[orx-fcurve] Add support for single constant values

orx-fcurve/src/commonMain/kotlin/FCurve.kt

@@ -477,6 +477,9 @@ private fun evaluateFCurveCommands(parts: List<String>): FCurve {
 }
 
 fun fcurve(d: String): FCurve {
+    val constantExpression = d.toDoubleOrNull()
+    if (constantExpression != null) {
+        return FCurve(listOf(Segment2D(Vector2(0.0, constantExpression), Vector2(0.0, constantExpression))))
+    }
     return evaluateFCurveCommands(fCurveCommands(d))
 }
-

orx-fcurve/src/commonTest/kotlin/TestEFCurve.kt

@@ -38,4 +38,31 @@ class TestEFCurve {
         val s = fc.sampler()
         assertEquals(0.0,  s(6.0))
     }
+
+    @Test
+    fun testConstantValue() {
+        val text = "10.5"
+        val fc = fcurve(efcurve(text))
+        assertEquals(10.5, fc.value(0.0))
+        assertEquals(10.5, fc.value(1.0))
+        assertEquals(10.5, fc.value(-1.0))
+
+        val normalizedSampler = fc.sampler(true)
+        assertEquals(10.5, normalizedSampler(0.0))
+        assertEquals(10.5, normalizedSampler(1.0))
+        assertEquals(10.5, normalizedSampler(-1.0))
+    }
+    @Test
+    fun testConstantExpression() {
+        val text = "${21.0 / 2.0}"
+        val fc = fcurve(efcurve(text))
+        assertEquals(10.5, fc.value(0.0))
+        assertEquals(10.5, fc.value(1.0))
+        assertEquals(10.5, fc.value(-1.0))
+
+        val normalizedSampler = fc.sampler(true)
+        assertEquals(10.5, normalizedSampler(0.0))
+        assertEquals(10.5, normalizedSampler(1.0))
+        assertEquals(10.5, normalizedSampler(-1.0))
+    }
 }

orx-fcurve/src/commonTest/kotlin/TestFCurve.kt

@@ -0,0 +1,19 @@
+import org.openrndr.extra.fcurve.fcurve
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class TestFCurve {
+    @Test
+    fun testConstantExpression() {
+        val text = "10.5"
+        val fc = fcurve(text)
+        assertEquals(10.5, fc.value(0.0))
+        assertEquals(10.5, fc.value(1.0))
+        assertEquals(10.5, fc.value(-1.0))
+
+        val normalizedSampler = fc.sampler(true)
+        assertEquals(10.5, normalizedSampler(0.0))
+        assertEquals(10.5, normalizedSampler(1.0))
+        assertEquals(10.5, normalizedSampler(-1.0))
+    }
+}