shader.hpp

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#pragma once
 
#include <string_view>
#include <type_traits>
 
namespace mbgl {
namespace gfx {
 
class Shader;
 
// Assert that a type is a valid shader for downcasting.
// A valid shader must:
//   * Inherit gfx::Shader
//   * Declare a public, unique type name (string_view T::Name)
//   * Be a final class
template<typename T>
inline constexpr bool is_shader_v =
    std::is_base_of_v<gfx::Shader, T> &&
    std::is_same_v<
        std::remove_cv_t<decltype(T::Name)>,
        std::string_view> &&
    std::is_final_v<T>;
 
 
class Shader {
    public:
        virtual ~Shader() = default;
 
        virtual const std::string_view typeName() const noexcept = 0;
 
        template<typename T,
            typename std::enable_if_t<is_shader_v<T>, bool>* = nullptr>
        T* to() noexcept {
            if (typeName() != T::Name) {
                return nullptr;
            }
            return static_cast<T*>(this);
        }
};
 
} // namespace gfx
} // namespace mbgl