[swift-evolution] Proposal: Extend CG(Rect)Geometry with center methods

D. Felipe Torres warorface at gmail.com
Fri Dec 11 15:17:35 CST 2015

Using the mid properties wouldn't help much as they are the middle of the
bounds (origin + length/2) and because it's a derived value from two
different structures, its not clear which structure you want to modify.

Either way, after thinking more about it, there is too much ambiguity to
the details of this. The intent is not always clear and looking into the
other functions, they all stand on their own. A CGRect doesn't have any
sense of hierarchy.

It only appears when you have layers/views (and those do have a way of
setting the center because the relationship/hierarchy is well defined).

I don't see any more reason to pursue this proposal.

On Fri, Dec 11, 2015 at 7:29 AM, Jacob Bandes-Storch <jtbandes at gmail.com>

> Would it make sense to achieve the same thing by giving midX and midY
> setters (they currently only have getters)?
> I'm don't think I like the idea of tying down any CGRect extensions to a
> "parent" rect, but saying "rect.midX = parent.midX" is pretty simple &
> clear.
> Jacob
> On Thu, Dec 10, 2015 at 6:17 AM, D. Felipe Torres via swift-evolution <
> swift-evolution at swift.org> wrote:
>> One of the task that is performed often is center a frame with respect to
>> it's parent.
>> The code for this is short and simple:
>> rect.origin.x = (rect.width-parent.width)/2 // or...
>> rect.origin.y = (rect.height-parent.height)/2
>> ## Current Problems
>> - It is very easy to get it wrong and confuse X or Y and their length
>> associations.
>> - Because this code is often found in a layout method, several other rect
>> variables may be defined in the scope which makes it easier to mistake one
>> variable with another if their names are close (and you are used to
>> autocomplete)
>> - And finally but most importantly, while the equation here is simple,
>> one must parse it and understand it and is not a very swifty approach.
>> ##Proposed Additions
>> 2 (actually 4) extensions in CGGeometry to CGRect:
>> extension CGRect {
>>       public func centerX(parentRect: CGRect) -> CGRect
>>       public mutating func centerXInPlace(parentRect: CGRect)
>>       public fun centerY(parentRect: CGRect) -> CGRect
>>       public mutating func centerYInPlace(parentRect: CGRect)
>> }
>> This extension allows very easily (and verbally) center a rect in respect
>> to a parent.
>> I'm pretty sure there are other pretty useful extensions that can be
>> added to CGGeometry as well but this one I think is basic and pretty
>> important.
>> --
>> ++++++++++++++++++++++++++
>> Diego Torres.
>> Web: dtorres.me
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution

Diego Torres.
Phone (Mobile Germany): +49 157 30070985
Phone (Landline Chile): +56 2 29790978
Web: dtorres.me
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