[JEWEL-368] Fix custom title bar mouse event (drag/press) not working correctly

platform/jewel/decorated-window/src/main/kotlin/org/jetbrains/jewel/window/DecoratedWindow.kt

@@ -44,6 +44,7 @@ import org.jetbrains.jewel.foundation.theme.JewelTheme
 import org.jetbrains.jewel.intui.standalone.window.Window
 import org.jetbrains.jewel.window.styling.DecoratedWindowStyle
 import org.jetbrains.jewel.window.utils.DesktopPlatform
+import org.jetbrains.jewel.window.utils.ClientRegion
 
 @Suppress("ModifierMissing")
 @Composable
@@ -279,7 +280,12 @@ public value class DecoratedWindowState(public val state: ULong) {
     }
 }
 
-internal data class TitleBarInfo(val title: String, val icon: Painter?)
+internal data class TitleBarInfo(
+    val title: String,
+    val icon: Painter?
+) {
+    val clientRegions: HashMap<String, ClientRegion> = hashMapOf()
+}
 
 internal val LocalTitleBarInfo: ProvidableCompositionLocal<TitleBarInfo> = compositionLocalOf {
     error("LocalTitleBarInfo not provided, TitleBar must be used in DecoratedWindow")

platform/jewel/decorated-window/src/main/kotlin/org/jetbrains/jewel/window/TitleBar.MacOS.kt

@@ -13,6 +13,7 @@ import androidx.compose.ui.unit.dp
 import com.jetbrains.JBR
 import org.jetbrains.jewel.foundation.theme.JewelTheme
 import org.jetbrains.jewel.window.styling.TitleBarStyle
+import org.jetbrains.jewel.window.utils.WindowMouseEventEffect
 import org.jetbrains.jewel.window.utils.macos.MacUtil
 
 public fun Modifier.newFullscreenControls(newControls: Boolean = true): Modifier =
@@ -78,8 +79,9 @@ internal fun DecoratedWindowScope.TitleBarOnMacOs(
 
     val titleBar = remember { JBR.getWindowDecorations().createCustomTitleBar() }
 
+    WindowMouseEventEffect(titleBar)
+
     TitleBarImpl(
-        modifier = modifier.customTitleBarMouseEventHandler(titleBar),
         gradientStartColor = gradientStartColor,
         style = style,
         applyTitleBar = { height, state ->

platform/jewel/decorated-window/src/main/kotlin/org/jetbrains/jewel/window/TitleBar.Windows.kt

@@ -7,17 +7,12 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.input.pointer.PointerEventPass
-import androidx.compose.ui.input.pointer.PointerEventType
-import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.unit.dp
 import com.jetbrains.JBR
-import com.jetbrains.WindowDecorations.CustomTitleBar
-import kotlinx.coroutines.currentCoroutineContext
-import kotlinx.coroutines.isActive
 import org.jetbrains.jewel.foundation.theme.JewelTheme
 import org.jetbrains.jewel.ui.util.isDark
 import org.jetbrains.jewel.window.styling.TitleBarStyle
+import org.jetbrains.jewel.window.utils.WindowMouseEventEffect
 
 @Composable
 internal fun DecoratedWindowScope.TitleBarOnWindows(
@@ -28,6 +23,8 @@ internal fun DecoratedWindowScope.TitleBarOnWindows(
 ) {
     val titleBar = remember { JBR.getWindowDecorations().createCustomTitleBar() }
 
+    WindowMouseEventEffect(titleBar)
+
     TitleBarImpl(
         modifier = modifier,
         gradientStartColor = gradientStartColor,
@@ -38,31 +35,7 @@ internal fun DecoratedWindowScope.TitleBarOnWindows(
             JBR.getWindowDecorations().setCustomTitleBar(window, titleBar)
             PaddingValues(start = titleBar.leftInset.dp, end = titleBar.rightInset.dp)
         },
-        backgroundContent = { Spacer(modifier = Modifier.fillMaxSize().customTitleBarMouseEventHandler(titleBar)) },
+        backgroundContent = { Spacer(modifier = Modifier.fillMaxSize()) },
         content = content,
     )
 }
-
-internal fun Modifier.customTitleBarMouseEventHandler(titleBar: CustomTitleBar): Modifier =
-    pointerInput(titleBar) {
-        val currentContext = currentCoroutineContext()
-        awaitPointerEventScope {
-            var inUserControl = false
-            while (currentContext.isActive) {
-                val event = awaitPointerEvent(PointerEventPass.Main)
-                event.changes.forEach {
-                    if (!it.isConsumed && !inUserControl) {
-                        titleBar.forceHitTest(false)
-                    } else {
-                        if (event.type == PointerEventType.Press) {
-                            inUserControl = true
-                        }
-                        if (event.type == PointerEventType.Release) {
-                            inUserControl = false
-                        }
-                        titleBar.forceHitTest(true)
-                    }
-                }
-            }
-        }
-    }

platform/jewel/decorated-window/src/main/kotlin/org/jetbrains/jewel/window/utils/ClientRegionHelper.kt

@@ -0,0 +1,115 @@
+package org.jetbrains.jewel.window.utils
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.LayoutCoordinates
+import androidx.compose.ui.layout.positionInWindow
+import androidx.compose.ui.node.CompositionLocalConsumerModifierNode
+import androidx.compose.ui.node.GlobalPositionAwareModifierNode
+import androidx.compose.ui.node.ModifierNodeElement
+import androidx.compose.ui.node.currentValueOf
+import androidx.compose.ui.platform.InspectorInfo
+import com.jetbrains.WindowDecorations
+import org.jetbrains.jewel.window.DecoratedWindowScope
+import org.jetbrains.jewel.window.LocalTitleBarInfo
+import org.jetbrains.jewel.window.TitleBarInfo
+import java.awt.event.MouseAdapter
+import java.awt.event.MouseEvent
+import kotlin.collections.set
+
+internal data class ClientRegion(
+    val x: Float,
+    val y: Float,
+    val width: Int,
+    val height: Int,
+)
+
+public fun Modifier.clientRegion(key: String): Modifier = then(RegisterClientRegionElement(key))
+
+private data class RegisterClientRegionElement(
+    private val key: String
+) : ModifierNodeElement<RegisterClientRegionNode>() {
+
+    override fun create() = RegisterClientRegionNode(key)
+
+    override fun update(node: RegisterClientRegionNode) = node.updateKey(key)
+
+    override fun InspectorInfo.inspectableProperties() {
+        name = "registerRegion"
+        properties["key"] = key
+    }
+}
+
+private class RegisterClientRegionNode(
+    var key: String
+) : Modifier.Node(), GlobalPositionAwareModifierNode, CompositionLocalConsumerModifierNode {
+
+    private var titleBarInfo: TitleBarInfo? = null
+
+    override fun onAttach() {
+        titleBarInfo = currentValueOf(LocalTitleBarInfo)
+    }
+
+    override fun onGloballyPositioned(coordinates: LayoutCoordinates) {
+        val info = titleBarInfo ?: return
+        val position = coordinates.positionInWindow()
+        val size = coordinates.size
+
+        info.clientRegions[key] = ClientRegion(
+            x = position.x,
+            y = position.y,
+            width = size.width,
+            height = size.height
+        )
+    }
+
+    override fun onDetach() {
+        titleBarInfo?.clientRegions?.remove(key)
+        titleBarInfo = null
+    }
+
+    fun updateKey(newKey: String) {
+        if (key != newKey) {
+            titleBarInfo?.clientRegions?.remove(key)
+            key = newKey
+        }
+    }
+}
+
+@Composable
+internal fun DecoratedWindowScope.WindowMouseEventEffect(titleBar: WindowDecorations.CustomTitleBar) {
+    val titleBarInfo = LocalTitleBarInfo.current
+
+    DisposableEffect(window, window.graphicsConfiguration, titleBar) {
+        val graphicsConfig = window.graphicsConfiguration
+        val scaleX = graphicsConfig?.defaultTransform?.scaleX ?: 1.0
+        val scaleY = graphicsConfig?.defaultTransform?.scaleY ?: 1.0
+        val listener = object : MouseAdapter() {
+            override fun mousePressed(e: MouseEvent) = updateHitTest(e)
+            override fun mouseReleased(e: MouseEvent) = updateHitTest(e)
+            override fun mouseDragged(e: MouseEvent) = updateHitTest(e)
+            override fun mouseMoved(e: MouseEvent) = updateHitTest(e)
+
+            private fun updateHitTest(e: MouseEvent) {
+                // Convert from AWT raw pixels to Compose positionInWindow() coordinates
+                val x = e.x * scaleX
+                val y = e.y * scaleY
+
+                val isClientRegion = titleBarInfo.clientRegions.any { region ->
+                    (x >= region.value.x && x <= region.value.x + region.value.width) &&
+                        (y >= region.value.y && y <= region.value.y + region.value.height)
+                }
+
+                titleBar.forceHitTest(isClientRegion)
+            }
+        }
+        window.addMouseListener(listener)
+        window.addMouseMotionListener(listener)
+
+        onDispose {
+            window.removeMouseListener(listener)
+            window.removeMouseMotionListener(listener)
+        }
+    }
+}

platform/jewel/samples/standalone/src/main/kotlin/org/jetbrains/jewel/samples/standalone/view/TitleBarView.kt

@@ -25,14 +25,15 @@ import org.jetbrains.jewel.ui.painter.hints.Size
 import org.jetbrains.jewel.window.DecoratedWindowScope
 import org.jetbrains.jewel.window.TitleBar
 import org.jetbrains.jewel.window.newFullscreenControls
+import org.jetbrains.jewel.window.utils.clientRegion
 
 @ExperimentalLayoutApi
 @Composable
 internal fun DecoratedWindowScope.TitleBarView() {
     TitleBar(Modifier.newFullscreenControls(), gradientStartColor = MainViewModel.projectColor) {
         Row(Modifier.align(Alignment.Start)) {
             Dropdown(
-                Modifier.height(30.dp),
+                Modifier.height(30.dp).clientRegion("dropdown"),
                 menuContent = {
                     MainViewModel.views.forEach {
                         selectableItem(
@@ -73,7 +74,7 @@ internal fun DecoratedWindowScope.TitleBarView() {
                 val jewelGithubLink = "https://github.com/JetBrains/intellij-community/tree/master/platform/jewel"
                 IconButton(
                     { Desktop.getDesktop().browse(URI.create(jewelGithubLink)) },
-                    Modifier.size(40.dp).padding(5.dp),
+                    Modifier.size(40.dp).padding(5.dp).clientRegion("github_link"),
                 ) {
                     Icon(ShowcaseIcons.gitHub, "Github")
                 }
@@ -99,7 +100,7 @@ internal fun DecoratedWindowScope.TitleBarView() {
                                 IntUiThemes.System -> IntUiThemes.Light
                             }
                     },
-                    Modifier.size(40.dp).padding(5.dp),
+                    Modifier.size(40.dp).padding(5.dp).clientRegion("switch_theme"),
                 ) {
                     when (MainViewModel.theme) {
                         IntUiThemes.Light ->