Added a basic message state that allows various other code to

easily present "system" message to the user while in-game.  They
will scroll up automatically, fade out, and so on.  We'll smooth
scroll them later.

Author: pspeed42

sim-eth-basic/src/main/java/example/GameSessionState.java

@@ -37,6 +37,7 @@
 package example;
 
 import com.jme3.app.Application;
+import com.jme3.math.ColorRGBA;
 
 import com.simsilica.event.EventBus;
 import com.simsilica.lemur.GuiGlobals;
@@ -52,7 +53,8 @@
 public class GameSessionState extends CompositeAppState {
 
     public GameSessionState() {
-        // super(); add normal states on the super-constructor
+        // add normal states on the super-constructor
+        super(new MessageState()); 
 
         // Add states that need to support enable/disable independent of
         // the outer state using addChild().
@@ -70,17 +72,24 @@ protected void initialize( Application app ) {
 
         EventBus.publish(GameSessionEvent.sessionStarted, new GameSessionEvent());
 
+        getState(MessageState.class).addMessage("> You have joined the game.", ColorRGBA.Yellow);
+
         InputMapper inputMapper = GuiGlobals.getInstance().getInputMapper();
         inputMapper.activateGroup(MainGameFunctions.IN_GAME);            
     }
 
     @Override   
     protected void cleanup( Application app ) {
-        super.cleanup(app);
 
         InputMapper inputMapper = GuiGlobals.getInstance().getInputMapper();
         inputMapper.deactivateGroup(MainGameFunctions.IN_GAME);        
 
         EventBus.publish(GameSessionEvent.sessionEnded, new GameSessionEvent());
+ 
+        // The below will fail because there is no message state anymore... so
+        // it wouldn't show the message anyway.       
+        // getState(MessageState.class).addMessage("> You have left the game.", ColorRGBA.Yellow);
+                
+        super.cleanup(app);
     }
 }

sim-eth-basic/src/main/java/example/MessageState.java

@@ -0,0 +1,180 @@
+/*
+ * $Id$
+ * 
+ * Copyright (c) 2016, Simsilica, LLC
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions 
+ * are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright 
+ *    notice, this list of conditions and the following disclaimer.
+ * 
+ * 2. Redistributions in binary form must reproduce the above copyright 
+ *    notice, this list of conditions and the following disclaimer in 
+ *    the documentation and/or other materials provided with the 
+ *    distribution.
+ * 
+ * 3. Neither the name of the copyright holder nor the names of its 
+ *    contributors may be used to endorse or promote products derived 
+ *    from this software without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package example;
+
+import java.util.*;
+
+import com.jme3.app.Application;
+import com.jme3.app.state.BaseAppState;
+import com.jme3.math.*;
+import com.jme3.scene.*;
+import com.jme3.util.SafeArrayList; 
+
+import com.simsilica.lemur.*;
+import com.simsilica.lemur.style.ElementId;
+
+/**
+ *  Pops up various types of messages from the bottom of the screen.
+ *
+ *  @author    Paul Speed
+ */
+public class MessageState extends BaseAppState {
+ 
+    public static final ElementId MESSAGE_LABEL_ID = new ElementId("message.label");
+ 
+    private Node messageRoot;
+ 
+    private SafeArrayList<Message> messages = new SafeArrayList<>(Message.class);
+ 
+    private float fadeRate = 1/8f; // 8 seconds
+    
+    public MessageState() {
+    }
+    
+    public Label addMessage( String message ) {
+        return addMessage(new Label(message, MESSAGE_LABEL_ID));
+    }
+
+    public Label addMessage( String message, ColorRGBA color ) {
+        Label result = new Label(message, MESSAGE_LABEL_ID);
+        result.setColor(color);
+        addMessage(result);
+        return result;
+    }
+    
+    public <T extends Panel> T addMessage( T label ) {
+        messages.add(0, new Message(label));
+        messageRoot.attachChild(label);
+        refreshLayout();
+        return label;
+    }
+    
+    @Override
+    protected void initialize( Application app ) {
+ 
+        // We keep a root node that we can slide as new
+        // messages come in.  Initially we can just pop the
+        // new messages up relative to the messageRoot but eventually
+        // we can also animate this node to slide up from a lower
+        // position to make it look like the messages are sliding
+        // up smoothly.
+        messageRoot = new Node("MessageRoot");            
+    }
+    
+    @Override
+    protected void cleanup( Application app ) {
+    }
+ 
+    float nextTime = 1;
+    protected void addTestMessages( float tpf ) {
+        nextTime -= tpf;
+        if( nextTime < 0 ) {
+            nextTime = (float)(Math.random() * 1.9) + 0.1f;
+            int count = (int)(Math.random() * 4) + 1;
+            for( int i = 0; i < count; i++ ) {
+                if( (i % 2) == 0 ) {
+                    addMessage("> Tick " + System.currentTimeMillis());
+                } else { 
+                    addMessage("> Tock " + System.currentTimeMillis());
+                }
+            }
+        }
+    }
+       
+    public void update( float tpf ) {
+
+        //addTestMessages(tpf);
+        
+        for( Message m : messages.getArray() ) {
+            m.update(tpf);
+        }
+    }
+    
+    @Override
+    protected void onEnable() {
+        Node gui = ((Main)getApplication()).getGuiNode();
+        gui.attachChild(messageRoot);
+        
+        // Set a small margin for the messages
+        messageRoot.setLocalTranslation(5, 5, 0);
+    }
+    
+    @Override
+    protected void onDisable() {
+        messageRoot.removeFromParent();
+    }           
+ 
+    protected void refreshLayout() {
+        int height = getApplication().getCamera().getHeight();
+        int width = getApplication().getCamera().getWidth();
+ 
+        float y = 0;
+        for( Message m : messages.getArray() ) {
+            Vector3f pref = m.label.getPreferredSize();
+            y += pref.y;
+            m.label.setLocalTranslation(0, y, 0);
+            if( y > height ) {
+                // Off the screen so remove it
+                m.label.removeFromParent();
+                messages.remove(m);
+            }           
+        } 
+    }
+ 
+    private class Message {
+        private float alpha;
+        private float overrideAlpha = 0;
+        private Panel label;
+ 
+        public Message( Panel label ) {
+            this(label, 1);
+        }
+        
+        public Message( Panel label, float initialAlpha ) {
+            this.alpha = initialAlpha;
+            this.label = label;
+        }
+        
+        public void update( float tpf ) {
+            alpha -= tpf * fadeRate;
+            if( alpha < 0 ) {
+                alpha = 0;
+            }            
+            label.setAlpha(Math.max(alpha, overrideAlpha));
+        }                
+    }       
+}