> On Dec 1, 2014, at 5:50 PM, Graham Cox <graham....@bigpond.com> wrote:
>
>> On 2 Dec 2014, at 6:19 am, Bill Cheeseman <wjcheese...@gmail.com
>> <mailto:wjcheese...@gmail.com>> wrote:
>>
>> Can anyone suggest another approach?
>
> Not another approach, but a possible alternative explanation. Antialiasing.
> Those curved corners will cause various nearby pixels to be rendered for
> antialiasing, and these may differ very slightly depending on all sorts of
> factors - line width, the colours used, the exact alignment of the path to
> the pixel grid, as well as the underlying curve algorithm. It's very hard to
> make two overlaid curves always hit exactly the same pixels even when using
> the same curve algorithm.
>
> Is there no way to avoid having to overlay two curves? Maybe clip the content
> to a round-cornered rect then finally draw the same path on top? (Not sure if
> that's actually what you want, it's a little hard to visualise from the
> verbal description).
Thanks, I'll look into these suggestions today.
Antialiasing issues seem unlikely because the exposed sliver of the underlying
fill color seems too wide to be caused by antialiasing. But perhaps the slimmer
sliver I see in some configurations could be explained by antialiasing.
I am looking into ways to avoid overlaying two paths. The problem is that
Yosemite's NSVisualEffectView is very poorly documented. It appears that the
only way to get "vibrancy" effects like those seen in the background fill
region of Apple's application switcher is to give the NSVisualEffectView a dark
"material" (which appears to be roughly equivalent to drawing a background fill
color) and then filling a subview in front of it with another color. So both
views need the same rounded corners in a transparent borderless window, which I
do by creating a mask image in the NSVisualEffectView and a mask layer in a
CALayer/CAShapeLayer on the subview.
The stacking order of my window view hierarchy is this currently (today I will
probably have to add another layer-hosting view between the inner visual effect
view and the icon image view):
window
content view
outer visual effect view filling window with rounded corners
layer-hosting view filling window with rounded corners and
returning YES in -allowsVibrancy
inner visual effect view covering small center area of window
icon image view covering small center area of window and
returning NO in -allowsVibrancy
--
Bill Cheeseman - b...@cheeseman.name
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