Draw the whole 3D view in place of the client's renderer

The full view is now the default. While the renderer process covers the whole
view (Channel::covering, set after each frame it presents), the adapter skips
the client's renderer's clears and draws, decided per frame; the client's
renderer still gets state and resources, and draws again as soon as the
renderer process stops covering the view.

The client's window no longer gets WS_CLIPCHILDREN: the client draws when its
window gets WM_PAINT, which a window entirely covered by clipped children never
gets (it fell to about one frame a second). The flip model swap chain shows
above the client's drawing anyway.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

adapter/engine.hpp

@@ -1,7 +1,10 @@
 #pragma once
-// The adapter's engine: what the client draws with. Everything goes to the client's own Direct3D renderer, which
-// still draws the whole 3D view, and is recorded for the renderer process, which draws its part on top (the right
-// half for now, to compare). If the renderer process fails, the client's renderer carries on alone.
+// The adapter's engine: what the client draws with. Everything is recorded for the renderer process, which draws the
+// 3D view. The client's own Direct3D renderer gets everything too (state and resources: it still draws into render
+// targets and reads textures back, which the renderer process doesn't yet), but while the renderer process covers the
+// whole view, the client's renderer skips its frames' clears and draws. When the renderer process doesn't cover it
+// (it failed, or shows only part of the view, for comparing) the client's renderer draws everything, from the next
+// frame on.
 
 #include <cstdint>
 #include <memory>
@@ -63,10 +66,13 @@ public:
 
 private:
     void setState(protocol::State state, std::uint32_t value);
+    // Whether the client's renderer should draw this frame's clears and draws.
+    [[nodiscard]] bool innerDraws() const { return !takenOver_; }
 
     imvu::SharedPtr<imvu::PiRenderEngine> inner_;
     std::shared_ptr<Recorder> recorder_;
     std::uint64_t frames_ = 0;
+    bool takenOver_ = false; // this frame is drawn by the renderer process only
     int foreignLogged_ = 0; // diagnostics: textures the client renderer made, render targets
 
     // Diagnostics: what the client draws, summed over 300 frames and logged (the first few times).