Upstream Chrome on iOS source code [6/11].

ios/chrome/browser/ui/overscroll_actions/overscroll_actions_controller.h

+// Copyright 2015 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_OVERSCROLL_ACTIONS_OVERSCROLL_ACTIONS_CONTROLLER_H_
+#define IOS_CHROME_BROWSER_UI_OVERSCROLL_ACTIONS_OVERSCROLL_ACTIONS_CONTROLLER_H_
+
+#import <UIKit/UIKit.h>
+
+#import "ios/chrome/browser/ui/overscroll_actions/overscroll_actions_view.h"
+#import "ios/chrome/browser/ui/util/relaxed_bounds_constraints_hittest.h"
+#import "ios/web/public/web_state/crw_web_controller_observer.h"
+#import "ios/web/public/web_state/crw_web_view_scroll_view_proxy.h"
+
+@class OverscrollActionsController;
+
+namespace ios_internal {
+// Describe the current state of the overscroll action controller.
+enum class OverscrollState {
+  NO_PULL_STARTED,  // No pull started.
+  STARTED_PULLING,  // Started pulling.
+  ACTION_READY      // Ready to take action on pull end.
+};
+
+// Notification sent when the overscroll actions controller will start
+// displaying the UI.
+extern NSString* const kOverscollActionsWillStart;
+// Notification sent when the overscroll actions controller did stop displaying
+// the UI.
+extern NSString* const kOverscollActionsDidEnd;
+}  // namespace ios_internal
+
+// The delegate of the OverscrollActionsController, it provides the headerView
+// on which the OverscrollActionsView will be added.
+// The scrollView is used to control the state of the
+// OverscrollActionsController.
+// The delegate must implement the shouldAllowOverscrollActions method in order
+// to allow overscroll actions.
+// Finally the overscrollActionsController:didTriggerActionAtIndex: method is
+// called when an action has been triggered.
+@protocol OverscrollActionsControllerDelegate<NSObject>
+// Called when an action has been triggered.
+// The action index holds the current triggered action which are numbered left
+// to right.
+- (void)overscrollActionsController:(OverscrollActionsController*)controller
+                   didTriggerAction:(ios_internal::OverscrollAction)action;
+// Should return true when the delegate wants to enable the overscroll actions.
+- (BOOL)shouldAllowOverscrollActions;
+// The toolbar snapshot view that will be used to fade in/out the toolbar.
+// This snapshot will be animated when performing the pull down animation
+// revealing the actions.
+- (UIView*)toolbarSnapshotView;
+// The header view over which the overscroll action view will be added.
+- (UIView<RelaxedBoundsConstraintsHitTestSupport>*)headerView;
+// Called to retrieve the top inset added to the scrollview for the header.
+- (CGFloat)overscrollActionsControllerHeaderInset:
+    (OverscrollActionsController*)controller;
+// Called to retrieve the current height of the header.
+- (CGFloat)overscrollHeaderHeight;
+@end
+
+// The OverscrollActionsController controls the display of an
+// OverscrollActionsView above the headerView provided by the delegate.
+// Pulling down the scrollview will start showing the OverscrollActionView.
+// Finally, the headerView frame will be resized in height during the process of
+// showing the overscrollActionsView.
+// The OverscrollActionsController can be used in two different modes depending
+// on what kind of scrollview it's using:
+// The first mode will use the scrollview provided by the
+// CRWWebControllerObserver. To use this mode the OverscrollActionsController
+// must be initialized with a nil scrollview. The -(instancetype)init
+// initializer will do that for you.
+// The second mode will use the scrollview provided during initialization and
+// will ignore calls from the CRWWebControllerObserver.
+// This second mode will typically be used in native tabs like the error tabs
+// or the NTP.
+
+@interface OverscrollActionsController
+    : NSObject<CRWWebControllerObserver, UIScrollViewDelegate>
+
+// Init the OverscrollActionsController with a nil scrollview.
+// If the scrollview is nil then the OverscrollActionsController will be
+// configured to use the scrollview from the CRWWebControllerObserver.
+- (instancetype)init;
+// Designated initializer, when initialized with a scrollview, the
+// OverscrollActionsController will not use the CRWWebControllerObserver to
+// configure the scrollview, it will directly use the passed scrollview.
+- (instancetype)initWithScrollView:(UIScrollView*)scrollView;
+
+// The scrollview the overscroll controller will control.
+@property(nonatomic, readonly) UIScrollView* scrollView;
+// The current state of the overscroll controller.
+@property(nonatomic, assign, readonly)
+    ios_internal::OverscrollState overscrollState;
+// The delegate must be set for the OverscrollActionsController to work
+// properly.
+@property(nonatomic, assign) id<OverscrollActionsControllerDelegate> delegate;
+
+// Used to clear state maintained by the controller and de-register from
+// notifications. After this call the controller ceases to function and will
+// clear its delegate.
+- (void)invalidate;
+// Force the controller to switch to NO_PULL_STARTED state.
+- (void)clear;
+// Disabling overscroll actions will stop showing the overscroll actions view on
+// top of the header when the user is pulling the webview's scrollview.
+// Disable/enableOverscrollActions method calls are ref counted, this means
+// that calls to disable must be compensated by the same amount of call to
+// enable in order to reenable overscroll actions.
+- (void)disableOverscrollActions;
+// Enabling overscroll actions will reverse the effect of a call to
+// -disableOverscrollActions.
+- (void)enableOverscrollActions;
+// Sets the style of the overscroll actions.
+- (void)setStyle:(ios_internal::OverscrollStyle)style;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_OVERSCROLL_ACTIONS_OVERSCROLL_ACTIONS_CONTROLLER_H_