2 files changed, 553 insertions, 5 deletions

diff --git a/src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx b/src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx
new file mode 100644
index 000000000..a52d4c70f
--- /dev/null
+++ b/src/drivers/X11/Fl_X11_Gl_Window_Driver.cxx
@@ -0,0 +1,549 @@
+//
+// Class Fl_X11_Gl_Window_Driver for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 2021 by Bill Spitzak and others.
+//
+// This library is free software. Distribution and use rights are outlined in
+// the file "COPYING" which should have been included with this file.  If this
+// file is missing or damaged, see the license at:
+//
+//     https://www.fltk.org/COPYING.php
+//
+// Please see the following page on how to report bugs and issues:
+//
+//     https://www.fltk.org/bugs.php
+//
+
+#include <config.h>
+#if HAVE_GL
+#include <FL/platform.H>
+#include "../../Fl_Gl_Choice.H"
+#include "../../Fl_Screen_Driver.H"
+#include "../../Fl_Window_Driver.H"
+#include "../../Fl_Gl_Window_Driver.H"
+#include "../Xlib/Fl_Font.H"
+#include "../Xlib/Fl_Xlib_Graphics_Driver.H"
+#  include <GL/glx.h>
+#  if ! defined(GLX_VERSION_1_3)
+#    typedef void *GLXFBConfig;
+#  endif
+
+class Fl_X11_Gl_Window_Driver : public Fl_Gl_Window_Driver {
+  friend class Fl_Gl_Window_Driver;
+  Fl_X11_Gl_Window_Driver(Fl_Gl_Window *win) : Fl_Gl_Window_Driver(win) {}
+  virtual float pixels_per_unit();
+  virtual void before_show(int& need_after);
+  virtual int mode_(int m, const int *a);
+  virtual void swap_buffers();
+  virtual void resize(int is_a_resize, int w, int h);
+  virtual char swap_type();
+  virtual Fl_Gl_Choice *find(int m, const int *alistp);
+  virtual GLContext create_gl_context(Fl_Window* window, const Fl_Gl_Choice* g, int layer = 0);
+  virtual void set_gl_context(Fl_Window* w, GLContext context);
+  virtual void delete_gl_context(GLContext);
+#if HAVE_GL_OVERLAY
+  virtual void make_overlay(void *&o);
+  virtual int can_do_overlay();
+  virtual void hide_overlay();
+  virtual int overlay_color(Fl_Color i);
+#endif
+  virtual void make_overlay_current();
+  virtual void redraw_overlay();
+  virtual void waitGL();
+  virtual void gl_visual(Fl_Gl_Choice*); // support for Fl::gl_visual()
+  virtual void gl_start();
+  virtual void draw_string_legacy(const char* str, int n);
+  virtual void gl_bitmap_font(Fl_Font_Descriptor *fl_fontsize);
+  virtual void get_list(Fl_Font_Descriptor *fd, int r);
+  virtual int genlistsize();
+#if !USE_XFT
+  virtual Fl_Font_Descriptor** fontnum_to_fontdescriptor(int fnum);
+#endif
+  public:
+  static GLContext create_gl_context(XVisualInfo* vis);
+};
+
+// Describes crap needed to create a GLContext.
+class Fl_X11_Gl_Choice : public Fl_Gl_Choice {
+  friend class Fl_X11_Gl_Window_Driver;
+private:
+  XVisualInfo *vis; /* the visual to use */
+  Colormap colormap; /* a colormap for that visual */
+  GLXFBConfig best_fb;
+public:
+  Fl_X11_Gl_Choice(int m, const int *alistp, Fl_Gl_Choice *n) : Fl_Gl_Choice(m, alistp, n) {
+    vis = NULL;
+    colormap = 0;
+    best_fb = NULL;
+  }
+};
+
+void Fl_X11_Gl_Window_Driver::draw_string_legacy(const char* str, int n) {
+  draw_string_legacy_get_list(str, n);
+}
+
+int Fl_X11_Gl_Window_Driver::genlistsize() {
+#if USE_XFT
+  return 256;
+#else
+  return 0x10000;
+#endif
+}
+
+void Fl_X11_Gl_Window_Driver::gl_bitmap_font(Fl_Font_Descriptor *fl_fontsize) {
+  /* This method should ONLY be triggered if our GL font texture pile mechanism
+   * is not working on this platform. This code might not reliably render glyphs
+   * from higher codepoints. */
+  if (!fl_fontsize->listbase) {
+#if USE_XFT
+    /* Ideally, for XFT, we need a glXUseXftFont implementation here... But we
+     * do not have such a thing. Instead, we try to find a legacy Xlib font that
+     * matches the current XFT font and use that.
+     * Ideally, we never come here - we hope the texture pile implementation
+     * will work correctly so that XFT can render the face directly without the
+     * need for this workaround. */
+    XFontStruct *font = fl_xfont.value();
+    int base = font->min_char_or_byte2;
+    int count = font->max_char_or_byte2 - base + 1;
+    fl_fontsize->listbase = glGenLists(genlistsize());
+    glXUseXFont(font->fid, base, count, fl_fontsize->listbase+base);
+#else
+    /* Not using XFT to render text - the legacy Xlib fonts can usually be rendered
+     * directly by using glXUseXFont mechanisms. */
+    fl_fontsize->listbase = glGenLists(genlistsize());
+#endif // !USE_XFT
+  }
+  glListBase(fl_fontsize->listbase);
+}
+
+
+void Fl_X11_Gl_Window_Driver::get_list(Fl_Font_Descriptor *fd, int r) {
+# if USE_XFT
+  /* We hope not to come here: We hope that any system using XFT will also
+   * have sufficient GL capability to support our font texture pile mechansim,
+   * allowing XFT to render the face directly. */
+  // Face already set by gl_bitmap_font in this case.
+# else
+  Fl_Xlib_Font_Descriptor *gl_fd = (Fl_Xlib_Font_Descriptor*)fd;
+  if (gl_fd->glok[r]) return;
+  gl_fd->glok[r] = 1;
+  unsigned int ii = r * 0x400;
+  for (int i = 0; i < 0x400; i++) {
+    XFontStruct *font = NULL;
+    unsigned short id;
+    fl_XGetUtf8FontAndGlyph(gl_fd->font, ii, &font, &id);
+    if (font) glXUseXFont(font->fid, id, 1, gl_fd->listbase+ii);
+    ii++;
+  }
+# endif
+}
+
+#if !USE_XFT
+Fl_Font_Descriptor** Fl_X11_Gl_Window_Driver::fontnum_to_fontdescriptor(int fnum) {
+  Fl_Xlib_Fontdesc *s = ((Fl_Xlib_Fontdesc*)fl_fonts) + fnum;
+  return &(s->first);
+}
+#endif
+
+
+static XVisualInfo *gl3_getvisual(const int *blist, GLXFBConfig *pbestFB)
+{
+  int glx_major, glx_minor;
+
+  // FBConfigs were added in GLX version 1.3.
+  if ( !glXQueryVersion(fl_display, &glx_major, &glx_minor) ||
+      ( ( glx_major == 1 ) && ( glx_minor < 3 ) ) || ( glx_major < 1 ) ) {
+    return NULL;
+  }
+
+  //printf( "Getting matching framebuffer configs\n" );
+  int fbcount;
+  GLXFBConfig* fbc = glXChooseFBConfig(fl_display, DefaultScreen(fl_display), blist, &fbcount);
+  if (!fbc) {
+    //printf( "Failed to retrieve a framebuffer config\n" );
+    return NULL;
+  }
+  //printf( "Found %d matching FB configs.\n", fbcount );
+
+  // Pick the FB config/visual with the most samples per pixel
+  int best_fbc = -1, worst_fbc = -1, best_num_samp = -1, worst_num_samp = 999;
+  for (int i = 0; i < fbcount; ++i)
+  {
+    XVisualInfo *vi = glXGetVisualFromFBConfig( fl_display, fbc[i] );
+    if (vi) {
+      int samp_buf, samples;
+      glXGetFBConfigAttrib(fl_display, fbc[i], GLX_SAMPLE_BUFFERS, &samp_buf);
+      glXGetFBConfigAttrib(fl_display, fbc[i], GLX_SAMPLES       , &samples );
+      /*printf( "  Matching fbconfig %d, visual ID 0x%2lx: SAMPLE_BUFFERS = %d, SAMPLES = %d\n",
+             i, vi -> visualid, samp_buf, samples );*/
+      if ( best_fbc < 0 || (samp_buf && samples > best_num_samp) )
+        best_fbc = i, best_num_samp = samples;
+      if ( worst_fbc < 0 || !samp_buf || samples < worst_num_samp )
+        worst_fbc = i, worst_num_samp = samples;
+    }
+    XFree(vi);
+  }
+
+  GLXFBConfig bestFbc = fbc[ best_fbc ];
+  // Be sure to free the FBConfig list allocated by glXChooseFBConfig()
+  XFree(fbc);
+  // Get a visual
+  XVisualInfo *vi = glXGetVisualFromFBConfig(fl_display, bestFbc);
+  *pbestFB = bestFbc;
+  return vi;
+}
+
+Fl_Gl_Choice *Fl_X11_Gl_Window_Driver::find(int m, const int *alistp)
+{
+  Fl_X11_Gl_Choice *g = (Fl_X11_Gl_Choice*)Fl_Gl_Window_Driver::find_begin(m, alistp);
+  if (g) return g;
+
+  const int *blist;
+  int list[32];
+
+  if (alistp)
+    blist = alistp;
+  else {
+    int n = 0;
+    if (m & FL_INDEX) {
+      list[n++] = GLX_BUFFER_SIZE;
+      list[n++] = 8; // glut tries many sizes, but this should work...
+    } else {
+      list[n++] = GLX_RGBA;
+      list[n++] = GLX_GREEN_SIZE;
+      list[n++] = (m & FL_RGB8) ? 8 : 1;
+      if (m & FL_ALPHA) {
+        list[n++] = GLX_ALPHA_SIZE;
+        list[n++] = (m & FL_RGB8) ? 8 : 1;
+      }
+      if (m & FL_ACCUM) {
+        list[n++] = GLX_ACCUM_GREEN_SIZE;
+        list[n++] = 1;
+        if (m & FL_ALPHA) {
+          list[n++] = GLX_ACCUM_ALPHA_SIZE;
+          list[n++] = 1;
+        }
+      }
+    }
+    if (m & FL_DOUBLE) {
+      list[n++] = GLX_DOUBLEBUFFER;
+    }
+    if (m & FL_DEPTH) {
+      list[n++] = GLX_DEPTH_SIZE; list[n++] = 1;
+    }
+    if (m & FL_STENCIL) {
+      list[n++] = GLX_STENCIL_SIZE; list[n++] = 1;
+    }
+    if (m & FL_STEREO) {
+      list[n++] = GLX_STEREO;
+    }
+#    if defined(GLX_VERSION_1_1) && defined(GLX_SGIS_multisample)
+    if (m & FL_MULTISAMPLE) {
+      list[n++] = GLX_SAMPLES_SGIS;
+      list[n++] = 4; // value Glut uses
+    }
+#    endif
+    list[n] = 0;
+    blist = list;
+  }
+
+  fl_open_display();
+  XVisualInfo *visp = NULL;
+  GLXFBConfig best_fb = NULL;
+  if (m & FL_OPENGL3) {
+    visp = gl3_getvisual((const int *)blist, &best_fb);
+  }
+  if (!visp) {
+    visp = glXChooseVisual(fl_display, fl_screen, (int *)blist);
+    if (!visp) {
+#     if defined(GLX_VERSION_1_1) && defined(GLX_SGIS_multisample)
+        if (m&FL_MULTISAMPLE) return find(m&~FL_MULTISAMPLE, 0);
+#     endif
+      return 0;
+    }
+  }
+
+  g = new Fl_X11_Gl_Choice(m, alistp, first);
+  first = g;
+
+  g->vis = visp;
+  g->best_fb = best_fb;
+
+  if (/*MaxCmapsOfScreen(ScreenOfDisplay(fl_display,fl_screen))==1 && */
+      visp->visualid == fl_visual->visualid &&
+      !fl_getenv("MESA_PRIVATE_CMAP"))
+    g->colormap = fl_colormap;
+  else
+    g->colormap = XCreateColormap(fl_display, RootWindow(fl_display,fl_screen),
+                                  visp->visual, AllocNone);
+  return g;
+}
+
+static bool ctxErrorOccurred = false;
+static int ctxErrorHandler( Display *dpy, XErrorEvent *ev )
+{
+  ctxErrorOccurred = true;
+  return 0;
+}
+
+GLContext Fl_X11_Gl_Window_Driver::create_gl_context(Fl_Window* window, const Fl_Gl_Choice* g, int layer) {
+  GLContext shared_ctx = 0;
+  if (context_list && nContext) shared_ctx = context_list[0];
+
+  typedef GLContext (*glXCreateContextAttribsARBProc)(Display*, GLXFBConfig, GLContext, Bool, const int*);
+  // It is not necessary to create or make current to a context before calling glXGetProcAddressARB
+  static glXCreateContextAttribsARBProc glXCreateContextAttribsARB =
+#if defined(HAVE_GLXGETPROCADDRESSARB)
+    (glXCreateContextAttribsARBProc)glXGetProcAddressARB((const GLubyte *)"glXCreateContextAttribsARB");
+#else
+  NULL;
+#endif
+
+  GLContext ctx = 0;
+  // Check for the GLX_ARB_create_context extension string and the function.
+  // If either is not present, use GLX 1.3 context creation method.
+  const char *glxExts = glXQueryExtensionsString(fl_display, fl_screen);
+  if (((Fl_X11_Gl_Choice*)g)->best_fb && strstr(glxExts, "GLX_ARB_create_context") && glXCreateContextAttribsARB ) {
+    int context_attribs[] =
+    {
+      GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
+      GLX_CONTEXT_MINOR_VERSION_ARB, 2,
+      //GLX_CONTEXT_FLAGS_ARB        , GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
+      //GLX_CONTEXT_PROFILE_MASK_ARB , GLX_CONTEXT_CORE_PROFILE_BIT_ARB,
+      None
+    };
+    ctxErrorOccurred = false;
+    XErrorHandler oldHandler = XSetErrorHandler(&ctxErrorHandler);
+    ctx = glXCreateContextAttribsARB(fl_display, ((Fl_X11_Gl_Choice*)g)->best_fb, shared_ctx, true, context_attribs);
+    XSync(fl_display, false); // Sync to ensure any errors generated are processed.
+    if (ctxErrorOccurred) ctx = 0;
+    XSetErrorHandler(oldHandler);
+  }
+  if (!ctx) { // use OpenGL 1-style context creation
+    ctx = glXCreateContext(fl_display, ((Fl_X11_Gl_Choice*)g)->vis, shared_ctx, true);
+  }
+  if (ctx)
+    add_context(ctx);
+//glXMakeCurrent(fl_display, fl_xid(window), ctx);printf("%s\n", glGetString(GL_VERSION));
+  return ctx;
+}
+
+GLContext Fl_X11_Gl_Window_Driver::create_gl_context(XVisualInfo *vis) {
+  GLContext shared_ctx = 0;
+  if (context_list && nContext) shared_ctx = context_list[0];
+  GLContext context = glXCreateContext(fl_display, vis, shared_ctx, 1);
+  if (context)
+    add_context(context);
+  return context;
+}
+
+void Fl_X11_Gl_Window_Driver::set_gl_context(Fl_Window* w, GLContext context) {
+  if (context != cached_context || w != cached_window) {
+    cached_context = context;
+    cached_window = w;
+    glXMakeCurrent(fl_display, fl_xid(w), context);
+  }
+}
+
+void Fl_X11_Gl_Window_Driver::delete_gl_context(GLContext context) {
+  if (cached_context == context) {
+    cached_context = 0;
+    cached_window = 0;
+    glXMakeCurrent(fl_display, 0, 0);
+  }
+  glXDestroyContext(fl_display, context);
+  del_context(context);
+}
+
+
+void Fl_X11_Gl_Window_Driver::make_overlay_current() {
+#if HAVE_GL_OVERLAY
+  if (overlay() != pWindow) {
+    ((Fl_Gl_Window*)overlay())->make_current();
+  } else
+#endif
+    glDrawBuffer(GL_FRONT);
+}
+
+void Fl_X11_Gl_Window_Driver::redraw_overlay() {
+  if (overlay() != pWindow)
+    ((Fl_Gl_Window*)overlay())->redraw();
+  else
+    pWindow->damage(FL_DAMAGE_OVERLAY);
+}
+
+#if HAVE_GL_OVERLAY
+
+// Methods on Fl_Gl_Window_Driver that create an overlay window.
+
+// Under X this is done by creating another window, of class _Fl_Gl_Overlay
+// which is a subclass of Fl_Gl_Window except it uses the overlay planes.
+// A pointer to this is stored in the "overlay" pointer of the Fl_Gl_Window.
+
+// If overlay hardware is unavailable, the overlay is
+// "faked" by drawing into the main layers.  This is indicated by
+// setting overlay == this.
+
+extern XVisualInfo *fl_find_overlay_visual();
+extern XVisualInfo *fl_overlay_visual;
+extern Colormap fl_overlay_colormap;
+extern unsigned long fl_transparent_pixel;
+//extern uchar fl_overlay;
+
+int Fl_X11_Gl_Window_Driver::overlay_color(Fl_Color i) {
+  if (Fl_Xlib_Graphics_Driver::fl_overlay) {glIndexi(int(fl_xpixel(i))); return 1;}
+  return 0;
+}
+
+
+class _Fl_Gl_Overlay : public Fl_Gl_Window {
+  void flush();
+  void draw();
+public:
+  void show();
+  _Fl_Gl_Overlay(int x, int y, int w, int h) :
+    Fl_Gl_Window(x,y,w,h) {
+    set_flag(INACTIVE);
+  }
+};
+
+void _Fl_Gl_Overlay::flush() {
+  make_current();
+#ifdef BOXX_BUGS
+  // The BoXX overlay is broken and you must not call swap-buffers. This
+  // code will make it work, but we lose because machines that do support
+  // double-buffered overlays will blink when they don't have to
+  glDrawBuffer(GL_FRONT);
+  draw();
+#else
+  draw();
+  swap_buffers();
+#endif
+  glFlush();
+  valid(1);
+}
+
+void _Fl_Gl_Overlay::draw() {
+  if (!valid()) glClearIndex((GLfloat)fl_transparent_pixel);
+  if (damage() != FL_DAMAGE_EXPOSE) glClear(GL_COLOR_BUFFER_BIT);
+  Fl_Gl_Window *w = (Fl_Gl_Window *)parent();
+  uchar save_valid = w->valid();
+  w->valid(valid());
+  Fl_Xlib_Graphics_Driver::fl_overlay = 1;
+  w->gl_driver()->draw_overlay();
+  Fl_Xlib_Graphics_Driver::fl_overlay = 0;
+  valid(w->valid());
+  w->valid(save_valid);
+}
+
+void _Fl_Gl_Overlay::show() {
+  if (!shown()) {
+    fl_background_pixel = int(fl_transparent_pixel);
+    Fl_X::make_xid(this, fl_overlay_visual, fl_overlay_colormap);
+    fl_background_pixel = -1;
+    // find the outermost window to tell wm about the colormap:
+    Fl_Window *w = window();
+    for (;;) {Fl_Window *w1 = w->window(); if (!w1) break; w = w1;}
+    XSetWMColormapWindows(fl_display, fl_xid(w), &(Fl_X::i(this)->xid), 1);
+    context(Fl_X11_Gl_Window_Driver::create_gl_context(fl_overlay_visual), 1);
+    valid(0);
+  }
+  Fl_Gl_Window::show();
+}
+
+void Fl_X11_Gl_Window_Driver::hide_overlay() {
+  if (overlay() && overlay() != pWindow) ((Fl_Gl_Window*)overlay())->hide();
+}
+
+int Fl_X11_Gl_Window_Driver::can_do_overlay() {
+  return fl_find_overlay_visual() != 0;
+}
+
+
+void Fl_X11_Gl_Window_Driver::make_overlay(void *&current) {
+  if (current) return;
+  if (can_do_overlay()) {
+    _Fl_Gl_Overlay* o = new _Fl_Gl_Overlay(0, 0, pWindow->w(), pWindow->h());
+    current = o;
+    pWindow->add(*o);
+    o->show();
+  } else {
+    current = pWindow; // fake the overlay
+  }
+}
+#endif // HAVE_GL_OVERLAY
+
+
+Fl_Gl_Window_Driver *Fl_Gl_Window_Driver::newGlWindowDriver(Fl_Gl_Window *w)
+{
+  return new Fl_X11_Gl_Window_Driver(w);
+}
+
+void Fl_X11_Gl_Window_Driver::before_show(int&) {
+  Fl_X11_Gl_Choice *g = (Fl_X11_Gl_Choice*)this->g();
+  Fl_X::make_xid(pWindow, g->vis, g->colormap);
+  if (overlay() && overlay() != pWindow) ((Fl_Gl_Window*)overlay())->show();
+}
+
+float Fl_X11_Gl_Window_Driver::pixels_per_unit()
+{
+  int ns = Fl_Window_Driver::driver(pWindow)->screen_num();
+  return Fl::screen_driver()->scale(ns);
+}
+
+int Fl_X11_Gl_Window_Driver::mode_(int m, const int *a) {
+  int oldmode = mode();
+  if (a) { // when the mode is set using the a array of system-dependent values, and if asking for double buffer,
+    // the FL_DOUBLE flag must be set in the mode_ member variable
+    const int *aa = a;
+    while (*aa) {
+      if (*(aa++) ==
+          GLX_DOUBLEBUFFER
+          ) { m |= FL_DOUBLE; break; }
+    }
+  }
+  Fl_X11_Gl_Choice* oldg = (Fl_X11_Gl_Choice*)g();
+  pWindow->context(0);
+  mode(m); alist(a);
+  if (pWindow->shown()) {
+    g( find(m, a) );
+    // under X, if the visual changes we must make a new X window (yuck!):
+    Fl_X11_Gl_Choice* g = (Fl_X11_Gl_Choice*)this->g();
+    if (!g || g->vis->visualid != oldg->vis->visualid || (oldmode^m)&FL_DOUBLE) {
+      pWindow->hide();
+      pWindow->show();
+    }
+  } else {
+    g(0);
+  }
+  return 1;
+}
+
+void Fl_X11_Gl_Window_Driver::swap_buffers() {
+  glXSwapBuffers(fl_display, fl_xid(pWindow));
+}
+
+void Fl_X11_Gl_Window_Driver::resize(int is_a_resize, int W, int H) {
+  if (is_a_resize && !pWindow->resizable() && overlay() && overlay() != pWindow) {
+    ((Fl_Gl_Window*)overlay())->resize(0,0,W,H);
+  }
+}
+
+char Fl_X11_Gl_Window_Driver::swap_type() {return copy;}
+
+void Fl_X11_Gl_Window_Driver::waitGL() {
+  glXWaitGL();
+}
+
+
+void Fl_X11_Gl_Window_Driver::gl_visual(Fl_Gl_Choice *c) {
+  Fl_Gl_Window_Driver::gl_visual(c);
+  fl_visual = ((Fl_X11_Gl_Choice*)c)->vis;
+  fl_colormap = ((Fl_X11_Gl_Choice*)c)->colormap;
+}
+
+void Fl_X11_Gl_Window_Driver::gl_start() {
+  glXWaitX();
+}
+
+#endif // HAVE_GL
diff --git a/src/drivers/X11/Fl_X11_Window_Driver.cxx b/src/drivers/X11/Fl_X11_Window_Driver.cxx
index 19fc70b09..d757aa752 100644
--- a/src/drivers/X11/Fl_X11_Window_Driver.cxx
+++ b/src/drivers/X11/Fl_X11_Window_Driver.cxx
@@ -40,7 +40,6 @@ extern XVisualInfo *fl_find_overlay_visual();
 extern XVisualInfo *fl_overlay_visual;
 extern Colormap fl_overlay_colormap;
 extern unsigned long fl_transparent_pixel;
-extern uchar fl_overlay; // changes how fl_color(x) works
 #endif
 
 Window fl_window;
@@ -595,13 +594,13 @@ void _Fl_Overlay::flush() {
 #if defined(FLTK_USE_CAIRO)
   if (Fl::cairo_autolink_context()) Fl::cairo_make_current(this); // capture gc changes automatically to update the cairo context adequately
 #endif
-  fl_overlay = 1;
+  Fl_Xlib_Graphics_Driver::fl_overlay = 1;
   Fl_Overlay_Window *w = (Fl_Overlay_Window *)parent();
   Fl_X *myi = Fl_X::i(this);
   if (damage() != FL_DAMAGE_EXPOSE) XClearWindow(fl_display, fl_xid(this));
   fl_clip_region(myi->region); myi->region = 0;
   w->draw_overlay();
-  fl_overlay = 0;
+  Fl_Xlib_Graphics_Driver::fl_overlay = 0;
 }
 #endif // HAVE_OVERLAY
 
@@ -648,10 +647,10 @@ void Fl_X11_Window_Driver::flush_menu() {
    // capture gc changes automatically to update the cairo context adequately
    if(Fl::autolink_context()) Fl::cairo_make_current(fl_graphics_driver->gc());
 # endif
-   fl_overlay = 1;
+  Fl_Xlib_Graphics_Driver::fl_overlay = 1;
    fl_clip_region(myi->region); myi->region = 0; current(pWindow);
    draw();
-   fl_overlay = 0;
+  Fl_Xlib_Graphics_Driver::fl_overlay = 0;
 #else
    flush_Fl_Window();
 #endif