Show and focus on the other Interface instance

interface/src/Application.cpp

@@ -23,6 +23,7 @@
 // include this before QGLWidget, which includes an earlier version of OpenGL
 #include "InterfaceConfig.h"
 
+#include <QAbstractNativeEventFilter>
 #include <QActionGroup>
 #include <QColorDialog>
 #include <QDesktopWidget>
@@ -147,6 +148,30 @@ const QString SKIP_FILENAME = QStandardPaths::writableLocation(QStandardPaths::D
 
 const QString DEFAULT_SCRIPTS_JS_URL = "http://s3.amazonaws.com/hifi-public/scripts/defaultScripts.js";
 
+#ifdef Q_OS_WIN
+class MyNativeEventFilter : public QAbstractNativeEventFilter {
+public:
+    static MyNativeEventFilter& getInstance() {
+        static MyNativeEventFilter staticInstance;
+        return staticInstance;
+    }
+
+    bool nativeEventFilter(const QByteArray &eventType, void* msg, long* result) Q_DECL_OVERRIDE {
+        if (eventType == "windows_generic_MSG") {
+            MSG* message = (MSG*)msg;
+            if (message->message == UWM_IDENTIFY_INSTANCES) {
+                *result = UWM_IDENTIFY_INSTANCES;
+                return true;
+            }
+            if (message->message == WM_SHOWWINDOW) {
+                Application::getInstance()->getWindow()->showNormal();
+            }
+        }
+        return false;
+    }
+};
+#endif
+
 void messageHandler(QtMsgType type, const QMessageLogContext& context, const QString& message) {
     QString logMessage = LogHandler::getInstance().printMessage((LogMsgType) type, context, message);
     
@@ -244,6 +269,10 @@ Application::Application(int& argc, char** argv, QElapsedTimer &startup_time) :
         _aboutToQuit(false),
         _notifiedPacketVersionMismatchThisDomain(false)
 {
+#ifdef Q_OS_WIN
+    installNativeEventFilter(&MyNativeEventFilter::getInstance());
+#endif
+
     _logger = new FileLogger(this);  // After setting organization name in order to get correct directory
     qInstallMessageHandler(messageHandler);
     

interface/src/Application.h

@@ -118,6 +118,11 @@ static const quint64 TOO_LONG_SINCE_LAST_SEND_DOWNSTREAM_AUDIO_STATS = 1 * USECS
 static const QString INFO_HELP_PATH = "html/interface-welcome-allsvg.html";
 static const QString INFO_EDIT_ENTITIES_PATH = "html/edit-entities-commands.html";
 
+#ifdef Q_OS_WIN
+static const UINT UWM_IDENTIFY_INSTANCES = 
+    RegisterWindowMessage("UWM_IDENTIFY_INSTANCES_{8AB82783-B74A-4258-955B-8188C22AA0D6}");
+#endif
+
 class Application;
 #if defined(qApp)
 #undef qApp

interface/src/main.cpp

@@ -17,6 +17,24 @@
 
 #include "Application.h"
 
+#ifdef Q_OS_WIN
+static BOOL CALLBACK enumWindowsCallback(HWND hWnd, LPARAM lParam) {
+    const UINT TIMEOUT = 200;  // ms
+    DWORD response;
+    LRESULT result = SendMessageTimeout(hWnd, UWM_IDENTIFY_INSTANCES, 0, 0, SMTO_BLOCK | SMTO_ABORTIFHUNG, TIMEOUT, &response);
+    if (result == 0) {  // Timeout; continue search.
+        return TRUE;
+    }
+    if (response == UWM_IDENTIFY_INSTANCES) {
+        HWND* target = (HWND*)lParam;
+        *target = hWnd;
+        return FALSE;  // Found; terminate search.
+    }
+    return TRUE;  // Not found; continue search.
+}
+#endif
+
+
 int main(int argc, const char * argv[]) {
 
 #ifdef Q_OS_WIN
@@ -25,6 +43,12 @@ int main(int argc, const char * argv[]) {
     DWORD result = GetLastError();
     if (result == ERROR_ALREADY_EXISTS || result == ERROR_ACCESS_DENIED) {
         // Interface is already running.
+        HWND otherInstance = NULL;
+        EnumWindows(enumWindowsCallback, (LPARAM)&otherInstance);
+        if (otherInstance) {
+            ShowWindow(otherInstance, SW_RESTORE);
+            SetForegroundWindow(otherInstance);
+        }
         return 0;
     }
 #endif