[orx-processing] Fix PShape conversion when multiple ShapeContours are present

Add a demo to show it works.

I tested this in Processing and noticed
it's necessary to avoid wrapping the first vertices in `s.beginContour()` / `s.endContour()`, otherwise
it does not render properly there.

I also noticed that `createShape()` in Processing creates a `PShape(PShape.GEOMETRY)` by default, but we create a `PShape.PATH`. I tried changing this but it failed to work without further tweaks, so I kept it as `PATH` for now.

Author: hamoid

orx-jvm/orx-processing/src/demo/kotlin/DemoPShape01.kt

@@ -2,13 +2,20 @@ import org.openrndr.application
 import org.openrndr.extra.processing.PShape
 import org.openrndr.extra.processing.toShape
 
+/**
+ * Demonstrates how to construct a Processing `PShape` out of an OPENRNDR
+ * `Shape` instance, and how to convert a `PShape` back into a `Shape.
+ *
+ * The program renders a rectangular `Shape` after converting to PShape and back.
+ *
+ */
 fun main() = application {
     program {
-        val c = drawer.bounds.offsetEdges(-100.0).shape
-        val ps = PShape(c)
-        val rc = ps.toShape()
+        val s = drawer.bounds.offsetEdges(-100.0).shape
+        val ps = PShape(s)
+        val rs = ps.toShape()
         extend {
-            drawer.shape(rc)
+            drawer.shape(rs)
         }
     }
 }

orx-jvm/orx-processing/src/demo/kotlin/DemoPShape02.kt

@@ -4,6 +4,16 @@ import org.openrndr.extra.processing.PShape
 import org.openrndr.extra.processing.toShape
 import org.openrndr.extra.shapes.primitives.regularStarRounded
 
+/**
+ * Demonstrates how to convert a `ShapeContour` into a Processing
+ * `PShape`, then converts the `PShape` to a `Shape`.
+ *
+ * The program renders both the original `ShapeContour` and
+ * the resulting `Shape` after being a `PShape`.
+ *
+ * Both elements are rendered with translucency and a slight offset
+ * so they can be visually compared.
+ */
 fun main() = application {
     program {
         val c = regularStarRounded(
@@ -15,10 +25,11 @@ fun main() = application {
             center = drawer.bounds.center
         )
         val ps = PShape(c)
-        val rc = ps.toShape()
+        val rs = ps.toShape()
         extend {
             drawer.fill = ColorRGBa.PINK.opacify(0.5)
-            drawer.shape(rc)
+            drawer.shape(rs)
+
             drawer.translate(15.0, 15.0)
             drawer.contour(c)
         }

orx-jvm/orx-processing/src/demo/kotlin/DemoPShape03.kt

@@ -0,0 +1,37 @@
+import org.openrndr.application
+import org.openrndr.color.ColorRGBa
+import org.openrndr.extra.processing.PShape
+import org.openrndr.extra.processing.toShape
+import org.openrndr.extra.shapes.operators.roundCorners
+import org.openrndr.shape.Shape
+
+/**
+ * Demonstrates how to convert a `Shape` with multiple `ShapeContour`s
+ * (an outer contour and two holes) into a Processing `PShape`,
+ * then converts it back to a `Shape`.
+ *
+ * The program renders both the original `Shape` and
+ * the resulting `Shape` with translucency and a slight offset
+ * so they can be visually compared.
+ */
+fun main() = application {
+    program {
+        val outlineRect = drawer.bounds.offsetEdges(-100.0)
+        val s = Shape(
+            listOf(
+                outlineRect.contour.roundCorners(60.0),
+                outlineRect.sub(0.25..0.45, 0.25..0.75).contour.reversed.roundCorners(30.0),
+                outlineRect.sub(0.55..0.75, 0.25..0.75).contour.reversed.roundCorners(30.0),
+            )
+        )
+        val ps = PShape(s)
+        val rs = ps.toShape()
+        extend {
+            drawer.fill = ColorRGBa.PINK.opacify(0.5)
+            drawer.shape(rs)
+
+            drawer.translate(15.0, 15.0)
+            drawer.shape(s)
+        }
+    }
+}

orx-jvm/orx-processing/src/main/kotlin/PShapeExtensions.kt

@@ -92,8 +92,8 @@ fun PShape(shape: Shape): PShape {
     } else {
         val ps = PShape(PShape.PATH)
         ps.beginShape()
-        for (contour in shape.contours) {
-            ps.beginContour()
+        shape.contours.forEachIndexed { i, contour ->
+            if(i > 0) ps.beginContour()
             ps.vertex(contour.segments[0].start)
             for (segment in contour.segments) {
                 when (segment.type) {
@@ -102,7 +102,7 @@ fun PShape(shape: Shape): PShape {
                     SegmentType.CUBIC -> ps.bezierVertex(segment.control[0], segment.control[1], segment.end)
                 }
             }
-            ps.endContour()
+            if(i > 0) ps.endContour()
         }
         ps.endShape(PShape.CLOSE)
         return ps