Introduce rendering engine flag for parallel drawing

src/openrct2/drawing/IDrawingEngine.h

@@ -32,6 +32,11 @@ enum DRAWING_ENGINE_FLAGS
      * Whether or not the engine will only draw changed blocks of the screen each frame.
      */
     DEF_DIRTY_OPTIMISATIONS = 1 << 0,
+
+    /**
+     * The drawing engine is capable of processing the drawing in parallel.
+     */
+    DEF_PARALLEL_DRAWING = 1 << 1,
 };
 
 struct rct_drawpixelinfo;

src/openrct2/drawing/X8DrawingEngine.cpp

@@ -284,7 +284,7 @@ rct_drawpixelinfo* X8DrawingEngine::GetDrawingPixelInfo()
 
 DRAWING_ENGINE_FLAGS X8DrawingEngine::GetFlags()
 {
-    return DEF_DIRTY_OPTIMISATIONS;
+    return static_cast<DRAWING_ENGINE_FLAGS>(DEF_DIRTY_OPTIMISATIONS | DEF_PARALLEL_DRAWING);
 }
 
 void X8DrawingEngine::InvalidateImage([[maybe_unused]] uint32_t image)

src/openrct2/interface/Viewport.cpp

@@ -996,6 +996,12 @@ void viewport_paint(
         _paintJobs.reset();
     }
 
+    bool useParallelDrawing = false;
+    if (useMultithreading && (dpi->DrawingEngine->GetFlags() & DEF_PARALLEL_DRAWING))
+    {
+        useParallelDrawing = true;
+    }
+
     // Create space to record sessions and keep track which index is being drawn
     size_t index = 0;
     if (recorded_sessions != nullptr)