report_keys[i] == 0:
                    self.report_keys[i] = keycode
                    return
            # All slots are filled.
            raise ValueError("Trying to press more than six keys at once.")

    def _remove_keycode_from_report(self, keycode):
        """Remove a single keycode from the report."""
        modifier = Keycode.modifier_bit(keycode)
        if modifier:
            # Turn off the bit for this modifier.
            self.report_modifier[0] &= ~modifier
        else:
            # Check all the slots, just in case there's a duplicate. (There should not be.)
            for i in range(_MAX_KEYPRESSES):
                if self.report_keys[i] == keycode:
                    self.report_keys[i] = 0