c++ - How to Get Max Number of Multitextured Units -

lets have function want user able select appropriate texture in type safe manner. instead of using glenum of gl_texturex define method follows.

void activate_enable_bind(uint32_t texture_num)  {   const uint32_t max_textures = gl_max_combined_texture_image_units - gl_texture0;   const uint32_t actual_texture = (gl_texture0 + texture_num);    if (texture_num > max_textures) {     throw std::runtime_error("error: texture::activate_enable_bind()");   }    glactivetexture(actual_texture);   glenable(target_type);   glbindtexture(target_type, texture_id_); } 

is guaranteed work under implementations based on opengl specification, or implementers allowed have

`gl_texture0 - gl_texture(gl_max_combined_texture_image_units -1)`  

defined in non-contiguous manner?

i modifying code aswell here in have:

void activate_enable_bind(uint32_t texture_num = 0)  {   glint max_textures = 0;   glgetintegerv(gl_max_combined_texture_image_units, &max_textures);   if (static_cast<glint>(texture_num) > max_textures - 1) {     throw std::runtime_error("error: texture::activate_enable_bind()");   }    const uint32_t actual_texture = (gl_texture0 + texture_num);    glactivetexture(actual_texture);   glenable(target_type);   glbindtexture(target_type, texture_id_); } 

i think gl_max_combined_texture_image_units not on own useful value, pass glget retrieve actual value. account that, you'd retrieve this:

glint max_combined_texture_image_units; glgetintegerv(gl_max_combined_texture_image_units, &max_combined_texture_image_units); // , maybe check errors 

as adding gl_texture0, safe; §3.8 of the opengl 3.2 core specification says this:

active­texture generates error invalid_­enum if invalid texture specified. texture symbolic constant of form texturei, indicating texture unit i modified. constants obey texturei = texture0+i (i in range 0 k − 1, k value of max_­combined_­texture_­image_­units).