[Buttons] Move MDCButton's defaultContentInset configuration to later…

… in init (#8069)

After digging in a bit, I've found that this is an issue with UIButton in iOS 13 (as of Xcode 11 beta 4). To reproduce:

1) Create a `UIButton`.
2) Create a `UIImage` and flip it using `imageWithHorizontallyFlippedOrientation`.
3) *Before setting the button's image*, give the button non-zero contentEdgeInsets (I used `{20, 10, 20, 10}`).
4) Set the image on the button.

You should be able to see that the image is not visible, and that the button's internal UIImageView's bounds.origin is `{ -(i.left + i.right), -(i.top + i.bottom) }` (where `i` is the button's contentEdgeInsets). In iOS 12, the button's imageView's bounds.origin is `{0, 0}`.


Closes #7983

components/Buttons/src/MDCButton.m

@@ -167,11 +167,6 @@ - (void)commonMDCButtonInit {
   self.adjustsImageWhenHighlighted = NO;
   self.showsTouchWhenHighlighted = NO;
 
-  // Default content insets
-  self.contentEdgeInsets = [self defaultContentEdgeInsets];
-  _minimumSize = CGSizeZero;
-  _maximumSize = CGSizeZero;
-
   self.layer.cornerRadius = MDCButtonDefaultCornerRadius;
   if (!self.layer.shapeGenerator) {
     self.layer.shadowPath = [self boundingPath].CGPath;
@@ -204,6 +199,19 @@ - (void)commonMDCButtonInit {
   _rippleView = [[MDCStatefulRippleView alloc] initWithFrame:self.bounds];
   _rippleView.rippleColor = [UIColor colorWithWhite:1 alpha:(CGFloat)0.12];
 
+  // Default content insets
+  // The default contentEdgeInsets are set here (instead of above, as they were previously) because
+  // of a UIButton bug introduced in the iOS 13 betas that is unresolved as of Xcode 11 beta 4
+  // (b/136088498) wherein setting self.contentEdgeInsets before accessing self.imageView causes the
+  // imageView's bounds.origin to be set to { -(i.left + i.right), -(i.top + i.bottom) }
+  // This causes images created by using imageWithHorizontallyFlippedOrientation to not display.
+  // Images that have not been created this way seem to be fine.
+  // This behavior can also be seen in vanilla UIButtons by setting contentEdgeInsets to non-zero
+  // inset values and then setting an image created with imageWithHorizontallyFlippedOrientation.
+  self.contentEdgeInsets = [self defaultContentEdgeInsets];
+  _minimumSize = CGSizeZero;
+  _maximumSize = CGSizeZero;
+
   // Uppercase all titles
   if (_uppercaseTitle) {
     [self updateTitleCase];

components/Buttons/tests/snapshot/ButtonsFlippedImageRenderingSnapshotTests.m

@@ -0,0 +1,65 @@
+// Copyright 2019-present the Material Components for iOS authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#import "MaterialSnapshot.h"
+
+#import <CoreGraphics/CoreGraphics.h>
+#import <UIKit/UIKit.h>
+
+#import "MaterialButtons.h"
+
+/** Snapshot tests for Buttons in different UIControlStates */
+@interface ButtonsFlippedImageRenderingSnapshotTests : MDCSnapshotTestCase
+@property(nonatomic, strong) MDCButton *button;
+@end
+
+@implementation ButtonsFlippedImageRenderingSnapshotTests
+
+- (void)setUp {
+  [super setUp];
+  self.button = [[MDCButton alloc] init];
+}
+
+- (void)tearDown {
+  self.button = nil;
+  [super tearDown];
+}
+
+- (void)generateSnapshotAndVerifyForView:(UIView *)view {
+  [view sizeToFit];
+  UIView *snapshotView = [view mdc_addToBackgroundView];
+  [self snapshotVerifyView:snapshotView];
+}
+
+// This test exists to exercise a bug in iOS 13 (Xcode 11 betas 1-4) where setting contentEdgeInsets
+// before a horizontally flipped UIImage causes the image to render outside of the UIImageView's
+// frame.
+- (void)testHorizontallyFlippedImageWithContentInsets {
+  // Given
+  if (@available(iOS 10.0, *)) {
+    // When
+    self.button.contentEdgeInsets = UIEdgeInsetsMake(10, 20, 10, 20);
+    UIImage *testImage =
+        [[UIImage mdc_testImageOfSize:CGSizeMake(24, 24)] imageWithHorizontallyFlippedOrientation];
+    [self.button setImage:testImage forState:UIControlStateNormal];
+  } else {
+    // Fallback on earlier versions
+  }
+
+  // Then
+  [self.button sizeToFit];
+  [self snapshotVerifyViewForIOS13:self.button];
+}
+
+@end