[idd] ensure the only active monitor is the IDD

idd/LGIddHelper/CNotifyWindow.cpp

@@ -32,6 +32,11 @@
 #define ID_MENU_SHOW_LOG 3000
 #define ID_MENU_SHOW_CONFIG 3001
 
+#define ID_DISPLAY_CHECK_TIMER 1
+#define DISPLAY_SETTLE_DELAY   250
+#define DISPLAY_RETRY_DELAY    1000
+#define DISPLAY_CHECK_INTERVAL 5000
+
 ATOM CNotifyWindow::s_atom = 0;
 UINT CNotifyWindow::s_taskbarCreated = 0;
 
@@ -86,6 +91,20 @@ LRESULT CNotifyWindow::handleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam)
     handleGPUNotification((bool)wParam);
     return 0;
 
+  case WM_DISPLAYCHANGE:
+    scheduleDisplayCheck(DISPLAY_SETTLE_DELAY);
+    return 0;
+
+  case WM_TIMER:
+    if (wParam == ID_DISPLAY_CHECK_TIMER)
+    {
+      KillTimer(m_hwnd, ID_DISPLAY_CHECK_TIMER);
+      const bool success = m_onDisplayChange && m_onDisplayChange();
+      scheduleDisplayCheck(success ? DISPLAY_CHECK_INTERVAL : DISPLAY_RETRY_DELAY);
+      return 0;
+    }
+    return CWindow::handleMessage(uMsg, wParam, lParam);
+
   default:
     if (s_taskbarCreated && uMsg == s_taskbarCreated)
     {
@@ -114,6 +133,7 @@ LRESULT CNotifyWindow::onClose()
 
 LRESULT CNotifyWindow::onDestroy()
 {
+  KillTimer(m_hwnd, ID_DISPLAY_CHECK_TIMER);
   Shell_NotifyIcon(NIM_DELETE, &m_iconData);
   return 0;
 }
@@ -239,3 +259,19 @@ void CNotifyWindow::close()
   closeRequested = true;
   PostMessage(m_hwnd, WM_CLOSE, 0, 0);
 }
+
+void CNotifyWindow::scheduleDisplayCheck(UINT delay)
+{
+  if (!m_onDisplayChange)
+    return;
+
+  KillTimer(m_hwnd, ID_DISPLAY_CHECK_TIMER);
+  if (!SetTimer(m_hwnd, ID_DISPLAY_CHECK_TIMER, delay, NULL))
+    DEBUG_ERROR_HR(GetLastError(), "Failed to schedule primary display check");
+}
+
+void CNotifyWindow::onDisplayChange(std::function<bool()> func)
+{
+  m_onDisplayChange = std::move(func);
+  scheduleDisplayCheck(DISPLAY_SETTLE_DELAY);
+}

idd/LGIddHelper/CNotifyWindow.h

@@ -39,10 +39,12 @@ class CNotifyWindow : public CWindow
   std::unique_ptr<CConfigWindow> m_config;
 
   std::function<void()> m_onSettingChange;
+  std::function<bool()> m_onDisplayChange;
 
   LRESULT onNotifyIcon(UINT uEvent, WORD wIconId, int x, int y);
   void registerIcon();
   void handleGPUNotification(bool hasGPU);
+  void scheduleDisplayCheck(UINT delay);
 
   virtual LRESULT handleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam) override;
   virtual LRESULT onCreate() override;
@@ -74,4 +76,5 @@ public:
   void close();
 
   void onSettingChange(std::function<void()> func) { m_onSettingChange = std::move(func); }
-};
+  void onDisplayChange(std::function<bool()> func);
+};

idd/LGIddHelper/CPipeClient.cpp

@@ -24,6 +24,83 @@
 
 #include <setupapi.h>
 #include <tchar.h>
+#include <vector>
+
+namespace
+{
+  struct DisplayState
+  {
+    DISPLAY_DEVICE device;
+    DEVMODE mode;
+    bool isLG;
+  };
+
+  bool IsLGDisplay(const DISPLAY_DEVICE& device)
+  {
+    static const TCHAR deviceId[] = _T("ROOT\\LGIDD");
+    const size_t deviceIdLength = _countof(deviceId) - 1;
+
+    if (_tcsnicmp(device.DeviceID, deviceId, deviceIdLength) == 0 &&
+      (device.DeviceID[deviceIdLength] == _T('\\') ||
+       device.DeviceID[deviceIdLength] == _T('\0')))
+      return true;
+
+    if (_tcsicmp(device.DeviceString,
+      _T("Looking Glass Indirect Display Device")) == 0)
+      return true;
+
+    DISPLAY_DEVICE monitor = {};
+    monitor.cb = sizeof(monitor);
+    for (DWORD i = 0; EnumDisplayDevices(device.DeviceName, i, &monitor, 0); ++i)
+    {
+      if (_tcsnicmp(monitor.DeviceID, _T("MONITOR\\LGD1DDD"), 15) == 0 ||
+        _tcsicmp(monitor.DeviceString, _T("Looking Glass")) == 0)
+        return true;
+
+      monitor = {};
+      monitor.cb = sizeof(monitor);
+    }
+
+    return false;
+  }
+
+  bool GetDisplayStates(std::vector<DisplayState>& displays, size_t& lgIndex)
+  {
+    lgIndex = SIZE_MAX;
+
+    DISPLAY_DEVICE device = {};
+    device.cb = sizeof(device);
+    for (DWORD i = 0; EnumDisplayDevices(NULL, i, &device, 0); ++i)
+    {
+      if ((device.StateFlags & DISPLAY_DEVICE_ATTACHED_TO_DESKTOP) &&
+        !(device.StateFlags & DISPLAY_DEVICE_MIRRORING_DRIVER))
+      {
+        DisplayState state = {};
+        state.device = device;
+        state.mode.dmSize = sizeof(state.mode);
+        state.isLG = IsLGDisplay(device);
+
+        if (!EnumDisplaySettingsEx(device.DeviceName, ENUM_CURRENT_SETTINGS,
+          &state.mode, 0))
+        {
+          DEBUG_WARN_HR(GetLastError(),
+            "Failed to query the current mode for %ls", device.DeviceName);
+          return false;
+        }
+
+        if (state.isLG && lgIndex == SIZE_MAX)
+          lgIndex = displays.size();
+
+        displays.emplace_back(state);
+      }
+
+      device = {};
+      device.cb = sizeof(device);
+    }
+
+    return lgIndex != SIZE_MAX;
+  }
+}
 
 CPipeClient g_pipe;
 
@@ -181,6 +258,115 @@ void CPipeClient::ReloadSettings()
   WriteMsg(msg);
 }
 
+bool CPipeClient::EnsureOnlyDisplayLocked()
+{
+  std::vector<DisplayState> displays;
+  size_t lgIndex;
+  if (!GetDisplayStates(displays, lgIndex))
+    return false;
+
+  // The only active display is necessarily the primary display.
+  if (displays.size() == 1)
+    return true;
+
+  for (unsigned int attempt = 0; attempt < 3; ++attempt)
+  {
+    UINT32 pathCount = 0;
+    UINT32 modeCount = 0;
+    LONG result = GetDisplayConfigBufferSizes(
+      QDC_ONLY_ACTIVE_PATHS, &pathCount, &modeCount);
+    if (result != ERROR_SUCCESS)
+    {
+      DEBUG_ERROR("GetDisplayConfigBufferSizes failed (%ld)", result);
+      return false;
+    }
+
+    std::vector<DISPLAYCONFIG_PATH_INFO> paths(pathCount);
+    std::vector<DISPLAYCONFIG_MODE_INFO> modes(modeCount);
+    result = QueryDisplayConfig(QDC_ONLY_ACTIVE_PATHS,
+      &pathCount, paths.data(), &modeCount, modes.data(), NULL);
+    if (result == ERROR_INSUFFICIENT_BUFFER)
+      continue;
+
+    if (result != ERROR_SUCCESS)
+    {
+      DEBUG_ERROR("QueryDisplayConfig failed (%ld)", result);
+      return false;
+    }
+
+    paths.resize(pathCount);
+    modes.resize(modeCount);
+
+    for (size_t i = 0; i < paths.size(); ++i)
+    {
+      DISPLAYCONFIG_SOURCE_DEVICE_NAME sourceName = {};
+      sourceName.header.type = DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_NAME;
+      sourceName.header.size = sizeof(sourceName);
+      sourceName.header.adapterId = paths[i].sourceInfo.adapterId;
+      sourceName.header.id = paths[i].sourceInfo.id;
+
+      result = DisplayConfigGetDeviceInfo(&sourceName.header);
+      if (result != ERROR_SUCCESS)
+        continue;
+
+      if (_tcsicmp(sourceName.viewGdiDeviceName,
+        displays[lgIndex].device.DeviceName) != 0)
+        continue;
+
+      const UINT32 sourceModeIndex = paths[i].sourceInfo.modeInfoIdx;
+      const UINT32 targetModeIndex = paths[i].targetInfo.modeInfoIdx;
+      if (sourceModeIndex == DISPLAYCONFIG_PATH_MODE_IDX_INVALID ||
+        sourceModeIndex >= modes.size() ||
+        targetModeIndex == DISPLAYCONFIG_PATH_MODE_IDX_INVALID ||
+        targetModeIndex >= modes.size() ||
+        modes[sourceModeIndex].infoType != DISPLAYCONFIG_MODE_INFO_TYPE_SOURCE ||
+        modes[targetModeIndex].infoType != DISPLAYCONFIG_MODE_INFO_TYPE_TARGET)
+      {
+        DEBUG_ERROR("Looking Glass display path has invalid mode indices");
+        return false;
+      }
+
+      DISPLAYCONFIG_PATH_INFO path = paths[i];
+      DISPLAYCONFIG_MODE_INFO selectedModes[2] = {
+        modes[sourceModeIndex], modes[targetModeIndex]
+      };
+
+      selectedModes[0].sourceMode.position.x = 0;
+      selectedModes[0].sourceMode.position.y = 0;
+      path.sourceInfo.modeInfoIdx = 0;
+      path.targetInfo.modeInfoIdx = 1;
+      path.flags |= DISPLAYCONFIG_PATH_ACTIVE;
+
+      result = SetDisplayConfig(1, &path, 2, selectedModes,
+        SDC_APPLY | SDC_USE_SUPPLIED_DISPLAY_CONFIG |
+        SDC_ALLOW_CHANGES | SDC_SAVE_TO_DATABASE);
+      if (result != ERROR_SUCCESS)
+      {
+        DEBUG_ERROR("Failed to apply the LG-only display topology (%ld)",
+          result);
+        return false;
+      }
+
+      DEBUG_INFO("Looking Glass display set as the only active display");
+      return true;
+    }
+
+    DEBUG_ERROR("Looking Glass display configuration path not found");
+    return false;
+  }
+
+  DEBUG_WARN("Display topology kept changing while selecting Looking Glass");
+  return false;
+}
+
+bool CPipeClient::EnsureOnlyDisplay()
+{
+  AcquireSRWLockExclusive(&m_displayLock);
+  const bool result = EnsureOnlyDisplayLocked();
+  ReleaseSRWLockExclusive(&m_displayLock);
+  return result;
+}
+
 void CPipeClient::Thread()
 {
   DEBUG_INFO("Pipe thread started");
@@ -305,16 +491,32 @@ void CPipeClient::HandleSetCursorPos(const LGPipeMsg& msg)
 
 void CPipeClient::HandleSetDisplayMode(const LGPipeMsg& msg)
 {
-  DEVMODE dm = {};
-  dm.dmSize             = sizeof(dm);
+  AcquireSRWLockExclusive(&m_displayLock);
+
+  std::vector<DisplayState> displays;
+  size_t lgIndex;
+  if (!GetDisplayStates(displays, lgIndex))
+  {
+    ReleaseSRWLockExclusive(&m_displayLock);
+    DEBUG_ERROR("Looking Glass display not found while setting its mode");
+    return;
+  }
+
+  DEVMODE dm = displays[lgIndex].mode;
   dm.dmPelsWidth        = msg.displayMode.width;
   dm.dmPelsHeight       = msg.displayMode.height;
   dm.dmDisplayFrequency = msg.displayMode.refresh;
-  dm.dmFields           = DM_PELSWIDTH | DM_PELSHEIGHT | DM_DISPLAYFREQUENCY;
+  dm.dmFields = DM_PELSWIDTH | DM_PELSHEIGHT | DM_DISPLAYFREQUENCY;
 
-  LONG result = ChangeDisplaySettingsEx(NULL, &dm, NULL, CDS_UPDATEREGISTRY, NULL);
+  LONG result = ChangeDisplaySettingsEx(displays[lgIndex].device.DeviceName,
+    &dm, NULL, CDS_UPDATEREGISTRY, NULL);
   if (result != DISP_CHANGE_SUCCESSFUL)
     DEBUG_ERROR("ChangeDisplaySettingsEx Failed (0x%08x)", result);
+
+  ReleaseSRWLockExclusive(&m_displayLock);
+
+  if (result == DISP_CHANGE_SUCCESSFUL)
+    EnsureOnlyDisplay();
 }
 
 void CPipeClient::HandleGPUStatus(const LGPipeMsg& msg)

idd/LGIddHelper/CPipeClient.h

@@ -39,6 +39,7 @@ private:
 
   bool m_running = false;
   bool m_connected = false;
+  SRWLOCK m_displayLock = SRWLOCK_INIT;
 
   static DWORD WINAPI _pipeThread(LPVOID lpParam) { ((CPipeClient*)lpParam)->Thread(); return 0; }
   void Thread();
@@ -46,6 +47,8 @@ private:
   void WriteMsg(const LGPipeMsg& msg);
 
   void SetActiveDesktop();
+
+  bool EnsureOnlyDisplayLocked();
   
   void HandleSetCursorPos(const LGPipeMsg& msg);
   void HandleSetDisplayMode(const LGPipeMsg& msg);
@@ -61,6 +64,7 @@ public:
   bool IsRunning() { return m_running; }
 
   void ReloadSettings();
+  bool EnsureOnlyDisplay();
 };
 
-extern CPipeClient g_pipe;
+extern CPipeClient g_pipe;

idd/LGIddHelper/main.cpp

@@ -124,6 +124,10 @@ int WINAPI WinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _
     g_pipe.ReloadSettings();
   });
 
+  window.onDisplayChange([]() {
+    return g_pipe.EnsureOnlyDisplay();
+  });
+
   HANDLE hWait;
   if (!RegisterWaitForSingleObject(&hWait, hParent.Get(), DestroyNotifyWindow, &window, INFINITE, WT_EXECUTEONLYONCE))
     DEBUG_ERROR_HR(GetLastError(), "Failed to RegisterWaitForSingleObject");
@@ -445,4 +449,4 @@ static void Launch()
 
   l_process.Attach(pi.hProcess);
   CloseHandle(pi.hThread);
-}
+}