// Fl_Gl_Window.C

#include <config.h>
#if HAVE_GL

#include <FL/Fl.H>
#include <FL/x.H>
#include <FL/Fl_Gl_Window.H>
#include "Fl_Gl_Choice.H"

////////////////////////////////////////////////////////////////

// The symbol SWAP_TYPE defines what is in the back buffer after doing
// a glXSwapBuffers().

// The OpenGl documentation says that the contents of the backbuffer
// are "undefined" after glXSwapBuffers().  However, if we know what
// is in the backbuffers then we can save a good deal of time.  For
// this reason you can define some symbols to describe what is left in
// the back buffer.

// The default of SWAP_SWAP works on an SGI, and will also work (but
// is sub-optimal) on machines that should be SWAP_COPY or SWAP_NODAMAGE.
// The win32 emulation of OpenGL can use COPY, but some (all?) OpenGL
// cards use SWAP.

// contents of back buffer after glXSwapBuffers():
#define UNDEFINED 0 	// unknown
#define SWAP 1		// former front buffer
#define COPY 2		// unchanged
#define NODAMAGE 3	// unchanged even by X expose() events

#ifdef MESA
#define SWAP_TYPE NODAMAGE
#else
#define SWAP_TYPE SWAP
#endif

////////////////////////////////////////////////////////////////

HDC fl_GetDC(HWND);

int Fl_Gl_Window::can_do(int a, const int *b) {
#ifdef WIN32
  Fl_Gl_Choice *g = Fl_Gl_Choice::find(a,b);
/*
  Is this necessary? Don't all windows have the same 
  support for pixel formats?
  HWND w = GetDesktopWindow();
  HDC dc = GetDC(w);
*/
  if (!fl_gc) fl_GetDC(0);
  int r = ChoosePixelFormat(fl_gc, &g->pfd);
  return r != 0;
#else
  return Fl_Gl_Choice::find(a,b) != 0;
#endif
}

void Fl_Gl_Window::show() {
#ifndef WIN32
  if (!shown()) {
    if (!g) {
      g = Fl_Gl_Choice::find(mode_,alist);
      if (!g) {Fl::error("Insufficient GL support"); return;}
    }
    Fl_X::make_xid(this, g->vis, g->colormap);
    if (overlay && overlay != this) ((Fl_Gl_Window*)overlay)->show();
  }
#endif
  Fl_Window::show();
}

void Fl_Gl_Window::invalidate() {
  valid(0);
#ifndef WIN32
  if (overlay) ((Fl_Gl_Window*)overlay)->valid(0);
#endif
}

extern GLXContext fl_first_context; // in Fl_Gl_Choice.C

int Fl_Gl_Window::mode(int m, const int *a) {
  if (m == mode_ && a == alist) return 0;
  mode_ = m; alist = a;
#ifdef WIN32
  // destroy context and g:
  if (shown()) {hide(); show();}
#else
  // under X, if the visual changes we must make a new X window (!):
  if (shown()) {
    Fl_Gl_Choice *g1 = g;
    g = Fl_Gl_Choice::find(mode_,alist);
    if (!g || g->vis->visualid != g1->vis->visualid || g->d != g1->d) {
      hide(); show();
    }
  }
#endif
  return 1;
}

#ifdef WIN32
extern char fl_direct_paint; // true when responding to WM_PAINT
#endif

void Fl_Gl_Window::make_current() {
#ifdef WIN32
  HDC hdc = fl_private_dc(this, mode_,&g);
  if (!context) {
    context = wglCreateContext(hdc);
    if (fl_first_context) wglShareLists(fl_first_context, (GLXContext)context);
    else fl_first_context = (GLXContext)context;
    valid(0);
  }
  wglMakeCurrent(hdc, (GLXContext)context);
#else
  if (!context) {
    context = glXCreateContext(fl_display, g->vis, fl_first_context, 1);
    if (!fl_first_context) fl_first_context = (GLXContext)context;
    valid(0);
  }
  glXMakeCurrent(fl_display, fl_xid(this), (GLXContext)context);
#endif
  glDrawBuffer(GL_BACK);
}

void Fl_Gl_Window::ortho() {
  glLoadIdentity();
  glViewport(0, 0, w(), h());
  glOrtho(0, w(), 0, h(), -1, 1);
}

void Fl_Gl_Window::swap_buffers() {
#ifdef WIN32
  SwapBuffers(Fl_X::i(this)->private_dc);
#else
  glXSwapBuffers(fl_display, fl_xid(this));
#endif
}

#if HAVE_GL_OVERLAY
#if WIN32
uchar fl_overlay; // changes how fl_color() works
#endif
#endif

void Fl_Gl_Window::flush() {
  make_current();

#if HAVE_GL_OVERLAY
#ifdef WIN32
  uchar save_valid = valid_;
  if (overlay && overlay!= this && damage() == 8) goto DRAW_OVERLAY_ONLY;
#endif
#endif

  if (g->d) {

#if SWAP_TYPE == NODAMAGE

    // don't draw if only overlay damage or expose events:
    if ((damage()&~0xA0) || !valid()) draw();
    swap_buffers();

#elif SWAP_TYPE == COPY

    // don't draw if only the overlay is damaged:
    if (damage() != 8 || !valid()) draw();
    swap_buffers();

#else // SWAP_TYPE == SWAP || SWAP_TYPE == UNDEFINED

    if (overlay == this) { // Use CopyPixels to act like SWAP_TYPE == COPY

      // don't draw if only the overlay is damaged:
      if (damage1_ || damage() != 8 || !valid()) draw();
      // we use a seperate context for the copy because rasterpos must be 0
      // and depth test needs to be off:
      static GLXContext ortho_context;
      int init = !ortho_context;
#ifdef WIN32
      if (init) ortho_context = wglCreateContext(Fl_X::i(this)->private_dc);
      wglMakeCurrent(Fl_X::i(this)->private_dc, ortho_context);
#else
      if (init)
	ortho_context = glXCreateContext(fl_display,g->vis,fl_first_context,1);
      glXMakeCurrent(fl_display, fl_xid(this), ortho_context);
#endif
      if (init) {
	glDisable(GL_DEPTH_TEST);
	glReadBuffer(GL_BACK);
	glDrawBuffer(GL_FRONT);
      }
      glCopyPixels(0,0,w(),h(),GL_COLOR);
      make_current(); // set current context back to draw overlay
      damage1_ = 0;

    } else {

#if SWAP_TYPE == SWAP
      uchar old_damage = damage();
      clear_damage(damage1_|old_damage); draw();
      swap_buffers();
      damage1_ = old_damage;
#else // SWAP_TYPE == UNDEFINED
      clear_damage(~0); draw();
      swap_buffers();
      damage1_ = ~0;
#endif

    }
#endif

    if (overlay==this) { // fake overlay in front buffer
      glDrawBuffer(GL_FRONT);
      draw_overlay();
      glDrawBuffer(GL_BACK);
      glFlush();
    }

  } else {	// single-buffered context is simpler:

    // this faking of the overlay is incorrect but worked good for
    // one in-house program:
    if (overlay != this || damage()!=8 || !Fl::pushed()) draw();
    if (overlay == this) draw_overlay();
    glFlush();

  }

#if HAVE_GL_OVERLAY
#ifdef WIN32
  if (overlay && overlay != this) {
  DRAW_OVERLAY_ONLY:
    valid_ = save_valid;
    wglMakeCurrent(Fl_X::i(this)->private_dc, (GLXContext)overlay);
    glDisable(GL_SCISSOR_TEST);
    fl_overlay = 1;
    glClear(GL_COLOR_BUFFER_BIT);
    draw_overlay();
    wglSwapLayerBuffers(Fl_X::i(this)->private_dc,WGL_SWAP_OVERLAY1);
    fl_overlay = 0;
  }
#endif
#endif

  valid(1);
}

void Fl_Gl_Window::resize(int X,int Y,int W,int H) {
  if (W != w() || H != h()) valid(0);
  Fl_Window::resize(X,Y,W,H);
}

void Fl_Gl_Window::hide() {
  if (context) {
#ifdef WIN32
    wglMakeCurrent(0, 0);
    if (context && context != fl_first_context)
      wglDeleteContext((GLXContext)context);
    g = 0;
#else
    glXMakeCurrent(fl_display, 0, 0);
    if (context != fl_first_context)
      glXDestroyContext(fl_display, (GLXContext)context);
#ifdef GLX_MESA_release_buffers
    glXReleaseBuffersMESA(fl_display, fl_xid(this));
#endif
#endif
    context = 0;
  }
  Fl_Window::hide();
}

Fl_Gl_Window::~Fl_Gl_Window() {
  hide();
//  delete overlay; this is done by ~Fl_Group
}

void Fl_Gl_Window::init() {
  end(); // we probably don't want any children
  box(FL_NO_BOX);
  mode_ = FL_RGB | FL_DEPTH | FL_DOUBLE;
  alist = 0;
  context = 0;
  g = 0;
  overlay = 0;
  damage1_ = 0;
}

void Fl_Gl_Window::draw_overlay() {}

#endif