This bug has been going on for years and still hasn't been acknowledged or fixed. It makes the game unplayable for Mac users. All versions of Minecraft java 1.3 and newer are effected by this issue. Mac users who use a regular mouse are unable to shift and scroll through the tool wheel, as this is an (unchangeable) shortcut that switches the scroll from vertical to horizontal, Minecraft isn't picking up the scrolling and therefor the user is unable to move in the tool wheel. I've seen too many people reporting this problem (two of my friends have also confirmed they are unable to play in 1.3+ so instead play in 1.8.9) and it not being fixed!