java/examples/Basics/Input/Constrain/applet/Constrain.java

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+import processing.core.*; 
+
+import java.applet.*; 
+import java.awt.*; 
+import java.awt.image.*; 
+import java.awt.event.*; 
+import java.io.*; 
+import java.net.*; 
+import java.text.*; 
+import java.util.*; 
+import java.util.zip.*; 
+import java.util.regex.*; 
+
+public class Constrain extends PApplet {
+
+/**
+ * Constrain. 
+ * 
+ * Move the mouse across the screen to move the circle. 
+ * The program constrains the circle to its box. 
+ */
+ 
+float mx;
+float my;
+float easing = 0.05f;
+float esize = 25.0f;
+int box = 30;
+
+public void setup() 
+{
+  size(200, 200);
+  noStroke(); 
+  smooth();
+  ellipseMode(CENTER_RADIUS);  
+}
+
+public void draw() 
+{ 
+  background(51);
+  
+  if(abs(mouseX - mx) > 0.1f) {
+    mx = mx + (mouseX - mx) * easing;
+  }
+  if(abs(mouseY - my) > 0.1f) {
+    my = my + (mouseY- my) * easing;
+  }
+  
+  float distance = esize * 2;
+  mx = constrain(mx, box+distance, width-box-distance);
+  my = constrain(my, box+distance, height-box-distance);
+  fill(76);
+  rect(box+esize, box+esize, box*3, box*3);
+  fill(255);  
+  ellipse(mx, my, esize, esize);
+}
+
+  static public void main(String args[]) {
+    PApplet.main(new String[] { "Constrain" });
+  }
+}