label_printer/print_measure_scale.py

"""
Print a measuring label to determine the printer's actual scale factors.

The problem: we render a correct 61 x 18 mm label, but it prints around 25 x 17 mm.
Two candidate causes predict different numbers, and both look similar at that size:

  (a) Resolution mismatch - the driver reports LOGPIXELSX=360 but the device is
      180 dpi, so content is compressed 2x along the tape. Predicts marks 10 mm
      apart appearing ~5 mm apart in X only.
  (b) Driver shrink-to-fit across the 24 mm media width. Predicts an equal
      shrink in X and Y: scale 24/65.05 = 0.37 -> marks 10 mm apart appear 3.7 mm.

This label makes the answer unambiguous: it draws ruler ticks at known spacings
in both axes, so reading one number off the tape identifies the cause.

Reading the print:
  * X ticks (along the tape) are laid out every 10 mm from 0 to 60.
  * Y ticks (across the tape) are laid out every 2 mm from 0 to 18.
  * A 10 x 10 mm reference square sits at a known position.

Measure the distance between tick "0" and tick "60" (intended 60 mm):
    ~60 mm  -> geometry correct; the problem lies elsewhere
    ~30 mm  -> case (a), 2x compression along the tape
    ~22 mm  -> case (b), shrink-to-fit on width
    other   -> report the measured value
"""

from __future__ import annotations

import os
import sys

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
os.chdir(os.path.dirname(os.path.abspath(__file__)))

from reportlab.lib.units import mm
from reportlab.pdfgen import canvas

from label_config import load_config
from print_area import query_print_area
from ptouch_label import LabelConfig

PRINTER = "Brother PT-E560BT"


def build_measure_pdf(cfg: LabelConfig, path: str) -> str:
    """Draw the measuring label at the configured content size."""
    page_w, page_h = cfg.page_size_mm
    ox, oy = cfg.origin_mm
    content_w, content_h = cfg.page_width_mm, cfg.page_height_mm

    c = canvas.Canvas(path, pagesize=(page_w * mm, page_h * mm))
    c.setTitle("PT-E560BT scale measurement")

    def X(v: float) -> float:
        return (ox + v) * mm

    def Y(v: float) -> float:
        return (oy + v) * mm

    # Outer frame exactly at the content bounds.
    c.setStrokeColorRGB(0, 0, 0)
    c.setLineWidth(0.4)
    c.rect(X(0), Y(0), content_w * mm, content_h * mm)

    # X ruler: a tick every 10 mm along the bottom, labelled.
    c.setFont("Helvetica", 5)
    for i in range(0, int(content_w) + 1, 10):
        tall = i % 20 == 0
        c.setLineWidth(0.6 if tall else 0.3)
        c.line(X(i), Y(0), X(i), Y(3.5 if tall else 1.8))
        if tall:
            c.drawString(X(i + 0.4), Y(3.8), str(i))

    # Y ruler: a tick every 2 mm up the left edge, labelled every 6 mm.
    for j in range(0, int(content_h) + 1, 2):
        tall = j % 6 == 0
        c.setLineWidth(0.6 if tall else 0.3)
        c.line(X(0), Y(j), X(2.5 if tall else 1.4), Y(j))
        if tall:
            c.drawString(X(2.8), Y(j + 0.3), str(j))

    # 10 x 10 mm reference square, for an independent scale check.
    c.setLineWidth(0.6)
    c.rect(X(30), Y(4), 10 * mm, 10 * mm)
    c.setFont("Helvetica-Bold", 4)
    c.drawString(X(30.6), Y(8.4), "10x10")
    c.drawString(X(30.6), Y(6.0), "mm")

    # Explanation printed on the label itself.
    c.setFont("Helvetica-Bold", 5)
    c.drawString(X(44), Y(15.4), "MEASURE:")
    c.setFont("Helvetica", 4)
    c.drawString(X(44), Y(13.4), "tick 0 to 60")
    c.drawString(X(44), Y(11.6), "should be 60 mm")
    c.drawString(X(44), Y(9.8), "square = 10 mm")
    c.drawString(X(44), Y(8.0), "frame =")
    c.drawString(X(44), Y(6.4), f"{content_w:.0f} x {content_h:.0f} mm")
    c.drawString(X(44), Y(4.8), "tape = 24 mm")

    c.showPage()
    c.save()
    return path


def main() -> int:
    cfg = load_config()

    # Use the printer's real printable area for this measurement.
    area = query_print_area(PRINTER)
    if area:
        print(f"Printable area: {area.printable_width_mm:.2f} x "
              f"{area.printable_height_mm:.2f} mm")
        cfg.media_width_mm = round(area.media_width_mm, 2)
        cfg.media_height_mm = round(area.media_height_mm, 2)
        cfg.page_width_mm = round(area.printable_width_mm - 0.1, 2)
        cfg.page_height_mm = round(area.printable_height_mm - 0.1, 2)

    os.makedirs("pdf_backup", exist_ok=True)
    out = os.path.join("pdf_backup", "measure_scale.pdf")
    build_measure_pdf(cfg, out)

    print(f"Content bounds : {cfg.page_width_mm:.2f} x {cfg.page_height_mm:.2f} mm")
    print(f"PDF page       : {cfg.page_size_mm[0]:.2f} x {cfg.page_size_mm[1]:.2f} mm")
    print(f"Origin         : {cfg.origin_mm}")
    print(f"Written        : {out}")

    if "--no-print" in sys.argv:
        print("(--no-print: not sending to printer)")
        return 0

    from print_label import print_to_printer

    settings = "noscale,paperkind=261"
    print(f"\nPrinting with -print-settings '{settings}' ...")
    ok = print_to_printer(PRINTER, out, settings=settings)
    print(f"Result: {'SENT' if ok else 'FAILED'}")
    return 0 if ok else 1


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