objective c - What does CALayer know that I do not when zooming -

how can draw smoothly calayer while zooming?

as seen in third (tallest) image white border drawn accurate, anti-aliased rendering.

however neither labels (even though set contentscalefactor) nor hand drawn circles (even though turn anti aliasing on) are.

how can have anti-aliased rendering either uikit components or hand-drawn graphics scale zooming factor smoothly calayer does?

what's magic?

the white border drawn using view's calayer:

    self.layer.cornerradius = frame.size.width / 2.0f ;     self.layer.bordercolor = [uicolor whitecolor].cgcolor ;     self.layer.borderwidth = 3.0f ; 

the numbers uilabel's

    cgfloat contentscale = self.zoomscale * [uiscreen mainscreen].scale; // handle retina     label.contentscalefactor = contentscale; 

and given:

    typedef struct {         cgrect      rect ;         cgcolorref  color ;     } eventcolor ; 

the 4 circles drawn using coregraphics

    ::cgcontextsetallowsantialiasing(context, true) ;     ::cgcontextsetshouldantialias(context, true) ;     // ...     eventcolor ec = ...     // ...     ::cgcontextsetfillcolorwithcolor(context, ec.color) ;     ::cgcontextfillellipseinrect(context, ec.rect) ; 

it turns out misunderstood contentscalefactor meant for, , discovered after calayer's contentscale.

the upshot drawrect method in whatever uiview subclass can go ahead , pretend zooming scale set 1.0 provided view's layer's contentscale set reflect current zoom level of scroll view.

- (void) scrollviewdidendzooming: (uiscrollview *) scrollview                         withview: (uiview *) view                          atscale: (float) scale {      scale *= [uiscreen mainscreen].scale ;     (uiview * v in view.subviews) {         v.layer.contentsscale = scale ;         [v setneedsdisplay] ;     } } 

the example above assumes scroll view contains non opaque container view in turn contains every actual views layer.contentscale needs adjusting.