Add the HorizontalReorderingLayout and refactor GridReorderingLayout.

Add the HorizontalReorderingLayout, which is the layout of the thumb
strip when reordering cells while the DragAndDrop flag is disabled.

Add a set of helper functions to be called by both the
HorizontalReorderingLayout and the GridReorderingLayout.

Change-Id: Id0b475c7e9cb97c537ce3b30d3936d0c82d1f2cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462125Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: Roberto Moura <mouraroberto@google.com>
Auto-Submit: Roberto Moura <mouraroberto@google.com>
Cr-Commit-Position: refs/heads/master@{#816775}

ios/chrome/browser/ui/tab_grid/grid/BUILD.gn

@@ -32,6 +32,8 @@ source_set("grid_ui") {
     "grid_view_controller.mm",
     "horizontal_layout.h",
     "horizontal_layout.mm",
+    "reordering_layout_util.h",
+    "reordering_layout_util.mm",
   ]
 
   configs += [ "//build/config/compiler:enable_arc" ]

ios/chrome/browser/ui/tab_grid/grid/grid_layout.mm

@@ -5,6 +5,7 @@
 #import "ios/chrome/browser/ui/tab_grid/grid/grid_layout.h"
 
 #import "ios/chrome/browser/ui/tab_grid/grid/grid_constants.h"
+#import "ios/chrome/browser/ui/tab_grid/grid/reordering_layout_util.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
@@ -75,38 +76,23 @@
 // default layout attributes.
 - (NSArray<__kindof UICollectionViewLayoutAttributes*>*)
     layoutAttributesForElementsInRect:(CGRect)rect {
-  NSArray* baseAttributes = [super layoutAttributesForElementsInRect:rect];
-  NSMutableArray<__kindof UICollectionViewLayoutAttributes*>* attributes =
-      [NSMutableArray array];
-  for (UICollectionViewLayoutAttributes* attribute in baseAttributes) {
-    UICollectionViewLayoutAttributes* newAttribute = [attribute copy];
-    newAttribute.alpha = kReorderingInactiveCellOpacity;
-    [attributes addObject:newAttribute];
-  }
-  return [attributes copy];
+  return CopyAttributesArrayAndSetInactiveOpacity(
+      [super layoutAttributesForElementsInRect:rect]);
 }
 
 - (UICollectionViewLayoutAttributes*)layoutAttributesForItemAtIndexPath:
     (NSIndexPath*)indexPath {
-  UICollectionViewLayoutAttributes* attributes =
-      [[super layoutAttributesForItemAtIndexPath:indexPath] copy];
-  attributes.alpha = kReorderingInactiveCellOpacity;
-  return attributes;
+  return CopyAttributesAndSetInactiveOpacity(
+      [super layoutAttributesForItemAtIndexPath:indexPath]);
 }
 
 - (UICollectionViewLayoutAttributes*)
     layoutAttributesForInteractivelyMovingItemAtIndexPath:
         (NSIndexPath*)indexPath
                                        withTargetPosition:(CGPoint)position {
-  UICollectionViewLayoutAttributes* attributes = [[super
+  return CopyAttributesAndSetActiveProperties([super
       layoutAttributesForInteractivelyMovingItemAtIndexPath:indexPath
-                                         withTargetPosition:position] copy];
-  // The moving item has regular opacity, but is scaled.
-  attributes.alpha = 1.0;
-  attributes.transform =
-      CGAffineTransformScale(attributes.transform, kReorderingActiveCellScale,
-                             kReorderingActiveCellScale);
-  return attributes;
+                                         withTargetPosition:position]);
 }
 
 @end

ios/chrome/browser/ui/tab_grid/grid/grid_view_controller.mm

@@ -81,6 +81,8 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
 @property(nonatomic, strong) HorizontalLayout* horizontalLayout;
 // The layout used while the grid is being reordered.
 @property(nonatomic, strong) UICollectionViewLayout* reorderingLayout;
+// The layout used while the thumb strip is being reordered.
+@property(nonatomic, strong) UICollectionViewLayout* horizontalReorderingLayout;
 // YES if, when reordering is enabled, the order of the cells has changed.
 @property(nonatomic, assign) BOOL hasChangedOrder;
 #if defined(__IPHONE_13_4)
@@ -150,6 +152,10 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
     collectionView.dragInteractionEnabled = YES;
   } else {
     self.reorderingLayout = [[GridReorderingLayout alloc] init];
+    if (IsThumbStripEnabled()) {
+      self.horizontalReorderingLayout =
+          [[HorizontalReorderingLayout alloc] init];
+    }
     self.itemReorderRecognizer = [[UILongPressGestureRecognizer alloc]
         initWithTarget:self
                 action:@selector(handleItemReorderingWithGesture:)];
@@ -858,8 +864,15 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
         self.itemReorderTouchPoint =
             CGPointMake(location.x - cellCenter.x, location.y - cellCenter.y);
         // Switch to the reordering layout.
-        [self.collectionView setCollectionViewLayout:self.reorderingLayout
-                                            animated:YES];
+        if (IsThumbStripEnabled() &&
+            self.defaultLayout == self.horizontalLayout) {
+          [self.collectionView
+              setCollectionViewLayout:self.horizontalReorderingLayout
+                             animated:YES];
+        } else {
+          [self.collectionView setCollectionViewLayout:self.reorderingLayout
+                                              animated:YES];
+        }
         // Immediately update the position of the moving item; otherwise, the
         // collection view may relayout its subviews and briefly show the moving
         // item at position (0,0).

ios/chrome/browser/ui/tab_grid/grid/horizontal_layout.h

@@ -11,4 +11,9 @@
 @interface HorizontalLayout : FlowLayout
 @end
 
+// A specialization of HorizontalLayout that shows the UI in its "reordering"
+// state, with the moving cell enlarged and the non-moving cells transparent.
+@interface HorizontalReorderingLayout : HorizontalLayout
+@end
+
 #endif  // IOS_CHROME_BROWSER_UI_TAB_GRID_GRID_HORIZONTAL_LAYOUT_H_

ios/chrome/browser/ui/tab_grid/grid/horizontal_layout.mm

@@ -5,6 +5,7 @@
 #import "ios/chrome/browser/ui/tab_grid/grid/horizontal_layout.h"
 
 #import "ios/chrome/browser/ui/tab_grid/grid/grid_constants.h"
+#import "ios/chrome/browser/ui/tab_grid/grid/reordering_layout_util.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
@@ -35,3 +36,33 @@
 }
 
 @end
+
+@implementation HorizontalReorderingLayout
+
+#pragma mark - UICollectionViewLayout
+
+// Both -layoutAttributesForElementsInRect: and
+// -layoutAttributesForItemAtIndexPath: need to be overridden to change the
+// default layout attributes.
+- (NSArray<__kindof UICollectionViewLayoutAttributes*>*)
+    layoutAttributesForElementsInRect:(CGRect)rect {
+  return CopyAttributesArrayAndSetInactiveOpacity(
+      [super layoutAttributesForElementsInRect:rect]);
+}
+
+- (UICollectionViewLayoutAttributes*)layoutAttributesForItemAtIndexPath:
+    (NSIndexPath*)indexPath {
+  return CopyAttributesAndSetInactiveOpacity(
+      [super layoutAttributesForItemAtIndexPath:indexPath]);
+}
+
+- (UICollectionViewLayoutAttributes*)
+    layoutAttributesForInteractivelyMovingItemAtIndexPath:
+        (NSIndexPath*)indexPath
+                                       withTargetPosition:(CGPoint)position {
+  return CopyAttributesAndSetActiveProperties([super
+      layoutAttributesForInteractivelyMovingItemAtIndexPath:indexPath
+                                         withTargetPosition:position]);
+}
+
+@end

ios/chrome/browser/ui/tab_grid/grid/reordering_layout_util.h

+// Copyright 2020 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.
+
+#ifndef IOS_CHROME_BROWSER_UI_TAB_GRID_GRID_REORDERING_LAYOUT_UTIL_H_
+#define IOS_CHROME_BROWSER_UI_TAB_GRID_GRID_REORDERING_LAYOUT_UTIL_H_
+
+#import <UIKit/UIKit.h>
+
+// Returns an array whose elements are copies with added transparency of the
+// elements of the |base_attributes_array| array.
+NSArray<__kindof UICollectionViewLayoutAttributes*>*
+CopyAttributesArrayAndSetInactiveOpacity(NSArray* base_attributes_array);
+
+// Returns a copy of the |base_attributes| object with added transparency.
+UICollectionViewLayoutAttributes* CopyAttributesAndSetInactiveOpacity(
+    UICollectionViewLayoutAttributes* base_attributes);
+
+// Returns a copy of the |base_attributes| object with added opacity and
+// scaling.
+UICollectionViewLayoutAttributes* CopyAttributesAndSetActiveProperties(
+    UICollectionViewLayoutAttributes* base_attributes);
+
+#endif  // IOS_CHROME_BROWSER_UI_TAB_GRID_GRID_REORDERING_LAYOUT_UTIL_H_

ios/chrome/browser/ui/tab_grid/grid/reordering_layout_util.mm

+// Copyright 2020 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/chrome/browser/ui/tab_grid/grid/reordering_layout_util.h"
+
+#import "ios/chrome/browser/ui/tab_grid/grid/grid_constants.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+NSArray<__kindof UICollectionViewLayoutAttributes*>*
+CopyAttributesArrayAndSetInactiveOpacity(NSArray* base_attributes_array) {
+  NSMutableArray<__kindof UICollectionViewLayoutAttributes*>* attributes_array =
+      [NSMutableArray array];
+  for (UICollectionViewLayoutAttributes* attributes in base_attributes_array) {
+    UICollectionViewLayoutAttributes* new_attributes =
+        CopyAttributesAndSetInactiveOpacity(attributes);
+    [attributes_array addObject:new_attributes];
+  }
+  return [attributes_array copy];
+}
+
+UICollectionViewLayoutAttributes* CopyAttributesAndSetInactiveOpacity(
+    UICollectionViewLayoutAttributes* base_attributes) {
+  UICollectionViewLayoutAttributes* attributes = [base_attributes copy];
+  attributes.alpha = kReorderingInactiveCellOpacity;
+  return attributes;
+}
+
+UICollectionViewLayoutAttributes* CopyAttributesAndSetActiveProperties(
+    UICollectionViewLayoutAttributes* base_attributes) {
+  UICollectionViewLayoutAttributes* attributes = [base_attributes copy];
+  // The moving item has regular opacity, but is scaled.
+  attributes.alpha = 1.0;
+  attributes.transform =
+      CGAffineTransformScale(attributes.transform, kReorderingActiveCellScale,
+                             kReorderingActiveCellScale);
+  return attributes;
+}