#include "gl_common.h"

/**
 * \brief adjusts the GL_UNPACK_ALGNMENT to fit the stride.
 * \param stride number of bytes per line for which alignment should fit.
 */
void glAdjustAlignment(int stride) {
  GLint gl_alignment;
  if (stride % 8 == 0)
    gl_alignment=8;
  else if (stride % 4 == 0)
    gl_alignment=4;
  else if (stride % 2 == 0)
    gl_alignment=2;
  else
    gl_alignment=1;
  glPixelStorei (GL_UNPACK_ALIGNMENT, gl_alignment);
}

#ifndef GL_WIN32
/**
 * Returns the XVisualInfo associated with Window win.
 * \param win Window whose XVisualInfo is returne.
 * \return XVisualInfo of the window. Caller must use XFree to free it.
 */
static XVisualInfo *getWindowVisualInfo(Window win) {
  XWindowAttributes xw_attr;
  XVisualInfo vinfo_template;
  int tmp;
  XGetWindowAttributes(mDisplay, win, &xw_attr);
  vinfo_template.visualid = XVisualIDFromVisual(xw_attr.visual);
  return XGetVisualInfo(mDisplay, VisualIDMask, &vinfo_template, &tmp);
}

/**
 * \brief Changes the window in which video is displayed.
 * If possible only transfers the context to the new window, otherwise
 * creates a new one, which must be initialized by the caller.
 * \param vinfo Currently used visual.
 * \param context Currently used context.
 * \param win window that should be used for drawing.
 * \return one of SET_WINDOW_FAILED, SET_WINDOW_OK or SET_WINDOW_REINIT.
 * In case of SET_WINDOW_REINIT the context could not be transfered
 * and the caller must initialize it correctly.
 */
int setGlWindow(XVisualInfo **vinfo, GLXContext *context, Window win)
{
  XVisualInfo *new_vinfo;
  GLXContext new_context = NULL;
  int keep_context = 0;

  // should only be needed when keeping context, but not doing glFinish
  // can cause flickering even when we do not keep it.
  glFinish();
  new_vinfo = getWindowVisualInfo(win);
  if (*context && *vinfo && new_vinfo &&
      (*vinfo)->visualid == new_vinfo->visualid) {
      // we can keep the GLXContext
      new_context = *context;
      XFree(new_vinfo);
      new_vinfo = *vinfo;
      keep_context = 1;
  } else {
    // create a context
    new_context = glXCreateContext(mDisplay, new_vinfo, NULL, True);
    if (!new_context) {
      mp_msg(MSGT_VO, MSGL_FATAL, "[gl] Could not create GLX context!\n");
      XFree(new_vinfo);
      return SET_WINDOW_FAILED;
    }
  }

  // set context
  if (!glXMakeCurrent(mDisplay, vo_window, new_context)) {
    mp_msg (MSGT_VO, MSGL_FATAL, "[gl] Could not set GLX context!\n");
    if (!keep_context) {
      glXDestroyContext (mDisplay, new_context);
      XFree(new_vinfo);
    }
    return SET_WINDOW_FAILED;
  }

  // set new values
  vo_window = win;
  {
    Window root;
    int tmp;
    XGetGeometry(mDisplay, vo_window, &root, &tmp, &tmp,
                  &vo_dwidth, &vo_dheight, &tmp, &tmp);
  }
  if (!keep_context) {
    if (*context)
      glXDestroyContext(mDisplay, *context);
    *context = new_context;
    if (*vinfo)
      XFree(*vinfo);
    *vinfo = new_vinfo;

    // and inform that reinit is neccessary
    return SET_WINDOW_REINIT;
  }
  return SET_WINDOW_OK;
}

/**
 * \brief free the VisualInfo and GLXContext of an OpenGL context.
 */
void releaseGlContext(XVisualInfo **vinfo, GLXContext *context) {
  if (*vinfo)
    XFree(*vinfo);
  *vinfo = NULL;
  if (*context)
    glXDestroyContext(mDisplay, *context);
  *context = 0;
}
#endif