Tweak the share screen animation

ios/chrome/share_extension/share_view_controller.mm

 // Copyright 2016 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 <MobileCoreServices/MobileCoreServices.h>
 
 #import "ios/chrome/share_extension/share_view_controller.h"
 
 #import "base/ios/block_types.h"
 #import "base/mac/foundation_util.h"
@@ skipping 41 matching lines @@
 // If |cancel| is true, |actionType| is ignored.
 - (void)queueActionItemURL:(NSURL*)URL
                      title:(NSString*)title
                     action:(app_group::ShareExtensionItemType)actionType
                     cancel:(BOOL)cancel
                 completion:(ProceduralBlock)completion;
 
 // Loads all the shared elements from the extension context and update the UI.
 - (void)loadElementsFromContext;
 
-// Performs a fade in animation for the whole widget.
-- (void)fadeIn;
-
 // Sets constaints to the widget so that margin are at least
 // kShareExtensionMargin points and widget width is closest up to
 // kShareExtensionMaxWidth points.
 - (void)constrainWidgetWidth;
 
 @end
 
 @implementation ShareViewController
 
 @synthesize maskView = _maskView;
 @synthesize shareView = _shareView;
 @synthesize itemType = _itemType;
 
+#pragma mark - UIViewController
+
 - (void)viewDidLoad {
   [super viewDidLoad];
 
   // This view shadows the screen under the share extension.
   UIView* maskView = [[UIView alloc] initWithFrame:CGRectZero];
   [self setMaskView:maskView];
   [self.maskView
       setBackgroundColor:[UIColor colorWithWhite:0 alpha:kMediumAlpha]];
   [self.view addSubview:self.maskView];
   ui_util::ConstrainAllSidesOfViewToView(self.view, self.maskView);
 
   // This view is the main view of the share extension.
   ShareExtensionView* shareView =
       [[ShareExtensionView alloc] initWithActionTarget:self];
   [self setShareView:shareView];
   [self.view addSubview:self.shareView];
 
   [self constrainWidgetWidth];
 
-  // Center the widget in the screen.
+  // Position the widget below the screen. It will be slided up with an
+  // animation.
   _centerYConstraint = [[shareView centerYAnchor]
       constraintEqualToAnchor:[self.view centerYAnchor]];
+  [_centerYConstraint setConstant:(self.view.frame.size.height +
+                                   self.shareView.frame.size.height) /
+                                  2];
   [_centerYConstraint setActive:YES];
   [[[shareView centerXAnchor] constraintEqualToAnchor:[self.view centerXAnchor]]
       setActive:YES];
 
   [self.maskView setTranslatesAutoresizingMaskIntoConstraints:NO];
   [self.shareView setTranslatesAutoresizingMaskIntoConstraints:NO];
 
   [self loadElementsFromContext];
-  [self fadeIn];
 }
 
+- (void)viewWillAppear:(BOOL)animated {
+  [super viewWillAppear:animated];
+
+  // Center the widget.
+  [_centerYConstraint setConstant:0];
+  [self.maskView setAlpha:0];
+  [UIView animateWithDuration:kAnimationDuration
+                   animations:^{
+                     [self.maskView setAlpha:1];

[Olivier, 2016/12/20 16:31:44]

Is this needed?
Will this not also fade in ?

[gambard, 2016/12/20 16:33:49]

The dark background view will fade in and the extension view will slide up.

+                     [self.view layoutIfNeeded];
+                   }];
+}
+
+#pragma mark - Private methods
+
 - (void)constrainWidgetWidth {
   // Setting the constraints.
   NSDictionary* views = @{ @"share" : self.shareView };
 
   NSDictionary* metrics = @{
     @"margin" : @(kShareExtensionMargin),
     @"maxWidth" : @(kShareExtensionMaxWidth),
   };
 
   NSArray* constraints = @[
@@ skipping 12 matching lines @@
                                                       views:views]];
   }
 
   // |self.shareView| must be as large as possible and in the center of the
   // screen.
   [self.shareView
       setContentCompressionResistancePriority:UILayoutPriorityDefaultHigh
                                       forAxis:UILayoutConstraintAxisHorizontal];
 }
 
-- (void)fadeIn {
-  // Fade in animation.
-  [self.maskView setAlpha:0];
-  [self.shareView setAlpha:0];
-  [UIView animateWithDuration:kAnimationDuration
-                   animations:^{
-                     [self.maskView setAlpha:kMediumAlpha];
-                     [self.shareView setAlpha:1];
-                   }];
-}
-
 - (void)loadElementsFromContext {
   NSString* typeURL = static_cast<NSString*>(kUTTypeURL);
   for (NSExtensionItem* item in self.extensionContext.inputItems) {
     for (NSItemProvider* itemProvider in item.attachments) {
       if ([itemProvider hasItemConformingToTypeIdentifier:typeURL]) {
         ItemBlock URLCompletion = ^(id idURL, NSError* error) {
           NSURL* URL = static_cast<NSURL*>(idURL);
           dispatch_async(dispatch_get_main_queue(), ^{
             _shareItem = [item copy];
             _shareURL = [URL copy];
@@ skipping 24 matching lines @@
 
         };
         [itemProvider loadPreviewImageWithOptions:imageOptions
                                 completionHandler:ImageCompletion];
       }
     }
   }
 }
 
 - (void)dismissAndReturnItem:(NSExtensionItem*)item {
-  // Set the Y center constraints so the whole extension slides up out of the
+  // Set the Y center constraints so the whole extension slides out of the
   // screen. Constant is relative to the center of the screen.
-  [_centerYConstraint setConstant:-(self.view.frame.size.height +
-                                    self.shareView.frame.size.height) /
+  // The direction (up or down) is relative to the output (cancel or submit).
+  NSInteger direction = item ? -1 : 1;
+  [_centerYConstraint setConstant:direction *
+                                  (self.view.frame.size.height +
+                                   self.shareView.frame.size.height) /
                                   2];
   [UIView animateWithDuration:kAnimationDuration
       animations:^{
         [self.maskView setAlpha:0];
         [self.view layoutIfNeeded];
       }
       completion:^(BOOL finished) {
         NSArray* returnItem = item ? @[ item ] : @[];
         [self.extensionContext completeRequestReturningItems:returnItem
                                            completionHandler:nil];
@@ skipping 77 matching lines @@
                   [self dismissAndReturnItem:_shareItem];
                 }];
 }
 
 - (void)shareExtensionView:(id)sender
                typeChanged:(app_group::ShareExtensionItemType)type {
   [self setItemType:type];
 }
 
 @end