Generate synthetic mouse button up if the mouse has left the window and the button is raised

app/streaming/input/input.cpp

@@ -19,6 +19,7 @@ SdlInputHandler::SdlInputHandler(StreamingPreferences& prefs, NvComputer*, int s
       m_StreamHeight(streamHeight),
       m_AbsoluteMouseMode(prefs.absoluteMouseMode),
       m_AbsoluteTouchMode(prefs.absoluteTouchMode),
+      m_PendingMouseLeaveButtonUp(0),
       m_LeftButtonReleaseTimer(0),
       m_RightButtonReleaseTimer(0),
       m_DragTimer(0),
@@ -192,6 +193,24 @@ void SdlInputHandler::raiseAllKeys()
     m_KeysDown.clear();
 }
 
+void SdlInputHandler::notifyMouseLeave()
+{
+#ifdef Q_OS_WIN32
+    // SDL on Windows doesn't send the mouse button up until the mouse re-enters the window
+    // after leaving it. This breaks some of the Aero snap gestures, so we'll fake it here.
+    if (m_AbsoluteMouseMode && isCaptureActive()) {
+        // NB: Not using SDL_GetGlobalMouseState() because we want our state not the system's
+        Uint32 mouseState = SDL_GetMouseState(nullptr, nullptr);
+        for (Uint32 button = SDL_BUTTON_LEFT; button <= SDL_BUTTON_X2; button++) {
+            if (mouseState & SDL_BUTTON(button)) {
+                m_PendingMouseLeaveButtonUp = button;
+                break;
+            }
+        }
+    }
+#endif
+}
+
 void SdlInputHandler::notifyFocusLost()
 {
     // Release mouse cursor when another window is activated (e.g. by using ALT+TAB).

app/streaming/input/input.h

@@ -69,6 +69,8 @@ public:
 
     void raiseAllKeys();
 
+    void notifyMouseLeave();
+
     void notifyFocusLost();
 
     bool isCaptureActive();
@@ -124,6 +126,7 @@ private:
     int m_StreamHeight;
     bool m_AbsoluteMouseMode;
     bool m_AbsoluteTouchMode;
+    Uint32 m_PendingMouseLeaveButtonUp;
 
     SDL_TouchFingerEvent m_TouchDownEvent[MAX_FINGERS];
     SDL_TimerID m_LeftButtonReleaseTimer;

app/streaming/input/mouse.cpp

@@ -122,5 +122,33 @@ Uint32 SdlInputHandler::mouseMoveTimerCallback(Uint32 interval, void *param)
         LiSendMouseMoveEvent(deltaX, deltaY);
     }
 
+#ifdef Q_OS_WIN32
+    // See comment in SdlInputHandler::notifyMouseLeave()
+    if (me->m_AbsoluteMouseMode && me->m_PendingMouseLeaveButtonUp != 0 && me->isCaptureActive()) {
+        int mouseX, mouseY;
+        int windowX, windowY;
+        Uint32 mouseState = SDL_GetGlobalMouseState(&mouseX, &mouseY);
+        SDL_GetWindowPosition(me->m_Window, &windowX, &windowY);
+
+        // If the button is now up, send the synthetic mouse up event
+        if ((mouseState & SDL_BUTTON(me->m_PendingMouseLeaveButtonUp)) == 0) {
+            SDL_Event event;
+
+            event.button.type = SDL_MOUSEBUTTONUP;
+            event.button.timestamp = SDL_GetTicks();
+            event.button.windowID = SDL_GetWindowID(me->m_Window);
+            event.button.which = 0;
+            event.button.button = me->m_PendingMouseLeaveButtonUp;
+            event.button.state = SDL_RELEASED;
+            event.button.clicks = 1;
+            event.button.x = mouseX - windowX;
+            event.button.y = mouseY - windowY;
+            SDL_PushEvent(&event);
+
+            me->m_PendingMouseLeaveButtonUp = 0;
+        }
+    }
+#endif
+
     return interval;
 }

app/streaming/session.cpp

@@ -1221,6 +1221,9 @@ void Session::exec(int displayOriginX, int displayOriginY)
             if (event.window.event == SDL_WINDOWEVENT_FOCUS_LOST) {
                 m_InputHandler->notifyFocusLost();
             }
+            else if (event.window.event == SDL_WINDOWEVENT_LEAVE) {
+                m_InputHandler->notifyMouseLeave();
+            }
 
             // Capture the mouse on SDL_WINDOWEVENT_ENTER if needed
             if (needsFirstEnterCapture && event.window.event == SDL_WINDOWEVENT_ENTER) {