Quote from : City of Glass Book

But-" Maia, still looking at Alec and Magnus, broke off and rasied her eyebrows. Simon turned to see what she was looking at - and stared. Alec had his arms around Magnus and was kissing him full on the mouth. Magnus, who appeared to be in a state of shock, stood frozen. Several groups of people - Shadowhunters and Downworlders alike - were staring and whispering. Glancing to the side, Simon saw the Lightwoods, their eyes widen, gaping at the display. Maryse had her hand over her mouth. Maia looked perplexed. "Wait a second," she said. "Do we all have to do that, too?