FlutterView.mm

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#import "flutter/shell/platform/darwin/ios/framework/Source/FlutterView.h"
 
#include "flutter/fml/platform/darwin/cf_utils.h"
#import "flutter/shell/platform/darwin/ios/framework/Source/FlutterSceneLifeCycle_Internal.h"
#import "flutter/shell/platform/darwin/ios/framework/Source/FlutterSharedApplication.h"
#import "flutter/shell/platform/darwin/ios/framework/Source/SemanticsObject.h"
 
FLUTTER_ASSERT_ARC
 
@interface FlutterView ()
@property(nonatomic, weak) id<FlutterViewEngineDelegate> delegate;
@property(nonatomic, weak) UIWindowScene* previousScene;
@end
 
@implementation FlutterAutoResizeLayoutConstraint
@end
 
@implementation FlutterView {
  BOOL _isWideGamutEnabled;
  CGSize _intrinsicSize;
}
 
- (instancetype)init {
  NSAssert(NO, @"FlutterView must initWithDelegate");
  return nil;
}
 
- (instancetype)initWithFrame:(CGRect)frame {
  NSAssert(NO, @"FlutterView must initWithDelegate");
  return nil;
}
 
- (instancetype)initWithCoder:(NSCoder*)aDecoder {
  NSAssert(NO, @"FlutterView must initWithDelegate");
  return nil;
}
 
- (UIScreen*)screen {
  return self.window.windowScene.screen;
}
 
// iOS has a concept of "intrinsicContentSize", which indicates the size a view would like to be
// based on its content. When an intrinsicContentSize is set, iOS will automatically add Auto Layout
// constraints for the width and/or height. However, the constraints use a private API. There are
// situations where we may want to filter these constraints. To avoid using a private API, Flutter
// creates a custom constraint called FlutterAutoResizeLayoutConstraint to add a width/height
// constraint that reflects the intrinsicContentSize.
- (void)setIntrinsicContentSize:(CGSize)size {
  if (!self.autoResizable) {
    return;
  }
 
  UIWindow* window = self.window;
  CGFloat scale = window ? self.window.windowScene.screen.scale : self.traitCollection.displayScale;
  CGSize scaledSize = CGSizeMake(size.width / scale, size.height / scale);
 
  CGSize roundedScaleSize = CGSizeMake(roundf(scaledSize.width), roundf(scaledSize.height));
  CGSize roundedIntrinsicSize =
      CGSizeMake(roundf(_intrinsicSize.width), roundf(_intrinsicSize.height));
 
  // If the size has not changed, don't update constraints.
  if (CGSizeEqualToSize(roundedIntrinsicSize, roundedScaleSize)) {
    return;
  }
  _intrinsicSize = scaledSize;
 
  self.translatesAutoresizingMaskIntoConstraints = false;
 
  // Remove any existing FlutterAutoResizeLayoutConstraint
  [self removeAutoResizeLayoutConstraints];
 
  FlutterAutoResizeLayoutConstraint* widthConstraint =
      [FlutterAutoResizeLayoutConstraint constraintWithItem:self
                                                  attribute:NSLayoutAttributeWidth
                                                  relatedBy:NSLayoutRelationEqual
                                                     toItem:nil
                                                  attribute:NSLayoutAttributeNotAnAttribute
                                                 multiplier:1.0
                                                   constant:scaledSize.width];
 
  FlutterAutoResizeLayoutConstraint* heightConstraint =
      [FlutterAutoResizeLayoutConstraint constraintWithItem:self
                                                  attribute:NSLayoutAttributeHeight
                                                  relatedBy:NSLayoutRelationEqual
                                                     toItem:nil
                                                  attribute:NSLayoutAttributeNotAnAttribute
                                                 multiplier:1.0
                                                   constant:scaledSize.height];
 
  [NSLayoutConstraint activateConstraints:@[ widthConstraint, heightConstraint ]];
  [self setNeedsLayout];
}
 
- (void)resetIntrinsicContentSize {
  _intrinsicSize = CGSizeMake(UIViewNoIntrinsicMetric, UIViewNoIntrinsicMetric);
  [self removeAutoResizeLayoutConstraints];
}
 
- (void)removeAutoResizeLayoutConstraints {
  for (NSLayoutConstraint* constraint in self.constraints) {
    if ([constraint isKindOfClass:[FlutterAutoResizeLayoutConstraint class]]) {
      constraint.active = NO;
    }
  }
}
 
- (MTLPixelFormat)pixelFormat {
  if ([self.layer isKindOfClass:[CAMetalLayer class]]) {
// It is a known Apple bug that CAMetalLayer incorrectly reports its supported
// SDKs. It is, in fact, available since iOS 8.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunguarded-availability-new"
    CAMetalLayer* layer = (CAMetalLayer*)self.layer;
    return layer.pixelFormat;
  }
  return MTLPixelFormatBGRA8Unorm;
}
- (BOOL)isWideGamutSupported {
  FML_DCHECK(self.screen);
 
  // Wide Gamut is not supported for iOS Extensions due to memory limitations
  // (see https://github.com/flutter/flutter/issues/165086).
  if (FlutterSharedApplication.isAppExtension) {
    return NO;
  }
 
  // This predicates the decision on the capabilities of the iOS device's
  // display.  This means external displays will not support wide gamut if the
  // device's display doesn't support it.  It practice that should be never.
  return self.screen.traitCollection.displayGamut != UIDisplayGamutSRGB;
}
 
- (instancetype)initWithDelegate:(id<FlutterViewEngineDelegate>)delegate
                          opaque:(BOOL)opaque
                 enableWideGamut:(BOOL)isWideGamutEnabled {
  if (delegate == nil) {
    NSLog(@"FlutterView delegate was nil.");
    return nil;
  }
 
  self = [super initWithFrame:CGRectNull];
 
  if (self) {
    _delegate = delegate;
    _isWideGamutEnabled = isWideGamutEnabled;
    self.layer.opaque = opaque;
    _autoResizable = NO;
    _intrinsicSize = CGSizeMake(UIViewNoIntrinsicMetric, UIViewNoIntrinsicMetric);
  }
 
  return self;
}
 
static void PrintWideGamutWarningOnce() {
  static BOOL did_print = NO;
  if (did_print) {
    return;
  }
  FML_DLOG(WARNING) << "Rendering wide gamut colors is turned on but isn't "
                       "supported, downgrading the color gamut to sRGB.";
  did_print = YES;
}
 
- (void)layoutSubviews {
  if ([self.layer isKindOfClass:[CAMetalLayer class]]) {
// It is a known Apple bug that CAMetalLayer incorrectly reports its supported
// SDKs. It is, in fact, available since iOS 8.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunguarded-availability-new"
    CAMetalLayer* layer = (CAMetalLayer*)self.layer;
#pragma clang diagnostic pop
    CGFloat screenScale = self.screen.scale;
    layer.allowsGroupOpacity = YES;
    layer.contentsScale = screenScale;
    layer.rasterizationScale = screenScale;
    layer.framebufferOnly = flutter::Settings::kSurfaceDataAccessible ? NO : YES;
    if (_isWideGamutEnabled && self.isWideGamutSupported) {
      fml::CFRef<CGColorSpaceRef> srgb(CGColorSpaceCreateWithName(kCGColorSpaceExtendedSRGB));
      layer.colorspace = srgb;
      layer.pixelFormat = MTLPixelFormatBGRA10_XR;
    } else if (_isWideGamutEnabled && !self.isWideGamutSupported) {
      PrintWideGamutWarningOnce();
    }
  }
 
  [super layoutSubviews];
}
 
+ (Class)layerClass {
  return flutter::GetCoreAnimationLayerClassForRenderingAPI(flutter::GetRenderingAPIForProcess());
}
 
- (void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context {
  TRACE_EVENT0("flutter", "SnapshotFlutterView");
 
  if (layer != self.layer || context == nullptr) {
    return;
  }
 
  auto screenshot = [_delegate takeScreenshot:flutter::Rasterizer::ScreenshotType::UncompressedImage
                              asBase64Encoded:NO];
 
  if (!screenshot.data || screenshot.data->isEmpty() || screenshot.frame_size.IsEmpty()) {
    return;
  }
 
  NSData* data = [NSData dataWithBytes:const_cast<void*>(screenshot.data->data())
                                length:screenshot.data->size()];
 
  fml::CFRef<CGDataProviderRef> image_data_provider(
      CGDataProviderCreateWithCFData(reinterpret_cast<CFDataRef>(data)));
 
  fml::CFRef<CGColorSpaceRef> colorspace(CGColorSpaceCreateDeviceRGB());
 
  // Defaults for RGBA8888.
  size_t bits_per_component = 8u;
  size_t bits_per_pixel = 32u;
  size_t bytes_per_row_multiplier = 4u;
  CGBitmapInfo bitmap_info =
      static_cast<CGBitmapInfo>(static_cast<uint32_t>(kCGImageAlphaPremultipliedLast) |
                                static_cast<uint32_t>(kCGBitmapByteOrder32Big));
 
  switch (screenshot.pixel_format) {
    case flutter::Rasterizer::ScreenshotFormat::kUnknown:
    case flutter::Rasterizer::ScreenshotFormat::kR8G8B8A8UNormInt:
      // Assume unknown is Skia and is RGBA8888. Keep defaults.
      break;
    case flutter::Rasterizer::ScreenshotFormat::kB8G8R8A8UNormInt:
      // Treat this as little endian with the alpha first so that it's read backwards.
      bitmap_info =
          static_cast<CGBitmapInfo>(static_cast<uint32_t>(kCGImageAlphaPremultipliedFirst) |
                                    static_cast<uint32_t>(kCGBitmapByteOrder32Little));
      break;
    case flutter::Rasterizer::ScreenshotFormat::kR16G16B16A16Float:
      bits_per_component = 16u;
      bits_per_pixel = 64u;
      bytes_per_row_multiplier = 8u;
      bitmap_info =
          static_cast<CGBitmapInfo>(static_cast<uint32_t>(kCGImageAlphaPremultipliedLast) |
                                    static_cast<uint32_t>(kCGBitmapFloatComponents) |
                                    static_cast<uint32_t>(kCGBitmapByteOrder16Little));
      break;
  }
 
  fml::CFRef<CGImageRef> image(CGImageCreate(
      screenshot.frame_size.width,                             // size_t width
      screenshot.frame_size.height,                            // size_t height
      bits_per_component,                                      // size_t bitsPerComponent
      bits_per_pixel,                                          // size_t bitsPerPixel,
      bytes_per_row_multiplier * screenshot.frame_size.width,  // size_t bytesPerRow
      colorspace,                                              // CGColorSpaceRef space
      bitmap_info,                                             // CGBitmapInfo bitmapInfo
      image_data_provider,                                     // CGDataProviderRef provider
      nullptr,                                                 // const CGFloat* decode
      false,                                                   // bool shouldInterpolate
      kCGRenderingIntentDefault                                // CGColorRenderingIntent intent
      ));
 
  const CGRect frame_rect =
      CGRectMake(0.0, 0.0, screenshot.frame_size.width, screenshot.frame_size.height);
  CGContextSaveGState(context);
  // If the CGContext is not a bitmap based context, this returns zero.
  CGFloat height = CGBitmapContextGetHeight(context);
  if (height == 0) {
    height = CGFloat(screenshot.frame_size.height);
  }
  CGContextTranslateCTM(context, 0.0, height);
  CGContextScaleCTM(context, 1.0, -1.0);
  CGContextDrawImage(context, frame_rect, image);
  CGContextRestoreGState(context);
}
 
- (BOOL)isAccessibilityElement {
  // iOS does not provide an API to query whether the voice control
  // is turned on or off. It is likely at least one of the assitive
  // technologies is turned on if this method is called. If we do
  // not catch it in notification center, we will catch it here.
  //
  // TODO(chunhtai): Remove this workaround once iOS provides an
  // API to query whether voice control is enabled.
  // https://github.com/flutter/flutter/issues/76808.
  [self.delegate flutterViewAccessibilityDidCall];
  return NO;
}
 
// Enables keyboard-based navigation when the user turns on
// full keyboard access (FKA), using existing accessibility information.
//
// iOS does not provide any API for monitoring or querying whether FKA is on,
// but it does call isAccessibilityElement if FKA is on,
// so the isAccessibilityElement implementation above will be called
// when the view appears and the accessibility information will most likely
// be available by the time the user starts to interact with the app using FKA.
//
// See SemanticsObject+UIFocusSystem.mm for more details.
- (NSArray<id<UIFocusItem>>*)focusItemsInRect:(CGRect)rect {
  NSObject* rootAccessibilityElement =
      [self.accessibilityElements count] > 0 ? self.accessibilityElements[0] : nil;
  return [rootAccessibilityElement isKindOfClass:[SemanticsObjectContainer class]]
             ? @[ [rootAccessibilityElement accessibilityElementAtIndex:0] ]
             : nil;
}
 
- (NSArray<id<UIFocusEnvironment>>*)preferredFocusEnvironments {
  // Occasionally we add subviews to FlutterView (text fields for example).
  // These views shouldn't be directly visible to the iOS focus engine, instead
  // the focus engine should only interact with the designated focus items
  // (SemanticsObjects).
  return nil;
}
 
- (void)willMoveToWindow:(UIWindow*)newWindow {
  // When a FlutterView moves windows, it may also be moving scenes. Add/remove the FlutterEngine
  // from the FlutterSceneLifeCycleProvider.sceneLifeCycleDelegate if it changes scenes.
  UIWindowScene* newScene = newWindow.windowScene;
  UIWindowScene* currentScene = self.window.windowScene;
 
  if (newScene == currentScene) {
    return;
  }
 
  // Remove the engine from the previous scene if it's no longer in that window and scene.
  FlutterPluginSceneLifeCycleDelegate* previousSceneLifeCycleDelegate =
      [FlutterPluginSceneLifeCycleDelegate fromScene:self.previousScene];
  if (previousSceneLifeCycleDelegate) {
    [previousSceneLifeCycleDelegate removeFlutterManagedEngine:(FlutterEngine*)self.delegate];
    self.previousScene = nil;
  }
 
  if (newScene) {
    // Add the engine to the new scene's lifecycle delegate.
    FlutterPluginSceneLifeCycleDelegate* newSceneLifeCycleDelegate =
        [FlutterPluginSceneLifeCycleDelegate fromScene:newScene];
    if (newSceneLifeCycleDelegate) {
      [newSceneLifeCycleDelegate addFlutterManagedEngine:(FlutterEngine*)self.delegate];
    }
  } else {
    // If the view is being removed from a window, store the current scene to remove the engine
    // from it later when the view is added to a new window.
    self.previousScene = currentScene;
  }
}
@end