Initial iOS floating cursor support (#1312)

## Proposed Changes

Initial iOS floating cursor support.


https://github.com/JetBrains/compose-multiplatform-core/assets/63979218/1c6681dc-5295-4712-80e0-f08f58f4687e


## Testing

Test: hold space bar and move the cursor

## Issues Fixed

Fixes: JetBrains/compose-multiplatform#4593

Co-authored-by: Andrei Salavei <Andrei.Salavei@jetbrains.com>

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/platform/IOSSkikoInput.uikit.kt

@@ -16,8 +16,17 @@
 
 package androidx.compose.ui.platform
 
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.unit.DpOffset
+
 internal interface IOSSkikoInput {
 
+    fun beginFloatingCursor(offset: DpOffset) {}
+
+    fun updateFloatingCursor(offset: DpOffset) {}
+
+    fun endFloatingCursor() {}
+
     /**
      * A Boolean value that indicates whether the text-entry object has any text.
      * https://developer.apple.com/documentation/uikit/uikeyinput/1614457-hastext

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/platform/UIKitTextInputService.uikit.kt

@@ -16,27 +16,33 @@
 
 package androidx.compose.ui.platform
 
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.Rect
+import androidx.compose.ui.graphics.Matrix
 import androidx.compose.ui.input.key.Key
 import androidx.compose.ui.input.key.KeyEvent
 import androidx.compose.ui.input.key.KeyEventType
 import androidx.compose.ui.input.key.key
 import androidx.compose.ui.input.key.type
 import androidx.compose.ui.scene.getConstraintsToFillParent
+import androidx.compose.ui.text.TextLayoutResult
 import androidx.compose.ui.text.input.CommitTextCommand
 import androidx.compose.ui.text.input.EditCommand
 import androidx.compose.ui.text.input.EditProcessor
 import androidx.compose.ui.text.input.FinishComposingTextCommand
 import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.text.input.ImeOptions
+import androidx.compose.ui.text.input.OffsetMapping
 import androidx.compose.ui.text.input.PlatformTextInputService
 import androidx.compose.ui.text.input.SetComposingRegionCommand
 import androidx.compose.ui.text.input.SetComposingTextCommand
 import androidx.compose.ui.text.input.SetSelectionCommand
 import androidx.compose.ui.text.input.TextFieldValue
 import androidx.compose.ui.unit.Density
+import androidx.compose.ui.unit.DpOffset
 import androidx.compose.ui.unit.asCGRect
 import androidx.compose.ui.unit.toDpRect
+import androidx.compose.ui.unit.toOffset
 import androidx.compose.ui.window.FocusStack
 import androidx.compose.ui.window.IntermediateTextInputUIView
 import androidx.compose.ui.window.KeyboardEventHandler
@@ -63,6 +69,7 @@ internal class UIKitTextInputService(
     private var currentImeOptions: ImeOptions? = null
     private var currentImeActionHandler: ((ImeAction) -> Unit)? = null
     private var textUIView: IntermediateTextInputUIView? = null
+    private var textLayoutResult : TextLayoutResult? = null
 
     /**
      * Workaround to prevent calling textWillChange, textDidChange, selectionWillChange, and
@@ -192,6 +199,25 @@ internal class UIKitTextInputService(
         }
     }
 
+    override fun updateTextLayoutResult(
+        textFieldValue: TextFieldValue,
+        offsetMapping: OffsetMapping,
+        textLayoutResult: TextLayoutResult,
+        textFieldToRootTransform: (Matrix) -> Unit,
+        innerTextFieldBounds: Rect,
+        decorationBoxBounds: Rect
+    ) {
+        super.updateTextLayoutResult(
+            textFieldValue,
+            offsetMapping,
+            textLayoutResult,
+            textFieldToRootTransform,
+            innerTextFieldBounds,
+            decorationBoxBounds
+        )
+        this.textLayoutResult = textLayoutResult
+    }
+
     private fun handleEnterKey(event: KeyEvent): Boolean {
         _tempImeActionIsCalledWithHardwareReturnKey = false
         return when (event.type) {
@@ -332,6 +358,28 @@ internal class UIKitTextInputService(
     }
 
     private fun createSkikoInput(value: TextFieldValue) = object : IOSSkikoInput {
+
+        private var floatingCursorTranslation : Offset? = null
+
+        override fun beginFloatingCursor(offset: DpOffset) {
+            val cursorPos = getCursorPos() ?: getState()?.selection?.start ?: return
+            val cursorRect = textLayoutResult?.getCursorRect(cursorPos) ?: return
+            floatingCursorTranslation = cursorRect.center - offset.toOffset(densityProvider())
+        }
+
+        override fun updateFloatingCursor(offset: DpOffset) {
+            val translation = floatingCursorTranslation ?: return
+            val offsetPx = offset.toOffset(densityProvider())
+            val pos = textLayoutResult
+                ?.getOffsetForPosition(offsetPx + translation) ?: return
+
+            sendEditCommand(SetSelectionCommand(pos, pos))
+        }
+
+        override fun endFloatingCursor() {
+            floatingCursorTranslation = null
+        }
+
         /**
          * A Boolean value that indicates whether the text-entry object has any text.
          * https://developer.apple.com/documentation/uikit/uikeyinput/1614457-hastext

compose/ui/ui/src/uikitMain/kotlin/androidx/compose/ui/window/IntermediateTextInputUIView.uikit.kt

@@ -16,12 +16,16 @@
 
 package androidx.compose.ui.window
 
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.platform.EmptyInputTraits
 import androidx.compose.ui.platform.IOSSkikoInput
 import androidx.compose.ui.platform.SkikoUITextInputTraits
 import androidx.compose.ui.platform.TextActions
 import androidx.compose.ui.platform.ViewConfiguration
 import androidx.compose.ui.uikit.utils.CMPEditMenuView
+import androidx.compose.ui.unit.DpOffset
+import androidx.compose.ui.unit.dp
+import kotlinx.cinterop.COpaquePointer
 import kotlin.time.Duration.Companion.milliseconds
 import kotlin.time.DurationUnit
 import kotlinx.cinterop.CValue
@@ -89,6 +93,18 @@ internal class IntermediateTextInputUIView(
 
     override fun canBecomeFirstResponder() = true
 
+    override fun beginFloatingCursorAtPoint(point: CValue<CGPoint>) {
+        input?.beginFloatingCursor(point.useContents { DpOffset(x.dp, y.dp) })
+    }
+
+    override fun updateFloatingCursorAtPoint(point: CValue<CGPoint>) {
+        input?.updateFloatingCursor(point.useContents { DpOffset(x.dp, y.dp) })
+    }
+
+    override fun endFloatingCursor() {
+        input?.endFloatingCursor()
+    }
+
     override fun pressesBegan(presses: Set<*>, withEvent: UIPressesEvent?) {
         keyboardEventHandler?.pressesBegan(presses, withEvent)
         super.pressesBegan(presses, withEvent)