Refactor to expose less internal API

 Without:    180,735
    With:    314,311
Increase:    133,576 (+74%)

  2,257,187 →   252,498 - bench-big (fast)
    458,880 →   117,304 - bench-big (full)

bench/big/src/demo/Main.scala

@@ -2,7 +2,6 @@ package demo
 
 import scala.scalajs.js.annotation.JSExport
 import scalacss.Defaults._
-import scalacss.js._
 
 @JSExport("Main")
 object Main {

bench/big/src/demo/Styles.scala

@@ -2,7 +2,6 @@ package demo
 
 import japgolly.univeq.UnivEq
 import scalacss.Defaults._
-import scalacss.{Pseudo, PseudoElement, StyleS}
 
 sealed trait Live
 case object Live extends Live
@@ -72,7 +71,7 @@ object Styles extends StyleSheet.Inline {
   private def deadColumnLabel(live: Live) =
     mixinIf(live == Dead)(textDecoration := ^.lineThrough)
 
-  private val hasTitle = Pseudo.Custom("[title]", PseudoElement)
+  private val hasTitle = Pseudo.Custom("[title]", PseudoType.Element)
 
   private val hoverShowsInfo = hasTitle(cursor.help)
 

bench/react-with/src/demo.scala

@@ -1,5 +1,4 @@
 import org.scalajs.dom.{console, document}
-import scala.scalajs.js
 import scala.scalajs.js.annotation.JSExport
 import japgolly.scalajs.react._, vdom.prefix_<^._, ScalazReact._
 

core/js/src/main/scala/scalacss/defaults/PlatformExports.scala

@@ -0,0 +1,59 @@
+package scalacss.defaults
+
+import org.scalajs.dom.document
+import org.scalajs.dom.raw.HTMLStyleElement
+import scalacss.internal.mutable.{StyleSheet, StyleSheetRegistry}
+import scalacss.internal.{Css, Env, Renderer}
+
+// ================
+// ====        ====
+// ====   JS   ====
+// ====        ====
+// ================
+
+object PlatformExports {
+
+  def createStyleElement(styleStr: String): HTMLStyleElement = {
+    val e = document.createElement("style").asInstanceOf[HTMLStyleElement]
+    e.`type` = "text/css"
+    e appendChild document.createTextNode(styleStr)
+    e
+  }
+
+  def installStyle(style: HTMLStyleElement): Unit =
+    document.head appendChild style
+
+
+  class StyleElementRenderer(s: Renderer[String]) extends Renderer[HTMLStyleElement] {
+    override def apply(css: Css) =
+      createStyleElement(s(css))
+  }
+
+  final class StyleSheetInlineJsOps(private val ss: StyleSheet.Inline) extends AnyVal {
+    /** Turns this StyleSheet into a `<style>` and adds it to the document DOM. */
+    def addToDocument()(implicit s: Renderer[HTMLStyleElement], e: Env): Unit =
+     installStyle(ss.render[HTMLStyleElement])
+  }
+
+  final class StyleSheetRegistryJsOps(private val r: StyleSheetRegistry) extends AnyVal {
+    /** Registered StyleSheets are turned into a `<style>` and added to the document DOM. */
+    def addToDocumentOnRegistration()(implicit s: Renderer[String], e: Env): Unit =
+      r.onRegistrationN { ss =>
+        val styleStr = ss.map(_.render[String]).mkString("\n")
+        val style = createStyleElement(styleStr)
+        installStyle(style)
+      }
+  }
+}
+
+trait PlatformExports {
+
+  implicit def toStyleSheetInlineJsOps(s: StyleSheet.Inline): PlatformExports.StyleSheetInlineJsOps =
+    new PlatformExports.StyleSheetInlineJsOps(s)
+
+  implicit def toStyleSheetRegistryJsOps(s: StyleSheetRegistry): PlatformExports.StyleSheetRegistryJsOps =
+    new PlatformExports.StyleSheetRegistryJsOps(s)
+
+  implicit final def cssStyleElementRenderer(implicit s: Renderer[String]): Renderer[HTMLStyleElement] =
+    new PlatformExports.StyleElementRenderer(s)
+}

core/js/src/main/scala/scalacss/internal/Platform.scala

@@ -0,0 +1,24 @@
+package scalacss.internal
+
+import scala.annotation.elidable
+
+// ================
+// ====        ====
+// ====   JS   ====
+// ====        ====
+// ================
+
+object Platform {
+
+  /**
+   * Use the scalac `-Xelide-below` flag to switch from development- to production-mode.
+   */
+  @elidable(elidable.ASSERTION)
+  @inline def DevMode: Boolean =
+    true
+//  @inline def DevMode: Boolean =
+//    scalajs.LinkingInfo.developmentMode
+
+  implicit def env: Env =
+    Env.empty
+}

core/js/src/main/scala/scalacss/mutable/Mutex.scala → core/js/src/main/scala/scalacss/internal/mutable/Mutex.scala

@@ -1,14 +1,14 @@
-package scalacss.mutable
+package scalacss.internal.mutable
 
 // ================
 // ====        ====
 // ====   JS   ====
 // ====        ====
 // ================
 
-
 final class Mutex {
-  @inline def apply[A](f: => A): A = f
+  @inline def apply[A](f: => A): A =
+    f
 }
 
 object Mutex {

core/js/src/main/scala/scalacss/js/JsEnv.scala → core/js/src/main/scala/scalacss/js/PlatformJsEnv.scala

@@ -1,7 +1,7 @@
 package scalacss.js
 
 import scalajs.js.UndefOr
-import scalacss.Env
+import scalacss.internal.Env
 import Env._
 
 /**
@@ -13,16 +13,15 @@ import Env._
  * Platform(Some(Chrome),Some(Blink),Some(40.0.2214.115),Some(Chrome 40.0.2214.115 on Linux 64-bit),None,None,Some(Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.115 Safari/537.36),Some(OS(Some(Bits64),Some(Linux),None)))
  * Platform(Some(Firefox),Some(Gecko),Some(36.0),Some(Firefox 36.0 on Linux 64-bit),None,None,Some(Mozilla/5.0 (X11; Linux x86_64; rv:36.0) Gecko/20100101 Firefox/36.0),Some(OS(Some(Bits64),Some(Linux),None)))
  */
-object JsEnv {
-
-  def value: Env =
-    Env.empty
-//    PlatformJs.value.fold(Env.empty)(p =>
-//      Env(platform(p), Media.empty(None)))
+object PlatformJsEnv {
 
   private implicit def undefToOption[A](a: UndefOr[A]): Option[A] =
     a.toOption.flatMap(Option(_))
 
+  def value: Option[Env] =
+    PlatformJs.value.map(p =>
+      Env(platform(p), Media.empty(None)))
+
   def platform(p: PlatformJs): Platform[Option] = {
     val envOs =
       p.os.map(i => OS[Option](

core/js/src/test/scala/scalacss/js/PlatformJsTest.scala

@@ -1,22 +1,19 @@
 package scalacss.js
 
-import utest._
-import scalacss._
-import TestUtil._
-
 import scala.scalajs.js.annotation.JSExport
+import utest._
 
 @JSExport("PlatformJsTest")
 object PlatformJsTest extends TestSuite {
 
   @JSExport("test")
-  def test: Unit = {
+  def test(): Unit = {
     println(PlatformJs.value)
-    println(JsEnv.value.platform)
-    println(JsEnv.value.media)
+    println(PlatformJsEnv.value.map(_.platform))
+    println(PlatformJsEnv.value.map(_.media))
   }
 
   override val tests = TestSuite {
-    test
+    test()
   }
 }

core/jvm/src/main/scala/scalacss/PlatformDefaults.scala → core/jvm/src/main/scala/scalacss/defaults/PlatformExports.scala

@@ -1,14 +1,9 @@
-package scalacss
+package scalacss.defaults
 
 // =================
 // ====         ====
 // ====   JVM   ====
 // ====         ====
 // =================
 
-
-trait PlatformDefaults {
-
-  implicit def env: Env =
-    Env.empty
-}
+trait PlatformExports

core/jvm/src/main/scala/scalacss/internal/Platform.scala

@@ -0,0 +1,23 @@
+package scalacss.internal
+
+import scala.annotation.elidable
+
+// =================
+// ====         ====
+// ====   JVM   ====
+// ====         ====
+// =================
+
+object Platform {
+
+  /**
+   * Use the scalac `-Xelide-below` flag to switch from development- to production-mode.
+   */
+  @elidable(elidable.ASSERTION)
+  @inline def DevMode: Boolean =
+    true
+
+  implicit def env: Env =
+    Env.empty
+
+}

core/jvm/src/main/scala/scalacss/mutable/Mutex.scala → core/jvm/src/main/scala/scalacss/internal/mutable/Mutex.scala

@@ -1,14 +1,14 @@
-package scalacss.mutable
+package scalacss.internal.mutable
 
 // =================
 // ====         ====
 // ====   JVM   ====
 // ====         ====
 // =================
 
-
 final class Mutex {
-  @inline def apply[A](f: => A): A = synchronized(f)
+  def apply[A](f: => A): A =
+    synchronized(f)
 }
 
 object Mutex {