computeSize method
Returns current Size of whole display.
Implementation
Size computeSize() {
final dividers = CharacterSegmentMap.dividerCharacters.values;
final charCount = characterCount ??
value.split('').where((c) => !dividers.contains(c)).length;
final dividerCharCount = value.split('').where(dividers.contains).length;
final charsWidth = charCount * (2 * segmentSize.width + segmentSize.height);
final dividersWidth = dividerCharCount * segmentSize.width;
final width = charsWidth + dividersWidth;
final widthOffset = characterSpacing * (charCount - 1) +
(characterSpacing * dividerCharCount);
final height = (2 * segmentSize.height) + (3 * segmentSize.width);
return Size(width + widthOffset, height);
}