[macOS] Implement hit testing and handle platform view cursor changes

shell/platform/darwin/macos/framework/Source/FlutterCompositor.h

@@ -8,20 +8,25 @@
 #include <functional>
 #include <list>
 #include <unordered_map>
+#include <variant>
 
 #include "flutter/fml/macros.h"
+#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorView.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterPlatformViewController.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterTimeConverter.h"
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterViewProvider.h"
 #include "flutter/shell/platform/embedder/embedder.h"
 
 @class FlutterMutatorView;
+@class FlutterCursorCoordinator;
 
 namespace flutter {
 
-class PlatformViewLayer;
+struct BackingStoreLayer {
+  std::vector<FlutterRect> paint_region;
+};
 
-typedef std::pair<PlatformViewLayer, size_t> PlatformViewLayerWithIndex;
+using LayerVariant = std::variant<PlatformViewLayer, BackingStoreLayer>;
 
 // FlutterCompositor creates and manages the backing stores used for
 // rendering Flutter content and presents Flutter content and Platform views.
@@ -67,13 +72,16 @@ class FlutterCompositor {
     ViewPresenter();
 
     void PresentPlatformViews(FlutterView* default_base_view,
-                              const std::vector<PlatformViewLayerWithIndex>& platform_views,
+                              const std::vector<LayerVariant>& layers,
                               const FlutterPlatformViewController* platform_views_controller);
 
    private:
     // Platform view to FlutterMutatorView that contains it.
     NSMapTable<NSView*, FlutterMutatorView*>* mutator_views_;
 
+    // Coordinates mouse cursor changes between platform views and overlays.
+    FlutterCursorCoordinator* cursor_coordinator_;
+
     // Presents the platform view layer represented by `layer`. `layer_index` is
     // used to position the layer in the z-axis. If the layer does not have a
     // superview, it will become subview of `default_base_view`.

shell/platform/darwin/macos/framework/Source/FlutterCompositor.mm

@@ -3,22 +3,31 @@
 // found in the LICENSE file.
 
 #import "flutter/shell/platform/darwin/macos/framework/Source/FlutterCompositor.h"
-#import "flutter/shell/platform/darwin/macos/framework/Source/FlutterMutatorView.h"
 
 #include "flutter/fml/logging.h"
 
 namespace flutter {
 
 namespace {
-std::vector<PlatformViewLayerWithIndex> CopyPlatformViewLayers(const FlutterLayer** layers,
-                                                               size_t layer_count) {
-  std::vector<PlatformViewLayerWithIndex> platform_views;
+std::vector<LayerVariant> CopyLayers(const FlutterLayer** layers, size_t layer_count) {
+  std::vector<LayerVariant> layers_copy;
   for (size_t i = 0; i < layer_count; i++) {
-    if (layers[i]->type == kFlutterLayerContentTypePlatformView) {
-      platform_views.push_back(std::make_pair(PlatformViewLayer(layers[i]), i));
+    const auto& layer = layers[i];
+    if (layer->type == kFlutterLayerContentTypePlatformView) {
+      layers_copy.push_back(PlatformViewLayer(layer));
+    } else if (layer->type == kFlutterLayerContentTypeBackingStore) {
+      std::vector<FlutterRect> rects;
+      auto present_info = layer->backing_store_present_info;
+      if (present_info != nullptr && present_info->paint_region != nullptr) {
+        rects.reserve(present_info->paint_region->rects_count);
+        std::copy(present_info->paint_region->rects,
+                  present_info->paint_region->rects + present_info->paint_region->rects_count,
+                  std::back_inserter(rects));
+      }
+      layers_copy.push_back(BackingStoreLayer{rects});
     }
   }
-  return platform_views;
+  return layers_copy;
 }
 }  // namespace
 
@@ -91,17 +100,16 @@
 
   // Notify block below may be called asynchronously, hence the need to copy
   // the layer information instead of passing the original pointers from embedder.
-  auto platform_views_layers = std::make_shared<std::vector<PlatformViewLayerWithIndex>>(
-      CopyPlatformViewLayers(layers, layers_count));
-
-  [view.surfaceManager presentSurfaces:surfaces
-                                atTime:presentation_time
-                                notify:^{
-                                  // Gets a presenter or create a new one for the view.
-                                  ViewPresenter& presenter = presenters_[view_id];
-                                  presenter.PresentPlatformViews(view, *platform_views_layers,
-                                                                 platform_view_controller_);
-                                }];
+  auto layers_copy = std::make_shared<std::vector<LayerVariant>>(CopyLayers(layers, layers_count));
+
+  [view.surfaceManager
+      presentSurfaces:surfaces
+               atTime:presentation_time
+               notify:^{
+                 // Gets a presenter or create a new one for the view.
+                 ViewPresenter& presenter = presenters_[view_id];
+                 presenter.PresentPlatformViews(view, *layers_copy, platform_view_controller_);
+               }];
 
   return true;
 }
@@ -111,18 +119,45 @@
 
 void FlutterCompositor::ViewPresenter::PresentPlatformViews(
     FlutterView* default_base_view,
-    const std::vector<PlatformViewLayerWithIndex>& platform_views,
+    const std::vector<LayerVariant>& layers,
     const FlutterPlatformViewController* platform_view_controller) {
   FML_DCHECK([[NSThread currentThread] isMainThread])
       << "Must be on the main thread to present platform views";
 
   // Active mutator views for this frame.
   NSMutableArray<FlutterMutatorView*>* present_mutators = [NSMutableArray array];
 
-  for (const auto& platform_view : platform_views) {
-    FlutterMutatorView* container = PresentPlatformView(
-        default_base_view, platform_view.first, platform_view.second, platform_view_controller);
-    [present_mutators addObject:container];
+  for (size_t i = 0; i < layers.size(); i++) {
+    const auto& layer = layers[i];
+    if (!std::holds_alternative<PlatformViewLayer>(layer)) {
+      continue;
+    }
+    const auto& platform_view = std::get<PlatformViewLayer>(layer);
+    FlutterMutatorView* mutator_view =
+        PresentPlatformView(default_base_view, platform_view, i, platform_view_controller);
+    [present_mutators addObject:mutator_view];
+
+    // Gather all overlay regions above this mutator view.
+    [mutator_view resetHitTestRegion];
+    for (size_t j = i + 1; j < layers.size(); j++) {
+      const auto& overlay_layer = layers[j];
+      if (!std::holds_alternative<BackingStoreLayer>(overlay_layer)) {
+        continue;
+      }
+      const auto& backing_store_layer = std::get<BackingStoreLayer>(overlay_layer);
+      for (const auto& flutter_rect : backing_store_layer.paint_region) {
+        double scale = default_base_view.layer.contentsScale;
+        CGRect rect = CGRectMake(flutter_rect.left / scale, flutter_rect.top / scale,
+                                 (flutter_rect.right - flutter_rect.left) / scale,
+                                 (flutter_rect.bottom - flutter_rect.top) / scale);
+        CGRect intersection = CGRectIntersection(rect, mutator_view.frame);
+        if (!CGRectIsNull(intersection)) {
+          intersection.origin.x -= mutator_view.frame.origin.x;
+          intersection.origin.y -= mutator_view.frame.origin.y;
+          [mutator_view addHitTestIgnoreRegion:intersection];
+        }
+      }
+    }
   }
 
   NSMutableArray<FlutterMutatorView*>* obsolete_mutators =
@@ -150,10 +185,15 @@
 
   FML_DCHECK(platform_view) << "Platform view not found for id: " << platform_view_id;
 
+  if (cursor_coordinator_ == nil) {
+    cursor_coordinator_ = [[FlutterCursorCoordinator alloc] initWithFlutterView:default_base_view];
+  }
+
   FlutterMutatorView* container = [mutator_views_ objectForKey:platform_view];
 
   if (!container) {
-    container = [[FlutterMutatorView alloc] initWithPlatformView:platform_view];
+    container = [[FlutterMutatorView alloc] initWithPlatformView:platform_view
+                                                cursorCoordiator:cursor_coordinator_];
     [mutator_views_ setObject:container forKey:platform_view];
     [default_base_view addSubview:container];
   }

shell/platform/darwin/macos/framework/Source/FlutterEngine.mm

@@ -86,7 +86,7 @@ - (instancetype)initWithConnection:(NSNumber*)connection
 /**
  * Private interface declaration for FlutterEngine.
  */
-@interface FlutterEngine () <FlutterBinaryMessenger>
+@interface FlutterEngine () <FlutterBinaryMessenger, FlutterMouseCursorPluginDelegate>
 
 /**
  * A mutable array that holds one bool value that determines if responses to platform messages are
@@ -466,6 +466,10 @@ @implementation FlutterEngine {
   // Map from ViewId to vsync waiter. Note that this is modified on main thread
   // but accessed on UI thread, so access must be @synchronized.
   NSMapTable<NSNumber*, FlutterVSyncWaiter*>* _vsyncWaiters;
+
+  // Weak reference to last view that received a pointer event. This is used to
+  // pair cursor change with a view.
+  __weak FlutterView* _lastViewWithPointerEvent;
 }
 
 - (instancetype)initWithName:(NSString*)labelPrefix project:(FlutterDartProject*)project {
@@ -981,6 +985,7 @@ - (void)updateWindowMetricsForViewController:(FlutterViewController*)viewControl
 
 - (void)sendPointerEvent:(const FlutterPointerEvent&)event {
   _embedderAPI.SendPointerEvent(_engine, &event, 1);
+  _lastViewWithPointerEvent = [self viewControllerForId:kFlutterImplicitViewId].flutterView;
 }
 
 - (void)sendKeyEvent:(const FlutterKeyEvent&)event
@@ -1167,7 +1172,8 @@ - (void)setUpNotificationCenterListeners {
 
 - (void)addInternalPlugins {
   __weak FlutterEngine* weakSelf = self;
-  [FlutterMouseCursorPlugin registerWithRegistrar:[self registrarForPlugin:@"mousecursor"]];
+  [FlutterMouseCursorPlugin registerWithRegistrar:[self registrarForPlugin:@"mousecursor"]
+                                         delegate:self];
   [FlutterMenuPlugin registerWithRegistrar:[self registrarForPlugin:@"menu"]];
   _settingsChannel =
       [FlutterBasicMessageChannel messageChannelWithName:kFlutterSettingsChannel
@@ -1182,6 +1188,13 @@ - (void)addInternalPlugins {
   }];
 }
 
+- (void)didUpdateMouseCursor:(NSCursor*)cursor {
+  // Mouse cursor plugin does not specify which view is responsible for changing the cursor,
+  // so the reasonable assumption here is that cursor change is a result of a mouse movement
+  // and thus the cursor will be paired with last Flutter view that reveived mouse event.
+  [_lastViewWithPointerEvent didUpdateMouseCursor:cursor];
+}
+
 - (void)applicationWillTerminate:(NSNotification*)notification {
   [self shutDownEngine];
 }

shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.h

@@ -10,6 +10,10 @@
 #import "flutter/shell/platform/darwin/common/framework/Headers/FlutterBinaryMessenger.h"
 #import "flutter/shell/platform/darwin/macos/framework/Headers/FlutterViewController.h"
 
+@protocol FlutterMouseCursorPluginDelegate <NSObject>
+- (void)didUpdateMouseCursor:(nonnull NSCursor*)cursor;
+@end
+
 /**
  * A plugin to handle mouse cursor.
  *
@@ -18,6 +22,9 @@
  */
 @interface FlutterMouseCursorPlugin : NSObject <FlutterPlugin>
 
++ (void)registerWithRegistrar:(nonnull id<FlutterPluginRegistrar>)registrar
+                     delegate:(nullable id<FlutterMouseCursorPluginDelegate>)delegate;
+
 @end
 
 #endif  // FLUTTER_SHELL_PLATFORM_DARWIN_MACOS_FRAMEWORK_SOURCE_FLUTTERMOUSECURSORPLUGIN_H_

shell/platform/darwin/macos/framework/Source/FlutterMouseCursorPlugin.mm

@@ -25,6 +25,11 @@
   // The following mapping must be kept in sync with Flutter framework's
   // mouse_cursor.dart
 
+  if ([kind isEqualToString:kKindValueNone]) {
+    NSImage* image = [[NSImage alloc] initWithSize:NSMakeSize(1, 1)];
+    return [[NSCursor alloc] initWithImage:image hotSpot:NSMakePoint(0, 0)];
+  }
+
   if (systemCursors == nil) {
     systemCursors = @{
       @"alias" : [NSCursor dragLinkCursor],
@@ -58,10 +63,8 @@
 }
 
 @interface FlutterMouseCursorPlugin ()
-/**
- * Whether the cursor is currently hidden.
- */
-@property(nonatomic) BOOL hidden;
+
+@property(nonatomic, weak) id<FlutterMouseCursorPluginDelegate> delegate;
 
 /**
  * Handles the method call that activates a system cursor.
@@ -79,11 +82,6 @@ - (FlutterError*)activateSystemCursor:(nonnull NSDictionary*)arguments;
  */
 - (void)displayCursorObject:(nonnull NSCursor*)cursorObject;
 
-/**
- * Hides the cursor.
- */
-- (void)hide;
-
 /**
  * Handles all method calls from Flutter.
  */
@@ -105,41 +103,22 @@ - (instancetype)init {
   return self;
 }
 
-- (void)dealloc {
-  if (_hidden) {
-    [NSCursor unhide];
-  }
-}
-
 - (FlutterError*)activateSystemCursor:(nonnull NSDictionary*)arguments {
   NSString* kindArg = arguments[kKindKey];
   if (!kindArg) {
     return [FlutterError errorWithCode:@"error"
                                message:@"Missing argument"
                                details:@"Missing argument while trying to activate system cursor"];
   }
-  if ([kindArg isEqualToString:kKindValueNone]) {
-    [self hide];
-    return nil;
-  }
+
   NSCursor* cursorObject = [FlutterMouseCursorPlugin cursorFromKind:kindArg];
   [self displayCursorObject:cursorObject];
   return nil;
 }
 
 - (void)displayCursorObject:(nonnull NSCursor*)cursorObject {
   [cursorObject set];
-  if (_hidden) {
-    [NSCursor unhide];
-  }
-  _hidden = NO;
-}
-
-- (void)hide {
-  if (!_hidden) {
-    [NSCursor hide];
-  }
-  _hidden = YES;
+  [self.delegate didUpdateMouseCursor:cursorObject];
 }
 
 + (NSCursor*)cursorFromKind:(NSString*)kind {
@@ -154,9 +133,15 @@ + (NSCursor*)cursorFromKind:(NSString*)kind {
 #pragma mark - FlutterPlugin implementation
 
 + (void)registerWithRegistrar:(id<FlutterPluginRegistrar>)registrar {
+  [self registerWithRegistrar:registrar delegate:nil];
+}
+
++ (void)registerWithRegistrar:(id<FlutterPluginRegistrar>)registrar
+                     delegate:(id<FlutterMouseCursorPluginDelegate>)delegate {
   FlutterMethodChannel* channel = [FlutterMethodChannel methodChannelWithName:kMouseCursorChannel
                                                               binaryMessenger:registrar.messenger];
   FlutterMouseCursorPlugin* instance = [[FlutterMouseCursorPlugin alloc] init];
+  instance.delegate = delegate;
   [registrar addMethodCallDelegate:instance channel:channel];
 }