Method ValidateShaderComposition

deps/LLGL/sources/Renderer/ShaderProgram.cpp:23–88

 */

bool ShaderProgram::ValidateShaderComposition(Shader* const * shaders, std::size_t numShaders)
{
    enum ShaderTypeBits
    {
        BitVert = (1 << static_cast<int>( ShaderType::Vertex         )),
        BitTesc = (1 << static_cast<int>( ShaderType::TessControl    )),
        BitTese = (1 << static_cast<int>( ShaderType::TessEvaluation )),
        BitGeom = (1 << static_cast<int>( ShaderType::Geometry       )),
        BitFrag = (1 << static_cast<int>( ShaderType::Fragment       )),
        BitComp = (1 << static_cast<int>( ShaderType::Compute        )),
    };

    /* Determine which shader types are attached */
    bool hasPostTessVertexShader = false;
    int bitmask = 0;

    for (std::size_t i = 0; i < numShaders; ++i)
    {
        if (auto shader = shaders[i])
        {
            /* Check if bit was already set */
            auto bit = (1 << static_cast<int>(shader->GetType()));

            if ((bitmask & bit) != 0)
                return false;

            bitmask |= bit;

            /* Check if a post-tessellation vertex shader is used to enable validation with Metal semantics */
            if (shader->IsPostTessellationVertex())
                hasPostTessVertexShader = true;
        }
    }

    /* Validate composition of attached shaders */
    if (hasPostTessVertexShader)
    {
        switch (bitmask)
        {
            case (          BitVert          ):
            case (          BitVert | BitFrag):
            case (BitComp                    ):
            case (BitComp | BitVert          ):
            case (BitComp | BitVert | BitFrag):
                return true;
        }
    }
    else
    {
        switch (bitmask)
        {
            case (BitVert                                        ):
            case (BitVert |                     BitGeom          ):
            case (BitVert | BitTesc | BitTese                    ):
            case (BitVert | BitTesc | BitTese | BitGeom          ):
            case (BitVert |                               BitFrag):
            case (BitVert |                     BitGeom | BitFrag):
            case (BitVert | BitTesc | BitTese |           BitFrag):