In the Three Kingdoms Period (220-280), the king of the Wei, Cao Rui, wanted to select a very capable man to work for him. He said to his ministers: 'When choosing a talented person, always beware of one with a false reputation. A false reputation is just like a picture of a cake; it can' t relieve hunger.' www.enfang.com
后来人们就用“画饼充饥”这个成语比喻用空想安慰自己,不能解决实际问题。
Later, this idiom came to be used to mean comforting oneself with unrealistic thoughts, without solving practical problems.