On 4 Oct 2013, at 21:52, Kyle Sluder <k...@ksluder.com> wrote:
> On Fri, Oct 4, 2013, at 01:31 PM, jonat...@mugginsoft.com wrote:
>> I have a fixed size custom OS X view that I load from a nib and want to
>> centre within a host view using auto layout.
>> Can this be done using VFL alone?
>
> No.
Thanks for the confirmation.
> But it's still really simple to do in code.
Simple and verbose. The VFL would be more concise.
In reality I am just trying to figure out auto layout.
>
> Again, why are you concerning yourself with the view's size here? It is
> not necessary to explicitly specify a size in order to get centering
> behavior.
>
I do see it as a necessity, given the approach listed.
If a view provides intrinsic size info then explicit size constrains will not
be required.
A raw NSView instance requires the width/attributes to display correctly as far
as my experiments have confirmed.
This agrees with dumping layout constraints added in IB.
In the following case auto layout fails because there are no size constraints.
self.customview.translatesAutoresizingMaskIntoConstraints = NO; // we don't
want any auto constraints applied
[self.window.contentView addSubview: self.customview];
// recreate the fixed size centering constraints explictly
/* [self.customview addConstraint:[NSLayoutConstraint
constraintWithItem:self.customview
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNotAnAttribute
multiplier:1.0
constant:width]];
[self.customview addConstraint:[NSLayoutConstraint
constraintWithItem:self.customview
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:nil
attribute:NSLayoutAttributeNotAnAttribute
multiplier:1.0
constant:height]]; */
[self.window.contentView addConstraint:[NSLayoutConstraint
constraintWithItem:self.customview
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:self.window.contentView
attribute:NSLayoutAttributeCenterX
multiplier:1.0
constant:0]];
[self.window.contentView addConstraint:[NSLayoutConstraint
constraintWithItem:self.customview
attribute:NSLayoutAttributeCenterY
relatedBy:NSLayoutRelationEqual
toItem:self.window.contentView
attribute:NSLayoutAttributeCenterY
multiplier:1.0
constant:0]];
Jonathan
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