[CP][ios][platform_view] workaround for non-tappable webview (#56804)

shell/platform/darwin/ios/BUILD.gn

@@ -165,6 +165,7 @@ source_set("flutter_framework_source") {
     "CoreVideo.framework",
     "IOSurface.framework",
     "QuartzCore.framework",
+    "WebKit.framework",
     "UIKit.framework",
   ]
   if (flutter_runtime_mode == "profile" || flutter_runtime_mode == "debug") {

shell/platform/darwin/ios/framework/Source/FlutterPlatformViews.mm

@@ -4,6 +4,8 @@
 
 #import "flutter/shell/platform/darwin/ios/framework/Source/FlutterPlatformViews_Internal.h"
 
+#import <WebKit/WebKit.h>
+
 #include "flutter/display_list/effects/dl_image_filter.h"
 #include "flutter/fml/platform/darwin/cf_utils.h"
 #import "flutter/shell/platform/darwin/ios/ios_surface.h"
@@ -569,6 +571,22 @@ - (void)blockGesture {
     case FlutterPlatformViewGestureRecognizersBlockingPolicyEager:
       // We block all other gesture recognizers immediately in this policy.
       self.delayingRecognizer.state = UIGestureRecognizerStateEnded;
+
+      // On iOS 18.2, WKWebView's internal recognizer likely caches the old state of its blocking
+      // recognizers (i.e. delaying recognizer), resulting in non-tappable links. See
+      // https://github.com/flutter/flutter/issues/158961. Removing and adding back the delaying
+      // recognizer solves the problem, possibly because UIKit notifies all the recognizers related
+      // to (blocking or blocked by) this recognizer. It is not possible to inject this workaround
+      // from the web view plugin level. Right now we only observe this issue for
+      // FlutterPlatformViewGestureRecognizersBlockingPolicyEager, but we should try it if a similar
+      // issue arises for the other policy.
+      if (@available(iOS 18.2, *)) {
+        if ([self.embeddedView isKindOfClass:[WKWebView class]]) {
+          [self removeGestureRecognizer:self.delayingRecognizer];
+          [self addGestureRecognizer:self.delayingRecognizer];
+        }
+      }
+
       break;
     case FlutterPlatformViewGestureRecognizersBlockingPolicyWaitUntilTouchesEnded:
       if (self.delayingRecognizer.touchedEndedWithoutBlocking) {

shell/platform/darwin/ios/framework/Source/FlutterPlatformViewsTest.mm

@@ -6,6 +6,7 @@
 
 #import <OCMock/OCMock.h>
 #import <UIKit/UIKit.h>
+#import <WebKit/WebKit.h>
 #import <XCTest/XCTest.h>
 
 #include <memory>
@@ -25,7 +26,7 @@
 FLUTTER_ASSERT_ARC
 
 @class FlutterPlatformViewsTestMockPlatformView;
-__weak static FlutterPlatformViewsTestMockPlatformView* gMockPlatformView = nil;
+__weak static UIView* gMockPlatformView = nil;
 const float kFloatCompareEpsilon = 0.001;
 
 @interface FlutterPlatformViewsTestMockPlatformView : UIView
@@ -88,6 +89,45 @@ @implementation FlutterPlatformViewsTestMockFlutterPlatformFactory
 
 @end
 
+@interface FlutterPlatformViewsTestMockWebView : NSObject <FlutterPlatformView>
+@property(nonatomic, strong) UIView* view;
+@property(nonatomic, assign) BOOL viewCreated;
+@end
+
+@implementation FlutterPlatformViewsTestMockWebView
+- (instancetype)init {
+  if (self = [super init]) {
+    _view = [[WKWebView alloc] init];
+    gMockPlatformView = _view;
+    _viewCreated = NO;
+  }
+  return self;
+}
+
+- (UIView*)view {
+  [self checkViewCreatedOnce];
+  return _view;
+}
+
+- (void)checkViewCreatedOnce {
+  if (self.viewCreated) {
+    abort();
+  }
+  self.viewCreated = YES;
+}
+@end
+
+@interface FlutterPlatformViewsTestMockWebViewFactory : NSObject <FlutterPlatformViewFactory>
+@end
+
+@implementation FlutterPlatformViewsTestMockWebViewFactory
+- (NSObject<FlutterPlatformView>*)createWithFrame:(CGRect)frame
+                                   viewIdentifier:(int64_t)viewId
+                                        arguments:(id _Nullable)args {
+  return [[FlutterPlatformViewsTestMockWebView alloc] init];
+}
+@end
+
 @interface FlutterPlatformViewsTestNilFlutterPlatformFactory : NSObject <FlutterPlatformViewFactory>
 @end
 
@@ -3048,6 +3088,132 @@ - (void)testFlutterPlatformViewTouchesEndedOrTouchesCancelledEventDoesNotFailThe
   [flutterPlatformViewsController reset];
 }
 
+- (void)
+    testFlutterPlatformViewBlockGestureUnderEagerPolicyShouldRemoveAndAddBackDelayingRecognizerForWebView {
+  flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
+
+  flutter::TaskRunners runners(/*label=*/self.name.UTF8String,
+                               /*platform=*/GetDefaultTaskRunner(),
+                               /*raster=*/GetDefaultTaskRunner(),
+                               /*ui=*/GetDefaultTaskRunner(),
+                               /*io=*/GetDefaultTaskRunner());
+  FlutterPlatformViewsController* flutterPlatformViewsController =
+      [[FlutterPlatformViewsController alloc] init];
+  flutterPlatformViewsController.taskRunner = GetDefaultTaskRunner();
+  auto platform_view = std::make_unique<flutter::PlatformViewIOS>(
+      /*delegate=*/mock_delegate,
+      /*rendering_api=*/mock_delegate.settings_.enable_impeller
+          ? flutter::IOSRenderingAPI::kMetal
+          : flutter::IOSRenderingAPI::kSoftware,
+      /*platform_views_controller=*/flutterPlatformViewsController,
+      /*task_runners=*/runners,
+      /*worker_task_runner=*/nil,
+      /*is_gpu_disabled_jsync_switch=*/std::make_shared<fml::SyncSwitch>());
+
+  FlutterPlatformViewsTestMockWebViewFactory* factory =
+      [[FlutterPlatformViewsTestMockWebViewFactory alloc] init];
+  [flutterPlatformViewsController
+                   registerViewFactory:factory
+                                withId:@"MockWebView"
+      gestureRecognizersBlockingPolicy:FlutterPlatformViewGestureRecognizersBlockingPolicyEager];
+  FlutterResult result = ^(id result) {
+  };
+  [flutterPlatformViewsController
+      onMethodCall:[FlutterMethodCall
+                       methodCallWithMethodName:@"create"
+                                      arguments:@{@"id" : @2, @"viewType" : @"MockWebView"}]
+            result:result];
+
+  XCTAssertNotNil(gMockPlatformView);
+
+  // Find touch inteceptor view
+  UIView* touchInteceptorView = gMockPlatformView;
+  while (touchInteceptorView != nil &&
+         ![touchInteceptorView isKindOfClass:[FlutterTouchInterceptingView class]]) {
+    touchInteceptorView = touchInteceptorView.superview;
+  }
+  XCTAssertNotNil(touchInteceptorView);
+
+  XCTAssert(touchInteceptorView.gestureRecognizers.count == 2);
+  UIGestureRecognizer* delayingRecognizer = touchInteceptorView.gestureRecognizers[0];
+  UIGestureRecognizer* forwardingRecognizer = touchInteceptorView.gestureRecognizers[1];
+
+  XCTAssert([delayingRecognizer isKindOfClass:[FlutterDelayingGestureRecognizer class]]);
+  XCTAssert([forwardingRecognizer isKindOfClass:[ForwardingGestureRecognizer class]]);
+
+  [(FlutterTouchInterceptingView*)touchInteceptorView blockGesture];
+
+  if (@available(iOS 18.2, *)) {
+    // Since we remove and add back delayingRecognizer, it would be reordered to the last.
+    XCTAssertEqual(touchInteceptorView.gestureRecognizers[0], forwardingRecognizer);
+    XCTAssertEqual(touchInteceptorView.gestureRecognizers[1], delayingRecognizer);
+  } else {
+    XCTAssertEqual(touchInteceptorView.gestureRecognizers[0], delayingRecognizer);
+    XCTAssertEqual(touchInteceptorView.gestureRecognizers[1], forwardingRecognizer);
+  }
+}
+
+- (void)
+    testFlutterPlatformViewBlockGestureUnderEagerPolicyShouldNotRemoveAndAddBackDelayingRecognizerForNonWebView {
+  flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;
+
+  flutter::TaskRunners runners(/*label=*/self.name.UTF8String,
+                               /*platform=*/GetDefaultTaskRunner(),
+                               /*raster=*/GetDefaultTaskRunner(),
+                               /*ui=*/GetDefaultTaskRunner(),
+                               /*io=*/GetDefaultTaskRunner());
+  FlutterPlatformViewsController* flutterPlatformViewsController =
+      [[FlutterPlatformViewsController alloc] init];
+  flutterPlatformViewsController.taskRunner = GetDefaultTaskRunner();
+  auto platform_view = std::make_unique<flutter::PlatformViewIOS>(
+      /*delegate=*/mock_delegate,
+      /*rendering_api=*/mock_delegate.settings_.enable_impeller
+          ? flutter::IOSRenderingAPI::kMetal
+          : flutter::IOSRenderingAPI::kSoftware,
+      /*platform_views_controller=*/flutterPlatformViewsController,
+      /*task_runners=*/runners,
+      /*worker_task_runner=*/nil,
+      /*is_gpu_disabled_jsync_switch=*/std::make_shared<fml::SyncSwitch>());
+
+  FlutterPlatformViewsTestMockFlutterPlatformFactory* factory =
+      [[FlutterPlatformViewsTestMockFlutterPlatformFactory alloc] init];
+  [flutterPlatformViewsController
+                   registerViewFactory:factory
+                                withId:@"MockFlutterPlatformView"
+      gestureRecognizersBlockingPolicy:FlutterPlatformViewGestureRecognizersBlockingPolicyEager];
+  FlutterResult result = ^(id result) {
+  };
+  [flutterPlatformViewsController
+      onMethodCall:[FlutterMethodCall methodCallWithMethodName:@"create"
+                                                     arguments:@{
+                                                       @"id" : @2,
+                                                       @"viewType" : @"MockFlutterPlatformView"
+                                                     }]
+            result:result];
+
+  XCTAssertNotNil(gMockPlatformView);
+
+  // Find touch inteceptor view
+  UIView* touchInteceptorView = gMockPlatformView;
+  while (touchInteceptorView != nil &&
+         ![touchInteceptorView isKindOfClass:[FlutterTouchInterceptingView class]]) {
+    touchInteceptorView = touchInteceptorView.superview;
+  }
+  XCTAssertNotNil(touchInteceptorView);
+
+  XCTAssert(touchInteceptorView.gestureRecognizers.count == 2);
+  UIGestureRecognizer* delayingRecognizer = touchInteceptorView.gestureRecognizers[0];
+  UIGestureRecognizer* forwardingRecognizer = touchInteceptorView.gestureRecognizers[1];
+
+  XCTAssert([delayingRecognizer isKindOfClass:[FlutterDelayingGestureRecognizer class]]);
+  XCTAssert([forwardingRecognizer isKindOfClass:[ForwardingGestureRecognizer class]]);
+
+  [(FlutterTouchInterceptingView*)touchInteceptorView blockGesture];
+
+  XCTAssertEqual(touchInteceptorView.gestureRecognizers[0], delayingRecognizer);
+  XCTAssertEqual(touchInteceptorView.gestureRecognizers[1], forwardingRecognizer);
+}
+
 - (void)testFlutterPlatformViewControllerSubmitFrameWithoutFlutterViewNotCrashing {
   flutter::FlutterPlatformViewsTestMockPlatformViewDelegate mock_delegate;