- return (VBO_VERT_BUFFER_SIZE - exec->vtx.buffer_used) /
- (exec->vtx.vertex_size * sizeof(GLfloat));
+ unsigned n = (VBO_VERT_BUFFER_SIZE - exec->vtx.buffer_used) /
+ (exec->vtx.vertex_size * sizeof(GLfloat));
+ if (n == 0)
+ return 0;
+ /* Subtract one so we're always sure to have room for an extra
+ * vertex for GL_LINE_LOOP -> GL_LINE_STRIP conversion.
+ */
+ n--;
+ return n;