Support iOS Drag&Drop

compose/mpp/demo/src/desktopMain/kotlin/androidx/compose/mpp/demo/components/DragAndDropExample.desktop.kt

@@ -19,6 +19,7 @@ package androidx.compose.mpp.demo.components
 import androidx.compose.foundation.BorderStroke
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
+import androidx.compose.foundation.content.contentReceiver
 import androidx.compose.foundation.draganddrop.dragAndDropSource
 import androidx.compose.foundation.draganddrop.dragAndDropTarget
 import androidx.compose.foundation.layout.Arrangement

compose/mpp/demo/src/uikitMain/kotlin/androidx/compose/mpp/demo/components/DragAndDropExample.uikit.kt

@@ -16,7 +16,6 @@
 
 package androidx.compose.mpp.demo.components
 
-import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.background
 import androidx.compose.foundation.draganddrop.dragAndDropSource
 import androidx.compose.foundation.draganddrop.dragAndDropTarget
@@ -38,14 +37,18 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
+import androidx.compose.ui.ExperimentalComposeUiApi
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draganddrop.DragAndDropEvent
 import androidx.compose.ui.draganddrop.DragAndDropTarget
-import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.draganddrop.DragAndDropTransferData
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.uikit.fromString
+import androidx.compose.ui.uikit.loadString
 import androidx.compose.ui.unit.dp
+import platform.UIKit.UIDragItem
 
-@OptIn(ExperimentalFoundationApi::class)
+@OptIn(ExperimentalComposeUiApi::class)
 @Composable
 actual fun DragAndDropExample() {
     Column(
@@ -74,15 +77,10 @@ actual fun DragAndDropExample() {
                 .padding(16.dp)
                 .fillMaxWidth(1f)
                 .height(200.dp)
-                .dragAndDropSource(
-                    drawDragDecoration = {
-                        drawRect(Color.Gray, Offset(0f, 0f), size)
-                    },
-                    transferData = { offset ->
-                        // TODO: Implement iOS specific transfer data creation
-                        null
-                    }
-                )
+                .dragAndDropSource {
+                    addLog("Sent: $text")
+                    DragAndDropTransferData(listOf(UIDragItem.fromString(text)))
+                }
                 .background(Color.DarkGray),
             color = Color.White,
             text = text
@@ -102,20 +100,11 @@ actual fun DragAndDropExample() {
                     shouldStartDragAndDrop = { true },
                     target = object : DragAndDropTarget {
                         override fun onDrop(event: DragAndDropEvent): Boolean {
-                            // TODO: finalize event and transferable API
-
-                            // stubs for `DragAndDropEvent` UIDragItem integration support
-//                            CoroutineScope(Dispatchers.Main).launch {
-//                                for (item in event.session.items) {
-//                                    val dragItem = item as UIDragItem
-//                                    dragItem.decodeString()?.let {
-//                                        dropText = it
-//                                    }
-//                                }
-//                            }
-
-                            addLog("DragAndDropTarget.onDrop with $event")
-
+                            addLog("Dropped")
+                            event.forEachString {
+                                dropText = it
+                                addLog("Received: $it")
+                            }
                             return true
                         }
                     }
@@ -131,4 +120,13 @@ actual fun DragAndDropExample() {
             }
         }
     }
-}
+}
+
+@OptIn(ExperimentalComposeUiApi::class)
+private fun DragAndDropEvent.forEachString(block: (String) -> Unit) {
+    items.forEach {
+        it.loadString { s, _ ->
+            s?.let(block)
+        }
+    }
+}

compose/ui/ui-uikit/src/uikitMain/objc/CMPUIKitUtils/CMPUIKitUtils/CMPDropInteractionProxy.h

@@ -36,8 +36,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-/// Helper category for decoding `UIDragItem` into some typed object
-@interface UIDragItem (CMPDecoding)
+/// Helper category for decoding `NSItemProvider` into some typed object
+@interface NSItemProvider (CMPDecoding)
 
 - (void)cmp_loadString:(void (^)(NSString  * _Nullable result, NSError *error))completionHandler;
 

compose/ui/ui-uikit/src/uikitMain/objc/CMPUIKitUtils/CMPUIKitUtils/CMPDropInteractionProxy.m

@@ -70,18 +70,18 @@ - (void)sessionDidExit:(id<UIDropSession>)session interaction:(UIDropInteraction
 
 @end
 
-@implementation UIDragItem (CMPDecoding)
+@implementation NSItemProvider (CMPDecoding)
 
 - (void)cmp_loadString:(void (^)(NSString  * _Nullable result, NSError *_Nullable error))completionHandler {
-    if ([self.itemProvider canLoadObjectOfClass:NSString.class]) {
-        [self.itemProvider loadObjectOfClass:NSString.class completionHandler:completionHandler];
+    if ([self canLoadObjectOfClass:NSString.class]) {
+        [self loadObjectOfClass:NSString.class completionHandler:completionHandler];
     } else {
         completionHandler(nil, nil);
     }
 }
 
 - (void)cmp_loadAny:(Class)objectClass onCompletion:(void (^)(id _Nullable result, NSError *_Nullable error))completionHandler {
-    // Check that an object of objectClass can be loaded from UIDragItem
+    // Check that an object of objectClass can be loaded from NSItemProvider
     if (![objectClass conformsToProtocol:@protocol(NSItemProviderReading)]) {
         NSDictionary *userInfo = @{
             @"description" : [NSString stringWithFormat:@"%@ doesn't conform to protocol NSItemProviderReading and thus can't be loaded", objectClass.description]
@@ -91,9 +91,9 @@ - (void)cmp_loadAny:(Class)objectClass onCompletion:(void (^)(id _Nullable resul
                                              code:0
                                          userInfo:userInfo];
         completionHandler(nil, error);
-    } else if ([self.itemProvider canLoadObjectOfClass:objectClass]) {
+    } else if ([self canLoadObjectOfClass:objectClass]) {
         // Try loading the object of this class
-        [self.itemProvider loadObjectOfClass:objectClass completionHandler:completionHandler];
+        [self loadObjectOfClass:objectClass completionHandler:completionHandler];
     } else {
         // This UIDragItem does't contain object of `objectClass`
         completionHandler(nil, nil);

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/draganddrop/DragAndDrop.uikit.kt

@@ -16,6 +16,7 @@
 
 package androidx.compose.ui.draganddrop
 
+import androidx.compose.ui.ExperimentalComposeUiApi
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.uikit.density
 import androidx.compose.ui.unit.asDpOffset
@@ -35,15 +36,22 @@ actual class DragAndDropEvent internal constructor(
 
     internal val session: UIDropSessionProtocol
         get() = dropSessionContext.session
+
+    @ExperimentalComposeUiApi
+    val items: List<UIDragItem>
+        get() = session.items.filterIsInstance<UIDragItem>()
 }
 
 /**
  * On iOS drag and drop session data is represented by [UIDragItem]s, which contains
  * information about how data can be transferred across processes boundaries and an optional
  * local object to be used in the same app.
  */
-actual class DragAndDropTransferData internal constructor (
-    internal val items: List<UIDragItem>
+actual class DragAndDropTransferData
+@ExperimentalComposeUiApi
+constructor(
+    @property:ExperimentalComposeUiApi
+    val items: List<UIDragItem>
 )
 
 /**
@@ -55,4 +63,4 @@ internal actual val DragAndDropEvent.positionInRoot: Offset
         session
             .locationInView(view)
             .asDpOffset()
-            .toOffset(view.density)
+            .toOffset(view.density)

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/uikit/UIDragItemExtensions.uikit.kt

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package androidx.compose.ui.uikit
+
+import androidx.compose.ui.ExperimentalComposeUiApi
+import androidx.compose.ui.uikit.utils.cmp_itemWithAny
+import androidx.compose.ui.uikit.utils.cmp_itemWithString
+import androidx.compose.ui.uikit.utils.cmp_loadAny
+import androidx.compose.ui.uikit.utils.cmp_loadString
+import kotlinx.cinterop.BetaInteropApi
+import kotlinx.cinterop.ObjCClass
+import platform.Foundation.NSError
+import platform.UIKit.UIDragItem
+import platform.darwin.NSObject
+
+/**
+ * Encodes [String] to [UIDragItem] for use in drag-and-drop operations.
+ *
+ * @param string The string representation of a drag item.
+ * @return A new [UIDragItem] instance created from the provided string.
+ */
+@ExperimentalComposeUiApi
+fun UIDragItem.Companion.fromString(string: String): UIDragItem =
+    UIDragItem.cmp_itemWithString(string)
+
+/**
+ * Encodes [NSObject] into [UIDragItem] for use in drag-and-drop operations.
+ *
+ * @param objectClass The [ObjCClass] representing the class of the object to be used in the drag item.
+ * @param nsObject The [NSObject] instance to be associated with the created [UIDragItem]. Can be null.
+ * @return A [UIDragItem] constructed using the provided [objectClass] and [nsObject]. Throws an exception if the resulting drag item is null.
+ */
+@OptIn(BetaInteropApi::class)
+@ExperimentalComposeUiApi
+fun <T: NSObject, NSItemProviderWriting> UIDragItem.Companion.fromNSObject(
+    objectClass: ObjCClass,
+    nsObject: T
+): UIDragItem =
+    requireNotNull(UIDragItem.cmp_itemWithAny(objectClass, nsObject))
+
+/**
+ * Loads a string provided by the drag-and-drop session.
+ *
+ * @param block Callback function that receives the loaded string and an [NSError] if applicable.
+ */
+@ExperimentalComposeUiApi
+fun UIDragItem.loadString(block: (String?, NSError?) -> Unit) {
+    itemProvider.cmp_loadString(block)
+}
+
+/**
+ * Loads a specified [NSObject] class from a [UIDragItem]'s item provider, invoking the provided block
+ * upon completion.
+ *
+ * @param objectClass The [ObjCClass] that represents the class of the object to be loaded.
+ * @param block A callback function that will receive the loaded object of type [T] and an associated [NSError] if the operation fails. The loaded object may be null.
+ */
+@OptIn(BetaInteropApi::class)
+@ExperimentalComposeUiApi
+fun <T: NSObject, NSItemProviderReading> UIDragItem.loadNSObject(
+    objectClass: ObjCClass,
+    block: (T?, NSError?) -> Unit
+) {
+    itemProvider.cmp_loadAny(objectClass) { any: Any?, nsError: NSError? ->
+        @Suppress("UNCHECKED_CAST")
+        block(any as T?, nsError)
+    }
+}

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/viewinterop/UIKitInteropProperties.uikit.kt

@@ -20,9 +20,6 @@ import androidx.compose.runtime.Immutable
 import androidx.compose.ui.ExperimentalComposeUiApi
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.semantics.semantics
-import androidx.compose.ui.window.DialogProperties
-import kotlinx.cinterop.CValue
-import platform.CoreGraphics.CGSize
 
 /**
  * Properties that are used to configure the behavior of the interop view.