[Banner] Support Dynamic Type in Banner (#7709)

Closes https://github.com/material-components/material-components-ios/issues/7621.

Screenshot:

|Adjusted Sizing Category 1 | Adjusted Sizing Category 2|
|---|---|
|![IMG_0789](https://user-images.githubusercontent.com/8836258/60121196-8a996f80-9750-11e9-818c-b82073d51e2c.PNG)|![IMG_0788](https://user-images.githubusercontent.com/8836258/60121199-8c633300-9750-11e9-824e-6ff2f5c95706.PNG)|

catalog/Podfile

@@ -73,6 +73,7 @@ target "MDCCatalog" do
   pod 'MaterialComponentsBeta', :path => '../', :testspecs => [
     'ActionSheet+ActionSheetThemer/UnitTests',
     'ActionSheet+ColorThemer/UnitTests',
+    'Banner/UnitTests',
     'BottomNavigation/UnitTests',
     'ButtonBar+Theming/UnitTests',
     'Tabs+TabBarView/UnitTests',

components/Banner/BUILD

@@ -18,6 +18,7 @@ load(
     "mdc_objc_library",
     "mdc_snapshot_objc_library",
     "mdc_snapshot_test",
+    "mdc_unit_test_suite",
 )
 
 licenses(["notice"])  # Apache 2.0
@@ -44,6 +45,7 @@ mdc_examples_objc_library(
         "//components/Buttons:Theming",
         "//components/schemes/Color",
         "//components/schemes/Container",
+        "//components/schemes/Typography",
     ],
 )
 
@@ -52,10 +54,37 @@ mdc_snapshot_objc_library(
     deps = [
         ":Banner",
         "//components/Buttons",
+        "//components/schemes/Typography",
     ],
 )
 
 mdc_snapshot_test(
     name = "snapshot_tests",
     deps = [":snapshot_test_lib"],
 )
+
+mdc_objc_library(
+    name = "unit_test_sources",
+    testonly = 1,
+    srcs = native.glob([
+        "tests/unit/*.m",
+        "tests/unit/*.h",
+    ]),
+    sdk_frameworks = [
+        "UIKit",
+        "XCTest",
+    ],
+    visibility = ["//visibility:private"],
+    deps = [
+        ":Banner",
+        "//components/Buttons",
+        "//components/Typography",
+    ],
+)
+
+mdc_unit_test_suite(
+    name = "unit_tests",
+    deps = [
+        ":unit_test_sources",
+    ],
+)

components/Banner/examples/BannerTypicalUseExampleViewController.m

@@ -16,6 +16,7 @@
 #import "MaterialButtons.h"
 #import "MaterialColorScheme.h"
 #import "MaterialTypography.h"
+#import "MaterialTypographyScheme.h"
 
 static const CGFloat exampleListTableViewHeight = 160.0f;
 static const CGFloat exampleBannerContentPadding = 10.0f;
@@ -80,6 +81,7 @@ @interface BannerTypicalUseExampleViewController
 @property(nonatomic, weak) MDCBannerView *bannerView;
 
 @property(nonatomic, strong) MDCSemanticColorScheme *colorScheme;
+@property(nonatomic, strong) MDCTypographyScheme *typographyScheme;
 
 @end
 
@@ -89,6 +91,7 @@ - (instancetype)init {
   self = [super init];
   if (self) {
     self.colorScheme = [[MDCSemanticColorScheme alloc] init];
+    self.typographyScheme = [[MDCTypographyScheme alloc] init];
   }
   return self;
 }
@@ -220,6 +223,8 @@ - (void)showSingleLineStyleBanner {
 
   MDCBannerView *bannerView = [[MDCBannerView alloc] init];
   bannerView.textLabel.text = exampleShortText;
+  bannerView.textLabel.font = self.typographyScheme.body2;
+  bannerView.mdc_adjustsFontForContentSizeCategory = YES;
   bannerView.backgroundColor = self.colorScheme.surfaceColor;
   UIEdgeInsets margins = UIEdgeInsetsZero;
   margins.left = exampleBannerContentPadding;
@@ -232,6 +237,7 @@ - (void)showSingleLineStyleBanner {
   [button setTitle:@"Dismiss" forState:UIControlStateNormal];
   button.uppercaseTitle = YES;
   [button setTitleColor:self.colorScheme.primaryColor forState:UIControlStateNormal];
+  [button setTitleFont:self.typographyScheme.button forState:UIControlStateNormal];
   button.backgroundColor = self.colorScheme.surfaceColor;
   bannerView.trailingButton.hidden = YES;
   bannerView.imageView.hidden = YES;

components/Banner/src/MDCBannerView.h

@@ -84,4 +84,16 @@ __attribute__((objc_subclassing_restricted)) @interface MDCBannerView : UIView
  */
 @property(nonatomic, readwrite, strong, nonnull) UIColor *dividerColor;
 
+/*
+ Indicates whether the banner should automatically update its font when the device’s
+ UIContentSizeCategory is changed.
+
+ If set to YES, the text fonts and buttons font will be based on the scalable fonts set on this
+ banner.
+
+ Default value is NO.
+ */
+@property(nonatomic, readwrite, setter=mdc_setAdjustsFontForContentSizeCategory:, assign)
+    BOOL mdc_adjustsFontForContentSizeCategory;
+
 @end

components/Banner/src/MDCBannerView.m

@@ -145,12 +145,14 @@ - (void)commonBannerViewInit {
   MDCButton *leadingButton = [[MDCButton alloc] init];
   leadingButton.translatesAutoresizingMaskIntoConstraints = NO;
   leadingButton.backgroundColor = UIColor.whiteColor;
+  leadingButton.adjustsFontForContentSizeCategoryWhenScaledFontIsUnavailable = NO;
   [buttonContainerView addSubview:leadingButton];
   _leadingButton = leadingButton;
 
   MDCButton *trailingButton = [[MDCButton alloc] init];
   trailingButton.translatesAutoresizingMaskIntoConstraints = NO;
   trailingButton.backgroundColor = UIColor.whiteColor;
+  trailingButton.adjustsFontForContentSizeCategoryWhenScaledFontIsUnavailable = NO;
   [buttonContainerView addSubview:trailingButton];
   _trailingButton = trailingButton;
 
@@ -515,4 +517,52 @@ - (BOOL)isAbleToFitTextLabel:(UILabel *)textLabel withWidthLimit:(CGFloat)widthL
   return size.width <= widthLimit;
 }
 
+#pragma mark - Font
+
+- (void)mdc_setAdjustsFontForContentSizeCategory:(BOOL)mdc_adjustsFontForContentSizeCategory {
+  _mdc_adjustsFontForContentSizeCategory = mdc_adjustsFontForContentSizeCategory;
+
+  if (mdc_adjustsFontForContentSizeCategory) {
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(contentSizeCategoryDidChange:)
+                                                 name:UIContentSizeCategoryDidChangeNotification
+                                               object:nil];
+  } else {
+    [[NSNotificationCenter defaultCenter] removeObserver:self
+                                                    name:UIContentSizeCategoryDidChangeNotification
+                                                  object:nil];
+  }
+
+  // Set mdc_adjustsFontForContentSizeCategory on buttons
+  self.leadingButton.mdc_adjustsFontForContentSizeCategory =
+      self.mdc_adjustsFontForContentSizeCategory;
+  self.trailingButton.mdc_adjustsFontForContentSizeCategory =
+      self.mdc_adjustsFontForContentSizeCategory;
+
+  [self updateBannerFont];
+}
+
+- (void)contentSizeCategoryDidChange:(__unused NSNotification *)notification {
+  [self updateBannerFont];
+}
+
+- (void)traitCollectionDidChange:(UITraitCollection *)previousTraitCollection {
+  [self updateBannerFont];
+}
+
+- (void)updateBannerFont {
+  [self updateTextFont];
+
+  [self invalidateIntrinsicContentSize];
+  [self setNeedsUpdateConstraints];
+}
+
+- (void)updateTextFont {
+  UIFont *textFont = self.textLabel.font;
+  if (self.mdc_adjustsFontForContentSizeCategory && textFont.mdc_scalingCurve) {
+    textFont = [textFont mdc_scaledFontForTraitEnvironment:self];
+  }
+  self.textLabel.font = textFont;
+}
+
 @end

components/Banner/tests/snapshot/MDCBannerSnapshotTests.m

@@ -16,17 +16,56 @@
 
 #import "MDCBannerView.h"
 #import "MaterialButtons.h"
+#import "MaterialTypographyScheme.h"
 
 static NSString *const kBannerShortText = @"tristique senectus et";
 static NSString *const kBannerLongText =
     @"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt.";
 static const CGFloat kBannerContentPadding = 10.0f;
 
+@interface MDCBannerViewSnapshotDynamicTypeContentSizeCategoryOverrideWindow : UIWindow
+
+/** Used to override the value of @c preferredContentSizeCategory. */
+@property(nonatomic, copy) UIContentSizeCategory contentSizeCategoryOverride;
+
+@end
+
+@implementation MDCBannerViewSnapshotDynamicTypeContentSizeCategoryOverrideWindow
+
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    self.contentSizeCategoryOverride = UIContentSizeCategoryLarge;
+  }
+  return self;
+}
+
+- (instancetype)initWithContentSizeCategoryOverride:
+    (UIContentSizeCategory)contentSizeCategoryOverride {
+  self = [super init];
+  if (self) {
+    self.contentSizeCategoryOverride = contentSizeCategoryOverride;
+  }
+  return self;
+}
+
+- (UITraitCollection *)traitCollection {
+  if (@available(iOS 10.0, *)) {
+    UITraitCollection *traitCollection = [UITraitCollection
+        traitCollectionWithPreferredContentSizeCategory:self.contentSizeCategoryOverride];
+    return traitCollection;
+  }
+  return [super traitCollection];
+}
+
+@end
+
 /** Snapshot tests for MDCBannerView. */
 @interface MDCBannerViewSnapshotTests : MDCSnapshotTestCase
 
 /** The view being tested. */
 @property(nonatomic, strong) MDCBannerView *bannerView;
+@property(nonatomic, strong) MDCTypographyScheme *typographyScheme;
 
 @end
 
@@ -37,7 +76,7 @@ - (void)setUp {
 
   // Uncomment below to recreate all the goldens (or add the following line to the specific
   // test you wish to recreate the golden for).
-  //  self.recordMode = YES;
+  // self.recordMode = YES;
 
   self.bannerView = [[MDCBannerView alloc] initWithFrame:CGRectZero];
   if (@available(iOS 11.0, *)) {
@@ -59,6 +98,25 @@ - (void)tearDown {
   [super tearDown];
 }
 
+- (UIWindow *)generateWindowWithView:(UIView *)view
+                 contentSizeCategory:(UIContentSizeCategory)sizeCategory
+                              insets:(UIEdgeInsets)insets {
+  MDCBannerViewSnapshotDynamicTypeContentSizeCategoryOverrideWindow *backgroundWindow =
+      [[MDCBannerViewSnapshotDynamicTypeContentSizeCategoryOverrideWindow alloc]
+          initWithFrame:CGRectMake(0, 0, CGRectGetWidth(view.bounds) + insets.left + insets.right,
+                                   CGRectGetHeight(view.bounds) + insets.top + insets.bottom)];
+  backgroundWindow.contentSizeCategoryOverride = sizeCategory;
+  backgroundWindow.backgroundColor = [UIColor colorWithWhite:(CGFloat)0.8 alpha:1];
+  [backgroundWindow addSubview:view];
+  backgroundWindow.hidden = NO;
+
+  CGRect frame = view.frame;
+  frame.origin = CGPointMake(insets.left, insets.top);
+  view.frame = frame;
+
+  return backgroundWindow;
+}
+
 - (void)generateSnapshotAndVerifyForView:(UIView *)view {
   CGSize aSize = [view sizeThatFits:CGSizeMake(350, INFINITY)];
   view.frame = CGRectMake(0, 0, aSize.width, aSize.height);
@@ -68,6 +126,25 @@ - (void)generateSnapshotAndVerifyForView:(UIView *)view {
   [self snapshotVerifyView:snapshotView];
 }
 
+// TODO(https://github.com/material-components/material-components-ios/issues/7487):
+// The size of the cell view sent for snapshot is not correct because Autolayout needs
+// to be used as an environment.
+- (void)generateSnapshotWithContentSizeCategoryAndNotificationPost:
+            (UIContentSizeCategory)sizeCategory
+                                                  andVerifyForView:(UIView *)view {
+  CGSize aSize = [view sizeThatFits:CGSizeMake(350, INFINITY)];
+  view.frame = CGRectMake(0, 0, aSize.width, aSize.height);
+  [view layoutIfNeeded];
+
+  UIWindow *snapshotWindow = [self generateWindowWithView:view
+                                      contentSizeCategory:sizeCategory
+                                                   insets:UIEdgeInsetsMake(10, 10, 10, 10)];
+  [NSNotificationCenter.defaultCenter
+      postNotificationName:UIContentSizeCategoryDidChangeNotification
+                    object:nil];
+  [self snapshotVerifyView:snapshotWindow];
+}
+
 - (void)changeViewToRTL:(UIView *)view {
   if (@available(iOS 9.0, *)) {
     view.semanticContentAttribute = UISemanticContentAttributeForceRightToLeft;
@@ -201,4 +278,29 @@ - (void)testSingleRowStyleLongTextWithSingleActionRTL {
   [self generateSnapshotAndVerifyForView:self.bannerView];
 }
 
+- (void)testDynamicTypeForContentSizeCategoryExtraExtraLarge {
+  if (@available(iOS 10.0, *)) {
+    // Given
+    self.bannerView = [[MDCBannerView alloc] init];
+    self.typographyScheme =
+        [[MDCTypographyScheme alloc] initWithDefaults:MDCTypographySchemeDefaultsMaterial201902];
+
+    // When
+    self.bannerView.textLabel.text = kBannerShortText;
+    self.bannerView.textLabel.font = self.typographyScheme.body2;
+    MDCButton *button = self.bannerView.leadingButton;
+    [button setTitle:@"Action" forState:UIControlStateNormal];
+    [button setTitleFont:self.typographyScheme.button forState:UIControlStateNormal];
+    button.uppercaseTitle = YES;
+    [button setTitleColor:UIColor.blackColor forState:UIControlStateNormal];
+    self.bannerView.trailingButton.hidden = YES;
+    self.bannerView.mdc_adjustsFontForContentSizeCategory = YES;
+
+    // Then
+    [self generateSnapshotWithContentSizeCategoryAndNotificationPost:
+              UIContentSizeCategoryExtraExtraLarge
+                                                    andVerifyForView:self.bannerView];
+  }
+}
+
 @end