[dxvk] Add method to use a context's command list directly

Also provide the descriptor pool for convenience.

src/dxvk/dxvk_context.cpp

@@ -114,6 +114,18 @@ namespace dxvk {
   }
 
 
+  DxvkContextObjects DxvkContext::beginExternalRendering() {
+    // Flush and invalidate everything
+    endCurrentCommands();
+    beginCurrentCommands();
+
+    DxvkContextObjects result;
+    result.cmd = m_cmd;
+    result.descriptorPool = m_descriptorPool;
+    return result;
+  }
+
+  
   void DxvkContext::beginQuery(const Rc<DxvkGpuQuery>& query) {
     m_queryManager.enableQuery(m_cmd, query);
   }

src/dxvk/dxvk_context.h

@@ -12,6 +12,17 @@
 
 namespace dxvk {
 
+  /**
+   * \brief Context-provided objects
+   *
+   * Useful when submitting raw Vulkan commands to a command list.
+   */
+  struct DxvkContextObjects {
+    Rc<DxvkCommandList> cmd;
+    Rc<DxvkDescriptorPool> descriptorPool;
+  };
+
+
   /**
    * \brief DXVK context
    * 
@@ -67,6 +78,14 @@ namespace dxvk {
      */
     void flushCommandList(DxvkSubmitStatus* status);
     
+    /**
+     * \brief Begins external rendering
+     *
+     * Invalidates all state and provides the caller
+     * with the objects necessary to start drawing.
+     */
+    DxvkContextObjects beginExternalRendering();
+
     /**
      * \brief Begins generating query data
      * \param [in] query The query to end