[ASTextNode] placeholder image shouldn't draw for zero area strings (#2069)

* placeholder should not draw if area is zero

* styling fix

* super precision

AsyncDisplayKit/ASTextNode.mm

@@ -27,6 +27,8 @@
 #import "ASInternalHelpers.h"
 #import "ASLayout.h"
 
+#import "CGRect+ASConvenience.h"
+
 static const NSTimeInterval ASTextNodeHighlightFadeOutDuration = 0.15;
 static const NSTimeInterval ASTextNodeHighlightFadeInDuration = 0.1;
 static const CGFloat ASTextNodeHighlightLightOpacity = 0.11;
@@ -910,7 +912,7 @@ static CGRect ASTextNodeAdjustRenderRectForShadowPadding(CGRect rendererRect, UI
   // FIXME: Replace this implementation with reusable CALayers that have .backgroundColor set.
   // This would completely eliminate the memory and performance cost of the backing store.
   CGSize size = self.calculatedSize;
-  if (CGSizeEqualToSize(size, CGSizeZero)) {
+  if ((size.width * size.height) < CGFLOAT_EPSILON) {
     return nil;
   }
   

AsyncDisplayKit/Details/CGRect+ASConvenience.h

@@ -14,6 +14,14 @@
 #import "ASBaseDefines.h"
 #import "ASLayoutController.h"
 
+#ifndef CGFLOAT_EPSILON
+  #if CGFLOAT_IS_DOUBLE
+    #define CGFLOAT_EPSILON DBL_EPSILON
+  #else
+    #define CGFLOAT_EPSILON FLT_EPSILON
+  #endif
+#endif
+
 NS_ASSUME_NONNULL_BEGIN
 
 ASDISPLAYNODE_EXTERN_C_BEGIN