Our original Ikea cupboard doors where 60mm too tall for the new ceilings upstairs so I decided to try and shorten them. I haven't had much luck with cutting glass in the past but I gave it another go and this time it worked out okay.
I had to score the mirror side with a glass cutter then turn the door over to cut almost all the way through with a circular saw. I then had to turn the door over very carefully and press on the mirror to make the break. It is nerve wrecking stuff as one crack in the wrong direction and it is off again to Ikea to buy another door.
To doors had straight cuts and the third door was an angled cut as you can see in the picture. I need to adapt two more doors with the angle cut to complete the front of the wardrobe.