> On Feb 10, 2015, at 15:34, Clark S. Cox III <clarkc...@gmail.com> wrote: > >> >> On Feb 10, 2015, at 12:20, Quincey Morris >> <quinceymor...@rivergatesoftware.com> wrote: >> >> On Feb 10, 2015, at 11:23 , Jerry Krinock <je...@ieee.org> wrote: >>> >>> I’ve always wondered why, when you’re dragging a window around a non-Retina >>> screen, the anti-aliasing doesn’t show a “comb filter” kind of effect, with >>> different lines getting fuzzy and sharp as they are dragged on and off >>> their pixels. Looking at this closely today, I think the explanation may >>> be that >>> >>> (1) Although you need to look carefully, Apple has constrained >>> dragging windows to “snap" to the grid of backing pixels. >>> You cannot move a window by one half pixel. >>> (2) A window’s intrinsic scrollers, title bars, etc. are also >>> on a 1-pixel grid. >>> (3) Any control or view that you place into Interface Builder >>> must be on a 1-pixel grid. I just tried entering a decimal >>> fraction, 139.5, and after I ended editing, it was rounded >>> down to 139. >> >> Case #3 is actually points, not pixels. Cases #1 and #2 may be points, too, >> but I don’t know. >> >> Then there’s #1A and #3A — meaning: positioning those elements >> programmatically. Even though you can’t place a button off the 1-point grid >> in IB, you might be able to do it programmatically. Or not. >> >> Also, be careful about conceptualizing backing “pixels”. On an iPhone 6+, >> the backing store is 2x, but the hardware is 3x. (Let’s hope I got that the >> right way round.) > > You got it backwards :) > > The app renders into a 3x backing store (i.e. each point is represented by a > 3x3 grid of pixels). > > As far as the app is concerned, it is rendering to a 1242 x 2208 pixel > (414x736 point) screen, but that is scaled down to the hardware resolution of > 1080x1920 pixels.
A good visualization of this: http://www.paintcodeapp.com/news/ultimate-guide-to-iphone-resolutions <http://www.paintcodeapp.com/news/ultimate-guide-to-iphone-resolutions>
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