Workaround for OpenGL renderer viewport panning, turn it into a hybrid

src/openrct2-ui/drawing/engines/opengl/OpenGLDrawingEngine.cpp

@@ -343,6 +343,11 @@ public:
 
     void PaintWindows() override
     {
+        WindowResetVisibilities();
+
+        // Redraw dirty regions before updating the viewports, otherwise
+        // when viewports get panned, they copy dirty pixels
+        DrawAllDirtyBlocks();
         WindowUpdateAllViewports();
         DrawAllDirtyBlocks();
     }
@@ -435,7 +440,7 @@ public:
 
     DrawingEngineFlags GetFlags() override
     {
-        return DrawingEngineFlag::dirtyOptimisations;
+        return {};
     }
 
     void InvalidateImage(uint32_t image) override

src/openrct2/interface/Viewport.cpp

@@ -526,6 +526,10 @@ namespace OpenRCT2
                 WindowDrawAll(dpi, left, top, right, bottom);
                 return;
             }
+            else
+            {
+                GfxInvalidateScreen();
+            }
         }
 
         Viewport view_copy = *viewport;
@@ -573,6 +577,10 @@ namespace OpenRCT2
             DrawPixelInfo& dpi = DrawingEngineGetDpi();
             ViewportShiftPixels(dpi, w, viewport, x_diff, y_diff);
         }
+        else
+        {
+            GfxInvalidateScreen();
+        }
 
         *viewport = view_copy;
     }