This feels like a dumb question, but the ACR CC2017 crop tool appears to have the magic 'flyout' triangle, but I am having much luck making it respond. What I want to do specifically is set the crop tool aspect ratio, and what I am resorting to right now is dragging a window across the entire image, and then Shift dragging a corner to preserve the aspect ratio. The Help file is not 'helping' so perhaps someone who actually uses Photoshop for processing photographs (which I seldom do nowadays) can put me on track.
I'll try setting GPU on/off for ACR after posting this.
Blimey. Turning on the GPU for Camera RAW fixed it. I can't remember why I turned it off, but I do remember it was messing me up, so fingers crossed.
Thanks anyway. I'll mark the Assumed Answered to save folk wasting time.