[WIP] Refactor Java2d backend

`frame.canvas()` now returns a `Resource[IO, Canvas]`, to manage the
resources a `Canvas` can control. Additionally, for the Java2d backend:

- Clear separation between Swing / Java threads and Cats Effect
components, makes reasoning easier
- Better concurrency control avoids deadlock
- Better resource management shutdowns cleanly when it should
- Miscellaneous simplifications

Still to be done:

- Remove debugging statements
- Simplify `Reified` representation

.github/workflows/ci.yml

@@ -156,7 +156,7 @@ jobs:
 
   dependency-submission:
     name: Submit Dependencies
-    if: github.event_name != 'pull_request'
+    if: github.event.repository.fork == false && github.event_name != 'pull_request'
     strategy:
       matrix:
         os: [ubuntu-latest]

.scalafix.conf

@@ -3,3 +3,4 @@ rules = [
 ]
 OrganizeImports.removeUnused = false
 OrganizeImports.coalesceToWildcardImportThreshold = 5
+OrganizeImports.targetDialect = Scala3

CHANGELOG.md

@@ -8,6 +8,8 @@
 
 - Fix monospaced font rendering on SVG (by `@kulsoom2003`)
 
+- Complete reworking of Java2D backend to remove race conditions and manage resources correctly.
+
 
 ## 0.23.0 26-Jul-2024
 

build.sbt

@@ -31,8 +31,7 @@ ThisBuild / developers := List(
   tlGitHubDev("noelwelsh", "Noel Welsh")
 )
 
-// true by default, set to false to publish to s01.oss.sonatype.org
-ThisBuild / tlSonatypeUseLegacyHost := true
+ThisBuild / sonatypeCredentialHost := xerial.sbt.Sonatype.sonatypeLegacy
 
 lazy val scala3 = "3.3.3"
 
@@ -62,6 +61,8 @@ commands += Command.command("build") { state =>
 lazy val css = taskKey[Unit]("Build the CSS")
 
 lazy val commonSettings = Seq(
+  // This is needed when running examples
+  Compile / run / fork := true,
   libraryDependencies ++= Seq(
     Dependencies.munit.value,
     Dependencies.munitScalaCheck.value

canvas/src/main/scala/doodle/canvas/algebra/Path.scala

@@ -19,7 +19,7 @@ package doodle.canvas.algebra
 import doodle.algebra.Algebra
 import doodle.algebra.generic.*
 import doodle.core.*
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 trait Path extends GenericPath[CanvasDrawing] {
   self: Algebra { type Drawing[A] = Finalized[CanvasDrawing, A] } =>

canvas/src/main/scala/doodle/canvas/algebra/Shape.scala

@@ -20,7 +20,7 @@ import doodle.algebra.Algebra
 import doodle.algebra.generic.*
 import doodle.core.ClosedPath
 import doodle.core.Point
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 trait Shape extends GenericShape[CanvasDrawing] {
   self: Algebra { type Drawing[A] = Finalized[CanvasDrawing, A] } =>

canvas/src/main/scala/doodle/canvas/algebra/Text.scala

@@ -19,8 +19,8 @@ package doodle.canvas.algebra
 import doodle.algebra.Algebra
 import doodle.algebra.generic.*
 import doodle.core.BoundingBox
+import doodle.core.Transform as Tx
 import doodle.core.font.Font
-import doodle.core.{Transform as Tx}
 import org.scalajs.dom
 
 trait Text extends GenericText[CanvasDrawing] {

canvas/src/main/scala/doodle/canvas/effect/Canvas.scala

@@ -17,6 +17,7 @@
 package doodle.canvas.effect
 
 import cats.effect.IO
+import cats.effect.Resource
 import doodle.algebra.generic.Finalized
 import doodle.canvas.Picture
 import doodle.canvas.algebra.CanvasAlgebra
@@ -74,14 +75,14 @@ final case class Canvas(target: dom.Node, frame: Frame) {
   }
 }
 object Canvas {
-  def fromFrame(frame: Frame): IO[Canvas] = {
+  def fromFrame(frame: Frame): Resource[IO, Canvas] = {
     IO {
       val target = dom.document.getElementById(frame.id)
       if target == null then {
         throw new java.util.NoSuchElementException(
           s"Doodle Canvas could not be created, as could not find a DOM element with the requested id ${frame.id}"
         )
       } else Canvas(target, frame)
-    }
+    }.toResource
   }
 }

canvas/src/main/scala/doodle/canvas/effect/CanvasRenderer.scala

@@ -17,13 +17,14 @@
 package doodle.canvas.effect
 
 import cats.effect.IO
+import cats.effect.Resource
 import doodle.canvas.Algebra
 import doodle.canvas.Picture
 import doodle.effect.Renderer
 
 object CanvasRenderer extends Renderer[Algebra, Frame, Canvas] {
 
-  def canvas(description: Frame): IO[Canvas] =
+  def canvas(description: Frame): Resource[IO, Canvas] =
     Canvas.fromFrame(description)
 
   def render[A](canvas: Canvas)(picture: Picture[A]): IO[A] =

core/jvm/src/main/scala/doodle/syntax/Base64WriterSyntax.scala

@@ -21,8 +21,8 @@ import cats.effect.IO
 import cats.effect.unsafe.IORuntime
 import doodle.algebra.Algebra
 import doodle.algebra.Picture
+import doodle.core.Base64 as B64
 import doodle.core.format.Format
-import doodle.core.{Base64 as B64}
 import doodle.effect.Base64Writer
 import doodle.effect.DefaultFrame
 

core/shared/src/main/scala/doodle/algebra/Transform.scala

@@ -18,8 +18,8 @@ package doodle
 package algebra
 
 import doodle.core.Angle
+import doodle.core.Transform as Tx
 import doodle.core.Vec
-import doodle.core.{Transform as Tx}
 
 trait Transform extends Algebra {
   def transform[A](img: Drawing[A], tx: Tx): Drawing[A]

core/shared/src/main/scala/doodle/algebra/generic/Finalized.scala

@@ -22,7 +22,7 @@ import cats.Eval
 import cats.Later
 import cats.data.*
 import doodle.core.BoundingBox
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 /** A [[Finalized]] represents an effect that, when run, produces all the
   * information needed to layout an image (it "finalizes" all the information

core/shared/src/main/scala/doodle/algebra/generic/GenericPath.scala

@@ -20,7 +20,7 @@ package generic
 
 import cats.data.State
 import doodle.core.*
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 import scala.annotation.tailrec
 

core/shared/src/main/scala/doodle/algebra/generic/GenericShape.scala

@@ -20,7 +20,7 @@ package generic
 
 import cats.data.State
 import doodle.core.BoundingBox
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 trait GenericShape[G[_]] extends Shape {
   self: Algebra { type Drawing[A] = Finalized[G, A] } =>

core/shared/src/main/scala/doodle/algebra/generic/GenericText.scala

@@ -20,8 +20,8 @@ package generic
 
 import cats.data.State
 import doodle.core.BoundingBox
+import doodle.core.Transform as Tx
 import doodle.core.font.Font
-import doodle.core.{Transform as Tx}
 
 trait GenericText[G[_]] extends Text {
   self: Algebra { type Drawing[A] = Finalized[G, A] } =>

core/shared/src/main/scala/doodle/algebra/generic/GenericTransform.scala

@@ -18,7 +18,7 @@ package doodle
 package algebra
 package generic
 
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 trait GenericTransform[G[_]] extends Transform {
   self: Algebra { type Drawing[A] = Finalized[G, A] } =>

core/shared/src/main/scala/doodle/algebra/generic/package.scala

@@ -20,7 +20,7 @@ package algebra
 import cats.*
 import cats.data.*
 import cats.syntax.all.*
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 package object generic {
   type ContextTransform = DrawingContext => DrawingContext

core/shared/src/main/scala/doodle/effect/Base64Writer.scala

@@ -20,8 +20,8 @@ package effect
 import cats.effect.IO
 import doodle.algebra.Algebra
 import doodle.algebra.Picture
+import doodle.core.Base64 as B64
 import doodle.core.format.Format
-import doodle.core.{Base64 as B64}
 
 /** The Base64Writer type represent the ability to encode an image as a Base64
   * String in a given format.

core/shared/src/main/scala/doodle/effect/Renderer.scala

@@ -18,6 +18,7 @@ package doodle
 package effect
 
 import cats.effect.IO
+import cats.effect.Resource
 import doodle.algebra.Algebra
 import doodle.algebra.Picture
 
@@ -28,7 +29,7 @@ import doodle.algebra.Picture
 trait Renderer[+Alg <: Algebra, Frame, Canvas] {
 
   /** Construct a Canvas from a description. */
-  def canvas(description: Frame): IO[Canvas]
+  def canvas(description: Frame): Resource[IO, Canvas]
 
   /** Render a picture to a Canvas. */
   def render[A](canvas: Canvas)(picture: Picture[Alg, A]): IO[A]

core/shared/src/main/scala/doodle/random.scala

@@ -20,7 +20,7 @@ import cats.Comonad
 import cats.free.Free
 
 import scala.annotation.tailrec
-import scala.util.{Random as Rng}
+import scala.util.Random as Rng
 
 object random {
   type Random[A] = Free[RandomOp, A]

core/shared/src/main/scala/doodle/syntax/AbstractRendererSyntax.scala

@@ -18,6 +18,7 @@ package doodle
 package syntax
 
 import cats.effect.IO
+import cats.effect.Resource
 import cats.effect.unsafe.IORuntime
 import doodle.algebra.Algebra
 import doodle.algebra.Picture
@@ -79,15 +80,15 @@ trait AbstractRendererSyntax {
     ): IO[A] =
       renderer
         .canvas(frame.default)
-        .flatMap(canvas => drawWithCanvasToIO(canvas))
+        .use(canvas => drawWithCanvasToIO(canvas))
 
     /** Create an effect that, when run, will draw the `Picture` using the given
       * `Frame` options.
       */
     def drawWithFrameToIO[Frame, Canvas](frame: Frame)(implicit
         renderer: Renderer[Alg, Frame, Canvas]
     ): IO[A] =
-      renderer.canvas(frame).flatMap(canvas => drawWithCanvasToIO(canvas))
+      renderer.canvas(frame).use(canvas => drawWithCanvasToIO(canvas))
 
     /** Create an effect that, when run, will draw the `Picture` on the given
       * `Canvas`.
@@ -102,7 +103,7 @@ trait AbstractRendererSyntax {
   implicit class RendererFrameOps[Frame](frame: Frame) {
     def canvas[Alg <: Algebra, Canvas]()(implicit
         renderer: Renderer[Alg, Frame, Canvas]
-    ): IO[Canvas] =
+    ): Resource[IO, Canvas] =
       renderer.canvas(frame)
   }
 }

core/shared/src/main/scala/doodle/syntax/TransformSyntax.scala

@@ -21,8 +21,8 @@ import doodle.algebra.Algebra
 import doodle.algebra.Picture
 import doodle.algebra.Transform
 import doodle.core.Angle
+import doodle.core.Transform as Tx
 import doodle.core.Vec
-import doodle.core.{Transform as Tx}
 
 trait TransformSyntax {
   implicit class TransformPictureOps[Alg <: Algebra, A](

core/shared/src/test/scala/doodle/algebra/generic/Generators.scala

@@ -22,7 +22,7 @@ import cats.instances.unit.*
 import doodle.algebra.generic.*
 import doodle.algebra.generic.reified.Reification
 import doodle.algebra.generic.reified.Reified
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 import org.scalacheck.*
 
 trait Generators extends doodle.core.Generators {

core/shared/src/test/scala/doodle/algebra/generic/GenericAlgebraSpec.scala

@@ -19,8 +19,8 @@ package algebra
 package generic
 
 import cats.instances.unit.*
-import org.scalacheck.Prop.*
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object GenericAlgebraspec extends Properties("Generic algebra properties") {
   implicit val algebra: TestAlgebra = TestAlgebra()

core/shared/src/test/scala/doodle/algebra/generic/LayoutSpec.scala

@@ -21,9 +21,9 @@ package generic
 import cats.implicits.*
 import doodle.algebra.generic.reified.Reification
 import doodle.core.BoundingBox
-import doodle.core.{Transform as Tx}
-import org.scalacheck.Prop.*
+import doodle.core.Transform as Tx
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object LayoutSpec extends Properties("Layout properties") {
   val style = TestAlgebra()

core/shared/src/test/scala/doodle/algebra/generic/SizeSpec.scala

@@ -20,9 +20,9 @@ package generic
 
 import cats.implicits.*
 import doodle.algebra.generic.reified.Reification
-import doodle.core.{Transform as Tx}
-import org.scalacheck.Prop.*
+import doodle.core.Transform as Tx
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object SizeSpec extends Properties("Size properties") {
   implicit val algebra: TestAlgebra = TestAlgebra()

core/shared/src/test/scala/doodle/algebra/generic/StyleSpec.scala

@@ -18,8 +18,8 @@ package doodle
 package algebra
 package generic
 
-import org.scalacheck.Prop.*
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object StyleSpec extends Properties("Style properties") {
   val style = TestAlgebra()

core/shared/src/test/scala/doodle/algebra/generic/TextSpec.scala

@@ -18,8 +18,8 @@ package doodle
 package algebra
 package generic
 
-import org.scalacheck.Prop.*
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object TextSpec extends Properties("Text properties") {
   val algebra = TestAlgebra()

core/shared/src/test/scala/doodle/algebra/generic/reified/Reified.scala

@@ -21,8 +21,8 @@ package reified
 
 import doodle.core.PathElement
 import doodle.core.Point
+import doodle.core.Transform as Tx
 import doodle.core.font.Font
-import doodle.core.{Transform as Tx}
 
 sealed abstract class Reified extends Product with Serializable {
   def transform: Tx

core/shared/src/test/scala/doodle/algebra/generic/reified/ReifiedPath.scala

@@ -22,7 +22,7 @@ package reified
 import cats.data.WriterT
 import doodle.algebra.generic.*
 import doodle.core.*
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 trait ReifiedPath extends GenericPath[Reification] {
   self: Algebra { type Drawing[A] = TestAlgebra.Drawing[A] } =>

core/shared/src/test/scala/doodle/algebra/generic/reified/ReifiedShape.scala

@@ -22,7 +22,7 @@ package reified
 import cats.data.WriterT
 import doodle.algebra.generic.*
 import doodle.core.Point
-import doodle.core.{Transform as Tx}
+import doodle.core.Transform as Tx
 
 trait ReifiedShape extends GenericShape[Reification] {
   self: Algebra { type Drawing[A] = TestAlgebra.Drawing[A] } =>

core/shared/src/test/scala/doodle/algebra/generic/reified/ReifiedText.scala

@@ -22,8 +22,8 @@ package reified
 import cats.data.WriterT
 import doodle.algebra.generic.*
 import doodle.core.BoundingBox
+import doodle.core.Transform as Tx
 import doodle.core.font.Font
-import doodle.core.{Transform as Tx}
 
 trait ReifiedText extends GenericText[Reification] {
   self: Algebra { type Drawing[A] = TestAlgebra.Drawing[A] } =>

core/shared/src/test/scala/doodle/core/AngleSpec.scala

@@ -17,8 +17,8 @@
 package doodle
 package core
 
-import org.scalacheck.Prop.*
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object AngleSpec extends Properties("Angle properties") {
   import doodle.arbitrary.*

core/shared/src/test/scala/doodle/core/ClosedPathSpec.scala

@@ -17,8 +17,8 @@
 package doodle
 package core
 
-import org.scalacheck.Prop.*
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object ClosedPathSpec extends Properties("ClosedPath properties") {
   import Generators.*

core/shared/src/test/scala/doodle/core/ColorSpec.scala

@@ -17,8 +17,8 @@
 package doodle
 package core
 
-import org.scalacheck.Prop.*
 import org.scalacheck.*
+import org.scalacheck.Prop.*
 
 object ColorSpec extends Properties("Color properties") {
   import doodle.arbitrary.*