Warn and assertion fail when mesh has no vertices/indexes before drawing.

src/IndexedMesh.cpp

@@ -15,7 +15,10 @@
 
 #include "IndexedMesh.h"
 
+#include <cassert>
+
 using namespace std;
+using namespace Corrade::Utility;
 
 namespace Magnum {
 
@@ -48,4 +51,13 @@ void IndexedMesh::draw() {
         glDisableVertexAttribArray(*it);
 }
 
+void IndexedMesh::finalize() {
+    if(!_indexCount) {
+        Error() << "IndexedMesh: the mesh has zero index count!";
+        assert(0);
+    }
+
+    Mesh::finalize();
+}
+
 }

src/IndexedMesh.h

@@ -76,6 +76,9 @@ class MAGNUM_EXPORT IndexedMesh: public Mesh {
          */
         void draw();
 
+    protected:
+        void finalize();
+
     private:
         Buffer _indexBuffer;
         GLsizei _indexCount;

src/Mesh.cpp

@@ -16,9 +16,11 @@
 #include "Mesh.h"
 #include "Buffer.h"
 
+#include <cassert>
 #include <iostream>
 
 using namespace std;
+using namespace Corrade::Utility;
 
 namespace Magnum {
 
@@ -68,6 +70,11 @@ void Mesh::finalize() {
     /* Already finalized */
     if(finalized) return;
 
+    if(!_vertexCount) {
+        Error() << "Mesh: the mesh has zero vertex count!";
+        assert(0);
+    }
+
     /* Finalize attribute positions for every buffer */
     for(map<Buffer*, pair<bool, vector<Attribute> > >::iterator it = _buffers.begin(); it != _buffers.end(); ++it) {
         /* Avoid confustion */

src/Mesh.h

@@ -214,7 +214,7 @@ class MAGNUM_EXPORT Mesh {
          * Computes location and stride of each attribute in its buffer. After
          * this function is called, no new attribute can be bound.
          */
-        void finalize();
+        virtual void finalize();
 
         /**
          * @brief Set the mesh dirty