casa-mp-base

https://github.com/synfig/synfig/issues/300

https://github.com/synfig/synfig/commit/4fcc3f490cc02498491b76e18e80d1be954d04be

--- src/gui/workarea.h.orig

+++ src/gui/workarea.h

@@ -130,7 +130,7 @@ class WorkAreaTile

              top + (surface ? cairo_image_surface_get_height(surface) : 0) ),

        surface() { }

-   bool operator< (const WorkAreaTile &other) { return refresh_id < other.refresh_id; }

+   bool operator< (const WorkAreaTile &other) const { return refresh_id < other.refresh_id; }

 };

 class WorkAreaTileBook