Optimize rendering so objects outside visible area but within parent that's rendered aren't drawn

forge-gui-mobile/src/forge/Forge.java

@@ -560,11 +560,13 @@ public class Forge implements ApplicationListener {
 
     public static class Graphics {
         private Rectangle bounds;
+        private Rectangle visibleBounds;
         private int failedClipCount;
         private float alphaComposite = 1;
 
         private Graphics() {
             bounds = new Rectangle(0, 0, screenWidth, screenHeight);
+            visibleBounds = new Rectangle(bounds);
         }
 
         public void startClip() {
@@ -595,8 +597,14 @@ public class Forge implements ApplicationListener {
             bounds = new Rectangle(parentBounds.x + displayObj.getLeft(), parentBounds.y + displayObj.getTop(), displayObj.getWidth(), displayObj.getHeight());
             displayObj.setScreenPosition(bounds.x, bounds.y);
 
-            if (bounds.overlaps(parentBounds)) { //avoid drawing object if it's not within visible region
+            Rectangle intersection = Utils.getIntersection(bounds, visibleBounds);
+            if (intersection != null) { //avoid drawing object if it's not within visible region
+                final Rectangle backup = visibleBounds;
+                visibleBounds = intersection;
+
                 displayObj.draw(this);
+
+                visibleBounds = backup;
             }
 
             bounds = parentBounds;

forge-gui-mobile/src/forge/util/Utils.java

@@ -1,6 +1,7 @@
 package forge.util;
 
 import com.badlogic.gdx.Gdx;
+import com.badlogic.gdx.math.Rectangle;
 import com.badlogic.gdx.math.Vector2;
 
 public class Utils {
@@ -84,4 +85,18 @@ public class Utils {
         result.y = (p1.y + p2.y) / 2;
         return result;
     }
+
+    //get rectangle defining the interestion between two other rectangles
+    public static Rectangle getIntersection(Rectangle r1, Rectangle r2) {
+        float left = Math.max(r1.x, r2.x);
+        float right = Math.min(r1.x + r1.width, r2.x + r2.width);
+        if (right > left) {
+            float top = Math.max(r1.y, r2.y);
+            float bottom = Math.min(r1.y + r1.height, r2.y + r2.height);
+            if (bottom > top) {
+                return new Rectangle(left, top, right - left, bottom - top);
+            }
+        }
+        return null;
+    }
 }