Index: network_gui.c
===================================================================
--- network_gui.c	(revision 3305)
+++ network_gui.c	(working copy)
@@ -6,6 +6,7 @@
 #include "strings.h"
 #include "table/sprites.h"
 #include "network.h"
+#include "debug.h"
 
 #include "hal.h" // for file list
 
@@ -1302,7 +1303,31 @@
 }
 
 
+static inline void ChatNickTabCompletion(Window *w)
+{
+	Textbuf *tb = &WP(w, querystr_d).text;
+	const NetworkClientInfo* ci;
+	int len, i;
 
+	for (ci = _network_client_info; ci != &_network_client_info[MAX_CLIENT_INFO]; ci++) {
+		// Skip non-active items
+		if (ci->client_index == NETWORK_EMPTY_INDEX) continue;
+
+		len = strlen(ci->client_name);
+		if(tb->length < len && strncmp(ci->client_name, tb->buf, tb->length) == 0) {
+			DeleteTextBufferAll(tb);
+
+			for(i = 0; i < len; i++)
+				InsertTextBufferChar(tb, ci->client_name[i]);
+
+			InsertTextBufferChar(tb, ':');
+			InsertTextBufferChar(tb, ' ');
+
+			break;
+		}
+	}
+}
+
 #define MAX_QUERYSTR_LEN 64
 
 static void ChatWindowWndProc(Window *w, WindowEvent *e)
@@ -1360,12 +1385,16 @@
 	} break;
 
 	case WE_KEYPRESS: {
-		switch(HandleEditBoxKey(w, 1, e)) {
-		case 1: // Return
-			goto press_ok;
-		case 2: // Escape
-			DeleteWindow(w);
-			break;
+		if(e->keypress.keycode == WKC_TAB) {
+			ChatNickTabCompletion(w);
+		} else {
+			switch(HandleEditBoxKey(w, 1, e)) {
+			case 1: // Return
+				goto press_ok;
+			case 2: // Escape
+				DeleteWindow(w);
+				break;
+			}
 		}
 	} break;