[idd] project: organize driver sources by responsibility

Group the IDD sources and Visual Studio filters by subsystem.

Split the device and swap-chain implementations into focused units,
rename the context classes, and reduce header coupling.

idd/LGIdd/config/CSettings.h

@@ -0,0 +1,54 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#pragma once
+#include <windows.h>
+#include <vector>
+#include <string>
+
+class CSettings
+{
+  public:
+    struct DisplayMode
+    {
+      unsigned width;
+      unsigned height;
+      unsigned refreshMilliHz;
+      bool     preferred;
+      bool     extraMode;
+    };
+    typedef std::vector<DisplayMode> DisplayModes;
+
+    CSettings();
+
+    DisplayModes LoadModes();
+    bool SetExtraMode(const DisplayMode & mode);
+    bool GetExtraMode(DisplayMode & mode);
+    unsigned GetDefaultRefreshMilliHz() const;
+
+    std::wstring ReadStringValue(const wchar_t* name, const wchar_t* defaultValue = nullptr);
+    bool ReadBoolValue(const wchar_t* name, bool defaultValue = false);
+
+  private:
+    bool ReadModesValue(std::vector<std::wstring> &out) const;
+    bool ParseModeString(const std::wstring& in, DisplayMode& out);
+};
+
+extern CSettings g_settings;