At 19:59 -0700 19/03/09, cocoa-dev-requ...@lists.apple.com wrote: >From: John Reppy <j...@cs.uchicago.edu> >Date: Thu, 19 Mar 2009 15:39:44 -0500 >Message-ID: <df94276e-b4ab-49c7-a425-7e7d2f220...@cs.uchicago.edu> > >I'm building a viewer for event logs that needs to support a wide range >of scales (say from seconds/inch to nanoseconds/inch). I've got a custom >subclass of NSView for displaying this information, which I want to embed >in an NSScrollView. The problem that I'm faced with is that the floating-point >coordinates used by Cocoa do not have enough precision at full magnification. > >I'm guessing that the best solution is to subclass NSScrollView to track the >visible rectangle's origin using doubles, but I'm not sure which NSScrollView >methods I should be overriding. Also, do I need to override NSClipView too? >Any pointers or suggestions would be appreciated.
In a similar situation, I didn't subclass NSScrollView. I subclassed NSView and inserted an NSScroller directly as its subview. I tracked the position with a 64-bit variable which I converted to a range suitable for the NSScroller just for setting its thumb position and size. I set my view as the NSScroller's target to convert back to my 64-bit position. In the subclass' -drawRect: method, I calculated the visible portion of the view, and simply drew that - no NSClipView required. For your case, you'd have an additional step involving the scale; be careful with loss of precision there. Despite being somewhat more work to implement, this proved to be more efficient and also a good learning experience regarding the view drawing mechanism. HTH, -- Rainer Brockerhoff <rai...@brockerhoff.net> Belo Horizonte, Brazil "In the affairs of others even fools are wise In their own business even sages err." Weblog: http://www.brockerhoff.net/bb/viewtopic.php _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
