Change input source through data display channel (DDC).

README.md

Change Input Source

A simple command line tool that uses ddccontrol to find named input sources and change to them.

Usage

cis -d *U3818DW* -s usb-c

There are two options that are needed:

• -d, --display — The name of the display. Wildcards are supported for partial matches.
• -s, --source — The exact name of the input source to switch to.

Requirements

• ddccontrol

cis

#!/usr/bin/env python3

import argparse
import re
import subprocess
import sys

####################################################################################################

# Matches the end of the detected list.
detectEndRE = re.compile(r"^Reading EDID")

# Matches the device path for the display.
deviceRE = re.compile(r"^\s*-\s*Device:\s*(.+)\s*")

# Matches the start of display information.
infoRE = re.compile(r"^=\s*(.+)\s*")

# Matches the end of input sources.
inputEndRE = re.compile(r"^\s*supported")

# Matches an input source.
inputSourceRE = re.compile(r"^\s*>\s*id=(.+) - name=USB-C, value=(.+)\s*")

# Matches the start of input sources.
inputStartRE = re.compile(r"^\s*>\s*id=inputsource.+address=(0x\d{2}).+")

# Matches the name for the display.
nameRE = re.compile(r"^\s*Monitor Name:\s*(.+)\s*")

def get_inputs(debug):
    """Queries for available displays and their source inputs."""

    # Probe for all devices.
    raw = subprocess\
        .check_output(['ddccontrol', '-p'])\
        .decode('ascii')\
        .split('\n')

    device = None
    inputs = {}
    name = None

    # Collect device information.
    while raw:
        line = raw.pop(0)

        if debug:
            print('Checking line: ' + line)

        # Check for device path.
        match = deviceRE.match(line)

        if match:
            if debug:
                print('Device path matched')

            device = match.group(1)

        # Check for device name.
        match = nameRE.match(line)

        if match:
            if debug:
                print('Device name matched');

            name = match.group(1)

        # Add to input dictionary.
        if device and name:
            if debug:
                print('Adding device info')

            inputs[name] = {
                'device': device,
                'sources': {}
            }

            device = None
            name = None

        # Check if end of detect list.
        if detectEndRE.match(line):
            if debug:
                print('End of device probe')

            break

    name = None
    inList = False

    # Collect device input sources.
    while raw:
        line = raw.pop(0)

        if debug:
            print('Checking line: ' + line)

        # Check for start of device information.
        match = infoRE.match(line)

        if match:
            if debug:
                print('Device info start matched')

            name = match.group(1)

        if name:

            # Check for source inputs start.
            match = inputStartRE.match(line)

            if match:
                if debug:
                    print('Device input source address matched')

                inputs[name]['address'] = match.group(1)
                inList = True

            if inList:

                # Check for source inputs end.
                match = inputEndRE.match(line)

                if match:
                    if debug:
                        print('Device input source list end matched')

                    name = None

                # Check for source input.
                match = inputSourceRE.match(line)

                if match:
                    if debug:
                        print('Device input source matched')

                    inputs[name]['sources'][match.group(1)] = match.group(2)

    return inputs

def set_input(device, address, value):
    """Sets the active source input."""

    subprocess.check_output(['ddccontrol', '-r', address, '-w', value, device])

####################################################################################################

# Parse the command line arguments.
parser = argparse.ArgumentParser(description='Change input source through ddccontrol.')
parser.add_argument(
    '-d', '--display',
    dest='display',
    required=True,
    help='The name of the display (wildcard, *, supported).'
)
parser.add_argument(
    '-s', '--source',
    dest='source',
    required=True,
    help='The name of the source.'
)
parser.add_argument(
    '-v', '--verbose',
    action='store_true',
    dest='verbose',
    help='Enables verbose output.'
)

args = parser.parse_args()

# Alert the user.
alertScript = '(echo 33; sleep 2; echo 66; sleep 1; echo 90; sleep 1; echo 100) | zenity --progress --title="Change Input Source" --text="Switching to ' + args.source + ' on ' + args.display + '..." --percentage=0 --auto-close'

subprocess.Popen(['nohup', 'bash', '-c', alertScript, '&'], close_fds=True)

# Get available display information.
displays = get_inputs(debug=args.verbose)

# Find first matching display
displayName = re.compile(args.display.replace('*', '(?:.*)'))

for display in displays.keys():
    if displayName.match(display):
        if displays[display]['sources'].get(args.source):
            set_input(
                displays[display]['device'],
                displays[display]['address'],
                displays[display]['sources'][args.source]
            )
        else:
            print(args.source + ": no such input source", file=sys.stderr)