replace Travis-CI with GitHub Actions

and:

* upgrade sbt to 1.5.5 (was 1.5.2)
* upgrade sbt-scala-module to 3.0.0 (was 2.3.0)
* upgrade Scala versions (2.12.15, 2.13.6, 3.0.2)
* upgrade ScalaTest to 3.2.10 (was 3.2.9)
* add JDK 17 to CI matrix
* a few other minor cleanups

Author: SethTisue

Diff for: .github/workflows/ci.yml

@@ -0,0 +1,25 @@
+name: test
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        java: [8, 11, 17]
+        scala: [2.11.12, 2.12.15, 2.13.6, 3.0.2]
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - uses: coursier/cache-action@v6
+    - uses: actions/setup-java@v2
+      with:
+        distribution: adopt
+        java-version: ${{matrix.java}}
+    - name: Test
+      run: sbt ++${{matrix.scala}} test package

Diff for: .github/workflows/release.yml

@@ -0,0 +1,21 @@
+name: Release
+on:
+  push:
+    tags: ["*"]
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-java@v2
+        with:
+          distribution: adopt
+          java-version: 8
+      - run: sbt versionCheck ci-release
+        env:
+          PGP_PASSPHRASE: ${{secrets.PGP_PASSPHRASE}}
+          PGP_SECRET: ${{secrets.PGP_SECRET}}
+          SONATYPE_PASSWORD: ${{secrets.SONATYPE_PASSWORD}}
+          SONATYPE_USERNAME: ${{secrets.SONATYPE_USERNAME}}

Diff for: .travis.yml

@@ -1,18 +1,16 @@
-lazy val scalaTestVersion = "3.2.9"
+lazy val scalaTestVersion = "3.2.10"
+
+ThisBuild / crossScalaVersions := Seq("3.0.2", "2.13.6", "2.12.15", "2.11.12")
+ThisBuild / scalaVersion := crossScalaVersions.value.head
 
 // We use <epoch>.<major>.<minor> like 99% of Scala libraries.
 // Versions are binary compatible within x.y.* but not within x.*.*
 ThisBuild / versionScheme := Some("pvp")
 ThisBuild / versionPolicyIntention := Compatibility.None  // 3.0.0
 
-lazy val commonSettings = Seq(
-  scalacOptions     ++= Seq("-deprecation", "-feature"),
-)
-
 lazy val swing = project.in(file("."))
   .settings(ScalaModulePlugin.scalaModuleSettings)
   .settings(ScalaModulePlugin.scalaModuleOsgiSettings)
-  .settings(commonSettings)
   .settings(
     name := "scala-swing",
     scalaModuleAutomaticModuleName := Some("scala.swing"),
@@ -34,25 +32,18 @@ lazy val swing = project.in(file("."))
         case _                       => sourceDir / "scala-2.13-"
       }
     },
-    // sources in (Compile, doc) := {
-    //   if (isDotty.value) Nil else (sources in (Compile, doc)).value // dottydoc is currently broken
-    // },
   )
 
 lazy val examples = project.in(file("examples"))
   .dependsOn(swing)
-  .settings(commonSettings)
   .settings(
-    scalaVersion := (swing / scalaVersion).value,
     run / fork := true,
     fork := true,
   )
 
 lazy val uitest = project.in(file("uitest"))
   .dependsOn(swing)
-  .settings(commonSettings)
   .settings(
-    scalaVersion := (swing / scalaVersion).value,
     run / fork := true,
     fork := true,
   )

Diff for: build.sbt

@@ -1 +1 @@
-sbt.version=1.5.2
+sbt.version=1.5.5

Diff for: project/build.properties

@@ -1,2 +1 @@
-addSbtPlugin("org.scala-lang.modules" % "sbt-scala-module"   % "2.3.0")
-addSbtPlugin("ch.epfl.scala"          % "sbt-version-policy" % "1.0.1")
+addSbtPlugin("org.scala-lang.modules" % "sbt-scala-module"   % "3.0.0")

Diff for: project/plugins.sbt

@@ -2,7 +2,6 @@ package scala.swing
 
 import javax.swing.{Icon, JInternalFrame, WindowConstants}
 
-import scala.swing.MenuBar.NoMenuBar
 import scala.swing.event.{InternalFrameActivated, InternalFrameClosed, InternalFrameClosing, InternalFrameDeactivated, InternalFrameDeiconified, InternalFrameIconified, InternalFrameOpened}