ios/web/web_state/ui/crw_web_view_content_view.mm

// Copyright 2015 The Chromium 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 "ios/web/public/web_state/ui/crw_web_view_content_view.h"

#import <WebKit/WebKit.h>

#include "base/logging.h"

#if !defined(__has_feature) || !__has_feature(objc_arc)
#error "This file requires ARC support."
#endif

namespace {

// Background color RGB values for the content view which is displayed when the
// |_webView| is offset from the screen due to user interaction. Displaying this
// background color is handled by UIWebView but not WKWebView, so it needs to be
// set in CRWWebViewContentView to support both. The color value matches that
// used by UIWebView.
const CGFloat kBackgroundRGBComponents[] = {0.75f, 0.74f, 0.76f};

}  // namespace

@interface CRWWebViewContentView () {
  // Backs up property of the same name if |_webView| is a WKWebView.
  CGFloat _topContentPadding;
}

// Changes web view frame to match |self.bounds| and optionally accomodates for
// |_topContentPadding| (iff |_webView| is a WKWebView).
- (void)updateWebViewFrame;

// The web view being shown.
@property(nonatomic, strong, readwrite) UIView* webView;
// The web view's scroll view.
@property(nonatomic, strong, readwrite) UIScrollView* scrollView;
@end

@implementation CRWWebViewContentView

@synthesize shouldUseInsetForTopPadding = _shouldUseInsetForTopPadding;
@synthesize webView = _webView;
@synthesize scrollView = _scrollView;

- (instancetype)initWithWebView:(UIView*)webView
                     scrollView:(UIScrollView*)scrollView {
  self = [super initWithFrame:CGRectZero];
  if (self) {
    DCHECK(webView);
    DCHECK(scrollView);
    DCHECK([scrollView isDescendantOfView:webView]);
    _webView = webView;
    _scrollView = scrollView;
  }
  return self;
}

- (instancetype)initForTesting {
  return [super initWithFrame:CGRectZero];
}

- (instancetype)initWithCoder:(NSCoder*)decoder {
  NOTREACHED();
  return nil;
}

- (instancetype)initWithFrame:(CGRect)frame {
  NOTREACHED();
  return nil;
}

- (void)didMoveToSuperview {
  [super didMoveToSuperview];
  if (self.superview) {
    self.autoresizingMask =
        UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    [self addSubview:_webView];
    self.backgroundColor = [UIColor colorWithRed:kBackgroundRGBComponents[0]
                                           green:kBackgroundRGBComponents[1]
                                            blue:kBackgroundRGBComponents[2]
                                           alpha:1.0];
  }
}

- (BOOL)becomeFirstResponder {
  return [_webView becomeFirstResponder];
}

- (void)setFrame:(CGRect)frame {
  if (CGRectEqualToRect(self.frame, frame))
    return;
  [super setFrame:frame];
  [self updateWebViewFrame];
}

- (void)setBounds:(CGRect)bounds {
  if (CGRectEqualToRect(self.bounds, bounds))
    return;
  [super setBounds:bounds];
  [self updateWebViewFrame];
}

#pragma mark Layout

- (void)layoutSubviews {
  [super layoutSubviews];
  [self updateWebViewFrame];
}

- (BOOL)isViewAlive {
  return YES;
}

- (CGFloat)topContentPadding {
  BOOL isSettingWebViewFrame = !self.shouldUseInsetForTopPadding;
  return isSettingWebViewFrame ? _topContentPadding
                               : [_scrollView contentInset].top;
}

- (void)setTopContentPadding:(CGFloat)newTopPadding {
  if (!self.shouldUseInsetForTopPadding) {
    if (_topContentPadding != newTopPadding) {
      // Update the content offset of the scroll view to match the padding
      // that will be included in the frame.
      CGFloat paddingChange = newTopPadding - _topContentPadding;
      CGPoint contentOffset = [_scrollView contentOffset];
      contentOffset.y += paddingChange;
      [_scrollView setContentOffset:contentOffset];
      _topContentPadding = newTopPadding;
      // Update web view frame immediately to make |topContentPadding|
      // animatable.
      [self updateWebViewFrame];
      // Setting WKWebView frame can mistakenly reset contentOffset. Change it
      // back to the initial value if necessary.
      // TODO(crbug.com/645857): Remove this workaround once WebKit bug is
      // fixed.
      if ([_scrollView contentOffset].y != contentOffset.y) {
        [_scrollView setContentOffset:contentOffset];
      }
    }
  } else {
    UIEdgeInsets inset = [_scrollView contentInset];
    inset.top = newTopPadding;
    [_scrollView setContentInset:inset];
  }
}

- (void)setShouldUseInsetForTopPadding:(BOOL)shouldUseInsetForTopPadding {
  if (_shouldUseInsetForTopPadding != shouldUseInsetForTopPadding) {
    CGFloat oldTopContentPadding = self.topContentPadding;
    self.topContentPadding = 0.0f;
    _shouldUseInsetForTopPadding = shouldUseInsetForTopPadding;
    self.topContentPadding = oldTopContentPadding;
  }
}

#pragma mark Private methods

- (void)updateWebViewFrame {
  CGRect webViewFrame = self.bounds;
  webViewFrame.size.height -= _topContentPadding;
  webViewFrame.origin.y += _topContentPadding;

  self.webView.frame = webViewFrame;
}

@end