Swiftgram/AsyncDisplayKit/Layout/ASInsetLayoutSpec.mm
Levi McCallum 25096117e7 Prevent ASInsetLayoutSpec from creating a computed layout when child is nil
Reviewers: scottg, schneider, ricky, garrett

Reviewed By: garrett

Subscribers: garrett, jenkins

Differential Revision: https://phabricator.pinadmin.com/D83683

JIRA Issue(s): BRIO-4729
2016-04-06 17:05:49 -07:00

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/*
* Copyright (c) 2014-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
*/
#import "ASInsetLayoutSpec.h"
#import "ASAssert.h"
#import "ASBaseDefines.h"
#import "ASInternalHelpers.h"
#import "ASLayout.h"
@interface ASInsetLayoutSpec ()
{
UIEdgeInsets _insets;
}
@end
/* Returns f if f is finite, substitute otherwise */
static CGFloat finite(CGFloat f, CGFloat substitute)
{
return isinf(f) ? substitute : f;
}
/* Returns f if f is finite, 0 otherwise */
static CGFloat finiteOrZero(CGFloat f)
{
return finite(f, 0);
}
/* Returns the inset required to center 'inner' in 'outer' */
static CGFloat centerInset(CGFloat outer, CGFloat inner)
{
return ASRoundPixelValue((outer - inner) / 2);
}
@implementation ASInsetLayoutSpec
- (instancetype)initWithInsets:(UIEdgeInsets)insets child:(id<ASLayoutable>)child;
{
if (!(self = [super init])) {
return nil;
}
ASDisplayNodeAssertNotNil(child, @"Child cannot be nil");
_insets = insets;
[self setChild:child];
return self;
}
+ (instancetype)insetLayoutSpecWithInsets:(UIEdgeInsets)insets child:(id<ASLayoutable>)child
{
return [[self alloc] initWithInsets:insets child:child];
}
- (void)setInsets:(UIEdgeInsets)insets
{
ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
_insets = insets;
}
/**
Inset will compute a new constrained size for it's child after applying insets and re-positioning
the child to respect the inset.
*/
- (ASLayout *)measureWithSizeRange:(ASSizeRange)constrainedSize
{
const CGFloat insetsX = (finiteOrZero(_insets.left) + finiteOrZero(_insets.right));
const CGFloat insetsY = (finiteOrZero(_insets.top) + finiteOrZero(_insets.bottom));
// if either x-axis inset is infinite, let child be intrinsic width
const CGFloat minWidth = (isinf(_insets.left) || isinf(_insets.right)) ? 0 : constrainedSize.min.width;
// if either y-axis inset is infinite, let child be intrinsic height
const CGFloat minHeight = (isinf(_insets.top) || isinf(_insets.bottom)) ? 0 : constrainedSize.min.height;
const ASSizeRange insetConstrainedSize = {
{
MAX(0, minWidth - insetsX),
MAX(0, minHeight - insetsY),
},
{
MAX(0, constrainedSize.max.width - insetsX),
MAX(0, constrainedSize.max.height - insetsY),
}
};
if (self.child == nil) {
ASDisplayNodeAssert(NO, @"Inset spec measured without a child. The spec will do nothing.");
return [ASLayout layoutWithLayoutableObject:self size:CGSizeZero];
}
ASLayout *sublayout = [self.child measureWithSizeRange:insetConstrainedSize];
const CGSize computedSize = ASSizeRangeClamp(constrainedSize, {
finite(sublayout.size.width + _insets.left + _insets.right, constrainedSize.max.width),
finite(sublayout.size.height + _insets.top + _insets.bottom, constrainedSize.max.height),
});
const CGFloat x = finite(_insets.left, constrainedSize.max.width -
(finite(_insets.right,
centerInset(constrainedSize.max.width, sublayout.size.width)) + sublayout.size.width));
const CGFloat y = finite(_insets.top,
constrainedSize.max.height -
(finite(_insets.bottom,
centerInset(constrainedSize.max.height, sublayout.size.height)) + sublayout.size.height));
sublayout.position = CGPointMake(x, y);
return [ASLayout layoutWithLayoutableObject:self size:computedSize sublayouts:@[sublayout]];
}
- (void)setChildren:(NSArray *)children
{
ASDisplayNodeAssert(NO, @"not supported by this layout spec");
}
- (NSArray *)children
{
ASDisplayNodeAssert(NO, @"not supported by this layout spec");
return nil;
}
@end