--- a/flys-artifacts/src/main/java/de/intevation/flys/artifacts/model/MainValuesWFacet.java	Fri May 25 09:05:07 2012 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/model/MainValuesWFacet.java	Fri May 25 09:13:43 2012 +0000
@@ -3,13 +3,18 @@
 import java.util.ArrayList;
 import java.util.List;
 
+import org.apache.log4j.Logger;
+
 import de.intevation.artifacts.Artifact;
 import de.intevation.artifacts.CallContext;
+import de.intevation.artifacts.DataProvider;
 
 import de.intevation.artifactdatabase.state.DefaultFacet;
 
 import de.intevation.flys.artifacts.MainValuesArtifact;
+import de.intevation.flys.artifacts.math.Linear;
 import de.intevation.flys.artifacts.model.FacetTypes;
+import de.intevation.flys.artifacts.model.WQDay;
 import de.intevation.flys.jfree.FLYSAnnotation;
 import de.intevation.flys.jfree.StickyAxisAnnotation;
 
@@ -21,6 +26,9 @@
 extends      DefaultFacet
 implements   FacetTypes {
 
+    /** Own logger. */
+    private static Logger logger = Logger.getLogger(RelativePointFacet.class);
+
     /** Do we want MainValues at Gauge (not interpolated)? */
     protected boolean isAtGauge;
 
@@ -34,6 +42,40 @@
 
 
     /**
+     * Set the hit-point in W where a line drawn from the axis would hit the
+     * curve in WQDay (if hit).
+     * Employ linear interpolation.
+     */
+    protected static void setHitPoint(WQDay wqday, StickyAxisAnnotation annotation) {
+        int idx = 0;
+        float w = annotation.getPos();
+        boolean wIncreases = wqday.getW(0) < wqday.getW(wqday.size()-1);
+        if (wIncreases) {
+            while (idx < wqday.size() && wqday.getW(idx) < w) {
+                idx++;
+            }
+        }
+        else {
+            idx = wqday.size() -1;
+            while (idx > 0 && wqday.getW(idx) > w) {
+                idx--;
+            }
+        }
+
+        double day = 0d;
+        int mod = (wIncreases) ? -1 : +1;
+        if (idx != 0 && idx <= wqday.size()-1) {
+            day = Linear.linear(w, wqday.getW(idx +mod), wqday.getW(idx),
+                wqday.getDay(idx+mod), wqday.getDay(idx));
+            annotation.setHitPoint((float)day);
+        }
+        else {
+            logger.debug("StickyAnnotation does not hit wqday curve");
+        }
+    }
+
+
+    /**
      * Returns the data this facet requires.
      *
      * @param artifact the owner artifact.
@@ -48,11 +90,30 @@
         List<NamedDouble>      ws = mvArtifact.getMainValuesW(isAtGauge);
         List<StickyAxisAnnotation> xy = new ArrayList<StickyAxisAnnotation>();
 
+        // BLACKBOARD/DURATIONCURVE / reference point ...
+        WQDay wqdays = null;
+        List<DataProvider> providers = context.
+            getDataProvider(DurationCurveFacet.BB_DURATIONCURVE);
+        if (providers.size() < 1) {
+            logger.warn("Could not find durationcurve data provider.");
+        }
+        else {
+            wqdays = (WQDay) providers.get(0).provideData(
+                DurationCurveFacet.BB_DURATIONCURVE,
+                null,
+                context);
+        }
+
         for (NamedDouble w: ws) {
-            xy.add(new StickyAxisAnnotation(
-                w.getName(),
-                (float) w.getValue(),
-                StickyAxisAnnotation.SimpleAxis.Y_AXIS));
+            StickyAxisAnnotation annotation =
+                new StickyAxisAnnotation(
+                    w.getName(),
+                    (float) w.getValue(),
+                    StickyAxisAnnotation.SimpleAxis.Y_AXIS);
+            xy.add(annotation);
+            if (wqdays != null) {
+                setHitPoint(wqdays, annotation);
+            }
         }
 
         return new FLYSAnnotation(description, xy);