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A narrower rail is not the wide one with less of the roll in it: its frames are a different number of pixels wide, so the scrollLeft the reader was standing on is a different frame. Opening the studio on a desk and switching to the phone layout left the strip standing further down the roll than the frame on the stage — with three hundred frames in the folder, frame 170 where frame 150 was open — and the frames of the open photo were off the rail. The rail is now put back on the frame in hand whenever its own width changes, the window is read from where it then stands, and the tiles the reader is being shown are the ones asked for.