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Fit the mnemonic font size to the column width of each card #30

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Fit the mnemonic font size to the column width of each card #30

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22 changes: 20 additions & 2 deletions slip39/layout/components.py
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Original file line number Diff line number Diff line change
Expand Up @@ -213,6 +213,13 @@ def element( self ):
Coordinate = namedtuple( 'Coordinate', ('x', 'y') )


# A SLIP-39 mnemonic cell is eg. "12 advocate": up to MNEM_CHARS (2 digits, a space, an 8-letter word)
# of monospaced font, each MONO_WIDTH of the font size wide; fit within MNEM_FIT of the column width.
MNEM_CHARS = 11
MONO_WIDTH = .6
MNEM_FIT = .9


def layout_card(
card_size: Coordinate,
card_margin: int,
Expand Down Expand Up @@ -314,6 +321,17 @@ def layout_card(
assert num_mnemonics in MNEM_ROWS_COLS, \
f"Invalid SLIP-39 mnemonic word count: {num_mnemonics}"
rows,cols = MNEM_ROWS_COLS[num_mnemonics]

def mnem_size( region, size_ratio ):
"""The mnemonic font size (points): from the height of each row, unless that is too wide for
the longest "NN word" (MNEM_CHARS mono characters) to fit in the width of each column."""
return min(
region.h / rows * PT_IN * size_ratio,
region.w / cols * PT_IN * MNEM_FIT / ( MNEM_CHARS * MONO_WIDTH ),
)

mnem_fontsize = mnem_size( card_mnemonics, 9/16 )
mnem_fontsize_big = mnem_size( card_mnemonics_big, 12/16 )
for r in range( rows ):
for c in range( cols ):
card_mnemonics.add_region_proportional(
Expand All @@ -325,7 +343,7 @@ def layout_card(
y2 = (r+1)/rows,
font = 'mono',
bold = True,
size_ratio = 9/16,
size = mnem_fontsize,
)
)
card_mnemonics_big.add_region_proportional(
Expand All @@ -337,7 +355,7 @@ def layout_card(
y2 = (r+1)/rows,
font = 'mono',
bold = True,
size_ratio = 12/16,
size = mnem_fontsize_big,
)
)

Expand Down
15 changes: 14 additions & 1 deletion slip39/output_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,8 @@
from fpdf import FPDF, FlexTemplate

from .layout import Region, Text, Image, Box, Coordinate
from .defaults import MM_IN
from .layout.components import layout_card, MNEM_CHARS, MONO_WIDTH
from .defaults import MM_IN, PT_IN, CARD_SIZES, MNEM_ROWS_COLS


def test_Region():
Expand Down Expand Up @@ -73,3 +74,15 @@ def test_Region():
tpl.render( offsetx = card_size.x * MM_IN, offsety = card_size.y * MM_IN )

#pdf.output( "test.pdf" ) # To view results in test.pdf, uncomment


def test_card_mnemonics_fit():
"""The longest mnemonic cell ("12 advocate") must fit within its column, for every card size."""
for card_size,((card_h,card_w),card_margin) in CARD_SIZES.items():
for num_mnemonics in MNEM_ROWS_COLS:
card = layout_card( Coordinate( y=card_h, x=card_w ), card_margin, num_mnemonics )
for e in card.elements():
if e['name'].startswith( 'mnem-' ):
cell_pt = ( e['x2'] - e['x1'] ) / MM_IN * PT_IN
assert e['size'] * MONO_WIDTH * MNEM_CHARS <= cell_pt, \
f"{card_size} card, {num_mnemonics} words: {e['name']} {e['size']:.2f}pt too big for a {cell_pt:.1f}pt column"
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