Swiftgram/AsyncDisplayKit/Layout/ASCenterLayoutSpec.mm
2015-08-21 21:03:40 -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 "ASCenterLayoutSpec.h"
#import "ASInternalHelpers.h"
#import "ASLayout.h"
@implementation ASCenterLayoutSpec
{
ASCenterLayoutSpecCenteringOptions _centeringOptions;
ASCenterLayoutSpecSizingOptions _sizingOptions;
id<ASLayoutable> _child;
}
- (instancetype)initWithCenteringOptions:(ASCenterLayoutSpecCenteringOptions)centeringOptions
sizingOptions:(ASCenterLayoutSpecSizingOptions)sizingOptions
child:(id<ASLayoutable>)child;
{
if (!(self = [super init])) {
return nil;
}
ASDisplayNodeAssertNotNil(child, @"Child cannot be nil");
_centeringOptions = centeringOptions;
_sizingOptions = sizingOptions;
_child = child;
return self;
}
+ (instancetype)centerLayoutSpecWithCenteringOptions:(ASCenterLayoutSpecCenteringOptions)centeringOptions
sizingOptions:(ASCenterLayoutSpecSizingOptions)sizingOptions
child:(id<ASLayoutable>)child
{
return [[self alloc] initWithCenteringOptions:centeringOptions sizingOptions:sizingOptions child:child];
}
- (void)setChild:(id<ASLayoutable>)child
{
ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
_child = child;
}
- (void)setCenteringOptions:(ASCenterLayoutSpecCenteringOptions)centeringOptions
{
ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
_centeringOptions = centeringOptions;
}
- (void)setSizingOptions:(ASCenterLayoutSpecSizingOptions)sizingOptions
{
ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
_sizingOptions = sizingOptions;
}
- (ASLayout *)measureWithSizeRange:(ASSizeRange)constrainedSize
{
CGSize size = {
constrainedSize.max.width,
constrainedSize.max.height
};
// Layout the child
const CGSize minChildSize = {
(_centeringOptions & ASCenterLayoutSpecCenteringX) != 0 ? 0 : constrainedSize.min.width,
(_centeringOptions & ASCenterLayoutSpecCenteringY) != 0 ? 0 : constrainedSize.min.height,
};
ASLayout *sublayout = [_child measureWithSizeRange:ASSizeRangeMake(minChildSize, constrainedSize.max)];
// If we have an undetermined height or width, use the child size to define the layout
// size
size = ASSizeRangeClamp(constrainedSize, {
isnan(size.width) ? sublayout.size.width : size.width,
isnan(size.height) ? sublayout.size.height : size.height
});
// If minimum size options are set, attempt to shrink the size to the size of the child
size = ASSizeRangeClamp(constrainedSize, {
MIN(size.width, (_sizingOptions & ASCenterLayoutSpecSizingOptionMinimumX) != 0 ? sublayout.size.width : size.width),
MIN(size.height, (_sizingOptions & ASCenterLayoutSpecSizingOptionMinimumY) != 0 ? sublayout.size.height : size.height)
});
// Compute the centered postion for the child
BOOL shouldCenterAlongX = (_centeringOptions & ASCenterLayoutSpecCenteringX);
BOOL shouldCenterAlongY = (_centeringOptions & ASCenterLayoutSpecCenteringY);
sublayout.position = {
ASRoundPixelValue(shouldCenterAlongX ? (size.width - sublayout.size.width) * 0.5f : 0),
ASRoundPixelValue(shouldCenterAlongY ? (size.height - sublayout.size.height) * 0.5f : 0)
};
return [ASLayout layoutWithLayoutableObject:self size:size sublayouts:@[sublayout]];
}
@end