Introduce gfx::drawable interface

libs/gfx/include/psemek/gfx/drawable.hpp

@@ -0,0 +1,13 @@
+#pragma once
+
+namespace psemek::gfx
+{
+
+	struct drawable
+	{
+		virtual void draw() const = 0;
+
+		virtual ~drawable() {}
+	};
+
+}

libs/gfx/include/psemek/gfx/mesh.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <psemek/gfx/gl.hpp>
+#include <psemek/gfx/drawable.hpp>
 
 #include <psemek/geom/vector.hpp>
 #include <psemek/geom/point.hpp>
@@ -386,6 +387,7 @@ namespace psemek::gfx
 	}
 
 	struct mesh
+		: drawable
 	{
 		static mesh null();
 
@@ -471,7 +473,7 @@ namespace psemek::gfx
 			load(simplices.data(), simplices.size(), usage);
 		}
 
-		void draw() const
+		void draw() const override
 		{
 			if (count_ == 0) return;
 
@@ -503,6 +505,7 @@ namespace psemek::gfx
 	};
 
 	struct indexed_mesh
+		: drawable
 	{
 		static indexed_mesh null();
 
@@ -593,7 +596,7 @@ namespace psemek::gfx
 			load(simplices.data(), simplices.size(), indices.data(), indices.size(), usage);
 		}
 
-		void draw() const
+		void draw() const override
 		{
 			if (count_ == 0) return;
 
@@ -627,6 +630,7 @@ namespace psemek::gfx
 	};
 
 	struct instanced_mesh
+		: drawable
 	{
 		static instanced_mesh null();
 
@@ -732,7 +736,7 @@ namespace psemek::gfx
 			load_instance(instances.data(), instances.size(), usage);
 		}
 
-		void draw() const
+		void draw() const override
 		{
 			if (count_ == 0) return;
 			if (instance_count_ == 0) return;