From 13d28be3d9a98c458da41da1f48130b07c4d3756 Mon Sep 17 00:00:00 2001
From: Tuukka Lehtonen <tuukka.lehtonen@semantum.fi>
Date: Thu, 3 Jun 2021 15:37:33 +0300
Subject: [PATCH] Add Simantics/Variables/{rviBinding,rviIsEmpty}

gitlab #720
---
 .../simantics/db/layer0/variable/Variables.java    | 10 ++++++++++
 .../scl/Simantics/Variables.scl                    | 14 +++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/variable/Variables.java b/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/variable/Variables.java
index 5fb0636a0..a35bcd355 100644
--- a/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/variable/Variables.java
+++ b/bundles/org.simantics.db.layer0/src/org/simantics/db/layer0/variable/Variables.java
@@ -814,4 +814,14 @@ final public class Variables {
         graph.claimLiteral(subject, predicate, L0.RVI, rvi, rviBinding);
     }
 
+    public static Binding rviBinding(ReadGraph graph) throws DatabaseException {
+        Databoard databoard = graph.getService(Databoard.class);
+        if (databoard == null) throw new DatabaseException("No databoard support in Session"); //$NON-NLS-1$
+        return databoard.getBindingUnchecked(RVI.class);
+    }
+
+    public static boolean isEmpty(RVI rvi) throws DatabaseException {
+        return rvi.parts.length == 0;
+    }
+
 }
diff --git a/bundles/org.simantics.scl.db/scl/Simantics/Variables.scl b/bundles/org.simantics.scl.db/scl/Simantics/Variables.scl
index 436e0a173..97c5644ac 100644
--- a/bundles/org.simantics.scl.db/scl/Simantics/Variables.scl
+++ b/bundles/org.simantics.scl.db/scl/Simantics/Variables.scl
@@ -84,7 +84,19 @@ Example:
     possibleConfigurationContext :: Resource -> <ReadGraph> Variable
 
     setRVIProperty :: Variable -> RVI -> <WriteGraph> ()
-    
+
+    """
+    Returns the Binding needed to read RVI type properties.
+    """
+    rviBinding :: <ReadGraph> Binding a
+
+    """
+    Returns True if the given RVI is empty in which case
+    `resolvePossible rvi var` would return `Just var`.
+    """
+    @JavaName isEmpty
+    rviIsEmpty :: RVI -> Boolean
+
 importJava "org.simantics.db.layer0.function.All" where
 
     standardGetValue1 :: Variable -> <ReadGraph> a
-- 
2.47.1