ImGUI Render

/// <summary>
/// Submit user interface buffers for rendering
/// </summary>
/// <param name="draw_data">ImGui render data to submit</param>
void RenderPassImgui::RenderGui(ImDrawData* draw_data)
{
    ImGuiIO& io = ImGui::GetIO();

    mContext->SetPipelineState(mGuiPS);
    mContext->SetRootSignature(mGuiRS);
    mContext->SetPrimitiveTopology(Graphics::TRIANGLELIST);
    mContext->SetConstants(0, DWParam(io.DisplaySize.x), DWParam(io.DisplaySize.y));
    mContext->GetCommandList()->Get()->SetGraphicsRootDescriptorTable(1, mGuiFont->GetSRV().mGpuHandle);

    // TODO: Grow index and vertex buffer if and when necessary

    for (int n = 0; n < draw_data->CmdListsCount; n++)
    {
        int idx_offset = 0;
        int vtx_offset = 0;

        const ImDrawList* cmd_list = draw_data->CmdLists[n];
        size_t verticesCount = cmd_list->VtxBuffer.size();
        size_t indicesCount = cmd_list->IdxBuffer.size();
        size_t verticesSize = verticesCount * sizeof(ImDrawVert);
        size_t indicesSize = indicesCount * sizeof(ImDrawIdx);

        mContext->TransitionResource(mGuiVBO, D3D12_RESOURCE_STATE_COPY_DEST, false);
        mContext->TransitionResource(mGuiIBO, D3D12_RESOURCE_STATE_COPY_DEST, true);
        mContext->WriteBuffer(mGuiVBO, 0, &cmd_list->VtxBuffer[0], verticesSize);
        mContext->WriteBuffer(mGuiIBO, 0, &cmd_list->IdxBuffer[0], indicesSize);
        mContext->TransitionResource(mGuiVBO, D3D12_RESOURCE_STATE_VERTEX_AND_CONSTANT_BUFFER, false);
        mContext->TransitionResource(mGuiIBO, D3D12_RESOURCE_STATE_INDEX_BUFFER, true);

        mContext->SetIndexBuffer(mGuiIBO->IndexBufferView(0, (unsigned int)indicesSize));
        mContext->SetVertexBuffer(0, mGuiVBO->VertexBufferView(0, (unsigned int)verticesSize, sizeof(ImDrawVert)));

        for (int cmd_i = 0; cmd_i < draw_data->CmdLists[n]->CmdBuffer.Size; cmd_i++)
        {
            const ImDrawCmd* pcmd = &draw_data->CmdLists[n]->CmdBuffer[cmd_i];
            if (pcmd->TextureId != io.Fonts->TexID)
            {
                D3D12_GPU_DESCRIPTOR_HANDLE handle;
                handle.ptr = (uint64_t)pcmd->TextureId;
                if (handle.ptr != 0)
                {
                    mContext->GetCommandList()->Get()->SetGraphicsRootDescriptorTable(1, handle);
                    if (pcmd->UserCallback)
                    {
                        pcmd->UserCallback(draw_data->CmdLists[n], pcmd);
                    }
                    else
                    {
                        mContext->SetScissorRect(pcmd->ClipRect.x, pcmd->ClipRect.y, pcmd->ClipRect.z, pcmd->ClipRect.w);
                        mContext->DrawIndexed(pcmd->ElemCount, idx_offset, vtx_offset);
                    }
                    mContext->GetCommandList()->Get()->SetGraphicsRootDescriptorTable(1, mGuiFont->GetSRV().mGpuHandle);
                }
            }
            else
            {
                if (pcmd->UserCallback)
                {
                    pcmd->UserCallback(draw_data->CmdLists[n], pcmd);
                }
                else
                {
                    mContext->SetScissorRect(pcmd->ClipRect.x, pcmd->ClipRect.y, pcmd->ClipRect.z, pcmd->ClipRect.w);
                    mContext->DrawIndexed(pcmd->ElemCount, idx_offset, vtx_offset);
                }
            }
            idx_offset += pcmd->ElemCount;
        }
        vtx_offset += draw_data->CmdLists[n]->VtxBuffer.size();
    }
}