6 files changed, 45 insertions, 41 deletions
diff --git a/core/src/ch/asynk/gdx/tabletop/ui/Assembly.java b/core/src/ch/asynk/gdx/tabletop/ui/Assembly.java
index 505bc2c..9facd26 100644
--- a/core/src/ch/asynk/gdx/tabletop/ui/Assembly.java
+++ b/core/src/ch/asynk/gdx/tabletop/ui/Assembly.java
@@ -45,9 +45,9 @@ public abstract class Assembly extends Element
         return false;
     }
 
-    @Override public void update()
+    @Override public void taint()
     {
-        children.forEach( c -> c.update() );
+        children.forEach( c -> c.taint() );
     }
 
     @Override public void draw(Batch batch)
diff --git a/core/src/ch/asynk/gdx/tabletop/ui/Button.java b/core/src/ch/asynk/gdx/tabletop/ui/Button.java
index cc9c6da..06688c9 100644
--- a/core/src/ch/asynk/gdx/tabletop/ui/Button.java
+++ b/core/src/ch/asynk/gdx/tabletop/ui/Button.java
@@ -8,11 +8,16 @@ import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
 public class Button extends Patch
 {
     private Label label;
-    private float spacing;
+    private float spacing;      // for label alignment;
 
     public Button(BitmapFont font, NinePatch patch)
     {
-        this(font, patch, 0, 0);
+        this(font, patch, 0);
+    }
+
+    public Button(BitmapFont font, NinePatch patch, float padding)
+    {
+        this(font, patch, padding, 0);
     }
 
     public Button(BitmapFont font, NinePatch patch, float padding, float spacing)
@@ -27,12 +32,8 @@ public class Button extends Patch
 
     public void write(String text)
     {
-        write(text, getX(), getY());
-    }
-
-    public void write(String text, float x, float y)
-    {
-        label.write(text, x, y);
+        label.write(text);
+        this.tainted = true;    // might impact Button's geometry
     }
 
     public void setLabelAlignment(Alignment alignment)
@@ -40,19 +41,19 @@ public class Button extends Patch
         label.setAlignment(alignment);
     }
 
-    @Override public void update()
+    @Override public void computeGeometry()
     {
-        label.preUpdate();      // compute width and height
-        rect.width = label.getWidth() + 2 * (padding + spacing);
-        rect.height = label.getHeight() + 2 * (padding + spacing);
-        super.update();
-        label.doUpdate();       // compute x and y
-        label.postUpdate();     // compute fx and fy
+        float dd = 2 * (padding + spacing);
+        rect.width = label.getWidth() + dd;
+        rect.height = label.getHeight() + dd;
+        super.computeGeometry();
+        label.computeGeometry();
     }
 
     @Override public void draw(Batch batch)
     {
         if (!visible) return;
+        if (tainted) computeGeometry();
         super.draw(batch);
         label.draw(batch);
     }
diff --git a/core/src/ch/asynk/gdx/tabletop/ui/Element.java b/core/src/ch/asynk/gdx/tabletop/ui/Element.java
index 17511a9..5b3c0fe 100644
--- a/core/src/ch/asynk/gdx/tabletop/ui/Element.java
+++ b/core/src/ch/asynk/gdx/tabletop/ui/Element.java
@@ -13,18 +13,20 @@ public abstract class Element implements Drawable, Touchable
     protected float padding;
     protected Element parent;
     protected Alignment alignment;
-    protected Rectangle rect;           // drawing coordinates
+    protected Rectangle rect;           // outer drawing coordinates
     protected float x, y;               // given position
+    protected boolean tainted;          // geometry must be computed
 
     protected Element()
     {
         this.blocked = false;
         this.visible = true;
         this.padding = 0;
-        this.rect = new Rectangle(0, 0, 0, 0);
         this.parent = null;
         this.alignment = alignment.RELATIVE;
+        this.rect = new Rectangle(0, 0, 0, 0);
         this.x = this.y = 0;
+        this.tainted = true;
     }
 
     @Override public final float getX()        { return rect.x; }
@@ -48,28 +50,37 @@ public abstract class Element implements Drawable, Touchable
         return rect.contains(x, y);
     }
 
+    public void taint()
+    {
+        this.tainted = true;
+    }
+
     @Override public void setPosition(float x, float y, float w, float h)
     {
         this.x = x;
         this.y = y;
-        rect.width = w;
-        rect.height = h;
-        // rect.set(rec.x, y, w, h);
+        this.rect.width = w;
+        this.rect.height = h;
+        this.tainted = true;
+        // rect.(x,y) will be set in computeGeometry
     }
 
     public void setParent(Element parent)
     {
         this.parent = parent;
+        this.tainted = true;
     }
 
     public void setPadding(float padding)
     {
         this.padding = padding;
+        this.tainted = true;
     }
 
     public void setAlignment(Alignment alignment)
     {
         this.alignment = alignment;
+        this.tainted = true;
     }
 
     public final void translate(float dx, float dy)
@@ -87,26 +98,18 @@ public abstract class Element implements Drawable, Touchable
        setPosition(x, y, rect.width, rect.height);
     }
 
-    protected void preUpdate() { }
-    protected void postUpdate() { }
-    protected void doUpdate()
+    protected void computeGeometry()
     {
         if (alignment == Alignment.ABSOLUTE || parent == null) {
             rect.x = x;
             rect.y = y;
         } else if (alignment == Alignment.RELATIVE) {
-            rect.x  = x + parent.getInnerX();
+            rect.x = x + parent.getInnerX();
             rect.y = y + parent.getInnerX();
         } else {
             rect.x = x + alignment.getX(parent, rect.width);
             rect.y = y + alignment.getY(parent, rect.height);
         }
-    }
-
-    public void update()
-    {
-        preUpdate();
-        doUpdate();
-        postUpdate();
+        this.tainted = false;
     }
 }
diff --git a/core/src/ch/asynk/gdx/tabletop/ui/Label.java b/core/src/ch/asynk/gdx/tabletop/ui/Label.java
index d2b5fc6..55eab83 100644
--- a/core/src/ch/asynk/gdx/tabletop/ui/Label.java
+++ b/core/src/ch/asynk/gdx/tabletop/ui/Label.java
@@ -39,17 +39,15 @@ public class Label extends Element
     public void write(String text, float x, float y)
     {
         this.text = text;
-        setPosition(x, y);
-    }
-
-    @Override protected void preUpdate()
-    {
         this.layout.setText(font, (text == null) ? "" : text);
-        super.setPosition(x, y, (layout.width + (2 * padding)), (layout.height + (2 * padding)));
+        this.rect.width = (layout.width + (2 * padding));
+        this.rect.height = (layout.height + (2 * padding));
+        this.tainted = true;
     }
 
-    @Override protected void postUpdate()
+    @Override protected void computeGeometry()
     {
+        super.computeGeometry();
         fx = getInnerX();
         fy = getInnerY() + layout.height;
     }
@@ -57,6 +55,7 @@ public class Label extends Element
     @Override public void draw(Batch batch)
     {
         if (!visible) return;
+        if (tainted) computeGeometry();
         font.draw(batch, layout, fx, fy);
     }
 }
diff --git a/core/src/ch/asynk/gdx/tabletop/ui/Patch.java b/core/src/ch/asynk/gdx/tabletop/ui/Patch.java
index c012f70..a829ce0 100644
--- a/core/src/ch/asynk/gdx/tabletop/ui/Patch.java
+++ b/core/src/ch/asynk/gdx/tabletop/ui/Patch.java
@@ -17,6 +17,7 @@ public class Patch extends Element
     @Override public void draw(Batch batch)
     {
         if (!visible) return;
+        if (tainted) computeGeometry();
         patch.draw(batch, getX(), getY(), getWidth(), getHeight());
     }
 }
diff --git a/core/src/ch/asynk/gdx/tabletop/ui/Root.java b/core/src/ch/asynk/gdx/tabletop/ui/Root.java
index f42a8df..99d63cf 100644
--- a/core/src/ch/asynk/gdx/tabletop/ui/Root.java
+++ b/core/src/ch/asynk/gdx/tabletop/ui/Root.java
@@ -11,6 +11,6 @@ public class Root extends Assembly
     public void resize(float width, float height)
     {
         setPosition(0, 0, width, height);
-        update();
+        taint();
     }
 }