GHOST_XrGraphicsBinding.cpp

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/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
 
#include <algorithm>
#include <list>
#include <sstream>
 
#if defined(WITH_GHOST_X11)
#  include "GHOST_ContextGLX.h"
#elif defined(WIN32)
#  include "GHOST_ContextD3D.h"
#  include "GHOST_ContextWGL.h"
#  include "GHOST_SystemWin32.h"
#endif
#include "GHOST_C-api.h"
#include "GHOST_Xr_intern.h"
 
#include "GHOST_IXrGraphicsBinding.h"
 
static std::optional<int64_t> choose_swapchain_format_from_candidates(
    const std::vector<int64_t> &gpu_binding_formats, const std::vector<int64_t> &runtime_formats)
{
  if (gpu_binding_formats.empty()) {
    return std::nullopt;
  }
 
  auto res = std::find_first_of(gpu_binding_formats.begin(),
                                gpu_binding_formats.end(),
                                runtime_formats.begin(),
                                runtime_formats.end());
  if (res == gpu_binding_formats.end()) {
    return std::nullopt;
  }
 
  return *res;
}
 
class GHOST_XrGraphicsBindingOpenGL : public GHOST_IXrGraphicsBinding {
 public:
  ~GHOST_XrGraphicsBindingOpenGL()
  {
    if (m_fbo != 0) {
      glDeleteFramebuffers(1, &m_fbo);
    }
  }
 
  bool checkVersionRequirements(GHOST_Context &ghost_ctx,
                                XrInstance instance,
                                XrSystemId system_id,
                                std::string *r_requirement_info) const override
  {
#if defined(WITH_GHOST_X11)
    GHOST_ContextGLX &ctx_gl = static_cast<GHOST_ContextGLX &>(ghost_ctx);
#else
    GHOST_ContextWGL &ctx_gl = static_cast<GHOST_ContextWGL &>(ghost_ctx);
#endif
    static PFN_xrGetOpenGLGraphicsRequirementsKHR s_xrGetOpenGLGraphicsRequirementsKHR_fn =
        nullptr;
    XrGraphicsRequirementsOpenGLKHR gpu_requirements = {XR_TYPE_GRAPHICS_REQUIREMENTS_OPENGL_KHR};
    const XrVersion gl_version = XR_MAKE_VERSION(
        ctx_gl.m_contextMajorVersion, ctx_gl.m_contextMinorVersion, 0);
 
    if (!s_xrGetOpenGLGraphicsRequirementsKHR_fn &&
        XR_FAILED(xrGetInstanceProcAddr(
            instance,
            "xrGetOpenGLGraphicsRequirementsKHR",
            (PFN_xrVoidFunction *)&s_xrGetOpenGLGraphicsRequirementsKHR_fn))) {
      s_xrGetOpenGLGraphicsRequirementsKHR_fn = nullptr;
    }
 
    s_xrGetOpenGLGraphicsRequirementsKHR_fn(instance, system_id, &gpu_requirements);
 
    if (r_requirement_info) {
      std::ostringstream strstream;
      strstream << "Min OpenGL version "
                << XR_VERSION_MAJOR(gpu_requirements.minApiVersionSupported) << "."
                << XR_VERSION_MINOR(gpu_requirements.minApiVersionSupported) << std::endl;
      strstream << "Max OpenGL version "
                << XR_VERSION_MAJOR(gpu_requirements.maxApiVersionSupported) << "."
                << XR_VERSION_MINOR(gpu_requirements.maxApiVersionSupported) << std::endl;
 
      *r_requirement_info = strstream.str();
    }
 
    return (gl_version >= gpu_requirements.minApiVersionSupported) &&
           (gl_version <= gpu_requirements.maxApiVersionSupported);
  }
 
  void initFromGhostContext(GHOST_Context &ghost_ctx) override
  {
#if defined(WITH_GHOST_X11)
    GHOST_ContextGLX &ctx_glx = static_cast<GHOST_ContextGLX &>(ghost_ctx);
    XVisualInfo *visual_info = glXGetVisualFromFBConfig(ctx_glx.m_display, ctx_glx.m_fbconfig);
 
    oxr_binding.glx.type = XR_TYPE_GRAPHICS_BINDING_OPENGL_XLIB_KHR;
    oxr_binding.glx.xDisplay = ctx_glx.m_display;
    oxr_binding.glx.glxFBConfig = ctx_glx.m_fbconfig;
    oxr_binding.glx.glxDrawable = ctx_glx.m_window;
    oxr_binding.glx.glxContext = ctx_glx.m_context;
    oxr_binding.glx.visualid = visual_info->visualid;
 
    XFree(visual_info);
#elif defined(WIN32)
    GHOST_ContextWGL &ctx_wgl = static_cast<GHOST_ContextWGL &>(ghost_ctx);
 
    oxr_binding.wgl.type = XR_TYPE_GRAPHICS_BINDING_OPENGL_WIN32_KHR;
    oxr_binding.wgl.hDC = ctx_wgl.m_hDC;
    oxr_binding.wgl.hGLRC = ctx_wgl.m_hGLRC;
#endif
 
    /* Generate a frame-buffer to use for blitting into the texture. */
    glGenFramebuffers(1, &m_fbo);
  }
 
  std::optional<int64_t> chooseSwapchainFormat(const std::vector<int64_t> &runtime_formats,
                                               bool &r_is_srgb_format) const override
  {
    std::vector<int64_t> gpu_binding_formats = {
        GL_RGBA8,
        GL_SRGB8_ALPHA8,
    };
 
    std::optional result = choose_swapchain_format_from_candidates(gpu_binding_formats,
                                                                   runtime_formats);
    r_is_srgb_format = result ? (*result == GL_SRGB8_ALPHA8) : false;
 
    return result;
  }
 
  std::vector<XrSwapchainImageBaseHeader *> createSwapchainImages(uint32_t image_count) override
  {
    std::vector<XrSwapchainImageOpenGLKHR> ogl_images(image_count);
    std::vector<XrSwapchainImageBaseHeader *> base_images;
 
    /* Need to return vector of base header pointers, so of a different type. Need to build a new
     * list with this type, and keep the initial one alive. */
    for (XrSwapchainImageOpenGLKHR &image : ogl_images) {
      image.type = XR_TYPE_SWAPCHAIN_IMAGE_OPENGL_KHR;
      base_images.push_back(reinterpret_cast<XrSwapchainImageBaseHeader *>(&image));
    }
 
    /* Keep alive. */
    m_image_cache.push_back(std::move(ogl_images));
 
    return base_images;
  }
 
  void submitToSwapchainImage(XrSwapchainImageBaseHeader &swapchain_image,
                              const GHOST_XrDrawViewInfo &draw_info) override
  {
    XrSwapchainImageOpenGLKHR &ogl_swapchain_image = reinterpret_cast<XrSwapchainImageOpenGLKHR &>(
        swapchain_image);
 
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, m_fbo);
 
    glFramebufferTexture2D(
        GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, ogl_swapchain_image.image, 0);
 
    glBlitFramebuffer(draw_info.ofsx,
                      draw_info.ofsy,
                      draw_info.ofsx + draw_info.width,
                      draw_info.ofsy + draw_info.height,
                      draw_info.ofsx,
                      draw_info.ofsy,
                      draw_info.ofsx + draw_info.width,
                      draw_info.ofsy + draw_info.height,
                      GL_COLOR_BUFFER_BIT,
                      GL_LINEAR);
 
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
  }
 
  bool needsUpsideDownDrawing(GHOST_Context &ghost_ctx) const override
  {
    return ghost_ctx.isUpsideDown();
  }
 
 private:
  std::list<std::vector<XrSwapchainImageOpenGLKHR>> m_image_cache;
  GLuint m_fbo = 0;
};
 
#ifdef WIN32
class GHOST_XrGraphicsBindingD3D : public GHOST_IXrGraphicsBinding {
 public:
  GHOST_XrGraphicsBindingD3D(GHOST_Context &ghost_ctx)
      : GHOST_IXrGraphicsBinding(), m_ghost_wgl_ctx(static_cast<GHOST_ContextWGL &>(ghost_ctx))
  {
    m_ghost_d3d_ctx = GHOST_SystemWin32::createOffscreenContextD3D();
  }
  ~GHOST_XrGraphicsBindingD3D()
  {
    if (m_shared_resource) {
      m_ghost_d3d_ctx->disposeSharedOpenGLResource(m_shared_resource);
    }
    if (m_ghost_d3d_ctx) {
      GHOST_SystemWin32::disposeContextD3D(m_ghost_d3d_ctx);
    }
  }
 
  bool checkVersionRequirements(
      GHOST_Context & /*ghost_ctx*/, /* Remember: This is the OpenGL context! */
      XrInstance instance,
      XrSystemId system_id,
      std::string *r_requirement_info) const override
  {
    static PFN_xrGetD3D11GraphicsRequirementsKHR s_xrGetD3D11GraphicsRequirementsKHR_fn = nullptr;
    XrGraphicsRequirementsD3D11KHR gpu_requirements = {XR_TYPE_GRAPHICS_REQUIREMENTS_D3D11_KHR};
 
    if (!s_xrGetD3D11GraphicsRequirementsKHR_fn &&
        XR_FAILED(xrGetInstanceProcAddr(
            instance,
            "xrGetD3D11GraphicsRequirementsKHR",
            (PFN_xrVoidFunction *)&s_xrGetD3D11GraphicsRequirementsKHR_fn))) {
      s_xrGetD3D11GraphicsRequirementsKHR_fn = nullptr;
    }
 
    s_xrGetD3D11GraphicsRequirementsKHR_fn(instance, system_id, &gpu_requirements);
 
    if (r_requirement_info) {
      std::ostringstream strstream;
      strstream << "Minimum DirectX 11 Feature Level " << gpu_requirements.minFeatureLevel
                << std::endl;
 
      *r_requirement_info = std::move(strstream.str());
    }
 
    return m_ghost_d3d_ctx->m_device->GetFeatureLevel() >= gpu_requirements.minFeatureLevel;
  }
 
  void initFromGhostContext(
      GHOST_Context & /*ghost_ctx*/ /* Remember: This is the OpenGL context! */
      ) override
  {
    oxr_binding.d3d11.type = XR_TYPE_GRAPHICS_BINDING_D3D11_KHR;
    oxr_binding.d3d11.device = m_ghost_d3d_ctx->m_device;
  }
 
  std::optional<int64_t> chooseSwapchainFormat(const std::vector<int64_t> &runtime_formats,
                                               bool &r_is_srgb_format) const override
  {
    std::vector<int64_t> gpu_binding_formats = {
        DXGI_FORMAT_R8G8B8A8_UNORM,
        DXGI_FORMAT_R8G8B8A8_UNORM_SRGB,
    };
 
    std::optional result = choose_swapchain_format_from_candidates(gpu_binding_formats,
                                                                   runtime_formats);
    r_is_srgb_format = result ? (*result == DXGI_FORMAT_R8G8B8A8_UNORM_SRGB) : false;
    return result;
  }
 
  std::vector<XrSwapchainImageBaseHeader *> createSwapchainImages(uint32_t image_count) override
  {
    std::vector<XrSwapchainImageD3D11KHR> d3d_images(image_count);
    std::vector<XrSwapchainImageBaseHeader *> base_images;
 
    /* Need to return vector of base header pointers, so of a different type. Need to build a new
     * list with this type, and keep the initial one alive. */
    for (XrSwapchainImageD3D11KHR &image : d3d_images) {
      image.type = XR_TYPE_SWAPCHAIN_IMAGE_D3D11_KHR;
      base_images.push_back(reinterpret_cast<XrSwapchainImageBaseHeader *>(&image));
    }
 
    /* Keep alive. */
    m_image_cache.push_back(std::move(d3d_images));
 
    return base_images;
  }
 
  void submitToSwapchainImage(XrSwapchainImageBaseHeader &swapchain_image,
                              const GHOST_XrDrawViewInfo &draw_info) override
  {
    XrSwapchainImageD3D11KHR &d3d_swapchain_image = reinterpret_cast<XrSwapchainImageD3D11KHR &>(
        swapchain_image);
 
#  if 0
    /* Ideally we'd just create a render target view for the OpenXR swap-chain image texture and
     * blit from the OpenGL context into it. The NV_DX_interop extension doesn't want to work with
     * this though. At least not with Optimus hardware. See:
     * https://github.com/mpv-player/mpv/issues/2949#issuecomment-197262807.
     */
 
    ID3D11RenderTargetView *rtv;
    CD3D11_RENDER_TARGET_VIEW_DESC rtv_desc(D3D11_RTV_DIMENSION_TEXTURE2D,
                                            DXGI_FORMAT_R8G8B8A8_UNORM);
 
    m_ghost_ctx->m_device->CreateRenderTargetView(d3d_swapchain_image.texture, &rtv_desc, &rtv);
    if (!m_shared_resource) {
      m_shared_resource = m_ghost_ctx->createSharedOpenGLResource(
          draw_info.width, draw_info.height, rtv);
    }
    m_ghost_ctx->blitFromOpenGLContext(m_shared_resource, draw_info.width, draw_info.height);
#  else
    if (!m_shared_resource) {
      m_shared_resource = m_ghost_d3d_ctx->createSharedOpenGLResource(draw_info.width,
                                                                      draw_info.height);
    }
    m_ghost_d3d_ctx->blitFromOpenGLContext(m_shared_resource, draw_info.width, draw_info.height);
 
    m_ghost_d3d_ctx->m_device_ctx->OMSetRenderTargets(0, nullptr, nullptr);
    m_ghost_d3d_ctx->m_device_ctx->CopyResource(
        d3d_swapchain_image.texture, m_ghost_d3d_ctx->getSharedTexture2D(m_shared_resource));
#  endif
  }
 
  bool needsUpsideDownDrawing(GHOST_Context &) const
  {
    return m_ghost_d3d_ctx->isUpsideDown();
  }
 
 private:
  GHOST_ContextWGL &m_ghost_wgl_ctx;
  GHOST_ContextD3D *m_ghost_d3d_ctx = nullptr;
  GHOST_SharedOpenGLResource *m_shared_resource = nullptr;
 
  std::list<std::vector<XrSwapchainImageD3D11KHR>> m_image_cache;
};
#endif  // WIN32
 
std::unique_ptr<GHOST_IXrGraphicsBinding> GHOST_XrGraphicsBindingCreateFromType(
    GHOST_TXrGraphicsBinding type, GHOST_Context &context)
{
  switch (type) {
    case GHOST_kXrGraphicsOpenGL:
      return std::make_unique<GHOST_XrGraphicsBindingOpenGL>();
#ifdef WIN32
    case GHOST_kXrGraphicsD3D11:
      return std::make_unique<GHOST_XrGraphicsBindingD3D>(context);
#endif
    default:
      return nullptr;
  }
 
  (void)context; /* Might be unused. */
}