Problems when using language tag in FormattedString

[frankrolf]

I am proofing Cyrillic, including Bulgarian alternates. This example makes two pages, one Russian, the other Bulgarian:

import os
import drawBot as db


def make_proof_page(language_tag):

    proof_text = 'вгджзийклнпттттфцчшщъьюѝ'

    font = 'SourceSerifPro-Light.otf'
    margin = 30
    pt_size = 40

    db.newPage(1200, 120)
    y_offset = db.height() - margin - pt_size
    fs = db.FormattedString(
        proof_text,
        font=font,
        language=language_tag,
        fontSize=pt_size,
    )

    db.text(fs, (margin, y_offset))
    print(fs.size().width)


db.newDrawing()
for language_tag in ['ru', 'bg']:
    make_proof_page(language_tag)

output_name = 'ru vs bgr.pdf'
db.saveImage(output_name)
os.system(f'open "{output_name}"')
db.endDrawing()

Issues I observe:

• the result of size().width is the same no matter which language (they are not visually the same)

• the Bulgarian string gets truncated after щ when using DrawBot from the command line:

• the rest of the Bulgarian string gets shoved somewhere below when using DrawBot desktop app – although there is no line break involved:

Test case (with font) attached: Formatted String + language tag.zip

[frankrolf]

I used DrawBot 3.126 (both module and packaged) on macOS 10.15.6.

[typemytype]

mm, Im unsure in CoreText when OT features are applied... I assume while doing the layout, so when a size of string is calculated there are no replacements done yet...

probably this is related @LettError variable arrows issue (cannot find it back directly)

if this is the case DrawBot needs to calculate the size based with laid out strings.

[LettError]

Reference for clipping in variable font text issue: https://github.com/typemytype/drawbot/issues/332

[typemytype]

you can check the typesetted bounds of a formattestring with textBoxCharacterBounds

this should probably by used for textSize() and formattedString.size()

import os
import drawBot as db


def make_proof_page(language_tag):

    proof_text = 'вгджзийклнпттттфцчшщъьюѝ'

    font = 'SourceSerifPro-Light.otf'
    margin = 30
    pt_size = 40

    db.newPage(1200, 120)
    y_offset = db.height() - margin - pt_size
    fs = db.FormattedString(
        proof_text,
        font=font,
        language=language_tag,
        fontSize=pt_size,
    )

    db.text(fs, (margin, y_offset))
    
    dummyHeight = 5000
    boxes = db.textBoxCharacterBounds(fs, (margin, y_offset, 5000, dummyHeight))
    for box in boxes:
        db.fill(1, 0, 0, .5)
        x, y, w, h = box.bounds
        db.rect(x, y-dummyHeight + fs.fontLineHeight() + fs.fontDescender(), w, h)
    print(fs.size().width)


db.newDrawing()
for language_tag in ['ru', 'bg']:
    make_proof_page(language_tag)

output_name = 'ru vs bgr.pdf'
db.saveImage(output_name)
#os.system(f'open "{output_name}"')
db.endDrawing()

[justvanrossum]

Simplified test:

size(600, 120)

proof_text = 'вгджзийклнпттттфцчшщъьюѝ'

font('../fonts/SourceSerifPro-Regular.otf')
fontSize(39)
text(proof_text, (12, 74))
language("bg")
text(proof_text, (12, 33))

The second line wraps, so the box calculation is not using the correct language setting.

[justvanrossum]

FWIW, drawbot-skia now supports language()

• https://github.com/justvanrossum/drawbot-skia/blob/master/tests/apitests/language.py
• https://github.com/justvanrossum/drawbot-skia/blob/master/tests/apitests_expected_output/language.png