GraphUI BoxLayout: Margin is only ignored for center Alignment w/o Fill scale. {Box,Grid}Layout: Always remove Bottom-Left delta and refine API doc of incl scale behavior

GraphUI BoxLayout: Margin is only ignored for center Alignment w/o Fill scale.
  Margin outside of a shape is not scaled and hence must be considered
  when using Fill scale.

{Box,Grid}Layout: Always remove Bottom-Left delta
  Previously we were only dropping the negative extend.

  However, since our scale and center algo uses the AABBox width and height,
  which excludes the bottom-left delta, we have to drop such offset.

  TODO: Otherwise, we would need adjust for the bottom-left extend
  when NOT centering for each direction!
  This might be a useful enhancement in case one likes to drop
  shapes as-is w/o centering.

{Box,Grid}Layout: Refine API doc of  incl scale behavior

6 files changed, 114 insertions, 102 deletions

diff --git a/src/demos/com/jogamp/opengl/demos/graph/ui/UILayoutBox01.java b/src/demos/com/jogamp/opengl/demos/graph/ui/UILayoutBox01.java
index 70db5d696..cef57d503 100644
--- a/src/demos/com/jogamp/opengl/demos/graph/ui/UILayoutBox01.java
+++ b/src/demos/com/jogamp/opengl/demos/graph/ui/UILayoutBox01.java
@@ -346,7 +346,15 @@ public class UILayoutBox01 {
             groups.add(g);
         }
         ++id;
+        nextPos.setX( nextPos.x() + sxy * cellGap );
+
+        if( true ) {
+            final Group g = fillDemoGroup(new Group( new BoxLayout( 1f, 1f, Alignment.FillCenter, margin, null ) ),
+                                          reqGLP, scene, zEps, sxy, nextPos, font, id, dragZoomRotateListener);
+            groups.add(g);
+        }
         nextPos.set(0, nextPos.y() + sxy * cellGap, 0);
+        ++id;
 
         //
         // 3. Row
@@ -385,7 +393,7 @@ public class UILayoutBox01 {
         ++id;
 
         if( true ) {
-            final Group g = fillDemoGroup(new Group( new BoxLayout( 1f, 1f, Alignment.Fill, new Margin(), padding ) ),
+            final Group g = fillDemoGroup(new Group( new BoxLayout( 1f, 1f, Alignment.Fill, margin, padding ) ),
                                           reqGLP, scene, zEps, sxy, nextPos, font, id, dragZoomRotateListener);
             groups.add(g);
         }
@@ -393,7 +401,7 @@ public class UILayoutBox01 {
         ++id;
 
         if( true ) {
-            final Group g = fillDemoGroup(new Group( new BoxLayout( 1f, 1f, Alignment.Fill, margin, padding ) ),
+            final Group g = fillDemoGroup(new Group( new BoxLayout( 1f, 1f, Alignment.FillCenter, margin, padding ) ),
                                           reqGLP, scene, zEps, sxy, nextPos, font, id, dragZoomRotateListener);
             groups.add(g);
         }
diff --git a/src/graphui/classes/com/jogamp/graph/ui/layout/Alignment.java b/src/graphui/classes/com/jogamp/graph/ui/layout/Alignment.java
index d8c6f8605..36671d32a 100644
--- a/src/graphui/classes/com/jogamp/graph/ui/layout/Alignment.java
+++ b/src/graphui/classes/com/jogamp/graph/ui/layout/Alignment.java
@@ -55,14 +55,14 @@ public final class Alignment {
         /** Top alignment. */
         Top ( ( 1 << 3 ) ),
 
+        /** Scale object to parent size, e.g. fill {@link GridLayout} or {@link BoxLayout} cell size. */
+        Fill ( ( 1 << 4 ) ),
+
         /** Horizontal center alignment. */
-        CenterHoriz ( ( 1 << 4 ) ),
+        CenterHoriz ( ( 1 << 5 ) ),
 
         /** Vertical center alignment. */
-        CenterVert ( ( 1 << 5 ) ),
-
-        /** Scale object to parent size, e.g. fill {@link GridLayout} or {@link BoxLayout} cell size. */
-        Fill ( ( 1 << 15 ) );
+        CenterVert ( ( 1 << 6 ) );
 
         Bit(final int v) { value = v; }
         public final int value;
diff --git a/src/graphui/classes/com/jogamp/graph/ui/layout/BoxLayout.java b/src/graphui/classes/com/jogamp/graph/ui/layout/BoxLayout.java
index 57a83b4e7..340060e02 100644
--- a/src/graphui/classes/com/jogamp/graph/ui/layout/BoxLayout.java
+++ b/src/graphui/classes/com/jogamp/graph/ui/layout/BoxLayout.java
@@ -44,8 +44,8 @@ import com.jogamp.opengl.util.PMVMatrix;
  * <ul>
  *   <li>Optionally centered {@link Alignment.Bit#CenterHoriz horizontally}, {@link Alignment.Bit#CenterVert vertically} or {@link Alignment#Center both}.</li>
  *   <li>Optionally scaled to cell-size if given and {@link Alignment#Fill}</li>
- *   <li>Padding is applied to each {@Shape} via {@link Shape#setPaddding(Padding)} if passed in constructor</li>
- *   <li>Margin is ignored on dimension with center {@link Alignment}</li>
+ *   <li>{@link Padding} is applied to each {@Shape} via {@link Shape#setPaddding(Padding)} if passed in constructor and is scaled if {@link Alignment.Bit#Fill}</li>
+ *   <li>{@link Margin} is applied unscaled if used and ignored with only center {@link Alignment} w/o {@link Alignment.Bit#Fill} scale</li>
  *   <li>Not implemented {@link Alignment}: {@link Alignment.Bit#Top Top}, {@link Alignment.Bit#Right Right}, {@link Alignment.Bit#Bottom Bottom}, {@link Alignment.Bit#Left Left}</li>
  * </ul>
  * </p>
@@ -53,8 +53,8 @@ import com.jogamp.opengl.util.PMVMatrix;
 public class BoxLayout implements Group.Layout {
     private final Vec2f cellSize;
     private final Alignment alignment;
-    private final Margin margin;
-    private final Padding padding;
+    private final Margin margin; // unscaled
+    private final Padding padding; // scaled
 
     private static final boolean TRACE_LAYOUT = false;
 
@@ -67,77 +67,88 @@ public class BoxLayout implements Group.Layout {
 
     /**
      *
-     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)}
+     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)} and is scaled if {@link Alignment.Bit#Fill}
      */
     public BoxLayout(final Padding padding) {
         this(0f, 0f, new Alignment(), new Margin(), padding);
     }
 
-    public BoxLayout(final float width, final float height) {
-        this(width, height, new Alignment(), new Margin(), null);
+    public BoxLayout(final float cellWidth, final float cellHeight) {
+        this(cellWidth, cellHeight, new Alignment(), new Margin(), null);
     }
 
     /**
      *
-     * @param width
-     * @param height
+     * @param cellWidth
+     * @param cellHeight
      * @param alignment
      */
-    public BoxLayout(final float width, final float height, final Alignment alignment) {
-        this(width, height, alignment, new Margin(), null);
+    public BoxLayout(final float cellWidth, final float cellHeight, final Alignment alignment) {
+        this(cellWidth, cellHeight, alignment, new Margin(), null);
     }
 
     /**
      *
-     * @param width
-     * @param height
-     * @param margin
+     * @param cellWidth
+     * @param cellHeight
+     * @param margin {@link Margin} is applied unscaled and ignored with only center {@link Alignment} w/o {@link Alignment.Bit#Fill} scale
      */
-    public BoxLayout(final float width, final float height, final Margin margin) {
-        this(width, height, new Alignment(), margin, null);
+    public BoxLayout(final float cellWidth, final float cellHeight, final Margin margin) {
+        this(cellWidth, cellHeight, new Alignment(), margin, null);
     }
 
     /**
      *
-     * @param width
-     * @param height
-     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)}
+     * @param cellWidth
+     * @param cellHeight
+     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)} and is scaled if {@link Alignment.Bit#Fill}
      */
-    public BoxLayout(final float width, final float height, final Padding padding) {
-        this(width, height, new Alignment(), new Margin(), padding);
+    public BoxLayout(final float cellWidth, final float cellHeight, final Padding padding) {
+        this(cellWidth, cellHeight, new Alignment(), new Margin(), padding);
     }
 
     /**
      *
-     * @param width
-     * @param height
-     * @param margin
-     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)}
+     * @param cellWidth
+     * @param cellHeight
+     * @param margin {@link Margin} is applied unscaled and ignored with only center {@link Alignment} w/o {@link Alignment.Bit#Fill} scale
+     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)} and is scaled if {@link Alignment.Bit#Fill}
      */
-    public BoxLayout(final float width, final float height, final Margin margin, final Padding padding) {
-        this(width, height, new Alignment(), margin, padding);
+    public BoxLayout(final float cellWidth, final float cellHeight, final Margin margin, final Padding padding) {
+        this(cellWidth, cellHeight, new Alignment(), margin, padding);
     }
 
     /**
      *
-     * @param width
-     * @param height
-     * @param margin
+     * @param cellWidth
+     * @param cellHeight
+     * @param margin {@link Margin} is applied unscaled
      */
-    public BoxLayout(final float width, final float height, final Alignment alignment, final Margin margin) {
-        this(width, height, alignment, margin, null);
+    public BoxLayout(final float cellWidth, final float cellHeight, final Alignment alignment, final Margin margin) {
+        this(cellWidth, cellHeight, alignment, margin, null);
     }
 
     /**
      *
-     * @param width
-     * @param height
+     * @param cellWidth
+     * @param cellHeight
      * @param alignment
-     * @param margin
-     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)}
+     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)} and is scaled if {@link Alignment.Bit#Fill}
      */
-    public BoxLayout(final float width, final float height, final Alignment alignment, final Margin margin, final Padding padding) {
-        this.cellSize = new Vec2f(Math.max(0f, width), Math.max(0f, height));
+    public BoxLayout(final float cellWidth, final float cellHeight, final Alignment alignment, final Padding padding) {
+        this(cellWidth, cellHeight, alignment, new Margin(), padding);
+    }
+
+    /**
+     *
+     * @param cellWidth
+     * @param cellHeight
+     * @param alignment
+     * @param margin {@link Margin} is applied unscaled and ignored with only center {@link Alignment} w/o {@link Alignment.Bit#Fill} scale
+     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)} and is scaled if {@link Alignment.Bit#Fill}
+     */
+    public BoxLayout(final float cellWidth, final float cellHeight, final Alignment alignment, final Margin margin, final Padding padding) {
+        this.cellSize = new Vec2f(Math.max(0f, cellWidth), Math.max(0f, cellHeight));
         this.alignment = alignment;
         this.margin = margin;
         this.padding = padding;
@@ -185,21 +196,26 @@ public class BoxLayout implements Group.Layout {
             }
 
             // IF isScaled: Uniform scale w/ lowest axis scale and center position on lower-scale axis
-            final float shapeWidthU     = sbox.getWidth() + margin.width();
-            final float shapeWidthU_LH  = ( sbox.getWidth()  * 0.5f ) + margin.left;   // left-half
-            final float shapeHeightU    = sbox.getHeight() + margin.height();
-            final float shapeHeightU_BH = ( sbox.getHeight() * 0.5f ) + margin.bottom; // bottom-half
+            final float shapeWidthU  = sbox.getWidth();
+            final float shapeHeightU = sbox.getHeight();
             final float sxy;
             float dxh = 0, dyh = 0;
             if( isScaled ) {
-                // scaling to cell size, implies center (horiz + vert)
-                final float cellWidth2 = hasCellWidth ? cellSize.x() : shapeWidthU;
-                final float cellHeight2 = hasCellHeight ? cellSize.y() : shapeHeightU;
+                // scaling to cell size
+                final float cellWidth2 = hasCellWidth ? cellSize.x() - margin.width() : shapeWidthU;
+                final float cellHeight2 = hasCellHeight ? cellSize.y() - margin.height() : shapeHeightU;
                 final float sx = cellWidth2 / shapeWidthU;
                 final float sy = cellHeight2/ shapeHeightU;
                 sxy = sx < sy ? sx : sy;
-                dxh += sxy * margin.left   + shapeWidthU_LH  * ( sx - sxy ); // adjustment for scale-axis
-                dyh += sxy * margin.bottom + shapeHeightU_BH * ( sy - sxy ); // ditto
+
+                if( isCenteredHoriz ) {
+                    dxh += shapeWidthU  * ( sx - sxy ) * 0.5f; // horiz-center (adjustment for scale-axis)
+                }
+                if( isCenteredVert ) {
+                    dyh += shapeHeightU * ( sy - sxy ) * 0.5f; // vert-center (adjustment for scale-axis)
+                }
+                dyh += margin.bottom;
+                dxh += margin.left;
                 if( TRACE_LAYOUT ) {
                     System.err.println("bl("+i+").s: "+sx+" x "+sy+" -> "+sxy+": +"+dxh+" / "+dyh+", U: s "+shapeWidthU+" x "+shapeHeightU+", sz "+cellWidth2+" x "+cellHeight2);
                 }
@@ -212,22 +228,19 @@ public class BoxLayout implements Group.Layout {
             final float cellHeightS = hasCellHeight ? cellSize.y() : shapeHeightS;
 
             if( !isScaled ) {
-                // Use half delta of net-size to center, margin is ignored when centering
-                final float shapeWidthS_H = sxy * sbox.getWidth() * 0.5f;
-                final float shapeHeightS_H = sxy * sbox.getHeight() * 0.5f;
-                final float cellWidthS_H = hasCellWidth ? cellSize.x() * 0.5f : shapeWidthS_H;
-                final float cellHeightS_H = hasCellHeight ? cellSize.y() * 0.5f : shapeHeightS_H;
+                // Center w/o scale and ignoring margin (not scaled)
                 if( isCenteredHoriz ) {
-                    dxh += cellWidthS_H - shapeWidthS_H; // horiz-center
+                    dxh += 0.5f * ( cellWidthS - shapeWidthS ); // horiz-center
                 } else {
-                    dxh += sxy * margin.left;
+                    dxh += margin.left;
                 }
                 if( isCenteredVert ) {
-                    dyh += cellHeightS_H - shapeHeightS_H; // vert-center
+                    dyh += 0.5f * ( cellHeightS - shapeHeightS ); // vert-center
                 } else {
-                    dyh += sxy * margin.bottom;
+                    dyh += margin.bottom;
                 }
             }
+
             if( TRACE_LAYOUT ) {
                 System.err.println("bl("+i+").m: "+x+" / "+y+" + "+dxh+" / "+dyh+", sxy "+sxy+", S: s "+shapeWidthS+" x "+shapeHeightS+", sz "+cellWidthS+" x "+cellHeightS);
             }
@@ -238,16 +251,12 @@ public class BoxLayout implements Group.Layout {
                 final float aY = y + dyh;
                 s.moveTo( aX, aY, s.getPosition().z() );
 
-                // remove the bottom-left delta
-                final Vec3f diffBL = new Vec3f();
-                final AABBox sbox0 = s.getBounds();
-                if( !diffBL.set( sbox0.getLow().x(), sbox0.getLow().y(), 0).min( zeroVec3 ).isZero() ) {
-                    // pmv.mulMvMatVec3f(diffBL).scale(-1f, -1f, 0f);
-                    final Vec3f ss = s.getScale();
-                    diffBL.scale(-1f*ss.x(), -1f*ss.y(), 0f);
-                }
+                // Remove the bottom-left delta
+                final Vec3f diffBL = new Vec3f(s.getBounds().getLow());
+                diffBL.setZ(0);
+                diffBL.scale(s.getScale()).scale(-1f);
                 if( TRACE_LAYOUT ) {
-                    System.err.println("bl("+i+").bl: sbox0 "+sbox0+", diffBL "+diffBL);
+                    System.err.println("bl("+i+").bl: sbox0 "+s.getBounds()+", diffBL_ "+diffBL);
                 }
                 s.move( diffBL.scale(sxy) );
 
diff --git a/src/graphui/classes/com/jogamp/graph/ui/layout/Gap.java b/src/graphui/classes/com/jogamp/graph/ui/layout/Gap.java
index 35174a87d..61d93c03c 100644
--- a/src/graphui/classes/com/jogamp/graph/ui/layout/Gap.java
+++ b/src/graphui/classes/com/jogamp/graph/ui/layout/Gap.java
@@ -30,7 +30,7 @@ package com.jogamp.graph.ui.layout;
 import com.jogamp.opengl.math.FloatUtil;
 
 /**
- * GraphUI CSS property Gap, spaceing between (grid) cells not belonging to the element.
+ * GraphUI CSS property Gap, spacing between (grid) cells not belonging to the element.
  * <p>
  * The CSS gap property defines the size of the gap between the rows and columns in a grid layout.
  * </p>
diff --git a/src/graphui/classes/com/jogamp/graph/ui/layout/GridLayout.java b/src/graphui/classes/com/jogamp/graph/ui/layout/GridLayout.java
index 8f83678c1..50f847df4 100644
--- a/src/graphui/classes/com/jogamp/graph/ui/layout/GridLayout.java
+++ b/src/graphui/classes/com/jogamp/graph/ui/layout/GridLayout.java
@@ -44,8 +44,9 @@ import com.jogamp.opengl.util.PMVMatrix;
  * <ul>
  *   <li>Optionally centered {@link Alignment.Bit#CenterHoriz horizontally}, {@link Alignment.Bit#CenterVert vertically} or {@link Alignment#Center both}.</li>
  *   <li>Optionally scaled to cell-size if given and {@link Alignment#Fill}</li>
- *   <li>Padding is applied to each {@Shape} via {@link Shape#setPaddding(Padding)} if passed in constructor</li>
- *   <li>Without cell-size behaves like a grid bag using individual shape sizes including padding</li>
+ *   <li>{@link Padding} is applied to each {@Shape} via {@link Shape#setPaddding(Padding)} if passed in constructor and is scaled if {@link Alignment.Bit#Fill}</li>
+ *   <li>Without cell-size behaves like a grid bag using individual shape sizes including {@link Padding}</li>
+ *   <li>{@link Gap} is applied unscaled if used.</li>
  *   <li>Can be filled in {@link Order#COLUMN} or {@link Order#ROW} major-order.</li>
  *   <li>Not implemented {@link Alignment}: {@link Alignment.Bit#Top Top}, {@link Alignment.Bit#Right Right}, {@link Alignment.Bit#Bottom Bottom}, {@link Alignment.Bit#Left Left}</li>
  *   <li>..</li>
@@ -66,7 +67,7 @@ public class GridLayout implements Group.Layout {
     private final Vec2f cellSize;
     private final Alignment alignment;
     private final Gap gap;
-    private final Padding padding;
+    private final Padding padding; // scaled!
     private int row_count, col_count;
 
     private static final boolean TRACE_LAYOUT = false;
@@ -88,7 +89,7 @@ public class GridLayout implements Group.Layout {
      * @param cellWidth
      * @param cellHeight
      * @param alignment TODO
-     * @param gap
+     * @param gap {@link Gap} is applied unscaled
      */
     public GridLayout(final int column_limit, final float cellWidth, final float cellHeight, final Alignment alignment, final Gap gap) {
         this(alignment, Math.max(1, column_limit), -1, cellWidth, cellHeight, gap, null);
@@ -100,8 +101,8 @@ public class GridLayout implements Group.Layout {
      * @param cellWidth
      * @param cellHeight
      * @param alignment TODO
-     * @param gap
-     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)}
+     * @param gap {@link Gap} is applied unscaled
+     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)} and is scaled if {@link Alignment.Bit#Fill}
      */
     public GridLayout(final int column_limit, final float cellWidth, final float cellHeight, final Alignment alignment, final Gap gap, final Padding padding) {
         this(alignment, Math.max(1, column_limit), -1, cellWidth, cellHeight, gap, padding);
@@ -112,7 +113,7 @@ public class GridLayout implements Group.Layout {
      * @param cellWidth
      * @param cellHeight
      * @param alignment TODO
-     * @param gap
+     * @param gap {@link Gap} is applied unscaled
      * @param row_limit [1..inf)
      */
     public GridLayout(final float cellWidth, final float cellHeight, final Alignment alignment, final Gap gap, final int row_limit) {
@@ -124,8 +125,8 @@ public class GridLayout implements Group.Layout {
      * @param cellWidth
      * @param cellHeight
      * @param alignment TODO
-     * @param gap
-     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)}
+     * @param gap {@link Gap} is applied unscaled
+     * @param padding {@link Padding} applied to each {@Shape} via {@link Shape#setPaddding(Padding)} and is scaled if {@link Alignment.Bit#Fill}
      * @param row_limit [1..inf)
      */
     public GridLayout(final float cellWidth, final float cellHeight, final Alignment alignment, final Gap gap, final Padding padding, final int row_limit) {
@@ -205,11 +206,11 @@ public class GridLayout implements Group.Layout {
             pmv.glPopMatrix();
             final AABBox sbox = sboxes[i];
 
+            final float shapeWidthU  = sbox.getWidth();
+            final float shapeHeightU = sbox.getHeight();
             final float sxy;
             if( isScaled ) {
                 // scaling to cell size
-                final float shapeWidthU = sbox.getWidth();
-                final float shapeHeightU = sbox.getHeight();
                 final float cellWidthU = hasCellWidth ? cellSize.x() : shapeWidthU;
                 final float cellHeightU = hasCellHeight ? cellSize.y() : shapeHeightU;
                 final float sx = cellWidthU / shapeWidthU;
@@ -218,8 +219,8 @@ public class GridLayout implements Group.Layout {
             } else {
                 sxy = 1;
             }
-            final float shapeWidthS = sxy*sbox.getWidth();
-            final float shapeHeightS = sxy*sbox.getHeight();
+            final float shapeWidthS = sxy * shapeWidthU;
+            final float shapeHeightS = sxy * shapeHeightU;
             final float cellWidthS = hasCellWidth ? cellSize.x() : shapeWidthS;
             final float cellHeightS = hasCellHeight ? cellSize.y() : shapeHeightS;
 
@@ -274,12 +275,12 @@ public class GridLayout implements Group.Layout {
             }
 
             // IF isScaled: Uniform scale w/ lowest axis scale and center position on lower-scale axis
+            final float shapeWidthU = sbox.getWidth();
+            final float shapeHeightU = sbox.getHeight();
             final float sxy;
             float dxh = 0, dyh = 0;
             if( isScaled ) {
                 // scaling to cell size
-                final float shapeWidthU = sbox.getWidth();
-                final float shapeHeightU = sbox.getHeight();
                 final float cellWidth2 = hasCellWidth ? cellSize.x() : shapeWidthU;
                 final float cellHeight2 = hasCellHeight ? cellSize.y() : shapeHeightU;
                 final float sx = cellWidth2 / shapeWidthU;
@@ -293,8 +294,8 @@ public class GridLayout implements Group.Layout {
             } else {
                 sxy = 1;
             }
-            final float shapeWidthS = sxy*sbox.getWidth();
-            final float shapeHeightS = sxy*sbox.getHeight();
+            final float shapeWidthS = sxy * shapeWidthU;
+            final float shapeHeightS = sxy * shapeHeightU;
             final float cellWidthS = hasCellWidth ? cellSize.x() : shapeWidthS;
             final float cellHeightS = hasCellHeight ? cellSize.y() : shapeHeightS;
 
@@ -317,17 +318,11 @@ public class GridLayout implements Group.Layout {
                 s.moveTo( aX, aY, s.getPosition().z() );
 
                 // Remove the bottom-left delta
-                final Vec3f diffBL = new Vec3f();
-                {
-                    final AABBox sbox0 = s.getBounds();
-                    if( !diffBL.set( sbox0.getLow().x(), sbox0.getLow().y(), 0).min( zeroVec3 ).isZero() ) {
-                        // pmv.mulMvMatVec3f(diffBL_).scale(-1f, -1f, 0f);
-                        final Vec3f ss = s.getScale();
-                        diffBL.scale(-1f*ss.x(), -1f*ss.y(), 0f);
-                    }
-                    if( TRACE_LAYOUT ) {
-                        System.err.println("gl("+i+")["+col_i+"]["+row_i+"].bl: sbox0 "+sbox0+", diffBL_ "+diffBL);
-                    }
+                final Vec3f diffBL = new Vec3f(s.getBounds().getLow());
+                diffBL.setZ(0);
+                diffBL.scale(s.getScale()).scale(-1f);
+                if( TRACE_LAYOUT ) {
+                    System.err.println("gl("+i+")["+col_i+"]["+row_i+"].bl: sbox0 "+s.getBounds()+", diffBL_ "+diffBL);
                 }
                 s.move( diffBL.scale(sxy) );
 
diff --git a/src/graphui/classes/com/jogamp/graph/ui/layout/Margin.java b/src/graphui/classes/com/jogamp/graph/ui/layout/Margin.java
index 6e4bef169..72d366ae2 100644
--- a/src/graphui/classes/com/jogamp/graph/ui/layout/Margin.java
+++ b/src/graphui/classes/com/jogamp/graph/ui/layout/Margin.java
@@ -35,7 +35,7 @@ import com.jogamp.opengl.math.FloatUtil;
  * The CSS margin properties are used to create space around elements, outside of any defined borders.
  * </p>
  * <p>
- * Center alignment is defined via {@link Alignment} and {@link Margin} ignored on centered dimension.
+ * Center alignment is defined via {@link Alignment} and {@link Margin} ignored with only center {@link Alignment} w/o {@link Alignment.Bit#Fill} scale.
  * </p>
  */
 public class Margin {