+unsigned TexUnit::get_n_units()
+{
+ static int count = -1;
+ if(count<0)
+ {
+ if(ARB_vertex_shader)
+ count = get_i(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS);
+ else if(ARB_multitexture)
+ count = get_i(GL_MAX_TEXTURE_UNITS);
+ else
+ count = 1;
+ }
+ return count;
+}
+
+TexUnit &TexUnit::get_unit(unsigned n)
+{
+ if(n>0)
+ static Require _req(ARB_multitexture);
+ if(n>=get_n_units())
+ throw out_of_range("TexUnit::get_unit");
+
+ if(units.size()<=n)
+ {
+ unsigned i = units.size();
+ units.resize(n+1, TexUnit());
+ for(; i<units.size(); ++i)
+ units[i].index = i;
+ }