[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/postprocess/effect/CDownsampleEffect.h

@@ -0,0 +1,71 @@
+/**
+ * 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 "CComputeEffect.h"
+
+#include <vector>
+#include <string>
+
+class CDownsampleEffect : public CComputeEffect
+{
+private:
+  struct Rule
+  {
+    bool greater = false;
+    unsigned x = 0;
+    unsigned y = 0;
+    unsigned targetX = 0;
+    unsigned targetY = 0;
+  };
+
+  struct Consts
+  {
+    float width;
+    float height;
+  } m_consts = {};
+
+  std::vector<Rule> m_rules;
+  ComPtr<ID3D12Resource> m_constBuffer;
+  DXGI_FORMAT m_format = DXGI_FORMAT_UNKNOWN;
+  double m_scaleX = 1.0;
+  double m_scaleY = 1.0;
+  unsigned m_width = 0;
+  unsigned m_height = 0;
+
+  bool ParseRules(const std::wstring& value);
+  const Rule * MatchRule(unsigned width, unsigned height) const;
+
+public:
+  const char * GetName() const override { return "Downsample"; }
+
+  bool Init(const ComPtr<ID3D12Device3>& device);
+
+  PostProcessStatus SetFormat(const ComPtr<ID3D12Device3>& device,
+    const D12FrameFormat& src, D12FrameFormat& dst) override;
+
+  void AdjustDamage(RECT dirtyRects[], unsigned * nbDirtyRects) override;
+
+  ComPtr<ID3D12Resource> Run(const ComPtr<ID3D12Device3>& device,
+    const ComPtr<ID3D12GraphicsCommandList>& commandList,
+    const ComPtr<ID3D12Resource>& src, RECT dirtyRects[],
+    unsigned * nbDirtyRects) override;
+};