Use monitor to wait for changes, rather than universally waiting for entire timeout period.

guacamole/src/main/java/org/glyptodon/guacamole/net/basic/CaptureClipboard.java

@@ -58,17 +58,11 @@ public class CaptureClipboard extends AuthenticatingHttpServlet {
         // Get clipboard
         final HttpSession session = request.getSession(true);
         final ClipboardState clipboard = getClipboardState(session);
-        
+
-        // FIXME: Don't do this
-        try {
-            Thread.sleep(CLIPBOARD_TIMEOUT);
-        }
-        catch (InterruptedException e) { /* ignore */ }
-       
         // Send clipboard contents
         try {
             response.setContentType("text/plain");
-            response.getWriter().print(clipboard.getContents());
+            response.getWriter().print(clipboard.waitForContents(CLIPBOARD_TIMEOUT));
         }
         catch (IOException e) {
             throw new GuacamoleServerException("Unable to send clipboard contents", e);

guacamole/src/main/java/org/glyptodon/guacamole/net/basic/ClipboardState.java

@@ -36,6 +36,11 @@ public class ClipboardState {
      */
     private String contents = "";
 
+    /**
+     * The timestamp of the last contents update.
+     */
+    private long last_update = 0;
+    
     /**
      * Returns the current clipboard contents.
      * @return The current clipboard contents
@@ -48,8 +53,31 @@ public class ClipboardState {
      * Sets the current clipboard contents.
      * @param contents The contents to assign to the clipboard.
      */
-    public void setContents(String contents) {
+    public synchronized void setContents(String contents) {
         this.contents = contents;
+        last_update = System.currentTimeMillis();
+        this.notifyAll();
+    }
+
+    /**
+     * Wait up to the given timeout for new clipboard data. If data more recent
+     * than the timeout period is available, return that.
+     * 
+     * @param timeout The amount of time to wait, in milliseconds.
+     * @return The current clipboard contents.
+     */
+    public synchronized String waitForContents(int timeout) {
+
+        // Wait for new contents if it's been a while
+        if (System.currentTimeMillis() - last_update > timeout) {
+            try {
+                this.wait(timeout);
+            }
+            catch (InterruptedException e) { /* ignore */ }
+        }
+
+        return getContents();
+
     }
     
 }