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/renderer_process.cpp

@@ -84,11 +84,14 @@ std::unique_ptr<RendererProcess> RendererProcess::start(HWND window, protocol::V
                            .view = view,
                            .capacity = protocol::channelCapacity,
                            .chunkSize = 0,
-                           .chunkFlags = 0};
-
-    // The renderer's window goes on top of the client's 3D view: keep the client's drawing out of it.
-    SetWindowLongW(window, GWL_STYLE, GetWindowLongW(window, GWL_STYLE) | WS_CLIPCHILDREN);
+                           .chunkFlags = 0,
+                           .covering = 0,
+                           .reserved = 0};
 
+    // The renderer's window goes on top of the client's 3D view, as a child window. The client's window mustn't clip
+    // its children (WS_CLIPCHILDREN): the client draws a frame when its window gets WM_PAINT, which a window entirely
+    // covered by clipped children never gets (it then drew about once a second). The renderer's swap chain is a flip
+    // model one, which the compositor shows above the client's drawing anyway.
     const auto exe = running_copy(module_folder() / L"t5de-renderer.exe");
     std::wstring command = std::format(L"\"{}\" --channel {} --parent {}", exe.wstring(), name, GetCurrentProcessId());
     STARTUPINFOW startup{.cb = sizeof(STARTUPINFOW)};