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consider allowing custom X positioning of display characters #2
Description
The hardware-based right justification is known to be buggy.
Given the existence of 1px-wide spaces (as discussed in #1), it is possible to fake right-justification (or indeed draw characters at any X position and with any desired spacing).
I prepared the following kludge to fix the right justification in a production environment:
_DISPLAY_WIDTH = 120
_CHARS_BY_WIDTH = {
3: b'.',
4: b'I1: ',
5: b'0-',
6: b'ABCDEFGHJKLMNOPQRSTUVWXYZ23456789',
}
_WIDTHS_BY_CHAR = {}
for width, chars in _CHARS_BY_WIDTH.items():
for char in chars:
_WIDTHS_BY_CHAR[char] = width
def pixel_width(string):
width = 0
for char in string:
if char not in _WIDTHS_BY_CHAR:
raise ValueError('unknown width for character "%s"' % char)
width += _WIDTHS_BY_CHAR[char]
return width
def fix_right_justification(bytestring):
if rb'\R' not in bytestring:
return bytestring
left_start = 7
left_end = bytestring.index(rb'\R', left_start)
right_start = left_end + len(rb'\R')
right_end = bytestring.index(
b'\n', right_start
) if b'\n' in bytestring[right_start:] else bytestring.index(
b'\r', right_start)
left = bytestring[left_start:left_end]
right = bytestring[right_start:right_end]
left_width = pixel_width(left)
right_width = pixel_width(right)
padding_width = _DISPLAY_WIDTH - 2 - left_width - right_width
padding = b''
space_width = _WIDTHS_BY_CHAR[ord(' ')]
while padding_width >= space_width:
padding += b' '
padding_width -= space_width
while padding_width > 0:
padding += b'\xff'
padding_width -= 1
return bytestring[:left_end] + padding + bytestring[right_start:]fix_right_justification takes bytes as returned by DisplayMessage.to_bytes() and further modifies them.
Think about how best this could be incorporated into the library.
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