better wiring mouse listener, wire ends if connected to a pin

src/main/java/de/neemann/digital/draw/elements/Circuit.java

@@ -212,6 +212,18 @@ public class Circuit implements Drawable {
         return null;
     }
 
+    public boolean isPinPos(Vector pos) {
+        VisualElement el = getElementAt(pos);
+        if (el == null) return false;
+
+        for (Pin p : el.getPins())
+            if (p.getPos().equals(pos))
+                return true;
+
+        return false;
+    }
+
+
     public void modified() {
         modified = true;
     }

src/main/java/de/neemann/digital/gui/components/CircuitComponent.java

@@ -216,10 +216,15 @@ public class CircuitComponent extends JComponent {
             if (e.getButton() == MouseEvent.BUTTON1) {
                 if (wire != null) {
                     circuit.add(wire);
-                    repaint();
+                    Vector startPos = raster(getPosVector(e));
+                    if (circuit.isPinPos(startPos))
+                        wire = null;
+                    else
+                        wire = new Wire(startPos, startPos);
+                } else {
+                    Vector startPos = raster(getPosVector(e));
+                    wire = new Wire(startPos, startPos);
                 }
-                Vector startPos = raster(getPosVector(e));
-                wire = new Wire(startPos, startPos);
                 repaint();
             } else {
                 if (wire != null) {