marijnh/CodeMirror — pull request #2392 by mightyguava (2014-03-20 20:43:17+00:00)
Title: [mac] Turn mouse cursor into crosshair when Alt held

On Macs, in native text editing apps with multiple selection available -- TextEdit and Xcode, and in the popular TextMate editor, the mouse cursor turns into a crosshair when alt is held to hint that the selection can be rectangular.

Might be useful for other platforms too, but I only see this behavior on Macs.