From 84b26f9efcd62cc8c41bf3cd867482080d16d7a0 Mon Sep 17 00:00:00 2001
From: Sven Gothel <sgothel@jausoft.com>
Date: Sat, 23 Sep 2023 20:38:50 +0200
Subject: Bug 1454 - GraphUI Scene: Elevate active (selected) shape (add
 z-offset) and select (pick) in Z descending order

Picking (select) a shape shall process all shapes in Z descending order,
i.e. top shape first. This is a bug currently.

Note: Picking (selecting) a shape using a (mouse-)pointer device
is active by mouse-moved and not only mouse-clicked.
Therefor, we select shapes by mouse-over.

The active selected shape shall have an elevated Z offset to be rendered on top
of the others on same plane.
- This avoids them being rendered below others while moving them around etc.
- This also avoids flickering of overlapping shapes with mouse over.
- This stabilizes the UI experience
---
 src/graphui/classes/com/jogamp/graph/ui/Scene.java | 15 ++++++++++++++-
 src/graphui/classes/com/jogamp/graph/ui/Shape.java | 14 ++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/graphui/classes/com/jogamp/graph/ui/Scene.java b/src/graphui/classes/com/jogamp/graph/ui/Scene.java
index 388b7c1e1..25733a21d 100644
--- a/src/graphui/classes/com/jogamp/graph/ui/Scene.java
+++ b/src/graphui/classes/com/jogamp/graph/ui/Scene.java
@@ -560,7 +560,7 @@ public final class Scene implements Container, GLEventListener {
         final Ray ray = new Ray();
         shape[0] = null;
 
-        forSortedAll(Shape.ZAscendingComparator, pmv, (final Shape s, final PMVMatrix4f pmv2) -> {
+        forSortedAll(Shape.ZDescendingComparator, pmv, (final Shape s, final PMVMatrix4f pmv2) -> {
             final boolean ok = s.isInteractive() && pmv.mapWinToRay(glWinX, glWinY, winZ0, winZ1, viewport, ray);
             if( ok ) {
                 final AABBox sbox = s.getBounds();
@@ -916,11 +916,24 @@ public final class Scene implements Container, GLEventListener {
     }
 
     public void releaseActiveShape() {
+        if( null != activeShape && !FloatUtil.isZero(lastActiveZOffset) ) {
+            activeShape.move(0, 0, -lastActiveZOffset);
+            lastActiveZOffset = 0f;
+        }
         activeShape = null;
     }
     private void setActiveShape(final Shape shape) {
+        if( activeShape != shape ) {
+            releaseActiveShape();
+            lastActiveZOffset = zOffsetScale * getZEpsilon(16);
+            if( null != shape && !FloatUtil.isZero(lastActiveZOffset) ) {
+                shape.move(0, 0, +lastActiveZOffset);
+            }
+        }
         activeShape = shape;
     }
+    private float lastActiveZOffset = 0f;
+    private static final float zOffsetScale = 10f;
 
     private final class SBCGestureListener implements GestureHandler.GestureListener {
         @Override
diff --git a/src/graphui/classes/com/jogamp/graph/ui/Shape.java b/src/graphui/classes/com/jogamp/graph/ui/Shape.java
index 70ceb9f95..db7d7d9c2 100644
--- a/src/graphui/classes/com/jogamp/graph/ui/Shape.java
+++ b/src/graphui/classes/com/jogamp/graph/ui/Shape.java
@@ -1559,6 +1559,20 @@ public abstract class Shape {
             }
         } };
 
+    public static Comparator<Shape> ZDescendingComparator = new Comparator<Shape>() {
+        @Override
+        public int compare(final Shape s1, final Shape s2) {
+            final float s1Z = s1.getScaledMinZ()+s1.getPosition().z();
+            final float s2Z = s2.getScaledMinZ()+s2.getPosition().z();
+            if( FloatUtil.isEqual2(s1Z, s2Z) ) {
+                return 0;
+            } else if( s1Z < s2Z ){
+                return 1;
+            } else {
+                return -1;
+            }
+        } };
+
     //
     //
     //
-- 
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