Texture/Source/Details/ASGraphicsContext.mm

//
//  ASGraphicsContext.mm
//  Texture
//
//  Copyright (c) Pinterest, Inc.  All rights reserved.
//  Licensed under Apache 2.0: http://www.apache.org/licenses/LICENSE-2.0
//

#import <AsyncDisplayKit/ASGraphicsContext.h>
#import <AsyncDisplayKit/ASAssert.h>
#import <AsyncDisplayKit/ASConfigurationInternal.h>
#import <AsyncDisplayKit/ASInternalHelpers.h>
#import <AsyncDisplayKit/ASAvailability.h>


#define ASPerformBlockWithTraitCollection(work, traitCollection) \
      UITraitCollection *uiTraitCollection = ASPrimitiveTraitCollectionToUITraitCollection(traitCollection); \
      [uiTraitCollection performAsCurrentTraitCollection:^{ \
        work(); \
      }];


NS_INLINE void ASConfigureExtendedRange(UIGraphicsImageRendererFormat *format)
{
    // nop. We always use automatic range on iOS >= 12.
}

UIImage *ASGraphicsCreateImageWithOptions(CGSize size, BOOL opaque, CGFloat scale, UIImage *sourceImage,
                                          asdisplaynode_iscancelled_block_t NS_NOESCAPE isCancelled,
                                          void (^NS_NOESCAPE work)())
{
  return ASGraphicsCreateImage(ASPrimitiveTraitCollectionMakeDefault(), size, opaque, scale, sourceImage, isCancelled, work);
}

UIImage *ASGraphicsCreateImage(ASPrimitiveTraitCollection traitCollection, CGSize size, BOOL opaque, CGFloat scale, UIImage * sourceImage, asdisplaynode_iscancelled_block_t NS_NOESCAPE isCancelled, void (NS_NOESCAPE ^work)()) {
  if (size.width <= 0 || size.height <= 0) {
    return nil;
  }
  
  if (ASActivateExperimentalFeature(ASExperimentalDrawingGlobal)) {
    // If they used default scale, reuse one of two preferred formats.
    static UIGraphicsImageRendererFormat *defaultFormat;
    static UIGraphicsImageRendererFormat *opaqueFormat;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
      defaultFormat = [UIGraphicsImageRendererFormat preferredFormat];
      opaqueFormat = [UIGraphicsImageRendererFormat preferredFormat];
      opaqueFormat.opaque = YES;
      ASConfigureExtendedRange(defaultFormat);
      ASConfigureExtendedRange(opaqueFormat);
    });

    UIGraphicsImageRendererFormat *format;
    if (sourceImage) {
      if (sourceImage.renderingMode == UIImageRenderingModeAlwaysTemplate) {
        // Template images will be black and transparent, so if we use
        // sourceImage.imageRenderFormat it will assume a grayscale color space.
        // This is not good because a template image should be able to tint to any color,
        // so we'll just use the default here.
        format = [UIGraphicsImageRendererFormat preferredFormat];
      } else {
        format = sourceImage.imageRendererFormat;
      }
      // We only want the private bits (color space and bits per component) from the image.
      // We have our own ideas about opacity and scale.
      format.opaque = opaque;
      format.scale = scale;
    } else if (scale == 0 || scale == ASScreenScale()) {
      format = opaque ? opaqueFormat : defaultFormat;
    } else {
      format = [UIGraphicsImageRendererFormat preferredFormat];
      if (opaque) format.opaque = YES;
      format.scale = scale;
      ASConfigureExtendedRange(format);
    }
    
    // Avoid using the imageWithActions: method because it does not support cancellation at the
    // last moment i.e. before actually creating the resulting image.
    __block UIImage *image;
    NSError *error;
    [[[UIGraphicsImageRenderer alloc] initWithSize:size format:format]
        runDrawingActions:^(UIGraphicsImageRendererContext *rendererContext) {
          ASDisplayNodeCAssert(UIGraphicsGetCurrentContext(), @"Should have a context!");
          ASPerformBlockWithTraitCollection(work, traitCollection);
        }
        completionActions:^(UIGraphicsImageRendererContext *rendererContext) {
          if (isCancelled == nil || !isCancelled()) {
            image = rendererContext.currentImage;
          }
        }
        error:&error];
    if (error) {
      NSCAssert(NO, @"Error drawing: %@", error);
    }
    return image;
  }

  // Bad OS or experiment flag. Use UIGraphics* API.
  UIGraphicsBeginImageContextWithOptions(size, opaque, scale);
  ASPerformBlockWithTraitCollection(work, traitCollection)
  UIImage *image = nil;
  if (isCancelled == nil || !isCancelled()) {
    image = UIGraphicsGetImageFromCurrentImageContext();
  }
  UIGraphicsEndImageContext();
  return image;
}

UIImage *ASGraphicsCreateImageWithTraitCollectionAndOptions(ASPrimitiveTraitCollection traitCollection, CGSize size, BOOL opaque, CGFloat scale, UIImage * sourceImage, void (NS_NOESCAPE ^work)()) {
  return ASGraphicsCreateImage(traitCollection, size, opaque, scale, sourceImage, nil, work);
}