Execute viewport offscreen frames through D3D12 host

new_editor/app/Application.cpp

@@ -464,8 +464,18 @@ bool Application::Initialize(HINSTANCE hInstance, int nCmdShow) {
         LogRuntimeTrace("app", "renderer initialization failed");
         return false;
     }
+    RECT clientRect = {};
+    GetClientRect(m_hwnd, &clientRect);
+    const int clientWidth = (std::max)(clientRect.right - clientRect.left, 1L);
+    const int clientHeight = (std::max)(clientRect.bottom - clientRect.top, 1L);
+    if (!m_windowRenderer.Initialize(m_hwnd, clientWidth, clientHeight)) {
+        LogRuntimeTrace("app", "d3d12 window renderer initialization failed");
+        return false;
+    }
     m_editorContext.AttachTextMeasurer(m_renderer);
     m_editorWorkspace.Initialize(repoRoot, m_renderer);
+    m_editorWorkspace.AttachViewportWindowRenderer(m_windowRenderer);
+    m_editorWorkspace.SetViewportSurfacePresentationEnabled(false);
     if (!m_editorWorkspace.GetBuiltInIconError().empty()) {
         LogRuntimeTrace("icons", m_editorWorkspace.GetBuiltInIconError());
     }
@@ -494,6 +504,7 @@ void Application::Shutdown() {
 
     m_autoScreenshot.Shutdown();
     m_editorWorkspace.Shutdown();
+    m_windowRenderer.Shutdown();
     m_renderer.Shutdown();
 
     if (m_hwnd != nullptr && IsWindow(m_hwnd)) {
@@ -541,11 +552,22 @@ void Application::RenderFrame() {
                         m_editorWorkspace.GetShellInteractionState()));
         }
 
+        const bool d3d12FrameBegun = m_windowRenderer.BeginFrame();
+        if (!d3d12FrameBegun) {
+            LogRuntimeTrace("viewport", "d3d12 frame begin failed");
+        }
+
         m_editorWorkspace.Update(
             m_editorContext,
             UIRect(0.0f, 0.0f, width, height),
             frameEvents,
             BuildCaptureStatusText());
+        if (d3d12FrameBegun) {
+            m_editorWorkspace.RenderRequestedViewports(m_windowRenderer.GetRenderContext());
+            if (!m_windowRenderer.SubmitFrame(false)) {
+                LogRuntimeTrace("viewport", "d3d12 offscreen frame submit failed");
+            }
+        }
         const UIEditorShellInteractionFrame& shellFrame =
             m_editorWorkspace.GetShellFrame();
         if (!frameEvents.empty() ||
@@ -710,6 +732,7 @@ void Application::OnResize(UINT width, UINT height) {
     }
 
     m_renderer.Resize(width, height);
+    m_windowRenderer.Resize(static_cast<int>(width), static_cast<int>(height));
 }
 
 void Application::OnDpiChanged(UINT dpi, const RECT& suggestedRect) {