Camera: add parameter to allow text centering

src/main/kotlin/graphics/scenery/Camera.kt

@@ -336,14 +336,30 @@ open class Camera : DefaultNode("Camera"), HasRenderable, HasMaterial, HasCustom
      *
      * It will be shown for [duration] milliseconds, with a default of 3000.
      */
-    @JvmOverloads fun showMessage(message: String, distance: Float = 0.75f, size: Float = 0.05f, messageColor: Vector4f = Vector4f(1.0f), backgroundColor: Vector4f = Vector4f(0.0f), duration: Int = 3000) {
+    @JvmOverloads
+    fun showMessage(
+        message: String,
+        distance: Float = 0.75f,
+        size: Float = 0.05f,
+        messageColor: Vector4f = Vector4f(1.0f),
+        backgroundColor: Vector4f = Vector4f(0.0f),
+        duration: Int = 3000,
+        centered: Boolean = false
+    ) {
         val tb = TextBoard()
         tb.fontColor = messageColor
         tb.backgroundColor = backgroundColor
         tb.text = message
+        // Calculate the offset for text centering based on message length.
+        // The second divisor was eyeballed and might need adjustment.
+        val offset = if (centered) {
+            size * message.length.toFloat() / 2f / 5f
+        } else {
+            0f
+        }
         tb.spatial {
             scale = Vector3f(size, size, size)
-            position = Vector3f(0.0f, 0.0f, -1.0f * distance)
+            position = Vector3f(0.0f - offset, 0.0f, -1.0f * distance)
         }
 
         @Suppress("UNCHECKED_CAST")