Add Focus Mode support to kotlin language

idea/idea-core/src/org/jetbrains/kotlin/idea/core/KotlinFocusModeProvider.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.core
+
+import com.intellij.codeInsight.daemon.impl.focusMode.FocusModeProvider
+import com.intellij.openapi.util.Segment
+import com.intellij.psi.PsiAnonymousClass
+import com.intellij.psi.PsiFile
+import com.intellij.psi.SyntaxTraverser
+import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.containingClass
+
+class KotlinFocusModeProvider : FocusModeProvider {
+    override fun calcFocusZones(file: PsiFile): MutableList<out Segment> =
+        SyntaxTraverser.psiTraverser(file)
+            .postOrderDfsTraversal()
+            .filter {
+                it is KtClassOrObject || it is KtFunction || it is KtClassInitializer
+            }
+            .filter {
+                val p = it.parent
+                p is KtFile || p is KtClassBody
+            }
+            .map {
+                it.textRange
+            }.toMutableList()
+}

idea/resources/META-INF/plugin-common.xml

@@ -853,6 +853,8 @@
 
     <usageToPsiElementProvider implementation="org.jetbrains.kotlin.idea.codeInsight.KotlinUsageToPsiElementProvider"/>
 
+    <focusModeProvider language="kotlin" implementationClass="org.jetbrains.kotlin.idea.core.KotlinFocusModeProvider" />
+
     <facetType implementation="org.jetbrains.kotlin.idea.facet.KotlinFacetTypeImpl"/>
 
     <lang.sliceProvider language="kotlin" implementationClass="org.jetbrains.kotlin.idea.slicer.KotlinSliceProvider"/>