Stop IntelliJ from hiding Undocked tool windows when they lose focus

src/main/kotlin/com/chylex/intellij/pinundockedtoolwindows/DynamicPluginListener.kt

@@ -0,0 +1,21 @@
+package com.chylex.intellij.pinundockedtoolwindows
+
+import com.chylex.intellij.pinundockedtoolwindows.patch.ToolWindowPatcher
+import com.intellij.ide.plugins.DynamicPluginListener
+import com.intellij.ide.plugins.IdeaPluginDescriptor
+
+const val PLUGIN_ID = "com.chylex.intellij.pinundockedtoolwindows"
+
+class DynamicPluginListener : DynamicPluginListener {
+	override fun pluginLoaded(pluginDescriptor: IdeaPluginDescriptor) {
+		if (pluginDescriptor.pluginId.idString == PLUGIN_ID) {
+			ToolWindowPatcher.apply()
+		}
+	}
+	
+	override fun beforePluginUnload(pluginDescriptor: IdeaPluginDescriptor, isUpdate: Boolean) {
+		if (pluginDescriptor.pluginId.idString == PLUGIN_ID) {
+			ToolWindowPatcher.revert()
+		}
+	}
+}

src/main/kotlin/com/chylex/intellij/pinundockedtoolwindows/ProjectActivityListener.kt

@@ -0,0 +1,12 @@
+package com.chylex.intellij.pinundockedtoolwindows
+
+import com.chylex.intellij.pinundockedtoolwindows.patch.ToolWindowPatcher
+import com.intellij.openapi.application.ApplicationManager
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.startup.ProjectActivity
+
+class ProjectActivityListener : ProjectActivity {
+	override suspend fun execute(project: Project) {
+		ApplicationManager.getApplication().invokeLater(ToolWindowPatcher::apply)
+	}
+}

src/main/kotlin/com/chylex/intellij/pinundockedtoolwindows/patch/PatchedAwtFocusListener.kt

@@ -0,0 +1,47 @@
+package com.chylex.intellij.pinundockedtoolwindows.patch
+
+import com.intellij.openapi.wm.IdeFocusManager
+import com.intellij.openapi.wm.ToolWindowManager
+import com.intellij.openapi.wm.ToolWindowType
+import com.intellij.openapi.wm.impl.ToolWindowManagerImpl
+import com.intellij.toolWindow.InternalDecoratorImpl
+import com.intellij.ui.ClientProperty
+import java.awt.AWTEvent
+import java.awt.Component
+import java.awt.event.AWTEventListener
+import java.awt.event.FocusEvent
+
+@Suppress("UnstableApiUsage")
+class PatchedAwtFocusListener(internal val original: AWTEventListener) : AWTEventListener {
+	override fun eventDispatched(event: AWTEvent?) {
+		if (event is FocusEvent && event.id == FocusEvent.FOCUS_LOST && shouldIgnoreFocusLostEvent(event.component)) {
+			return
+		}
+		
+		original.eventDispatched(event)
+	}
+	
+	private fun shouldIgnoreFocusLostEvent(currentlyFocused: Component?): Boolean {
+		val project = IdeFocusManager.getGlobalInstance().lastFocusedFrame?.project ?: return false
+		if (project.isDisposed || project.isDefault) {
+			return false
+		}
+		
+		val toolWindowManager = ToolWindowManager.getInstance(project)
+		val toolWindowId = getToolWindowIdForComponent(currentlyFocused) ?: return false
+		val toolWindow = toolWindowManager.getToolWindow(toolWindowId) ?: return false
+		
+		return toolWindow.type == ToolWindowType.SLIDING
+	}
+	
+	private fun getToolWindowIdForComponent(component: Component?): String? {
+		var c = component
+		while (c != null) {
+			if (c is InternalDecoratorImpl) {
+				return c.toolWindowId
+			}
+			c = ClientProperty.get(c, ToolWindowManagerImpl.PARENT_COMPONENT) ?: c.parent
+		}
+		return null
+	}
+}

src/main/kotlin/com/chylex/intellij/pinundockedtoolwindows/patch/ToolWindowPatcher.kt

@@ -0,0 +1,43 @@
+package com.chylex.intellij.pinundockedtoolwindows.patch
+
+import java.awt.AWTEvent
+import java.awt.Toolkit
+import java.awt.event.AWTEventListenerProxy
+
+object ToolWindowPatcher {
+	private const val EVENT_MASK = AWTEvent.FOCUS_EVENT_MASK or AWTEvent.WINDOW_FOCUS_EVENT_MASK
+	
+	private var activePatch: ActivePatch? = null
+	
+	private data class ActivePatch(val listener: PatchedAwtFocusListener, val eventMask: Long)
+	
+	fun apply() {
+		if (activePatch != null) {
+			return
+		}
+		
+		val toolkit = Toolkit.getDefaultToolkit()
+		for (listenerProxy in toolkit.getAWTEventListeners(EVENT_MASK)) {
+			if (listenerProxy is AWTEventListenerProxy) {
+				val listener = listenerProxy.listener
+				if (listener.javaClass.name == "com.intellij.openapi.wm.impl.ToolWindowManagerImpl\$ToolWindowManagerAppLevelHelper\$MyListener") {
+					val patch = ActivePatch(PatchedAwtFocusListener(listener), listenerProxy.eventMask)
+					toolkit.removeAWTEventListener(listener)
+					toolkit.addAWTEventListener(patch.listener, patch.eventMask)
+					activePatch = patch
+					return
+				}
+			}
+		}
+	}
+	
+	fun revert() {
+		val patch = activePatch
+		if (patch != null) {
+			val toolkit = Toolkit.getDefaultToolkit()
+			toolkit.removeAWTEventListener(patch.listener)
+			toolkit.addAWTEventListener(patch.listener.original, patch.eventMask)
+			activePatch = null
+		}
+	}
+}