[ASTextNode] Add Fast-Paths For Text Measurement and Drawing (#2392)

* Add test case for TextKit truncation style

* Add fast path for text node measurement with default truncation

* Use fast path more often

* Reverse options order

* Simplify implementation – no functional change

* Share "isScaled" variable

* Intersect with constrained rect

* Add a failing test case for fast-path truncation

* Add some more truncation tests, using slow path as reference image

* Update the tests

* In ASTextKitRenderer, intersect bounds with constrained rect

* Add test case for TextKit truncation style

* Add fast path for text node measurement with default truncation

* Use fast path more often

* Reverse options order

* Simplify implementation – no functional change

* Share "isScaled" variable

* Intersect with constrained rect

* Add a failing test case for fast-path truncation

* Add some more truncation tests, using slow path as reference image

* Update the tests

* In ASTextKitRenderer, intersect bounds with constrained rect

* Use maximumNumberOfLines property in text kit fast path

Add reference images

Disable fast-path for max-one-line case

* Remove unneeded snapshot files

AsyncDisplayKit/ASTextNode.mm

@@ -1356,7 +1356,7 @@ static NSAttributedString *DefaultTruncationAttributedString()
   }
 
   // If we've reached this point, both _additionalTruncationMessage and
-  // _truncationAttributedString are present.  Compose them.
+  // _truncationAttributedText are present.  Compose them.
 
   NSMutableAttributedString *newComposedTruncationString = [[NSMutableAttributedString alloc] initWithAttributedString:_truncationAttributedText];
   [newComposedTruncationString replaceCharactersInRange:NSMakeRange(newComposedTruncationString.length, 0) withString:@" "];

AsyncDisplayKit/TextKit/ASTextKitRenderer.mm

@@ -35,11 +35,20 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
   return truncationCharacterSet;
 }
 
+@interface ASTextKitRenderer()
+/**
+ * This object is lazily created. It is provided to the NSAttributedString
+ * drawing methods used by the fast-paths in the size calculation and drawing
+ * instance methods.
+ */
+@property (nonatomic, strong, readonly) NSStringDrawingContext *stringDrawingContext;
+@end
+
 @implementation ASTextKitRenderer {
   CGSize _calculatedSize;
   BOOL _sizeIsCalculated;
 }
-@synthesize attributes = _attributes, context = _context, shadower = _shadower, truncater = _truncater, fontSizeAdjuster = _fontSizeAdjuster;
+@synthesize attributes = _attributes, context = _context, shadower = _shadower, truncater = _truncater, fontSizeAdjuster = _fontSizeAdjuster, stringDrawingContext = _stringDrawingContext;
 
 #pragma mark - Initialization
 
@@ -50,6 +59,7 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
     _constrainedSize = constrainedSize;
     _attributes = attributes;
     _sizeIsCalculated = NO;
+    _currentScaleFactor = 1;
   }
   return self;
 }
@@ -106,6 +116,19 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
   return _context;
 }
 
+- (NSStringDrawingContext *)stringDrawingContext
+{
+  if (_stringDrawingContext == nil) {
+    _stringDrawingContext = [[NSStringDrawingContext alloc] init];
+
+    if (isinf(_constrainedSize.width) == NO && _attributes.maximumNumberOfLines > 0) {
+      ASDisplayNodeAssert(_attributes.maximumNumberOfLines != 1, @"Max line count 1 is not supported in fast-path.");
+      [_stringDrawingContext setValue:@(_attributes.maximumNumberOfLines) forKey:@"maximumNumberOfLines"];
+    }
+  }
+  return _stringDrawingContext;
+}
+
 #pragma mark - Sizing
 
 - (CGSize)size
@@ -145,8 +168,17 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
     _currentScaleFactor = [[self fontSizeAdjuster] scaleFactor];
   }
 
-  __block NSTextStorage *scaledTextStorage = nil;
+  // If we do not scale, do exclusion, or do custom truncation, we should just use NSAttributedString drawing for a fast-path.
+  if (self.canUseFastPath) {
+    CGRect rect = [_attributes.attributedString boundingRectWithSize:_constrainedSize options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingTruncatesLastVisibleLine context:self.stringDrawingContext];
+    // Intersect with constrained rect, in case text kit goes out-of-bounds.
+    rect = CGRectIntersection(rect, {CGPointZero, _constrainedSize});
+    _calculatedSize = [self.shadower outsetSizeWithInsetSize:rect.size];
+    return;
+  }
+
   BOOL isScaled = [self isScaled];
+  __block NSTextStorage *scaledTextStorage = nil;
   if (isScaled) {
     // apply the string scale before truncating or else we may truncate the string after we've done the work to shrink it.
     [[self context] performBlockWithLockedTextKitComponents:^(NSLayoutManager *layoutManager, NSTextStorage *textStorage, NSTextContainer *textContainer) {
@@ -161,15 +193,13 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
   
   [[self truncater] truncate];
   
+  CGRect constrainedRect = {CGPointZero, _constrainedSize};
+  __block CGRect boundingRect;
+
   // Force glyph generation and layout, which may not have happened yet (and isn't triggered by
   // -usedRectForTextContainer:).
   [[self context] performBlockWithLockedTextKitComponents:^(NSLayoutManager *layoutManager, NSTextStorage *textStorage, NSTextContainer *textContainer) {
     [layoutManager ensureLayoutForTextContainer:textContainer];
-  }];
-  
-  CGRect constrainedRect = {CGPointZero, _constrainedSize};
-  __block CGRect boundingRect;
-  [[self context] performBlockWithLockedTextKitComponents:^(NSLayoutManager *layoutManager, NSTextStorage *textStorage, NSTextContainer *textContainer) {
     boundingRect = [layoutManager usedRectForTextContainer:textContainer];
     if (isScaled) {
       // put the non-scaled version back
@@ -181,13 +211,33 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
   // TextKit often returns incorrect glyph bounding rects in the horizontal direction, so we clip to our bounding rect
   // to make sure our width calculations aren't being offset by glyphs going beyond the constrained rect.
   boundingRect = CGRectIntersection(boundingRect, {.size = constrainedRect.size});
-  CGSize boundingSize = [_shadower outsetSizeWithInsetSize:boundingRect.size];
+  _calculatedSize = [_shadower outsetSizeWithInsetSize:boundingRect.size];
-  _calculatedSize = CGSizeMake(boundingSize.width, boundingSize.height);
 }
 
 - (BOOL)isScaled
 {
-  return (self.currentScaleFactor > 0 && self.currentScaleFactor < 1.0);
+  return (_currentScaleFactor > 0 && _currentScaleFactor < 1.0);
+}
+
+- (BOOL)usesCustomTruncation
+{
+  // NOTE: This code does not correctly handle if they set `…` with different attributes.
+  return _attributes.avoidTailTruncationSet != nil || [_attributes.truncationAttributedString.string isEqualToString:@"\u2026"] == NO;
+}
+
+- (BOOL)usesExclusionPaths
+{
+  return _attributes.exclusionPaths.count > 0;
+}
+
+- (BOOL)canUseFastPath
+{
+  return self.isScaled == NO
+    && self.usesCustomTruncation == NO
+    && self.usesExclusionPaths == NO
+    // NSAttributedString drawing methods ignore usesLineFragmentOrigin if max line count 1,
+    // rendering them useless:
+    && (_attributes.maximumNumberOfLines != 1 || isinf(_constrainedSize.width));
 }
 
 #pragma mark - Drawing
@@ -198,11 +248,12 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
   ASDisplayNodeAssertNotNil(context, @"This is no good without a context.");
   
   // This renderer may not be the one that did the sizing. If that is the case its truncation and currentScaleFactor may not have been evaluated.
-  // If there's any possibility we need to truncate or scale (e.g. width is not infinite, perform the size calculation.
+  // If there's any possibility we need to truncate or scale (i.e. width is not infinite), perform the size calculation.
   if (_sizeIsCalculated == NO && isinf(_constrainedSize.width) == NO) {
     [self _calculateSize];
   }
 
+  bounds = CGRectIntersection(bounds, { .size = _constrainedSize });
   CGRect shadowInsetBounds = [[self shadower] insetRectWithConstrainedRect:bounds];
 
   CGContextSaveGState(context);
@@ -211,10 +262,15 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
 
   LOG(@"%@, shadowInsetBounds = %@",self, NSStringFromCGRect(shadowInsetBounds));
 
+  // If we use default options, we can use NSAttributedString for a
+  // fast path.
+  if (self.canUseFastPath) {
+    [_attributes.attributedString drawWithRect:shadowInsetBounds options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingTruncatesLastVisibleLine context:self.stringDrawingContext];
+  } else {
+    BOOL isScaled = [self isScaled];
     [[self context] performBlockWithLockedTextKitComponents:^(NSLayoutManager *layoutManager, NSTextStorage *textStorage, NSTextContainer *textContainer) {
       
       NSTextStorage *scaledTextStorage = nil;
-    BOOL isScaled = [self isScaled];
 
       if (isScaled) {
         // if we are going to scale the text, swap out the non-scaled text for the scaled version.
@@ -227,6 +283,7 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
       }
       
       LOG(@"usedRect: %@", NSStringFromCGRect([layoutManager usedRectForTextContainer:textContainer]));
+
       NSRange glyphRange = [layoutManager glyphRangeForBoundingRect:CGRectMake(0,0,textContainer.size.width, textContainer.size.height) inTextContainer:textContainer];
       LOG(@"boundingRect: %@", NSStringFromCGRect([layoutManager boundingRectForGlyphRange:glyphRange inTextContainer:textContainer]));
       
@@ -239,6 +296,7 @@ static NSCharacterSet *_defaultAvoidTruncationCharacterSet()
         [textStorage addLayoutManager:layoutManager];
       }
     }];
+  }
 
   UIGraphicsPopContext();
   CGContextRestoreGState(context);

AsyncDisplayKitTests/ASSnapshotTestCase.h

@@ -29,6 +29,9 @@ NSOrderedSet *ASSnapshotTestCaseDefaultSuffixes(void);
 #define ASSnapshotVerifyLayer(layer__, identifier__) \
   FBSnapshotVerifyLayerWithOptions(layer__, identifier__, ASSnapshotTestCaseDefaultSuffixes(), 0);
 
+#define ASSnapshotVerifyView(view__, identifier__) \
+	FBSnapshotVerifyViewWithOptions(view__, identifier__, ASSnapshotTestCaseDefaultSuffixes(), 0);
+
 @interface ASSnapshotTestCase : FBSnapshotTestCase
 
 /**

AsyncDisplayKitTests/ASTextNodePerformanceTests.m

@@ -108,7 +108,7 @@ static NSString *const kTestCaseUIKitWithReusedContext = @"UIKitReusedContext";
   ctx.results[kTestCaseASDK].userInfo[@"size"] = NSStringFromCGSize(asdkSize);
   
   ASXCTAssertEqualSizes(uiKitSize, asdkSize);
-  ASXCTAssertRelativePerformanceInRange(ctx, kTestCaseASDK, 0.2, 0.5);
+  ASXCTAssertRelativePerformanceInRange(ctx, kTestCaseASDK, 0.5, 0.9);
 }
 
 - (void)testPerformance_OneParagraphLatinWithTruncation

AsyncDisplayKitTests/ASTextNodeSnapshotTests.m

@@ -72,7 +72,24 @@
   textNode.highlightRange = NSMakeRange(0, textNode.attributedText.length);
 
   [ASSnapshotTestCase hackilySynchronouslyRecursivelyRenderNode:textNode];
-  ASSnapshotVerifyLayer(backgroundView.layer, nil);
+  ASSnapshotVerifyView(backgroundView, nil);
+}
+
+- (void)testThatFastPathTruncationWorks
+{
+  ASTextNode *textNode = [[ASTextNode alloc] init];
+  textNode.attributedText = [[NSAttributedString alloc] initWithString:@"Quality is Important" attributes:@{ NSForegroundColorAttributeName: [UIColor blueColor], NSFontAttributeName: [UIFont italicSystemFontOfSize:24] }];
+  [textNode layoutThatFits:ASSizeRangeMake(CGSizeZero, CGSizeMake(100, 50))];
+  ASSnapshotVerifyNode(textNode, nil);
+}
+
+- (void)testThatSlowPathTruncationWorks
+{
+  ASTextNode *textNode = [[ASTextNode alloc] init];
+  textNode.attributedText = [[NSAttributedString alloc] initWithString:@"Quality is Important" attributes:@{ NSForegroundColorAttributeName: [UIColor blueColor], NSFontAttributeName: [UIFont italicSystemFontOfSize:24] }];
+  [textNode layoutThatFits:ASSizeRangeMake(CGSizeZero, CGSizeMake(100, 50))];
+  textNode.exclusionPaths = @[ [UIBezierPath bezierPath] ];
+  ASSnapshotVerifyNode(textNode, nil);
 }
 
 @end