Re: Core Animation geometry, layer hosting, and resolution independence

FROM : Nathan Vander Wilt
DATE : Thu Mar 13 00:38:47 2008

--- Jens Alfke <<email_removed>> escribió:

>
> On 12 Mar '08, at 2:49 PM, Nathan Vander Wilt wrote:
>
> > I don't understand what this "base" coordinate
> system
> > is (not the window's, otherwise the conversions
> would
> > likely be offset by the view's position therein,
> > right?). But whatever it is, it seems to be shared
> by
> > the CALayer.
>
>
> The Cocoa Drawing Guide, under "Pixel-Exact
> Drawing", says:
> "These convenience methods make it possible to
> convert values to and 
> from the base (device) coordinate system. They take
> into account the 
> current backing store configuration for the view,
> including whether it 
> is backed by a layer."
>
> In a layer-backed NSView, it seems that the
> 'device', aka backing 
> store, is the view's CALayer; so these methods will
> convert to/from 
> the layer's coordinates.


Most excellent! Glad to have a documentation reference
that seems to guarantee correct behaviour in this
situation. Between that an the individual geometry
guides, I think I should be able to eventually build a
sense for how it all meshes.

It'd still be nice to have a single "go-to" document
that describes all the various coordinate systems as
they meet in a custom drawn layer hosting view. Maybe
some of the individual places could be clearer as
well. I hate filing bugs like this against
documentation, because I really don't know what would
help until I've read it, but I'll try file at least
one.

thanks much,
-natevw

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