Reuse context menu in StaticHTMLViewController

ios/web/web_state/ui/crw_context_menu_controller.mm

+// Copyright 2017 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/web/web_state/ui/crw_context_menu_controller.h"
+
+#import <objc/runtime.h>
+#include <stddef.h>
+
+#import "base/ios/weak_nsobject.h"
+#include "base/logging.h"
+#include "base/mac/foundation_util.h"
+#include "base/metrics/histogram.h"
+#include "base/strings/sys_string_conversions.h"
+#include "components/url_formatter/url_formatter.h"
+#include "ios/web/public/referrer_util.h"
+#import "ios/web/public/web_state/context_menu_params.h"
+#import "ios/web/public/web_state/ui/crw_context_menu_delegate.h"
+
+namespace {
+// The long press detection duration must be shorter than the WKWebView's
+// long click gesture recognizer's minimum duration. That is 0.55s.
+// If our detection duration is shorter, our gesture recognizer will fire
+// first, and if it fails the long click gesture (processed simultaneously)
+// still is able to complete.
+const NSTimeInterval kLongPressDurationSeconds = 0.55 - 0.1;
+
+// If there is a movement bigger than |kLongPressMoveDeltaPixels|, the context
+// menu will not be triggered.
+const CGFloat kLongPressMoveDeltaPixels = 10.0;
+
+// Cancels touch events for the given gesture recognizer.
+void CancelTouches(UIGestureRecognizer* gesture_recognizer) {
+  if (gesture_recognizer.enabled) {
+    gesture_recognizer.enabled = NO;
+    gesture_recognizer.enabled = YES;
+  }
+}
+}  // namespace
+
+@interface CRWContextMenuController ()<UIGestureRecognizerDelegate>
+
+// Sets the specified recognizer to take priority over any recognizers in the
+// view that have a description containing the specified text fragment.
++ (void)requireGestureRecognizerToFail:(UIGestureRecognizer*)recognizer
+                                inView:(UIView*)view
+                 containingDescription:(NSString*)fragment;
+
+// The |webView|.
+@property(nonatomic, readonly) WKWebView* webView;
+// The delegate that allow execute javascript.
+@property(nonatomic, readonly) id<CRWContextMenuJavaScriptDelegate>
+    javaScriptDelegate;
+// The scroll view of |webView|.
+@property(nonatomic, readonly) id<CRWContextMenuDelegate> delegate;
+// Returns the x, y offset the content has been scrolled.
+@property(nonatomic, readonly) CGPoint scrollPosition;
+
+// Called when the window has determined there was a long-press and context menu
+// must be shown.
+- (void)showContextMenu:(UIGestureRecognizer*)gestureRecognizer;
+// Extracts context menu information from the given DOM element.
+- (web::ContextMenuParams)contextMenuParamsForElement:(NSDictionary*)element;
+// Cancels all touch events in the web view (long presses, tapping, scrolling).
+- (void)cancelAllTouches;
+// Asynchronously fetches full width of the rendered web page.
+- (void)fetchWebPageWidthWithCompletionHandler:(void (^)(CGFloat))handler;
+// Asynchronously fetches information about DOM element for the given point (in
+// UIView coordinates). |handler| can not be nil. See |_DOMElementForLastTouch|
+// for element format description.
+- (void)fetchDOMElementAtPoint:(CGPoint)point
+             completionHandler:(void (^)(NSDictionary*))handler;
+// Sets the value of |_DOMElementForLastTouch|.
+- (void)setDOMElementForLastTouch:(NSDictionary*)element;
+// Forwards the execution of |script| to |javaScriptDelegate| and if it is nil,
+// to |webView|.
+- (void)executeJavaScript:(NSString*)script
+        completionHandler:(web::JavaScriptResultBlock)completionHandler;
+@end
+
+@implementation CRWContextMenuController {
+  id<CRWContextMenuDelegate> _delegate;
+  id<CRWContextMenuJavaScriptDelegate> _javaScriptDelegate;
+  WKWebView* _webView;

[Eugene But (OOO till 7-30), 2017/01/13 18:23:42]

Sorry, missed in the previous round. If this can not be ARC file, then please
use WeakNSObject for all weak members. This class works asynchronously and web
view and delegates may die at any moment.

[Olivier, 2017/01/13 18:49:55]

Done.

+
+  // Long press recognizer that allows showing context menus.
+  base::scoped_nsobject<UILongPressGestureRecognizer> _contextMenuRecognizer;
+  // DOM element information for the point where the user made the last touch.
+  // Can be nil if has not been calculated yet. Precalculation is necessary
+  // because retreiving DOM element relies on async API so element info can not
+  // be built on demand. May contain the following keys: @"href", @"src",
+  // @"title", @"referrerPolicy". All values are strings.
+  base::scoped_nsobject<NSDictionary> _DOMElementForLastTouch;
+}
+
+@synthesize delegate = _delegate;
+@synthesize javaScriptDelegate = _javaScriptDelegate;
+@synthesize webView = _webView;
+
+- (instancetype)initWithWebView:(WKWebView*)webView
+             javaScriptDelegate:
+                 (id<CRWContextMenuJavaScriptDelegate>)javaScriptDelegate

[Eugene But (OOO till 7-30), 2017/01/13 18:23:42]

Evaluator?

[Olivier, 2017/01/13 18:49:55]

Done.

+                       delegate:(id<CRWContextMenuDelegate>)delegate {
+  DCHECK(webView);
+  self = [super init];
+  if (self) {
+    _webView = webView;
+    _delegate = delegate;
+    _javaScriptDelegate = javaScriptDelegate;
+
+    // The system context menu triggers after 0.55 second. Add a gesture
+    // recognizer with a shorter delay to be able to cancel the system menu if
+    // needed.
+    _contextMenuRecognizer.reset([[UILongPressGestureRecognizer alloc]
+        initWithTarget:self
+                action:@selector(showContextMenu:)]);
+    [_contextMenuRecognizer setMinimumPressDuration:kLongPressDurationSeconds];
+    [_contextMenuRecognizer setAllowableMovement:kLongPressMoveDeltaPixels];
+    [_contextMenuRecognizer setDelegate:self];
+    [_webView addGestureRecognizer:_contextMenuRecognizer];
+    // Certain system gesture handlers are known to conflict with our context
+    // menu handler, causing extra events to fire when the context menu is
+    // active.
+
+    // A number of solutions have been investigated. The lowest-risk solution
+    // appears to be to recurse through the web controller's recognizers,
+    // looking
+    // for fingerprints of the recognizers known to cause problems, which are
+    // then
+    // de-prioritized (below our own long click handler).
+    // Hunting for description fragments of system recognizers is undeniably
+    // brittle for future versions of iOS. If it does break the context menu
+    // events may leak (regressing b/5310177), but the app will otherwise work.
+    // TODO(crbug.com/680930): This code is not needed anymore in iOS9+ and has
+    // to be removed.
+    [CRWContextMenuController
+        requireGestureRecognizerToFail:_contextMenuRecognizer
+                                inView:_webView
+                 containingDescription:
+                     @"action=_highlightLongPressRecognized:"];
+  }
+  return self;
+}
+
+- (UIScrollView*)webScrollView {
+  return [_webView scrollView];
+}
+
+- (CGPoint)scrollPosition {
+  return self.webScrollView.contentOffset;
+}
+
+- (void)executeJavaScript:(NSString*)script
+        completionHandler:(web::JavaScriptResultBlock)completionHandler {
+  if (_javaScriptDelegate) {
+    [_javaScriptDelegate executeJavaScript:script
+                         completionHandler:completionHandler];
+  } else {
+    [_webView evaluateJavaScript:script completionHandler:completionHandler];
+  }
+}
+
+- (void)showContextMenu:(UIGestureRecognizer*)gestureRecognizer {
+  // If the gesture has already been handled, ignore it.
+  if ([gestureRecognizer state] != UIGestureRecognizerStateBegan)
+    return;
+
+  if (![_DOMElementForLastTouch count])
+    return;
+
+  web::ContextMenuParams params =
+      [self contextMenuParamsForElement:_DOMElementForLastTouch.get()];
+  params.view.reset([_webView retain]);
+  params.location = [gestureRecognizer locationInView:_webView];
+  if ([_delegate webView:_webView handleContextMenu:params]) {
+    // Cancelling all touches has the intended side effect of suppressing the
+    // system's context menu.
+    [self cancelAllTouches];
+  }
+}
+
++ (void)requireGestureRecognizerToFail:(UIGestureRecognizer*)recognizer
+                                inView:(UIView*)view
+                 containingDescription:(NSString*)fragment {
+  for (UIGestureRecognizer* iRecognizer in [view gestureRecognizers]) {
+    if (iRecognizer != recognizer) {
+      NSString* description = [iRecognizer description];
+      if ([description rangeOfString:fragment].length) {
+        [iRecognizer requireGestureRecognizerToFail:recognizer];
+        // requireGestureRecognizerToFail: doesn't retain the recognizer, so it
+        // is possible for |iRecognizer| to outlive |recognizer| and end up with
+        // a dangling pointer. Add a retaining associative reference to ensure
+        // that the lifetimes work out.
+        // Note that normally using the value as the key wouldn't make any
+        // sense, but here it's fine since nothing needs to look up the value.
+        objc_setAssociatedObject(view, recognizer, recognizer,
+                                 OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+      }
+    }
+  }
+}
+
+- (web::ContextMenuParams)contextMenuParamsForElement:(NSDictionary*)element {
+  web::ContextMenuParams params;
+  NSString* title = nil;
+  NSString* href = element[@"href"];
+  if (href) {
+    params.link_url = GURL(base::SysNSStringToUTF8(href));
+    if (params.link_url.SchemeIs(url::kJavaScriptScheme)) {
+      title = @"JavaScript";
+    } else {
+      base::string16 URLText = url_formatter::FormatUrl(params.link_url);
+      title = base::SysUTF16ToNSString(URLText);
+    }
+  }
+  NSString* src = element[@"src"];
+  if (src) {
+    params.src_url = GURL(base::SysNSStringToUTF8(src));
+    if (!title)
+      title = [[src copy] autorelease];
+    if ([title hasPrefix:base::SysUTF8ToNSString(url::kDataScheme)])
+      title = nil;
+  }
+  NSString* titleAttribute = element[@"title"];
+  if (titleAttribute)
+    title = titleAttribute;
+  if (title) {
+    params.menu_title.reset([title copy]);
+  }
+  NSString* referrerPolicy = element[@"referrerPolicy"];
+  if (referrerPolicy) {
+    params.referrer_policy =
+        web::ReferrerPolicyFromString(base::SysNSStringToUTF8(referrerPolicy));
+  }
+  NSString* innerText = element[@"innerText"];
+  if ([innerText length] > 0) {
+    params.link_text.reset([innerText copy]);
+  }
+  return params;
+}
+
+- (void)cancelAllTouches {
+  // Disable web view scrolling.
+  CancelTouches(self.webView.scrollView.panGestureRecognizer);
+
+  // All user gestures are handled by a subview of web view scroll view
+  // (WKContentView).
+  for (UIView* subview in self.webScrollView.subviews) {
+    for (UIGestureRecognizer* recognizer in subview.gestureRecognizers) {
+      CancelTouches(recognizer);
+    }
+  }
+
+  // Just disabling/enabling the gesture recognizers is not enough to suppress
+  // the click handlers on the JS side. This JS performs the function of
+  // suppressing these handlers on the JS side.
+  NSString* suppressNextClick = @"__gCrWeb.suppressNextClick()";
+  [self executeJavaScript:suppressNextClick completionHandler:nil];
+}
+
+- (void)setDOMElementForLastTouch:(NSDictionary*)element {
+  _DOMElementForLastTouch.reset([element copy]);
+}
+
+#pragma mark -
+#pragma mark UIGestureRecognizerDelegate
+
+- (BOOL)gestureRecognizer:(UIGestureRecognizer*)gestureRecognizer
+    shouldRecognizeSimultaneouslyWithGestureRecognizer:
+        (UIGestureRecognizer*)otherGestureRecognizer {
+  // Allows the custom UILongPressGestureRecognizer to fire simultaneously with
+  // other recognizers.
+  return YES;
+}
+
+- (BOOL)gestureRecognizer:(UIGestureRecognizer*)gestureRecognizer
+       shouldReceiveTouch:(UITouch*)touch {
+  // Expect only _contextMenuRecognizer.
+  DCHECK([gestureRecognizer isEqual:_contextMenuRecognizer]);
+
+  // This is custom long press gesture recognizer. By the time the gesture is
+  // recognized the web controller needs to know if there is a link under the
+  // touch. If there a link, the web controller will reject system's context
+  // menu and show another one. If for some reason context menu info is not
+  // fetched - system context menu will be shown.
+  [self setDOMElementForLastTouch:nil];
+  base::WeakNSObject<CRWContextMenuController> weakSelf(self);
+  [self fetchDOMElementAtPoint:[touch locationInView:_webView]
+             completionHandler:^(NSDictionary* element) {
+               [weakSelf setDOMElementForLastTouch:element];
+             }];
+  return YES;
+}
+
+- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer*)gestureRecognizer {
+  // Expect only _contextMenuRecognizer.
+  DCHECK([gestureRecognizer isEqual:_contextMenuRecognizer]);
+  // Fetching is considered as successful even if |_DOMElementForLastTouch| is
+  // empty. However if |_DOMElementForLastTouch| is empty then custom context
+  // menu should not be shown.
+  UMA_HISTOGRAM_BOOLEAN("WebController.FetchContextMenuInfoAsyncSucceeded",
+                        !!_DOMElementForLastTouch);
+  return [_DOMElementForLastTouch count];
+}
+
+#pragma mark -
+#pragma mark Web Page Features
+
+- (void)fetchWebPageWidthWithCompletionHandler:(void (^)(CGFloat))handler {
+  [self executeJavaScript:@"__gCrWeb.getPageWidth();"
+        completionHandler:^(id pageWidth, NSError*) {
+          handler([base::mac::ObjCCastStrict<NSNumber>(pageWidth) floatValue]);
+        }];
+}
+
+- (void)fetchDOMElementAtPoint:(CGPoint)point
+             completionHandler:(void (^)(NSDictionary*))handler {
+  DCHECK(handler);
+  // Convert point into web page's coordinate system (which may be scaled and/or
+  // scrolled).
+  CGPoint scrollOffset = self.scrollPosition;
+  CGFloat webViewContentWidth = self.webScrollView.contentSize.width;
+  base::WeakNSObject<CRWContextMenuController> weakSelf(self);
+  [self fetchWebPageWidthWithCompletionHandler:^(CGFloat pageWidth) {
+    CGFloat scale = pageWidth / webViewContentWidth;
+    CGPoint localPoint = CGPointMake((point.x + scrollOffset.x) * scale,
+                                     (point.y + scrollOffset.y) * scale);
+    NSString* const kGetElementScript =
+        [NSString stringWithFormat:@"__gCrWeb.getElementFromPoint(%g, %g);",
+                                   localPoint.x, localPoint.y];
+    [self executeJavaScript:kGetElementScript
+          completionHandler:^(id element, NSError*) {
+            handler(base::mac::ObjCCastStrict<NSDictionary>(element));
+          }];
+  }];
+}
+
+@end