label_printer/set_printer_resolution.py

"""
Read or change the PT-E560BT driver's print resolution.

Why this exists: the Brother driver offers two resolution modes

    180 x 180 dpi   balanced, matches the 128-dot head in both axes
    180 x 360 dpi   anisotropic - 2x the resolution along the tape feed

In the anisotropic mode the driver reports the media as 24 x 65 mm but rasters
along the tape at 360 dpi, so a page authored for the media dimensions can be
scaled by the wrong factor and printed short. This tool lets the mode be switched
from the command line so the effect can be tested without clicking through the
printer properties dialog.

Changing the resolution modifies a system printer default, so it is reversible:
use --restore, or simply re-run with the other value. Administrator rights are
required; without them the script reports what to change by hand.

Usage:
    python set_printer_resolution.py                 # show current setting
    python set_printer_resolution.py --mode 180      # symmetric 180x180
    python set_printer_resolution.py --mode 360      # anisotropic 180x360
    python set_printer_resolution.py --restore       # put back the old value
"""

from __future__ import annotations

import argparse
import json
import os
import sys

PRINTER = "Brother PT-E560BT"
STATE_FILE = ".printer_resolution_backup.json"

# DEVMODE field flags
DM_PRINTQUALITY = 0x00000400
DM_YRESOLUTION = 0x00040000
DM_MODIFY = 0x00000008
DM_IN_BUFFER = 0x00000008
DM_OUT_BUFFER = 0x00000002


def _devmode_field_bits():
    return DM_PRINTQUALITY | DM_YRESOLUTION


def current_settings():
    """Return the printer's current resolution-related DEVMODE values."""
    import win32print

    handle = win32print.OpenPrinter(PRINTER)
    try:
        info = win32print.GetPrinter(handle, 2)
        dm = info["pDevMode"]
        return {
            "port": info.get("pPortName"),
            "paper_size": dm.PaperSize,
            "paper_width": dm.PaperWidth,
            "paper_length": dm.PaperLength,
            "orientation": dm.Orientation,
            "print_quality": dm.PrintQuality,
            "y_resolution": dm.YResolution,
            "fields": dm.Fields,
        }
    finally:
        win32print.ClosePrinter(handle)


def measure_dc():
    """Read the resolution and paper dimensions the driver reports via a DC."""
    try:
        import win32ui
    except ImportError:
        return None

    try:
        dc = win32ui.CreateDC()
        dc.CreatePrinterDC(PRINTER)
    except Exception as exc:  # noqa: BLE001
        print(f"  Could not create DC: {exc}")
        return None

    try:
        return {
            "logpixelsx": dc.GetDeviceCaps(88),
            "logpixelsy": dc.GetDeviceCaps(90),
            "physicalwidth": dc.GetDeviceCaps(110),
            "physicalheight": dc.GetDeviceCaps(111),
            "horzres": dc.GetDeviceCaps(8),
            "vertres": dc.GetDeviceCaps(10),
        }
    finally:
        try:
            dc.DeleteDC()
        except Exception:  # noqa: BLE001
            pass


def show(label=""):
    settings = current_settings()
    caps = measure_dc()

    print(f"\n{label}")
    print(f"  DEVMODE PrintQuality : {settings['print_quality']}")
    print(f"  DEVMODE YResolution  : {settings['y_resolution']}")
    print(f"  DEVMODE PaperSize    : {settings['paper_size']} "
          f"({settings['paper_width']/10:.1f} x {settings['paper_length']/10:.1f} mm)")
    if caps:
        x, y = caps["logpixelsx"], caps["logpixelsy"]
        if x and y:
            print(f"  DC resolution        : {x} x {y} dpi", end="")
            if max(x, y) / min(x, y) >= 1.9:
                print("   <-- ANISOTROPIC (2x mismatch between axes)")
            else:
                print("   (symmetric)")
        print(f"  Physical page        : {caps['physicalwidth']} x "
              f"{caps['physicalheight']} dots = "
              f"{caps['physicalwidth']/max(x,1)*25.4:.2f} x "
              f"{caps['physicalheight']/max(y,1)*25.4:.2f} mm")
        print(f"  Printable area       : {caps['horzres']} x {caps['vertres']} dots")
    return settings


def apply_mode(mode: str) -> bool:
    """Set the driver resolution mode. mode is '180' or '360'."""
    import win32print

    y_res = 360 if mode == "360" else 0
    try:
        handle = win32print.OpenPrinter(
            PRINTER, {"DesiredAccess": win32print.PRINTER_ALL_ACCESS}
        )
    except Exception as exc:  # noqa: BLE001
        print(f"Cannot open printer for writing: {exc}")
        print("Re-run this from an elevated (Administrator) terminal.")
        return False

    try:
        info = win32print.GetPrinter(handle, 2)
        dm = info["pDevMode"]
        dm.PrintQuality = 180
        dm.YResolution = y_res
        dm.Fields |= _devmode_field_bits()

        info["pDevMode"] = dm
        win32print.SetPrinter(handle, 2, info, 0)
        print(f"Applied resolution mode {mode} (YResolution={y_res}).")
        return True
    except Exception as exc:  # noqa: BLE001
        print(f"Failed to set resolution: {exc}")
        print("This normally needs Administrator rights.")
        return False
    finally:
        win32print.ClosePrinter(handle)


def main() -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument("--mode", choices=["180", "360"], help="resolution mode to set")
    parser.add_argument("--restore", action="store_true", help="restore the saved value")
    args = parser.parse_args()

    before = show("BEFORE")

    if args.restore:
        if not os.path.exists(STATE_FILE):
            print(f"\nNo backup found at {STATE_FILE}; nothing to restore.")
            return 1
        with open(STATE_FILE) as handle:
            saved = json.load(handle)
        mode = "360" if saved.get("y_resolution") else "180"
        print(f"\nRestoring YResolution={saved.get('y_resolution')} (mode {mode})")
        if apply_mode(mode):
            show("AFTER")
        return 0

    if not args.mode:
        print("\n(no --mode given; nothing changed)")
        return 0

    # Save the previous value so the change can be undone.
    with open(STATE_FILE, "w") as handle:
        json.dump(before, handle, indent=2)
    print(f"\nSaved previous setting to {STATE_FILE}")

    if apply_mode(args.mode):
        show("AFTER")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())