write_flow_break.py

The Python file of the “Breaking an overlong word” example. A word longer than the column that holds it: the library leaves it whole, or cuts it at the column's edge.

Python 129 lines

What this example is for

This example sets the same paragraph twice in a column too narrow for one of its words: every layout eventually meets the word that will not fit — a chemical name, a German compound, a web address, an order reference nobody thought about. The word turns up in production, in one record out of a thousand, long after the team signed the layout off, and it comes back with the next reference, whatever width the column is given. The overlong setting decides: overflow leaves the whole word to run past the edge, break cuts it after the last glyph that fits.

What this example shows

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
"""Sets one paragraph in a column too narrow for a word in it, twice: above as it
comes, below cut to the column.

The Python twin of the `write_flow_break` example in Rust.

The paragraph and the two headings are held in `Words`, once per language, and
`HQF_PDF_LANG` picks which set is drawn. Each heading opens with the name the library
gives its setting, which is the same in every language.

Usage: python examples/write_flow_break.py [out.pdf] [font.ttf]
       HQF_PDF_LANG=fr python examples/write_flow_break.py
"""

from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path

import _language
import _licence
import _out

import hqf_pdf

# The payment reference the paragraph carries: one word to a line breaker, longer than
# the column it is put in, and the same in every language.
REFERENCE = "GB29NWBK60161331926819-2026-07-DEPOSIT"


@dataclass(frozen=True)
class Words:
    """Every word the page draws, in one language.

    What is not language stays out of it: the payment reference reads the same wherever
    the page is read, and each heading opens with the name the library gives the setting
    it stands over.
    """

    # The heading over the setting that leaves the long word whole.
    overflow: str
    # The heading over the setting that cuts it.
    breaking: str
    # The paragraph, cut where the reference goes into it.
    paragraph_before: str
    paragraph_after: str

    def paragraph(self) -> str:
        """Return the paragraph both settings are given, with the reference in it."""
        return f"{self.paragraph_before}{REFERENCE}{self.paragraph_after}"


# The page in English.
ENGLISH = Words(
    overflow="Overflow: the word is left whole, and runs past the edge.",
    breaking="Break: the word is cut after its last glyph that fits.",
    paragraph_before="Paid by bank transfer, reference ",
    paragraph_after=(
        ", to be matched against the purchase order before the accounts are closed."
    ),
)

# The page in French.
FRENCH = Words(
    overflow="Overflow : le mot reste entier et déborde du bord.",
    breaking="Break : le mot est coupé après son dernier glyphe qui tient.",
    paragraph_before="Réglé par virement, référence ",
    paragraph_after=", à rapprocher du bon de commande avant la clôture des comptes.",
)


# Every language the example is written in. A language is added by writing its own set
# of words and naming it here.
WORDS = {_language.ENGLISH: ENGLISH, _language.FRENCH: FRENCH}

COLUMN = 150.0

# The left edge of both columns. They are stacked rather than set side by side, so that
# the overflowing line runs out into the margin and not through the text of the other
# setting.
X = 80.0


def main() -> None:
    language = _language.from_environment()
    words = _language.words_of(WORDS, language)
    paragraph = words.paragraph()

    # A named file is written as named; the default one carries the language, so the two
    # languages do not overwrite each other in `tmp/`.
    out = _out.output_path(Path(_language.file_name("flow_break.pdf", language)).stem)

    document = hqf_pdf.Document()
    document.set_license(_licence.licensed())
    handle = document.add_font(hqf_pdf.Font.from_path(_out.font_path()))

    content = hqf_pdf.Content()

    for top, label, overlong in (
        (760.0, words.overflow, hqf_pdf.Overlong.Overflow),
        (620.0, words.breaking, hqf_pdf.Overlong.Break),
    ):
        heading = hqf_pdf.TextFlow(handle, 8.0)
        heading_lines = heading.break_lines(label, 400.0)
        heading.draw(content, heading_lines, X, top, 400.0)

        text_top = top - 20.0
        flow = hqf_pdf.TextFlow(handle, 11.0, leading=15.0, overlong=overlong)
        lines = flow.break_lines(paragraph, COLUMN)
        flow.draw(content, lines, X, text_top, COLUMN)

        # The column's edge, to show what each setting does about it.
        height = flow.height(lines)
        content.save_state()
        content.set_stroke(hqf_pdf.Rgb.gray(0.8))
        content.set_line_width(0.5)
        content.rect(X, text_top - height, COLUMN, height)
        content.stroke()
        content.restore_state()

    page = hqf_pdf.Page.a4()
    page.set_content(content)
    document.add_page(page)

    written = document.write(out)
    print(f"wrote {out}: {written} bytes")


if __name__ == "__main__":
    main()