Merge pull request #905 from facebook/RemoveWorkingWindow

[ASRangeController] Implement #if that controls removal of the offscreen UIWindow used for render-ahead.  Leave enabled for now.

Author: appleguy

AsyncDisplayKit/ASDisplayNode.mm

@@ -197,6 +197,29 @@ + (Class)layerClass
   return [_ASDisplayLayer class];
 }
 
++ (void)scheduleNodeForDisplay:(ASDisplayNode *)node
+{
+  ASDisplayNodeAssertMainThread();
+  static NSMutableSet *nodesToDisplay = nil;
+  static BOOL displayScheduled = NO;
+  if (!nodesToDisplay) {
+    nodesToDisplay = [[NSMutableSet alloc] init];
+  }
+  [nodesToDisplay addObject:node];
+  if (!displayScheduled) {
+    displayScheduled = YES;
+    // It's essenital that any layout pass that is scheduled during the current
+    // runloop has a chance to be applied / scheduled, so always perform this after the current runloop.
+    dispatch_async(dispatch_get_main_queue(), ^{
+      displayScheduled = NO;
+      for (ASDisplayNode *node in nodesToDisplay) {
+        [node __recursivelyTriggerDisplayAndBlock:NO];
+      }
+      nodesToDisplay = nil;
+    });
+  }
+}
+
 #pragma mark - Lifecycle
 
 - (void)_staticInitialize
@@ -710,6 +733,7 @@ - (void)displayImmediately
 - (void)recursivelyDisplayImmediately
 {
   ASDN::MutexLocker l(_propertyLock);
+  
   for (ASDisplayNode *child in _subnodes) {
     [child recursivelyDisplayImmediately];
   }
@@ -1453,7 +1477,7 @@ - (void)_tearDownPlaceholderLayer
   [_placeholderLayer removeFromSuperlayer];
 }
 
-void recursivelyEnsureDisplayForLayer(CALayer *layer)
+void recursivelyTriggerDisplayForLayer(CALayer *layer, BOOL shouldBlock)
 {
   // This recursion must handle layers in various states:
   // 1. Just added to hierarchy, CA hasn't yet called -display
@@ -1472,26 +1496,26 @@ void recursivelyEnsureDisplayForLayer(CALayer *layer)
 
   // Kick off the recursion first, so that all necessary display calls are sent and the displayQueue is full of parallelizable work.
   for (CALayer *sublayer in layer.sublayers) {
-    recursivelyEnsureDisplayForLayer(sublayer);
+    recursivelyTriggerDisplayForLayer(sublayer, shouldBlock);
   }
 
-  // As the recursion unwinds, verify each transaction is complete and block if it is not.
-  // While blocking on one transaction, others may be completing concurrently, so it doesn't matter which blocks first.
-  BOOL waitUntilComplete = (!node.shouldBypassEnsureDisplay);
-  if (waitUntilComplete) {
-    for (_ASAsyncTransaction *transaction in [layer.asyncdisplaykit_asyncLayerTransactions copy]) {
-      // Even if none of the layers have had a chance to start display earlier, they will still be allowed to saturate a multicore CPU while blocking main.
-      // This significantly reduces time on the main thread relative to UIKit.
-      [transaction waitUntilComplete];
+  if (shouldBlock) {
+    // As the recursion unwinds, verify each transaction is complete and block if it is not.
+    // While blocking on one transaction, others may be completing concurrently, so it doesn't matter which blocks first.
+    BOOL waitUntilComplete = (!node.shouldBypassEnsureDisplay);
+    if (waitUntilComplete) {
+      for (_ASAsyncTransaction *transaction in [layer.asyncdisplaykit_asyncLayerTransactions copy]) {
+        // Even if none of the layers have had a chance to start display earlier, they will still be allowed to saturate a multicore CPU while blocking main.
+        // This significantly reduces time on the main thread relative to UIKit.
+        [transaction waitUntilComplete];
+      }
     }
   }
 }
 
-- (void)recursivelyEnsureDisplay
+- (void)__recursivelyTriggerDisplayAndBlock:(BOOL)shouldBlock
 {
   ASDisplayNodeAssertMainThread();
-  ASDisplayNodeAssert(self.isNodeLoaded, @"Node must have layer or view loaded to use -recursivelyEnsureDisplay");
-  ASDisplayNodeAssert(self.inHierarchy && (self.isLayerBacked || self.view.window != nil), @"Node must be in a hierarchy to use -recursivelyEnsureDisplay");
 
   CALayer *layer = self.layer;
   // -layoutIfNeeded is recursive, and even walks up to superlayers to check if they need layout,
@@ -1500,7 +1524,12 @@ - (void)recursivelyEnsureDisplay
   if ([layer needsLayout]) {
     [layer layoutIfNeeded];
   }
-  recursivelyEnsureDisplayForLayer(layer);
+  recursivelyTriggerDisplayForLayer(layer, shouldBlock);
+}
+
+- (void)recursivelyEnsureDisplay
+{
+  [self __recursivelyTriggerDisplayAndBlock:YES];
 }
 
 - (void)setShouldBypassEnsureDisplay:(BOOL)shouldBypassEnsureDisplay
@@ -2127,6 +2156,9 @@ - (BOOL)_isMarkedForReplacement
   return _replaceAsyncSentinel != nil;
 }
 
+// FIXME: This method doesn't appear to be called, and could be removed.
+// However, it may be useful for an API similar to what Paper used to create a new node hierarchy,
+// trigger asynchronous measurement and display on it, and have it swap out and replace an old hierarchy.
 - (ASSentinel *)_asyncReplaceSentinel
 {
   ASDN::MutexLocker l(_propertyLock);

AsyncDisplayKit/Details/ASRangeHandlerRender.mm

@@ -17,8 +17,9 @@ @interface ASRangeHandlerRender ()
 @end
 
 @implementation ASRangeHandlerRender
-@synthesize workingWindow = _workingWindow;
 
+#if USE_WORKING_WINDOW
+@synthesize workingWindow = _workingWindow;
 - (UIWindow *)workingWindow
 {
   ASDisplayNodeAssertMainThread();
@@ -45,6 +46,7 @@ - (void)dealloc
     [self node:node exitedRangeOfType:ASLayoutRangeTypeRender];
   }
 }
+#endif
 
 - (void)node:(ASDisplayNode *)node enteredRangeOfType:(ASLayoutRangeType)rangeType
 {
@@ -60,12 +62,17 @@ - (void)node:(ASDisplayNode *)node enteredRangeOfType:(ASLayoutRangeType)rangeTy
   // The node un-suspends display.
   [node enterInterfaceState:ASInterfaceStateDisplay];
 
+  
+#if USE_WORKING_WINDOW
   // Add the node's layer to an off-screen window to trigger display and mark its contents as non-volatile.
   // Use the layer directly to avoid the substantial overhead of UIView heirarchy manipulations.
   // Any view-backed nodes will still create their views in order to assemble the layer heirarchy, and they will
   // also assemble a view subtree for the node, but we avoid the much more significant expense triggered by a view
   // being added or removed from an onscreen window (responder chain setup, will/DidMoveToWindow: recursive calls, etc)
   [[[self workingWindow] layer] addSublayer:node.layer];
+#else
+  [node recursivelyEnsureDisplay];  // Need to do this without waiting
+#endif
 }
 
 - (void)node:(ASDisplayNode *)node exitedRangeOfType:(ASLayoutRangeType)rangeType
@@ -93,6 +100,7 @@ - (void)node:(ASDisplayNode *)node exitedRangeOfType:(ASLayoutRangeType)rangeTyp
   // The node calls clearCurrentContents and suspends display
   [node exitInterfaceState:ASInterfaceStateDisplay];
 
+#if USE_WORKING_WINDOW
   if (node.layer.superlayer != [[self workingWindow] layer]) {
     // In this case, the node has previously passed through the working range (or it is zero), and it has now fallen outside the working range.
     if (![node isLayerBacked]) {
@@ -104,6 +112,13 @@ - (void)node:(ASDisplayNode *)node exitedRangeOfType:(ASLayoutRangeType)rangeTyp
 
   // At this point, the node's layer may validly be present either in the workingWindow, or in the contentsView of a cell.
   [node.layer removeFromSuperlayer];
+#else
+  if (![node isLayerBacked]) {
+    [node.view removeFromSuperview];
+  } else {
+    [node.layer removeFromSuperlayer];
+  }
+#endif
 }
 
 @end

AsyncDisplayKit/Details/_ASDisplayLayer.mm

@@ -147,11 +147,9 @@ + (id)defaultValueForKey:(NSString *)key
 
 - (void)displayImmediately
 {
-  // REVIEW: Should this respect isDisplaySuspended?  If so, we'd probably want to synchronously display when
-  // setDisplaySuspended:No is called, rather than just scheduling.  The thread affinity for the displayImmediately
-  // call will be tricky if we need to support this, though.  It probably should just execute if displayImmediately is
-  // called directly.  The caller should be responsible for not calling displayImmediately if it wants to obey the
-  // suspended state.
+  // This method is a low-level bypass that avoids touching CA, including any reset of the
+  // needsDisplay flag, until the .contents property is set with the result.
+  // It is designed to be able to block the thread of any caller and fully execute the display.
 
   ASDisplayNodeAssertMainThread();
   [self display:NO];

AsyncDisplayKit/Layout/ASAsciiArtBoxCreator.m

@@ -111,7 +111,7 @@ + (NSString *)horizontalBoxStringForChildren:(NSArray *)children parent:(NSStrin
       [paddedLines addObject:paddedLine];
     }
     concatenatedLines = paddedLines;
-    totalLineLength += difference;
+    // totalLineLength += difference;
   }
   concatenatedLines = [self appendTopAndBottomToBoxString:concatenatedLines parent:parent];
   return [concatenatedLines componentsJoinedByString:@"\n"];

AsyncDisplayKit/Private/ASDisplayNode+AsyncDisplay.mm

@@ -304,10 +304,9 @@ - (void)displayAsyncLayer:(_ASDisplayLayer *)asyncLayer asynchronously:(BOOL)asy
   // for async display, capture the current displaySentinel value to bail early when the job is executed if another is
   // enqueued
   // for sync display, just use nil for the displaySentinel and go
-  //
-  // REVIEW: what about the degenerate case where we are calling setNeedsDisplay faster than the jobs are dequeuing
-  // from the displayQueue?  do we want to put in some kind of timer to not cancel early fails from displaySentinel
-  // changes?
+  
+  // FIXME: what about the degenerate case where we are calling setNeedsDisplay faster than the jobs are dequeuing
+  // from the displayQueue?  Need to not cancel early fails from displaySentinel changes.
   ASSentinel *displaySentinel = (asynchronously ? _displaySentinel : nil);
   int64_t displaySentinelValue = [displaySentinel increment];
 

AsyncDisplayKit/Private/ASDisplayNode+FrameworkPrivate.h

@@ -19,6 +19,10 @@
 #import "ASThread.h"
 #import "ASLayoutOptions.h"
 
+// Project-wide control for whether the offscreen UIWindow is used for display, or if
+// ASDK's internal system for coalescing and triggering display events is used.
+#define USE_WORKING_WINDOW 1
+
 /**
  Hierarchy state is propogated from nodes to all of their children when certain behaviors are required from the subtree.
  Examples include rasterization and external driving of the .interfaceState property.

AsyncDisplayKit/Private/ASDisplayNode+UIViewBridge.mm

@@ -221,6 +221,8 @@ - (void)__setSafeFrame:(CGRect)rect
 
 - (void)setNeedsDisplay
 {
+  _bridge_prologue;
+
   if (_hierarchyState & ASHierarchyStateRasterized) {
     ASPerformBlockOnMainThread(^{
       // The below operation must be performed on the main thread to ensure against an extremely rare deadlock, where a parent node
@@ -238,7 +240,19 @@ - (void)setNeedsDisplay
       [rasterizedContainerNode setNeedsDisplay];
     });
   } else {
-    [_layer setNeedsDisplay];
+    // If not rasterized (and therefore we certainly have a view or layer),
+    // Send the message to the view/layer first, as scheduleNodeForDisplay may call -displayIfNeeded.
+    // Wrapped / synchronous nodes created with initWithView/LayerBlock: do not need scheduleNodeForDisplay,
+    // as they don't need to display in the working range at all - since at all times onscreen, one
+    // -setNeedsDisplay to the CALayer will result in a synchronous display in the next frame.
+
+    _messageToViewOrLayer(setNeedsDisplay);
+
+#if !USE_WORKING_WINDOW
+    if (_layer && !self.isSynchronous) {
+      [ASDisplayNode scheduleNodeForDisplay:self];
+    }
+#endif
   }
 }
 

AsyncDisplayKit/Private/ASDisplayNodeInternal.h

@@ -108,6 +108,8 @@ typedef NS_OPTIONS(NSUInteger, ASDisplayNodeMethodOverrides)
 
 }
 
++ (void)scheduleNodeForDisplay:(ASDisplayNode *)node;
+
 // The _ASDisplayLayer backing the node, if any.
 @property (nonatomic, readonly, retain) _ASDisplayLayer *asyncLayer;