/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright 2014 Blender Foundation. All rights reserved. */

/** \file
 * \ingroup GHOST
 *
 * Definition of GHOST_ContextGLX class.
 */

#include "GHOST_ContextGLX.h"
#include "GHOST_SystemX11.h"

#include <vector>

#include <cassert>
#include <cstdio>
#include <cstring>

/* Needed for Intel drivers (works with MESA-software-rasterizer (`swrast`) & NVIDIA). */
#define USE_GLXEW_INIT_WORKAROUND

#ifdef USE_GLXEW_INIT_WORKAROUND
static GLuint _glewStrLen(const GLubyte *s);
static GLboolean _glewSearchExtension(const char *name, const GLubyte *start, const GLubyte *end);
#endif

GLXContext GHOST_ContextGLX::s_sharedContext = None;
int GHOST_ContextGLX::s_sharedCount = 0;

GHOST_ContextGLX::GHOST_ContextGLX(bool stereoVisual,
                                   Window window,
                                   Display *display,
                                   GLXFBConfig fbconfig,
                                   int contextProfileMask,
                                   int contextMajorVersion,
                                   int contextMinorVersion,
                                   int contextFlags,
                                   int contextResetNotificationStrategy)
    : GHOST_Context(stereoVisual),
      m_display(display),
      m_fbconfig(fbconfig),
      m_window(window),
      m_contextProfileMask(contextProfileMask),
      m_contextMajorVersion(contextMajorVersion),
      m_contextMinorVersion(contextMinorVersion),
      m_contextFlags(contextFlags),
      m_contextResetNotificationStrategy(contextResetNotificationStrategy),
      m_context(None)
{
  assert(m_display != nullptr);
}

GHOST_ContextGLX::~GHOST_ContextGLX()
{
  if (m_display != nullptr) {
    if (m_context != None) {
      if (m_window != 0 && m_context == ::glXGetCurrentContext()) {
        ::glXMakeCurrent(m_display, None, nullptr);
      }
      if (m_context != s_sharedContext || s_sharedCount == 1) {
        assert(s_sharedCount > 0);

        s_sharedCount--;

        if (s_sharedCount == 0) {
          s_sharedContext = nullptr;
        }

        ::glXDestroyContext(m_display, m_context);
      }
    }
  }
}

GHOST_TSuccess GHOST_ContextGLX::swapBuffers()
{
  ::glXSwapBuffers(m_display, m_window);

  return GHOST_kSuccess;
}

GHOST_TSuccess GHOST_ContextGLX::activateDrawingContext()
{
  if (m_display == nullptr) {
    return GHOST_kFailure;
  }
  return ::glXMakeCurrent(m_display, m_window, m_context) ? GHOST_kSuccess : GHOST_kFailure;
}

GHOST_TSuccess GHOST_ContextGLX::releaseDrawingContext()
{
  if (m_display == nullptr) {
    return GHOST_kFailure;
  }
  return ::glXMakeCurrent(m_display, None, nullptr) ? GHOST_kSuccess : GHOST_kFailure;
}

GHOST_TSuccess GHOST_ContextGLX::initializeDrawingContext()
{
  GHOST_X11_ERROR_HANDLERS_OVERRIDE(handler_store);

  /* -------------------------------------------------------------------- */
  /* Begin Inline GLEW. */

#ifdef USE_GLXEW_INIT_WORKAROUND
  const GLubyte *extStart = (GLubyte *)"";
  const GLubyte *extEnd;
  if (glXQueryExtension(m_display, nullptr, nullptr)) {
    extStart = (const GLubyte *)glXGetClientString(m_display, GLX_EXTENSIONS);
    if ((extStart == nullptr) ||
        (glXChooseFBConfig = (PFNGLXCHOOSEFBCONFIGPROC)glXGetProcAddressARB(
             (const GLubyte *)"glXChooseFBConfig")) == nullptr ||
        (glXCreateContextAttribsARB = (PFNGLXCREATECONTEXTATTRIBSARBPROC)glXGetProcAddressARB(
             (const GLubyte *)"glXCreateContextAttribsARB")) == nullptr ||
        (glXCreatePbuffer = (PFNGLXCREATEPBUFFERPROC)glXGetProcAddressARB(
             (const GLubyte *)"glXCreatePbuffer")) == nullptr) {
      extStart = (GLubyte *)"";
    }
  }
  extEnd = extStart + _glewStrLen(extStart);

#  undef GLXEW_ARB_create_context
  const bool GLXEW_ARB_create_context = _glewSearchExtension(
      "GLX_ARB_create_context", extStart, extEnd);
#  undef GLXEW_ARB_create_context_profile
  const bool GLXEW_ARB_create_context_profile = _glewSearchExtension(
      "GLX_ARB_create_context_profile", extStart, extEnd);
#  undef GLXEW_ARB_create_context_robustness
  const bool GLXEW_ARB_create_context_robustness = _glewSearchExtension(
      "GLX_ARB_create_context_robustness", extStart, extEnd);
#  ifdef WITH_GLEW_ES
#    undef GLXEW_EXT_create_context_es_profile
  const bool GLXEW_EXT_create_context_es_profile = _glewSearchExtension(
      "GLX_EXT_create_context_es_profile", extStart, extEnd);
#    undef GLXEW_EXT_create_context_es2_profile
  const bool GLXEW_EXT_create_context_es2_profile = _glewSearchExtension(
      "GLX_EXT_create_context_es2_profile", extStart, extEnd);
#  endif /* WITH_GLEW_ES */

  /* End Inline GLEW. */
  /* -------------------------------------------------------------------- */
#else
  /* Important to initialize only GLXEW (_not_ GLEW),
   * since this breaks w/ Mesa's `swrast`, see: T46431. */
  glxewInit();
#endif /* USE_GLXEW_INIT_WORKAROUND */

  if (GLXEW_ARB_create_context) {
    int profileBitCore = m_contextProfileMask & GLX_CONTEXT_CORE_PROFILE_BIT_ARB;
    int profileBitCompat = m_contextProfileMask & GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB;

#ifdef WITH_GLEW_ES
    int profileBitES = m_contextProfileMask & GLX_CONTEXT_ES_PROFILE_BIT_EXT;
#endif

    if (!GLXEW_ARB_create_context_profile && profileBitCore) {
      fprintf(stderr, "Warning! OpenGL core profile not available.\n");
    }
    if (!GLXEW_ARB_create_context_profile && profileBitCompat) {
      fprintf(stderr, "Warning! OpenGL compatibility profile not available.\n");
    }

#ifdef WITH_GLEW_ES
    if (!GLXEW_EXT_create_context_es_profile && profileBitES && m_contextMajorVersion == 1)
      fprintf(stderr, "Warning! OpenGL ES profile not available.\n");

    if (!GLXEW_EXT_create_context_es2_profile && profileBitES && m_contextMajorVersion == 2)
      fprintf(stderr, "Warning! OpenGL ES2 profile not available.\n");
#endif

    int profileMask = 0;

    if (GLXEW_ARB_create_context_profile && profileBitCore) {
      profileMask |= profileBitCore;
    }
    if (GLXEW_ARB_create_context_profile && profileBitCompat) {
      profileMask |= profileBitCompat;
    }

#ifdef WITH_GLEW_ES
    if (GLXEW_EXT_create_context_es_profile && profileBitES)
      profileMask |= profileBitES;
#endif

    if (profileMask != m_contextProfileMask) {
      fprintf(stderr, "Warning! Ignoring untested OpenGL context profile mask bits.");
    }
    /* max 10 attributes plus terminator */
    int attribs[11];
    int i = 0;

    if (profileMask) {
      attribs[i++] = GLX_CONTEXT_PROFILE_MASK_ARB;
      attribs[i++] = profileMask;
    }

    if (m_contextMajorVersion != 0) {
      attribs[i++] = GLX_CONTEXT_MAJOR_VERSION_ARB;
      attribs[i++] = m_contextMajorVersion;
      attribs[i++] = GLX_CONTEXT_MINOR_VERSION_ARB;
      attribs[i++] = m_contextMinorVersion;
    }

    if (m_contextFlags != 0) {
      attribs[i++] = GLX_CONTEXT_FLAGS_ARB;
      attribs[i++] = m_contextFlags;
    }

    if (m_contextResetNotificationStrategy != 0) {
      if (GLXEW_ARB_create_context_robustness) {
        attribs[i++] = GLX_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB;
        attribs[i++] = m_contextResetNotificationStrategy;
      }
      else {
        fprintf(stderr, "Warning! Cannot set the reset notification strategy.");
      }
    }
    attribs[i++] = 0;

    /* Some drivers don't like having a true off-screen context.
     * Create a pixel buffer instead of a window to render to.
     * even if it will never be used for drawing. */
    int pbuffer_attribs[] = {GLX_PBUFFER_WIDTH, 1, GLX_PBUFFER_HEIGHT, 1, None};

    /* Create a GL 3.x context */
    if (m_fbconfig) {
      m_context = glXCreateContextAttribsARB(
          m_display, m_fbconfig, s_sharedContext, true, attribs);

      if (!m_window) {
        m_window = (Window)glXCreatePbuffer(m_display, m_fbconfig, pbuffer_attribs);
      }
    }
    else {
      GLXFBConfig *framebuffer_config = nullptr;
      {
        int glx_attribs[64];
        int fbcount = 0;

        GHOST_X11_GL_GetAttributes(glx_attribs, 64, m_stereoVisual, false, true);

        framebuffer_config = glXChooseFBConfig(
            m_display, DefaultScreen(m_display), glx_attribs, &fbcount);
      }

      if (framebuffer_config) {
        m_context = glXCreateContextAttribsARB(
            m_display, framebuffer_config[0], s_sharedContext, True, attribs);

        if (!m_window) {
          m_window = (Window)glXCreatePbuffer(m_display, framebuffer_config[0], pbuffer_attribs);
        }

        m_fbconfig = framebuffer_config[0];
        XFree(framebuffer_config);
      }
    }
  }
  else {
    /* Don't create legacy context */
    fprintf(stderr, "Error! GLX_ARB_create_context not available.\n");
  }

  GHOST_TSuccess success;

  if (m_context != nullptr) {
    const uchar *version;

    if (!s_sharedContext) {
      s_sharedContext = m_context;
    }
    s_sharedCount++;

    glXMakeCurrent(m_display, m_window, m_context);

    if (m_window) {
      initClearGL();
      ::glXSwapBuffers(m_display, m_window);
    }

    version = glGetString(GL_VERSION);

    if (!version || version[0] < '3' || ((version[0] == '3') && (version[2] < '3'))) {
      success = GHOST_kFailure;
    }
    else {
      success = GHOST_kSuccess;
    }
  }
  else {
    /* freeing well clean up the context initialized above */
    success = GHOST_kFailure;
  }

  GHOST_X11_ERROR_HANDLERS_RESTORE(handler_store);

  return success;
}

GHOST_TSuccess GHOST_ContextGLX::releaseNativeHandles()
{
  m_window = 0;

  return GHOST_kSuccess;
}

GHOST_TSuccess GHOST_ContextGLX::setSwapInterval(int interval)
{
  if (epoxy_has_glx_extension(m_display, DefaultScreen(m_display), "GLX_EXT_swap_control")) {
    ::glXSwapIntervalEXT(m_display, m_window, interval);
    return GHOST_kSuccess;
  }
  return GHOST_kFailure;
}

GHOST_TSuccess GHOST_ContextGLX::getSwapInterval(int &intervalOut)
{
  if (epoxy_has_glx_extension(m_display, DefaultScreen(m_display), "GLX_EXT_swap_control")) {
    uint interval = 0;

    ::glXQueryDrawable(m_display, m_window, GLX_SWAP_INTERVAL_EXT, &interval);

    intervalOut = int(interval);

    return GHOST_kSuccess;
  }
  return GHOST_kFailure;
}

/**
 * Utility function to get GLX attributes.
 *
 * \param for_fb_config: There are some small differences in
 * #glXChooseVisual and #glXChooseFBConfig's attribute encoding.
 *
 * \note Similar to SDL's 'X11_GL_GetAttributes'
 */
int GHOST_X11_GL_GetAttributes(
    int *attribs, int attribs_max, bool is_stereo_visual, bool need_alpha, bool for_fb_config)
{
  int i = 0;

  if (is_stereo_visual) {
    attribs[i++] = GLX_STEREO;
    if (for_fb_config) {
      attribs[i++] = True;
    }
  }

  if (for_fb_config) {
    attribs[i++] = GLX_RENDER_TYPE;
    attribs[i++] = GLX_RGBA_BIT;
  }
  else {
    attribs[i++] = GLX_RGBA;
  }

  attribs[i++] = GLX_DOUBLEBUFFER;
  if (for_fb_config) {
    attribs[i++] = True;
  }

  attribs[i++] = GLX_RED_SIZE;
  attribs[i++] = True;

  attribs[i++] = GLX_BLUE_SIZE;
  attribs[i++] = True;

  attribs[i++] = GLX_GREEN_SIZE;
  attribs[i++] = True;

  if (need_alpha) {
    attribs[i++] = GLX_ALPHA_SIZE;
    attribs[i++] = True;
  }

  attribs[i++] = 0;

  GHOST_ASSERT(i <= attribs_max, "attribute size too small");

  (void)attribs_max;

  return i;
}

/* Excuse inlining part of GLEW. */
#ifdef USE_GLXEW_INIT_WORKAROUND
static GLuint _glewStrLen(const GLubyte *s)
{
  GLuint i = 0;
  if (s == nullptr) {
    return 0;
  }
  while (s[i] != '\0') {
    i++;
  }
  return i;
}

static GLuint _glewStrCLen(const GLubyte *s, GLubyte c)
{
  GLuint i = 0;
  if (s == nullptr) {
    return 0;
  }
  while (s[i] != '\0' && s[i] != c) {
    i++;
  }
  return (s[i] == '\0' || s[i] == c) ? i : 0;
}

static GLboolean _glewStrSame(const GLubyte *a, const GLubyte *b, GLuint n)
{
  GLuint i = 0;
  if (a == nullptr || b == nullptr) {
    return (a == nullptr && b == nullptr && n == 0) ? GL_TRUE : GL_FALSE;
  }
  while (i < n && a[i] != '\0' && b[i] != '\0' && a[i] == b[i]) {
    i++;
  }
  return i == n ? GL_TRUE : GL_FALSE;
}

static GLboolean _glewSearchExtension(const char *name, const GLubyte *start, const GLubyte *end)
{
  const GLubyte *p;
  GLuint len = _glewStrLen((const GLubyte *)name);
  p = start;
  while (p < end) {
    GLuint n = _glewStrCLen(p, ' ');
    if (len == n && _glewStrSame((const GLubyte *)name, p, n)) {
      return GL_TRUE;
    }
    p += n + 1;
  }
  return GL_FALSE;
}
#endif /* USE_GLXEW_INIT_WORKAROUND */