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Use a sentinel NSUInteger for node layout data #trivial #428

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merged 3 commits into from
Jul 10, 2017
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Use a sentinel NSUInteger for node layout data #trivial #428

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Use a sentinel NSUInteger for node layout data
Adlai-Holler Jul 9, 2017
05a0e52
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Adlai-Holler Jul 9, 2017
8f2be9a
Address feedback from @appleguy
Adlai-Holler Jul 9, 2017
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25 changes: 13 additions & 12 deletions Source/ASDisplayNode+Layout.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -82,21 +82,19 @@ - (ASLayout *)layoutThatFits:(ASSizeRange)constrainedSize parentSize:(CGSize)par
}

ASLayout *layout = nil;
if (_calculatedDisplayNodeLayout->isValidForConstrainedSizeParentSize(constrainedSize, parentSize)) {
NSUInteger version = _layoutVersion;
if (_calculatedDisplayNodeLayout->isValid(constrainedSize, parentSize, version)) {
ASDisplayNodeAssertNotNil(_calculatedDisplayNodeLayout->layout, @"-[ASDisplayNode layoutThatFits:parentSize:] _calculatedDisplayNodeLayout->layout should not be nil! %@", self);
// Our calculated layout is suitable for this constrainedSize, so keep using it and
// invalidate any pending layout that has been generated in the past.
_pendingDisplayNodeLayout = nullptr;
layout = _calculatedDisplayNodeLayout->layout;
} else if (_pendingDisplayNodeLayout != nullptr && _pendingDisplayNodeLayout->isValidForConstrainedSizeParentSize(constrainedSize, parentSize)) {
} else if (_pendingDisplayNodeLayout != nullptr && _pendingDisplayNodeLayout->isValid(constrainedSize, parentSize, version)) {
ASDisplayNodeAssertNotNil(_pendingDisplayNodeLayout->layout, @"-[ASDisplayNode layoutThatFits:parentSize:] _pendingDisplayNodeLayout->layout should not be nil! %@", self);
layout = _pendingDisplayNodeLayout->layout;
} else {
// Create a pending display node layout for the layout pass
layout = [self calculateLayoutThatFits:constrainedSize
restrictedToSize:self.style.size
relativeToParentSize:parentSize];
_pendingDisplayNodeLayout = std::make_shared<ASDisplayNodeLayout>(layout, constrainedSize, parentSize);
_pendingDisplayNodeLayout = std::make_shared<ASDisplayNodeLayout>(layout, constrainedSize, parentSize, version);
ASDisplayNodeAssertNotNil(layout, @"-[ASDisplayNode layoutThatFits:parentSize:] newly calculated layout should not be nil! %@", self);
}

Expand Down Expand Up @@ -308,7 +306,7 @@ - (void)_locked_measureNodeWithBoundsIfNecessary:(CGRect)bounds
// Prefer _pendingDisplayNodeLayout over _calculatedDisplayNodeLayout (if exists, it's the newest)
// If there is no _pending, check if _calculated is valid to reuse (avoiding recalculation below).
if (_pendingDisplayNodeLayout == nullptr) {
if (_calculatedDisplayNodeLayout->isDirty() == NO
if (_calculatedDisplayNodeLayout->version >= _layoutVersion
&& (_calculatedDisplayNodeLayout->requestedLayoutFromAbove == YES
|| CGSizeEqualToSize(_calculatedDisplayNodeLayout->layout.size, boundsSizeForLayout))) {
return;
Expand Down Expand Up @@ -337,8 +335,8 @@ - (void)_locked_measureNodeWithBoundsIfNecessary:(CGRect)bounds
BOOL pendingLayoutApplicable = NO;
if (nextLayout == nullptr) {
as_log_verbose(ASLayoutLog(), "No pending layout.");
} else if (nextLayout->isDirty()) {
as_log_verbose(ASLayoutLog(), "Pending layout is invalid.");
} else if (nextLayout->version < _layoutVersion) {
as_log_verbose(ASLayoutLog(), "Pending layout is stale.");
} else if (layoutSizeDifferentFromBounds) {
as_log_verbose(ASLayoutLog(), "Pending layout size %@ doesn't match bounds size.", NSStringFromCGSize(nextLayout->layout.size));
} else {
Expand All @@ -349,12 +347,13 @@ - (void)_locked_measureNodeWithBoundsIfNecessary:(CGRect)bounds
if (!pendingLayoutApplicable) {
as_log_verbose(ASLayoutLog(), "Measuring with previous constrained size.");
// Use the last known constrainedSize passed from a parent during layout (if never, use bounds).
NSUInteger version = _layoutVersion;
ASSizeRange constrainedSize = [self _locked_constrainedSizeForLayoutPass];
ASLayout *layout = [self calculateLayoutThatFits:constrainedSize
restrictedToSize:self.style.size
relativeToParentSize:boundsSizeForLayout];

nextLayout = std::make_shared<ASDisplayNodeLayout>(layout, constrainedSize, boundsSizeForLayout);
nextLayout = std::make_shared<ASDisplayNodeLayout>(layout, constrainedSize, boundsSizeForLayout, version);
}

if (didCreateNewContext) {
Expand Down Expand Up @@ -425,7 +424,7 @@ - (void)_layoutSublayouts
ASLayout *layout;
{
ASDN::MutexLocker l(__instanceLock__);
if (_calculatedDisplayNodeLayout->isDirty()) {
if (_calculatedDisplayNodeLayout->version < _layoutVersion) {
return;
}
layout = _calculatedDisplayNodeLayout->layout;
Expand Down Expand Up @@ -569,6 +568,7 @@ - (void)transitionLayoutWithSizeRange:(ASSizeRange)constrainedSize
}

// Perform a full layout creation pass with passed in constrained size to create the new layout for the transition
NSUInteger newLayoutVersion = _layoutVersion;
ASLayout *newLayout;
{
ASDN::MutexLocker l(__instanceLock__);
Expand Down Expand Up @@ -609,7 +609,8 @@ - (void)transitionLayoutWithSizeRange:(ASSizeRange)constrainedSize
auto previousLayout = _calculatedDisplayNodeLayout;
auto pendingLayout = std::make_shared<ASDisplayNodeLayout>(newLayout,
constrainedSize,
constrainedSize.max);
constrainedSize.max,
newLayoutVersion);
[self _locked_setCalculatedDisplayNodeLayout:pendingLayout];

// Setup pending layout transition for animation
Expand Down
9 changes: 2 additions & 7 deletions Source/ASDisplayNode.mm
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Expand Up @@ -285,6 +285,7 @@ - (void)_initializeInstance

_calculatedDisplayNodeLayout = std::make_shared<ASDisplayNodeLayout>();
_pendingDisplayNodeLayout = nullptr;
_layoutVersion = 1;

_defaultLayoutTransitionDuration = 0.2;
_defaultLayoutTransitionDelay = 0.0;
Expand Down Expand Up @@ -882,12 +883,7 @@ - (void)invalidateCalculatedLayout
{
ASDN::MutexLocker l(__instanceLock__);

// This will cause the next layout pass to compute a new layout instead of returning
// the cached layout in case the constrained or parent size did not change
_calculatedDisplayNodeLayout->invalidate();
if (_pendingDisplayNodeLayout != nullptr) {
_pendingDisplayNodeLayout->invalidate();
}
_layoutVersion++;

_unflattenedLayout = nil;

Expand Down Expand Up @@ -924,7 +920,6 @@ - (void)__layout
// This method will confirm that the layout is up to date (and update if needed).
// Importantly, it will also APPLY the layout to all of our subnodes if (unless parent is transitioning).
[self _locked_measureNodeWithBoundsIfNecessary:bounds];
_pendingDisplayNodeLayout = nullptr;
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Why is this removed? Although it may be valid, I think we should revert this change if it's not necessary, as it adds at least a touch of risk that would be better to do in a diff focused on the _pending layout storage.

For example, I'm not sure if there is ever a case where the _pending is not copied to _calculated, such as if the _calculated matches the current bounds but _pending does not. In this case it would change the behavior of other calls that would use _pending later, compared to before this change.

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My aim here is to converge our handling of invalidation. If the _pendingDisplayNodeLayout is still valid, we should keep it around and use it freely. It may be a behavior change but I think it'll be for the better. If _pending and _calculated both have the same version, and it's the current version, then we should be comfortable arbitrarily using either one (minus size constraints) since neither has fresher layout data.

I believe that if I'm wrong, and I may well be, then the solution is to fix our understanding of layout freshness and perhaps find the right place to bump _layoutVersion to avoid using this pending layout again, rather than relying on this one-off (this is the only place where we explicitly clear pending layout). Thoughts? I'd also like to hear @maicki 's take on this if possible.


[self _locked_layoutPlaceholderIfNecessary];
}
Expand Down
5 changes: 4 additions & 1 deletion Source/Private/ASDisplayNodeInternal.h
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Expand Up @@ -34,7 +34,6 @@ NS_ASSUME_NONNULL_BEGIN
@protocol _ASDisplayLayerDelegate;
@class _ASDisplayLayer;
@class _ASPendingState;
@class ASSentinel;
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This was just a leftover – the ASSentinel class was removed in favor of atomic integers.

struct ASDisplayNodeFlags;

BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector);
Expand Down Expand Up @@ -160,6 +159,10 @@ FOUNDATION_EXPORT NSString * const ASRenderingEngineDidDisplayNodesScheduledBefo
std::shared_ptr<ASDisplayNodeLayout> _calculatedDisplayNodeLayout;
std::shared_ptr<ASDisplayNodeLayout> _pendingDisplayNodeLayout;

/// Sentinel for layout data. Incremented when we get -setNeedsLayout / -invalidateCalculatedLayout.
/// Starts at 1.
std::atomic<NSUInteger> _layoutVersion;

ASDisplayNodeViewBlock _viewBlock;
ASDisplayNodeLayerBlock _layerBlock;
NSMutableArray<ASDisplayNodeDidLoadBlock> *_onDidLoadBlocks;
Expand Down
23 changes: 7 additions & 16 deletions Source/Private/ASDisplayNodeLayout.h
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Expand Up @@ -30,35 +30,26 @@ struct ASDisplayNodeLayout {
ASSizeRange constrainedSize;
CGSize parentSize;
BOOL requestedLayoutFromAbove;
BOOL _dirty;
NSUInteger version;

/*
* Create a new display node layout with
* @param layout The layout to associate, usually returned from a call to -layoutThatFits:parentSize:
* @param constrainedSize Constrained size used to create the layout
* @param parentSize Parent size used to create the layout
* @param version The version of the source layout data – see ASDisplayNode's _layoutVersion.
*/
ASDisplayNodeLayout(ASLayout *layout, ASSizeRange constrainedSize, CGSize parentSize)
: layout(layout), constrainedSize(constrainedSize), parentSize(parentSize), requestedLayoutFromAbove(NO), _dirty(NO) {};
ASDisplayNodeLayout(ASLayout *layout, ASSizeRange constrainedSize, CGSize parentSize, NSUInteger version)
: layout(layout), constrainedSize(constrainedSize), parentSize(parentSize), requestedLayoutFromAbove(NO), version(version) {};

/*
* Creates a layout without any layout associated. By default this display node layout is dirty.
*/
ASDisplayNodeLayout()
: layout(nil), constrainedSize({{0, 0}, {0, 0}}), parentSize({0, 0}), requestedLayoutFromAbove(NO), _dirty(YES) {};
: layout(nil), constrainedSize({{0, 0}, {0, 0}}), parentSize({0, 0}), requestedLayoutFromAbove(NO), version(0) {};

/**
* Returns if the display node layout is dirty as it was invalidated or it was created without a layout.
* Returns whether this is valid for a given constrained size, parent size, and version
*/
BOOL isDirty();

/**
* Returns if ASDisplayNode is still valid for a given constrained and parent size
*/
BOOL isValidForConstrainedSizeParentSize(ASSizeRange constrainedSize, CGSize parentSize);

/**
* Invalidate the display node layout
*/
void invalidate();
BOOL isValid(ASSizeRange constrainedSize, CGSize parentSize, NSUInteger version);
};
23 changes: 5 additions & 18 deletions Source/Private/ASDisplayNodeLayout.mm
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Expand Up @@ -17,23 +17,10 @@

#import <AsyncDisplayKit/ASDisplayNodeLayout.h>

BOOL ASDisplayNodeLayout::isDirty()
BOOL ASDisplayNodeLayout::isValid(ASSizeRange theConstrainedSize, CGSize theParentSize, NSUInteger versionArg)
{
return _dirty || layout == nil;
}

BOOL ASDisplayNodeLayout::isValidForConstrainedSizeParentSize(ASSizeRange theConstrainedSize, CGSize theParentSize)
{
// Only generate a new layout if:
// - The current layout is dirty
// - The passed constrained size is different than the original layout's parent or constrained size
return (layout != nil
&& _dirty == NO
&& CGSizeEqualToSize(parentSize, theParentSize)
&& ASSizeRangeEqualToSizeRange(constrainedSize, theConstrainedSize));
}

void ASDisplayNodeLayout::invalidate()
{
_dirty = YES;
return version >= versionArg
&& layout != nil
&& CGSizeEqualToSize(parentSize, theParentSize)
&& ASSizeRangeEqualToSizeRange(constrainedSize, theConstrainedSize);
}