Hi,
LED matrix that's what they use for all that stuff, not 7-segment displays.
You can map the most complex and/or largest unicode or whatever language character onto a piece of graph paper - really high tech stuff. When you know how many maximum squares are filled by a character in the vertical and the horizontal planes, you can count how many LEDs you will need to make a square, rectangle or circle or any shape in fact LED matrix.
Think London, New York, Mumbai, Tokyo, anywhere with huge LED advertising matrixes/screens, or modern bus numbers and destinations, or airports and train stations - they all use (LED) matrixes of small and building-size dimensions.