Using `drawViewHierarchyInRect` instead of `renderInContext` for snapshot tests

Summary:
We found that `-[CALayer renderInContext:]` produces bad results in some cases (which is actually documented thing!),
so we decided to replace it with `-[UIView drawViewHierarchyInRect:]` which is more reliable (I hope).
As part of this change I completly removed support of `CALayer` from local fork of `RNTesterIntegrationTests`.

See https://github.com/facebook/react-native/pull/14011#issuecomment-303844580 for more details.

janicduplessis

Reviewed By: javache

Differential Revision: D5129492

fbshipit-source-id: 6a9227037c85bb8f862d55267f5301e177985ad9

Libraries/RCTTest/FBSnapshotTestCase/FBSnapshotTestCase.h

@@ -18,44 +18,6 @@
 #define FB_REFERENCE_IMAGE_DIR "\"$(SOURCE_ROOT)/$(PROJECT_NAME)Tests/ReferenceImages\""
 #endif
 
-/**
- Similar to our much-loved XCTAssert() macros. Use this to perform your test. No need to write an explanation, though.
- @param view The view to snapshot
- @param identifier An optional identifier, used if there are multiple snapshot tests in a given -test method.
- @param referenceImageDirectorySuffix An optional suffix, appended to the reference image directory path, such as "_iOS8"
- */
-#define FBSnapshotVerifyViewWithReferenceDirectorySuffix(view__, identifier__, referenceImagesDirectorySuffix__) \
-{ \
-NSError *error__ = nil; \
-NSString *referenceImagesDirectory__ = [NSString stringWithFormat:@"%s%@", FB_REFERENCE_IMAGE_DIR, referenceImagesDirectorySuffix__]; \
-BOOL comparisonSuccess__ = [self compareSnapshotOfView:(view__) referenceImagesDirectory:referenceImagesDirectory__ identifier:(identifier__) error:&error__]; \
-XCTAssertTrue(comparisonSuccess__, @"Snapshot comparison failed: %@", error__); \
-}
-
-#define FBSnapshotVerifyView(view__, identifier__) \
-{ \
-FBSnapshotVerifyViewWithReferenceDirectorySuffix(view__, identifier__, @""); \
-}
-
-/**
- Similar to our much-loved XCTAssert() macros. Use this to perform your test. No need to write an explanation, though.
- @param layer The layer to snapshot
- @param identifier An optional identifier, used is there are multiple snapshot tests in a given -test method.
- @param referenceImageDirectorySuffix An optional suffix, appended to the reference image directory path, such as "_iOS8"
- */
-#define FBSnapshotVerifyLayerWithReferenceDirectorySuffix(layer__, identifier__, referenceImagesDirectorySuffix__) \
-{ \
-NSError *error__ = nil; \
-NSString *referenceImagesDirectory__ = [NSString stringWithFormat:@"%s%@", FB_REFERENCE_IMAGE_DIR, referenceImagesDirectorySuffix__]; \
-BOOL comparisonSuccess__ = [self compareSnapshotOfLayer:(layer__) referenceImagesDirectory:referenceImagesDirectory__ identifier:(identifier__) error:&error__]; \
-XCTAssertTrue(comparisonSuccess__, @"Snapshot comparison failed: %@", error__); \
-}
-
-#define FBSnapshotVerifyLayer(layer__, identifier__) \
-{ \
-FBSnapshotVerifyLayerWithReferenceDirectorySuffix(layer__, identifier__, @""); \
-}
-
 /**
  The base class of view snapshotting tests. If you have small UI component, it's often easier to configure it in a test
  and compare an image of the view to a reference image that write lots of complex layout-code tests.
@@ -70,19 +32,6 @@ FBSnapshotVerifyLayerWithReferenceDirectorySuffix(layer__, identifier__, @""); \
  */
 @property (readwrite, nonatomic, assign) BOOL recordMode;
 
-/**
- Performs the comparisons or records a snapshot of the layer if recordMode is YES.
- @param layer The Layer to snapshot
- @param referenceImagesDirectory The directory in which reference images are stored.
- @param identifier An optional identifier, used if there are multiple snapshot tests in a given -test method.
- @param error An error to log in an XCTAssert() macro if the method fails (missing reference image, images differ, etc).
- @returns YES if the comparison (or saving of the reference image) succeeded.
- */
-- (BOOL)compareSnapshotOfLayer:(CALayer *)layer
-      referenceImagesDirectory:(NSString *)referenceImagesDirectory
-                    identifier:(NSString *)identifier
-                         error:(NSError **)errorPtr;
-
 /**
  Performs the comparisons or records a snapshot of the view if recordMode is YES.
  @param view The view to snapshot

Libraries/RCTTest/FBSnapshotTestCase/FBSnapshotTestCase.m

@@ -42,41 +42,16 @@
   self.snapshotController.recordMode = recordMode;
 }
 
-- (BOOL)compareSnapshotOfLayer:(CALayer *)layer
-      referenceImagesDirectory:(NSString *)referenceImagesDirectory
-                    identifier:(NSString *)identifier
-                         error:(NSError **)errorPtr
-{
-  return [self _compareSnapshotOfViewOrLayer:layer
-                    referenceImagesDirectory:referenceImagesDirectory
-                                  identifier:identifier
-                                       error:errorPtr];
-}
-
 - (BOOL)compareSnapshotOfView:(UIView *)view
      referenceImagesDirectory:(NSString *)referenceImagesDirectory
                    identifier:(NSString *)identifier
                         error:(NSError **)errorPtr
-{
-  return [self _compareSnapshotOfViewOrLayer:view
-                    referenceImagesDirectory:referenceImagesDirectory
-                                  identifier:identifier
-                                       error:errorPtr];
-}
-
-#pragma mark -
-#pragma mark Private API
-
-- (BOOL)_compareSnapshotOfViewOrLayer:(id)viewOrLayer
-             referenceImagesDirectory:(NSString *)referenceImagesDirectory
-                           identifier:(NSString *)identifier
-                                error:(NSError **)errorPtr
 {
   _snapshotController.referenceImagesDirectory = referenceImagesDirectory;
-  return [_snapshotController compareSnapshotOfViewOrLayer:viewOrLayer
+  return [_snapshotController compareSnapshotOfView:view
-                                                  selector:self.invocation.selector
+                                           selector:self.invocation.selector
-                                                identifier:identifier
+                                         identifier:identifier
-                                                     error:errorPtr];
+                                              error:errorPtr];
 }
 
 @end

Libraries/RCTTest/FBSnapshotTestCase/FBSnapshotTestController.h

@@ -41,7 +41,7 @@ extern NSString *const FBReferenceImageFilePathKey;
 @property(readwrite, nonatomic, assign) BOOL recordMode;
 
 /**
- @param testClass The subclass of FBSnapshotTestCase that is using this controller.d.
+ @param testClass The subclass of FBSnapshotTestCase that is using this controller.
  @returns An instance of FBSnapshotTestController.
  */
 - (id)initWithTestClass:(Class)testClass;
@@ -53,19 +53,6 @@ extern NSString *const FBReferenceImageFilePathKey;
  */
 - (id)initWithTestName:(NSString *)testName;
 
-
-/**
- Performs the comparison of the layer.
- @param layer The Layer to snapshot.
- @param identifier An optional identifier, used is there are muliptle snapshot tests in a given -test method.
- @param errorPtr An error to log in an XCTAssert() macro if the method fails (missing reference image, images differ, etc).
- @returns YES if the comparison (or saving of the reference image) succeeded.
- */
-- (BOOL)compareSnapshotOfLayer:(CALayer *)layer
-                      selector:(SEL)selector
-                    identifier:(NSString *)identifier
-                         error:(NSError **)errorPtr;
-
 /**
  Performs the comparison of the view.
  @param view The view to snapshot.
@@ -79,20 +66,6 @@ extern NSString *const FBReferenceImageFilePathKey;
                    identifier:(NSString *)identifier
                         error:(NSError **)errorPtr;
 
-/**
- Performs the comparison of a view or layer.
- @param viewOrLayer The view or layer to snapshot.
- @param selector selector
- @param identifier An optional identifier, used is there are muliptle snapshot tests in a given -test method.
- @param errorPtr An error to log in an XCTAssert() macro if the method fails (missing reference image, images differ, etc).
- @returns YES if the comparison (or saving of the reference image) succeeded.
- */
-- (BOOL)compareSnapshotOfViewOrLayer:(id)viewOrLayer
-                            selector:(SEL)selector
-                          identifier:(NSString *)identifier
-                               error:(NSError **)errorPtr;
-
-
 /**
  The directory in which reference images are stored.
  */

Libraries/RCTTest/FBSnapshotTestCase/FBSnapshotTestController.m

@@ -10,13 +10,13 @@
 
 #import "FBSnapshotTestController.h"
 
-#import "UIImage+Compare.h"
-#import "UIImage+Diff.h"
-
 #import <objc/runtime.h>
 
 #import <UIKit/UIKit.h>
 
+#import "UIImage+Compare.h"
+#import "UIImage+Diff.h"
+
 NSString *const FBSnapshotTestControllerErrorDomain = @"FBSnapshotTestControllerErrorDomain";
 
 NSString *const FBReferenceImageFilePathKey = @"FBReferenceImageFilePathKey";
@@ -39,15 +39,14 @@ typedef struct RGBAPixel {
   NSFileManager *_fileManager;
 }
 
-#pragma mark -
+#pragma mark - Lifecycle
-#pragma mark Lifecycle
 
-- (id)initWithTestClass:(Class)testClass;
+- (instancetype)initWithTestClass:(Class)testClass;
 {
     return [self initWithTestName:NSStringFromClass(testClass)];
 }
 
-- (id)initWithTestName:(NSString *)testName
+- (instancetype)initWithTestName:(NSString *)testName
 {
     if ((self = [super init])) {
         _testName = [testName copy];
@@ -56,16 +55,14 @@ typedef struct RGBAPixel {
     return self;
 }
 
-#pragma mark -
+#pragma mark - Properties
-#pragma mark Properties
 
 - (NSString *)description
 {
   return [NSString stringWithFormat:@"%@ %@", [super description], _referenceImagesDirectory];
 }
 
-#pragma mark -
+#pragma mark - Public API
-#pragma mark Public API
 
 - (UIImage *)referenceImageForSelector:(SEL)selector
                             identifier:(NSString *)identifier
@@ -211,8 +208,7 @@ typedef struct RGBAPixel {
   return NO;
 }
 
-#pragma mark -
+#pragma mark - Private API
-#pragma mark Private API
 
 typedef NS_ENUM(NSUInteger, FBTestSnapshotFileNameType) {
   FBTestSnapshotFileNameTypeReference,
@@ -280,51 +276,28 @@ typedef NS_ENUM(NSUInteger, FBTestSnapshotFileNameType) {
   return filePath;
 }
 
-- (BOOL)compareSnapshotOfLayer:(CALayer *)layer
+- (BOOL)compareSnapshotOfView:(id)view
-                      selector:(SEL)selector
-                    identifier:(NSString *)identifier
-                         error:(NSError **)errorPtr
-{
-  return [self compareSnapshotOfViewOrLayer:layer
-                                   selector:selector
-                                 identifier:identifier
-                                      error:errorPtr];
-}
-
-- (BOOL)compareSnapshotOfView:(UIView *)view
                      selector:(SEL)selector
                    identifier:(NSString *)identifier
                         error:(NSError **)errorPtr
-{
-  return [self compareSnapshotOfViewOrLayer:view
-                                   selector:selector
-                                 identifier:identifier
-                                      error:errorPtr];
-}
-
-- (BOOL)compareSnapshotOfViewOrLayer:(id)viewOrLayer
-                            selector:(SEL)selector
-                          identifier:(NSString *)identifier
-                               error:(NSError **)errorPtr
 {
   if (self.recordMode) {
-    return [self _recordSnapshotOfViewOrLayer:viewOrLayer selector:selector identifier:identifier error:errorPtr];
+    return [self _recordSnapshotOfView:view selector:selector identifier:identifier error:errorPtr];
   } else {
-    return [self _performPixelComparisonWithViewOrLayer:viewOrLayer selector:selector identifier:identifier error:errorPtr];
+    return [self _performPixelComparisonWithView:view selector:selector identifier:identifier error:errorPtr];
   }
 }
 
-#pragma mark -
+#pragma mark - Private API
-#pragma mark Private API
 
-- (BOOL)_performPixelComparisonWithViewOrLayer:(UIView *)viewOrLayer
+- (BOOL)_performPixelComparisonWithView:(UIView *)view
-                                      selector:(SEL)selector
+                               selector:(SEL)selector
-                                    identifier:(NSString *)identifier
+                             identifier:(NSString *)identifier
-                                         error:(NSError **)errorPtr
+                                  error:(NSError **)errorPtr
 {
   UIImage *referenceImage = [self referenceImageForSelector:selector identifier:identifier error:errorPtr];
   if (nil != referenceImage) {
-    UIImage *snapshot = [self _snapshotViewOrLayer:viewOrLayer];
+    UIImage *snapshot = [self _snapshotView:view];
     BOOL imagesSame = [self compareReferenceImage:referenceImage toImage:snapshot error:errorPtr];
     if (!imagesSame) {
       [self saveFailedReferenceImage:referenceImage
@@ -338,46 +311,33 @@ typedef NS_ENUM(NSUInteger, FBTestSnapshotFileNameType) {
   return NO;
 }
 
-- (BOOL)_recordSnapshotOfViewOrLayer:(id)viewOrLayer
+- (BOOL)_recordSnapshotOfView:(UIView *)view
-                            selector:(SEL)selector
+                     selector:(SEL)selector
-                          identifier:(NSString *)identifier
+                   identifier:(NSString *)identifier
-                               error:(NSError **)errorPtr
+                        error:(NSError **)errorPtr
 {
-  UIImage *snapshot = [self _snapshotViewOrLayer:viewOrLayer];
+  UIImage *snapshot = [self _snapshotView:view];
   return [self saveReferenceImage:snapshot selector:selector identifier:identifier error:errorPtr];
 }
 
-- (UIImage *)_snapshotViewOrLayer:(id)viewOrLayer
+- (UIImage *)_snapshotView:(UIView *)view
 {
-  CALayer *layer = nil;
+  [view layoutIfNeeded];
 
-  if ([viewOrLayer isKindOfClass:[UIView class]]) {
+  CGRect bounds = view.bounds;
-    return [self _renderView:viewOrLayer];
-  } else if ([viewOrLayer isKindOfClass:[CALayer class]]) {
-    layer = (CALayer *)viewOrLayer;
-    [layer layoutIfNeeded];
-    return [self _renderLayer:layer];
-  } else {
-    [NSException raise:@"Only UIView and CALayer classes can be snapshotted" format:@"%@", viewOrLayer];
-  }
-  return nil;
-}
 
-- (UIImage *)_renderLayer:(CALayer *)layer
+  NSAssert1(CGRectGetWidth(bounds), @"Zero width for view %@", view);
-{
+  NSAssert1(CGRectGetHeight(bounds), @"Zero height for view %@", view);
-  CGRect bounds = layer.bounds;
-
-  NSAssert1(CGRectGetWidth(bounds), @"Zero width for layer %@", layer);
-  NSAssert1(CGRectGetHeight(bounds), @"Zero height for layer %@", layer);
 
   UIGraphicsBeginImageContextWithOptions(bounds.size, NO, 0);
   CGContextRef context = UIGraphicsGetCurrentContext();
-  NSAssert1(context, @"Could not generate context for layer %@", layer);
+  NSAssert1(context, @"Could not generate context for view %@", view);
 
   UIGraphicsPushContext(context);
   CGContextSaveGState(context);
   {
-    [layer renderInContext:context];
+    BOOL success = [view drawViewHierarchyInRect:bounds afterScreenUpdates:YES];
+    NSAssert1(success, @"Could not create snapshot for view %@", view);
   }
   CGContextRestoreGState(context);
   UIGraphicsPopContext();
@@ -388,10 +348,4 @@ typedef NS_ENUM(NSUInteger, FBTestSnapshotFileNameType) {
   return snapshot;
 }
 
-- (UIImage *)_renderView:(UIView *)view
-{
-  [view layoutIfNeeded];
-  return [self _renderLayer:view.layer];
-}
-
 @end