#!/usr/bin/python3
# Note: use system python3, not /usr/bin/env, because whichever python3 is on
# $PATH may not have dbus, but the system python3 does.

"""Toggle display scaling between 100% and 200%.

Based on https://gist.github.com/strycore/ca11203fd63cafcac76d4b04235d8759

For data structure definitions, see
https://gitlab.gnome.org/GNOME/mutter/blob/master/src/org.gnome.Mutter.DisplayConfig.xml
"""

import dbus
import sys

namespace = "org.gnome.Mutter.DisplayConfig"
dbus_path = "/org/gnome/Mutter/DisplayConfig"

session_bus = dbus.SessionBus()
obj = session_bus.get_object(namespace, dbus_path)
interface = dbus.Interface(obj, dbus_interface=namespace)

current_state = interface.GetCurrentState()
serial = current_state[0]
connected_monitors = current_state[1]
logical_monitors = current_state[2]

# Multiple monitors are more complicated. For now, since I only use one monitor
# in Ubuntu, everything is hard-coded so that only info about the first monitor
# is used, and only it will be connected after running the script.
#
# If someday updating this script: a logical monitor may appear on mutiple
# connected monitors due to mirroring.
connector = connected_monitors[0][0][0]
current_mode = None
# ApplyMonitorsConfig() needs (connector name, mode ID) for each connected
# monitor of a logical monitor, but GetCurrentState() only returns the
# connector name for each connected monitor of a logical monitor. So iterate
# through the globally connected monitors to find the mode ID.
for mode in connected_monitors[0][1]:
    if mode[6].get("is-current", False):
        current_mode = mode[0]

x, y, scale, transform, primary, monitors, props = logical_monitors[0]
available_resolutions = [
    str(item)
    for item in map(lambda item: f"{item[1]}x{item[2]}", connected_monitors[0][1])
]
available_resolutions = sorted(
    set(available_resolutions), key=lambda item: int(item.split("x")[0]), reverse=True
)

try:
    wanted_resolution = str(sys.argv[1])
except IndexError:
    print("Desired resolution not provided. Example: `./display_scale.py 1920x1080`")
    print("Available resolutions are:\n" + "\n".join(available_resolutions))
    sys.exit(1)

wanted_scale = 1
try:
    wanted_scale = float(sys.argv[2])
except IndexError:
    print("Desired scale not provided. Example: `./display_scale.py 1920x1080 2`")
    print("Defaulting to a scale of 1")

matching_resolutions = [
    item
    for item in filter(
        lambda item: wanted_resolution in item[0], connected_monitors[0][1]
    )
]

try:
    matched_resolution = matching_resolutions[0][0]
except IndexError:
    print("Desired resolution not available.")
    print("Available resolutions are:\n" + "\n".join(available_resolutions))
    sys.exit(1)

print(
    f"Found {len(matching_resolutions)} matching resolutions."
    f"Using {matched_resolution} scaled by {wanted_scale}."
)
updated_connected_monitors = [[connector, matched_resolution, {}]]

monitor_config = [[x, y, wanted_scale, transform, primary, updated_connected_monitors]]

# Change the 1 to a 2 if you want a "Revert Settings / Keep Changes" dialog
interface.ApplyMonitorsConfig(serial, 1, monitor_config, {})