[FlexibleHeader] Fixes to support scroll views with Safe Area insets. (…

…#2063)

* [FlexibleHeader] Fixes to support scroll views with Safe Area insets.

* Fix typo

* [FlexibleHeader] Update header height when safe area changes.

* [FlexibleHeader] Only adjust sizes and margins on iOS11+.

* [FlexibleHeader] Bring back hardocded status bar const.

* [Catalog] Fix unintended hidden status bar when in landscape.

* Code reviews

* [Podspec] Add MaterialApplication as a dependency on MDCAppBar

* [FlexibleHeader] Make Xcode 8 stop complaining about unused parameter.

* [FlexibleHeader] Fix typo.

* [UnitTest] Remove hardcoded status bar height.

MaterialComponents.podspec

@@ -73,6 +73,7 @@ Pod::Spec.new do |s|
       sss.dependency "MaterialComponents/HeaderStackView"
       sss.dependency "MaterialComponents/NavigationBar"
       sss.dependency "MaterialComponents/Typography"
+      sss.dependency "MaterialComponents/private/Application"
 
       # Flexible header + shadow
       sss.dependency "MaterialComponents/FlexibleHeader"

catalog/MDCCatalog/Info.plist

@@ -2,8 +2,6 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
-	<key>UIViewControllerBasedStatusBarAppearance</key>
-	<false/>
 	<key>CFBundleDevelopmentRegion</key>
 	<string>en</string>
 	<key>CFBundleExecutable</key>

catalog/MDCCatalog/MDCCatalogComponentsController.swift

@@ -171,6 +171,10 @@ class MDCCatalogComponentsController: UICollectionViewController, MDCInkTouchCon
     return self.headerViewController
   }
 
+  override var childViewControllerForStatusBarHidden: UIViewController? {
+    return self.headerViewController
+  }
+
 #if swift(>=3.2)
   @available(iOS 11, *)
   override func viewSafeAreaInsetsDidChange() {

catalog/MDCCatalog/MDCNodeListViewController.swift

@@ -133,6 +133,10 @@ class MDCNodeListViewController: CBCNodeListViewController {
   override var childViewControllerForStatusBarStyle: UIViewController? {
     return appBar.headerViewController
   }
+
+  override var childViewControllerForStatusBarHidden: UIViewController? {
+    return appBar.headerViewController
+  }
 }
 
 // MARK: UIScrollViewDelegate

components/AppBar/src/MDCAppBar.m

@@ -18,6 +18,7 @@
 
 #import "MDCAppBarContainerViewController.h"
 
+#import "MaterialApplication.h"
 #import "MaterialFlexibleHeader.h"
 #import "MaterialIcons+ic_arrow_back.h"
 #import "MaterialRTL.h"
@@ -33,7 +34,7 @@
 static NSString *const MDCAppBarHeaderViewControllerKey = @"MDCAppBarHeaderViewControllerKey";
 static NSString *const MDCAppBarNavigationBarKey = @"MDCAppBarNavigationBarKey";
 static NSString *const MDCAppBarHeaderStackViewKey = @"MDCAppBarHeaderStackViewKey";
-static const CGFloat kStatusBarHeight = 20;
+static const CGFloat kPreIOS11StatusBarHeight = 20;
 
 // The Bundle for string resources.
 static NSString *const kMaterialAppBarBundle = @"MaterialAppBar.bundle";
@@ -300,20 +301,28 @@ - (void)viewDidLoad {
   [self.view addSubview:self.headerStackView];
 
   // Bar stack expands vertically, but has a margin above it for the status bar.
-
   NSArray<NSLayoutConstraint *> *horizontalConstraints = [NSLayoutConstraint
       constraintsWithVisualFormat:[NSString stringWithFormat:@"H:|[%@]|", kBarStackKey]
                           options:0
                           metrics:nil
                             views:@{kBarStackKey : self.headerStackView}];
   [self.view addConstraints:horizontalConstraints];
 
+  CGFloat topMargin = kPreIOS11StatusBarHeight;
+#if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
+  if (@available(iOS 11.0, *)) {
+    // Starting from iOS 11, the top margin should be the actual status bar height.
+    // This is because the flexible header could be smaller in height when in landscape mode
+    // due to the status bar being hidden by default on some devices (like the iPhone X).
+    topMargin = [UIApplication mdc_safeSharedApplication].statusBarFrame.size.height;
+  }
+#endif
   NSArray<NSLayoutConstraint *> *verticalConstraints = [NSLayoutConstraint
       constraintsWithVisualFormat:[NSString stringWithFormat:@"V:|-%@-[%@]|", kStatusBarHeightKey,
                                                              kBarStackKey]
                           options:0
                           metrics:@{
-                            kStatusBarHeightKey : @(kStatusBarHeight)
+                            kStatusBarHeightKey : @(topMargin)
                           }
                             views:@{kBarStackKey : self.headerStackView}];
   [self.view addConstraints:verticalConstraints];

components/FlexibleHeader/examples/FlexibleHeaderHorizontalPagingExample.m

@@ -146,6 +146,7 @@ - (instancetype)initWithCoder:(NSCoder *)aDecoder {
 
 - (void)commonMDCFlexibleHeaderViewControllerInit {
   self.fhvc = [[MDCFlexibleHeaderViewController alloc] initWithNibName:nil bundle:nil];
+  self.fhvc.headerView.sharedWithManyScrollViews = YES;
   [self addChildViewController:_fhvc];
 }
 

components/FlexibleHeader/examples/supplemental/FlexibleHeaderTopLayoutGuideSupplemental.m

@@ -49,7 +49,10 @@ - (void)setupScrollViewContent {
   UIColor *color =
       [UIColor colorWithRed:(97.0 / 255.0) green:(97.0 / 255.0) blue:(97.0 / 255.0) alpha:1.0];
   UIView *scrollViewContent =
-      [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.scrollView.frame.size.width, 700)];
+      [[UIView alloc] initWithFrame:CGRectMake(0,
+                                               0,
+                                               self.scrollView.frame.size.width,
+                                               self.scrollView.frame.size.height * 2)];
   scrollViewContent.autoresizingMask =
       UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
   UILabel *pullDownLabel = [[UILabel alloc]

components/FlexibleHeader/src/MDCFlexibleHeaderView.m

@@ -16,16 +16,17 @@
 
 #import "MDCFlexibleHeaderView.h"
 
+#import "MaterialApplication.h"
 #import "private/MDCStatusBarShifter.h"
 
 #if TARGET_IPHONE_SIMULATOR
 float UIAnimationDragCoefficient(void);  // Private API for simulator animation speed
 #endif
 
-static const CGFloat kExpectedStatusBarHeight = 20;
+static const CGFloat kPreIOS11ExpectedStatusBarHeight = 20;
 
-// The default maximum height for the header. Includes the status bar height.
-static const CGFloat kFlexibleHeaderDefaultHeight = 76;
+// The default maximum height for the header. Does not include the status bar height.
+static const CGFloat kFlexibleHeaderDefaultHeight = 56;
 
 // The maximum default opacity of the shadow.
 static const float kDefaultVisibleShadowOpacity = 0.4f;
@@ -109,6 +110,12 @@ @interface MDCFlexibleHeaderScrollViewInfo : NSObject
 // The amount injected into scrollIndicatorInsets.top
 @property(nonatomic) CGFloat injectedTopScrollIndicatorInset;
 
+// The adjustment we've made to account for the scroll view's Safe Area.
+@property(nonatomic) CGFloat topSafeAreaInsetAdjustment;
+
+// Whether or not we've adjusted the inset to account for the scroll view's Safe Area.
+@property(nonatomic) BOOL hasTopSafeAreaInsetAdjustment;
+
 @end
 
 @implementation MDCFlexibleHeaderView {
@@ -125,6 +132,10 @@ @implementation MDCFlexibleHeaderView {
   // is interacting with the header or if we're presently animating it.
   BOOL _wantsToBeHidden;
 
+  // This will help us track if the size has been explicitly set or if we're using the defaults.
+  BOOL _hasExplicitlySetMinHeight;
+  BOOL _hasExplicitlySetMaxHeight;
+
   // Shift behavior state
 
   // Prevents delta calculations on first update pass.
@@ -287,8 +298,16 @@ - (void)commonMDCFlexibleHeaderViewInit {
   _headerContentImportance = MDCFlexibleHeaderContentImportanceDefault;
   _statusBarHintCanOverlapHeader = YES;
 
-  _minimumHeight = kFlexibleHeaderDefaultHeight;
-  _maximumHeight = kFlexibleHeaderDefaultHeight;
+  _minimumHeight = kFlexibleHeaderDefaultHeight + kPreIOS11ExpectedStatusBarHeight;
+#if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
+  if (@available(iOS 11.0, *)) {
+    // Starting from iOS 11, we should adapt the size of this component to take into account
+    // the new status bar sizes and the "no status bar in landscape" functionality.
+    CGFloat statusBarHeight = [UIApplication mdc_safeSharedApplication].statusBarFrame.size.height;
+    _minimumHeight = kFlexibleHeaderDefaultHeight + statusBarHeight;
+  }
+#endif
+  _maximumHeight = _minimumHeight;
   _visibleShadowOpacity = kDefaultVisibleShadowOpacity;
   _canOverExtend = YES;
 
@@ -414,6 +433,36 @@ - (void)setBackgroundColor:(UIColor *)backgroundColor {
   _defaultShadowLayer.backgroundColor = self.backgroundColor.CGColor;
 }
 
+- (void)safeAreaInsetsDidChange {
+#if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
+  if (@available(iOS 11.0, *)) {
+    [self fhv_adjustInsetsForSafeAreaInScrollView:_trackingScrollView];
+
+    // If the min/max height hasn't been explicitly set, we need to update the layout to reflect
+    // the change in the Safe Area insets.
+    if (_hasExplicitlySetMinHeight && _hasExplicitlySetMaxHeight) {
+      return;
+    }
+    if (!_hasExplicitlySetMinHeight) {
+      // Edge case for UITableViewController: If we're a subview of _trackingScrollView,
+      // we need to get the Safe Area insets from there and not use ours.
+      if ([self isDescendantOfView:_trackingScrollView]) {
+        _minimumHeight = kFlexibleHeaderDefaultHeight + _trackingScrollView.safeAreaInsets.top;
+      } else {
+        _minimumHeight = kFlexibleHeaderDefaultHeight + self.safeAreaInsets.top;
+      }
+    }
+    if (!_hasExplicitlySetMaxHeight) {
+      _maximumHeight = _minimumHeight;
+    }
+    if (_maximumHeight < _minimumHeight) {
+      _maximumHeight = _minimumHeight;
+    }
+    [self fhv_updateLayout];
+  }
+#endif
+}
+
 #pragma mark - Private (fhv_ prefix)
 
 - (void)fhv_removeInsetsFromScrollView:(UIScrollView *)scrollView {
@@ -468,6 +517,42 @@ - (MDCFlexibleHeaderScrollViewInfo *)fhv_addInsetsToScrollView:(UIScrollView *)s
   return info;
 }
 
+- (void)fhv_adjustInsetsForSafeAreaInScrollView:(UIScrollView *)scrollView {
+  if (!scrollView) {
+    return;
+  }
+#if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
+  if (@available(iOS 11.0, *)) {
+    if (scrollView.contentInsetAdjustmentBehavior == UIScrollViewContentInsetAdjustmentAlways ||
+        scrollView.contentInsetAdjustmentBehavior == UIScrollViewContentInsetAdjustmentAutomatic) {
+
+      // For Automatic: If contentInset and adjustedContentInset are the same, no-op.
+      if (scrollView.contentInset.top == scrollView.adjustedContentInset.top) {
+        return;
+      }
+
+      // If the injected Safe Area inset hasn't changed, no-op.
+      MDCFlexibleHeaderScrollViewInfo *info = [_trackedScrollViews objectForKey:scrollView];
+      if (!info || info.topSafeAreaInsetAdjustment == scrollView.safeAreaInsets.top) {
+        return;
+      }
+
+      UIEdgeInsets insets = scrollView.contentInset;
+      if (info.hasTopSafeAreaInsetAdjustment) {
+        insets.top += info.topSafeAreaInsetAdjustment;
+      }
+      info.topSafeAreaInsetAdjustment = scrollView.safeAreaInsets.top;
+      insets.top -= info.topSafeAreaInsetAdjustment;
+      info.hasTopSafeAreaInsetAdjustment = YES;
+      scrollView.contentInset = insets;
+
+      // Update injectedTopContentInset to account for the scroll view's Safe Area inset.
+      info.injectedTopContentInset = _maximumHeight - info.topSafeAreaInsetAdjustment;
+    }
+  }
+#endif
+}
+
 - (void)fhv_updateShadowPath {
   UIBezierPath *path =
       [UIBezierPath bezierPathWithRect:CGRectInset(self.bounds, -self.layer.shadowRadius, 0)];
@@ -509,7 +594,8 @@ - (CGFloat)fhv_projectedHeaderBottomEdge {
 
 - (CGFloat)fhv_accumulatorMax {
   BOOL shouldCollapseToStatusBar = [self fhv_shouldCollapseToStatusBar];
-  return (shouldCollapseToStatusBar ? _minimumHeight - kExpectedStatusBarHeight : _minimumHeight);
+  CGFloat statusBarHeight = [UIApplication mdc_safeSharedApplication].statusBarFrame.size.height;
+  return (shouldCollapseToStatusBar ? _minimumHeight - statusBarHeight : _minimumHeight);
 }
 
 #pragma mark Logical short forms
@@ -560,7 +646,9 @@ - (void)fhv_recalculatePhase {
     _scrollPhaseValue = frame.origin.y + _minimumHeight;
     CGFloat adjustedHeight = _minimumHeight;
     if ([self fhv_shouldCollapseToStatusBar]) {
-      adjustedHeight -= kExpectedStatusBarHeight;
+      CGFloat statusBarHeight =
+          [UIApplication mdc_safeSharedApplication].statusBarFrame.size.height;
+      adjustedHeight -= statusBarHeight;
     }
     if (adjustedHeight > 0) {
       _scrollPhasePercentage = -frame.origin.y / adjustedHeight;
@@ -718,8 +806,15 @@ - (void)fhv_accumulatorDidChange {
   scrollIndicatorInsets.top -= _trackingInfo.injectedTopScrollIndicatorInset;
 
   _trackingInfo.injectedTopScrollIndicatorInset = frame.size.height - boundedAccumulator;
-  scrollIndicatorInsets.top += _trackingInfo.injectedTopScrollIndicatorInset;
 
+  // If on iOS 11, take into account the scroll view's Safe Area insets.
+#if defined(__IPHONE_11_0) && (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_11_0)
+  if (@available(iOS 11.0, *)) {
+    _trackingInfo.injectedTopScrollIndicatorInset -= _trackingScrollView.safeAreaInsets.top;
+  }
+#endif
+
+  scrollIndicatorInsets.top += _trackingInfo.injectedTopScrollIndicatorInset;
   _trackingScrollView.scrollIndicatorInsets = scrollIndicatorInsets;
 }
 
@@ -985,6 +1080,10 @@ - (void)setTrackingScrollView:(UIScrollView *)trackingScrollView {
   if (!_sharedWithManyScrollViews || !_trackingInfo) {
     [self fhv_addInsetsToScrollView:_trackingScrollView];
   }
+
+  // Before we update the layout, take into account the scroll view's Safe Area insets.
+  [self fhv_adjustInsetsForSafeAreaInScrollView:_trackingScrollView];
+
   void (^animate)(void) = ^{
     [self fhv_updateLayout];
   };
@@ -1009,6 +1108,10 @@ - (void)setTrackingScrollView:(UIScrollView *)trackingScrollView {
 }
 
 - (void)trackingScrollViewDidScroll {
+  // This could've been triggered by a change in the scroll view's Safe Area, so we need to check
+  // if it did. If it didn't, this is a no-op.
+  [self fhv_adjustInsetsForSafeAreaInScrollView:_trackingScrollView];
+
   [self fhv_contentOffsetDidChange];
 }
 
@@ -1140,6 +1243,7 @@ - (void)stopForwardingTouchEventsForView:(UIView *)view {
 }
 
 - (void)setMinimumHeight:(CGFloat)minimumHeight {
+  _hasExplicitlySetMinHeight = YES;
   if (_minimumHeight == minimumHeight) {
     return;
   }
@@ -1154,6 +1258,7 @@ - (void)setMinimumHeight:(CGFloat)minimumHeight {
 }
 
 - (void)setMaximumHeight:(CGFloat)maximumHeight {
+  _hasExplicitlySetMaxHeight = YES;
   if (_maximumHeight == maximumHeight) {
     return;
   }

components/FlexibleHeader/src/MDCFlexibleHeaderViewController.m

@@ -16,6 +16,7 @@
 
 #import "MDCFlexibleHeaderViewController.h"
 
+#import "MaterialApplication.h"
 #import "MDCFlexibleHeaderContainerViewController.h"
 #import "MDCFlexibleHeaderView.h"
 #import "MDFTextAccessibility.h"
@@ -145,7 +146,9 @@ - (void)viewWillAppear:(BOOL)animated {
 }
 
 - (UIStatusBarStyle)preferredStatusBarStyle {
-  return (ShouldUseLightStatusBarOnBackgroundColor(_headerView.backgroundColor)
+  UIColor *backgroundColor =
+      [MDCFlexibleHeaderView appearance].backgroundColor ?: _headerView.backgroundColor;
+  return (ShouldUseLightStatusBarOnBackgroundColor(backgroundColor)
               ? UIStatusBarStyleLightContent
               : UIStatusBarStyleDefault);
 }
@@ -223,9 +226,13 @@ - (void)updateTopLayoutGuide {
 }
 
 - (CGFloat)headerViewControllerHeight {
+  BOOL shiftEnabledForStatusBar =
+      _headerView.shiftBehavior == MDCFlexibleHeaderShiftBehaviorEnabledWithStatusBar;
+  CGFloat statusBarHeight =
+      [UIApplication mdc_safeSharedApplication].statusBarFrame.size.height;
   CGFloat height =
       MAX(_headerView.frame.origin.y + _headerView.frame.size.height,
-          _headerView.shiftBehavior == MDCFlexibleHeaderShiftBehaviorEnabledWithStatusBar ? 0 : 20);
+          shiftEnabledForStatusBar ? 0 : statusBarHeight);
   return height;
 }