Fixed 'flush()' code for single, double, and overlay buffering

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3-porting@11359 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

22 files changed, 593 insertions, 193 deletions

diff --git a/src/Fl.cxx b/src/Fl.cxx
index 88f82a151..5e725cfcc 100644
--- a/src/Fl.cxx
+++ b/src/Fl.cxx
@@ -1826,13 +1826,7 @@ void Fl_Widget::damage(uchar fl, int X, int Y, int W, int H) {
   }
   Fl::damage(FL_DAMAGE_CHILD);
 }
-void Fl_Window::flush() {
-  if (!shown()) return;
-  make_current();
-//if (damage() == FL_DAMAGE_EXPOSE && can_boxcheat(box())) fl_boxcheat = this;
-  fl_clip_region(i->region); i->region = 0;
-  draw();
-}
+
 
 #ifdef WIN32
 #  include "Fl_win32.cxx"
diff --git a/src/Fl_Double_Window.cxx b/src/Fl_Double_Window.cxx
index 49e890e22..701f53274 100644
--- a/src/Fl_Double_Window.cxx
+++ b/src/Fl_Double_Window.cxx
@@ -56,40 +56,6 @@ void Fl_Double_Window::show() {
 }*/
 
 
-/**
-  Forces the window to be redrawn.
-*/
-void Fl_Double_Window::flush()
-{
-  flush(0);
-}
-
-
-/**
-  Forces the window to be redrawn.
-  \param[in] eraseoverlay non-zero to erase overlay, zero to ignore
-
-  Fl_Overlay_Window relies on flush(1) copying the back buffer to the
-  front everywhere, even if damage() == 0, thus erasing the overlay,
-  and leaving the clip region set to the entire window.
-*/
-void Fl_Double_Window::flush(int eraseoverlay) {
-  if (!shown()) return;
-  make_current(); // make sure fl_gc is non-zero
-  Fl_X *myi = Fl_X::i(this);
-  if (!myi) return; // window not yet created
-  int retval = driver()->double_flush(eraseoverlay);
-  if (retval) return;
-  if (eraseoverlay) fl_clip_region(0);
-  // on Irix (at least) it is faster to reduce the area copied to
-  // the current clip region:
-  if (myi->other_xid) {
-    int X,Y,W,H; fl_graphics_driver->clip_box(0,0,w(),h(),X,Y,W,H);
-    fl_graphics_driver->copy_offscreen(X, Y, W, H, myi->other_xid, X, Y);
-  }
-}
-
-
 void Fl_Double_Window::resize(int X,int Y,int W,int H) {
   int ow = w();
   int oh = h();
@@ -108,6 +74,12 @@ void Fl_Double_Window::hide() {
 }
 
 
+void Fl_Double_Window::flush()
+{
+  driver()->flush_double();
+}
+
+
 /**
   The destructor <I>also deletes all the children</I>. This allows a
   whole tree to be deleted at once, without having to keep a pointer to
diff --git a/src/Fl_Overlay_Window.cxx b/src/Fl_Overlay_Window.cxx
index c1ae2728e..07065fbb0 100644
--- a/src/Fl_Overlay_Window.cxx
+++ b/src/Fl_Overlay_Window.cxx
@@ -53,20 +53,9 @@ void Fl_Overlay_Window::hide() {
   Fl_Double_Window::hide();
 }
 
-void Fl_Overlay_Window::flush() {
-#ifdef BOXX_BUGS
-  if (overlay_ && overlay_ != this && overlay_->shown()) {
-    // all drawing to windows hidden by overlay windows is ignored, fix this
-    XUnmapWindow(fl_display, fl_xid(overlay_));
-    Fl_Double_Window::flush(0);
-    XMapWindow(fl_display, fl_xid(overlay_));
-    return;
-  }
-#endif
-  int erase_overlay = (damage()&FL_DAMAGE_OVERLAY) | (overlay_ == this);
-  clear_damage((uchar)(damage()&~FL_DAMAGE_OVERLAY));
-  Fl_Double_Window::flush(erase_overlay);
-  if (overlay_ == this) draw_overlay();
+void Fl_Overlay_Window::flush()
+{
+  driver()->flush_overlay();
 }
 
 void Fl_Overlay_Window::resize(int X, int Y, int W, int H) {
diff --git a/src/Fl_Printer.cxx b/src/Fl_Printer.cxx
index 58db4cca8..47ae9748d 100644
--- a/src/Fl_Printer.cxx
+++ b/src/Fl_Printer.cxx
@@ -63,6 +63,8 @@ const char *Fl_Printer::property_cancel = NULL;
 
 #else
 
+#include "Fl_GDI_Printer.cxx"
+
 // print dialog customization strings
 /** [this text may be customized at run-time] */
 const char *Fl_Printer::dialog_title = "Print";
diff --git a/src/Fl_Single_Window.cxx b/src/Fl_Single_Window.cxx
index fd871a3b8..c5e37fabc 100644
--- a/src/Fl_Single_Window.cxx
+++ b/src/Fl_Single_Window.cxx
@@ -31,12 +31,6 @@ void Fl_Single_Window::show()
 }
 
 
-void Fl_Single_Window::flush() 
-{
-  Fl_Window::flush();
-}
-
-
 Fl_Single_Window::Fl_Single_Window(int W, int H, const char *l)
 : Fl_Window(W,H,l) 
 {
diff --git a/src/Fl_Window.cxx b/src/Fl_Window.cxx
index 97045174b..98882591e 100644
--- a/src/Fl_Window.cxx
+++ b/src/Fl_Window.cxx
@@ -435,6 +435,46 @@ int Fl_Window::decorated_h()
 }
 
 
+void Fl_Window::flush()
+{
+  driver()->flush_single();
+}
+
+
+void Fl_Window::draw()
+{
+  pWindowDriver->draw_begin();
+
+  // The following is similar to Fl_Group::draw(), but ...
+  //
+  //  - draws the box at (0,0), i.e. with x=0 and y=0 instead of x() and y()
+  //  - does NOT draw the label (text)
+  //  - draws the image only if FL_ALIGN_INSIDE is set
+  //
+  // Note: The label (text) of top level windows is drawn in the title bar.
+  //   Other windows do not draw their labels at all, unless drawn by their
+  //   parent widgets or by special draw() methods (derived classes).
+
+  if (damage() & ~FL_DAMAGE_CHILD) {	 // draw the entire thing
+    draw_box(box(),0,0,w(),h(),color()); // draw box with x/y = 0
+
+    if (image() && (align() & FL_ALIGN_INSIDE)) { // draw the image only
+      Fl_Label l1;
+      memset(&l1,0,sizeof(l1));
+      l1.align_ = align();
+      l1.image = image();
+      if (!active_r() && l1.image && l1.deimage) l1.image = l1.deimage;
+      l1.type = labeltype();
+      l1.draw(0,0,w(),h(),align());
+    }
+  }
+  draw_children();
+
+  pWindowDriver->draw_end();
+}
+
+
+
 //
 // End of "$Id$".
 //
diff --git a/src/Fl_Window_Driver.cxx b/src/Fl_Window_Driver.cxx
index 9908fde9d..eda8c2901 100644
--- a/src/Fl_Window_Driver.cxx
+++ b/src/Fl_Window_Driver.cxx
@@ -22,6 +22,7 @@
 #include "config_lib.h"
 #include <FL/Fl_Window_Driver.H>
 #include <FL/Fl.H>
+#include <FL/Fl_Overlay_Window.H>
 #include <FL/fl_draw.H>
 
 
@@ -37,41 +38,47 @@ Fl_Window_Driver::~Fl_Window_Driver()
 }
 
 
-/*
- Used in Fl::focus(Fl_Window).
- Default implementation does not need to do anything.
- - reimplemented for OS X Cocoa
- - reimplemented for X11
- */
 void Fl_Window_Driver::take_focus()
 {
+  // nothing to do
 }
 
 
-int Fl_Window_Driver::double_flush(int eraseoverlay) {
-  /* This is a working, platform-independent implementation.
-   Some platforms may re-implement it for their own logic:
-   - on Mac OS, the system double buffers all windows, so it is
-   reimplemented to do the same as Fl_Window::flush(), except for
-   Fl_Overlay_Window's which fall back on this implementation.
-   - on Xlib, it is reimplemented if the Xdbe extension is available.
-   */
+void Fl_Window_Driver::flush_single()
+{
   Fl_X *i = Fl_X::i(pWindow);
-  
-  if (!i->other_xid) {
-    i->other_xid = fl_create_offscreen(pWindow->w(), pWindow->h());
-    pWindow->clear_damage(FL_DAMAGE_ALL);
-  }
-  if (pWindow->damage() & ~FL_DAMAGE_EXPOSE) {
-    fl_clip_region(i->region); i->region = 0;
-    fl_begin_offscreen(i->other_xid);
-    fl_graphics_driver->clip_region( 0 );
-    draw();
-    fl_end_offscreen();
-  }
-  return 0;
+  if (!i) return;
+  fl_clip_region(i->region);
+  i->region = 0;
+  pWindow->draw();
 }
 
+
+void Fl_Window_Driver::flush_double()
+{
+  flush_single();
+}
+
+
+void Fl_Window_Driver::flush_overlay()
+{
+  flush_single();
+}
+
+
+void Fl_Window_Driver::draw_begin()
+{
+  // nothing to do
+}
+
+
+void Fl_Window_Driver::draw_end()
+{
+  // nothing to do
+}
+
+
+
 void Fl_Window_Driver::destroy_double_buffer() {
   Fl_X *i = Fl_X::i(pWindow);
   /* This is a working, platform-independent implementation.
@@ -113,7 +120,6 @@ void Fl_Window_Driver::draw() {
 # endif
 }
 
-void Fl_Window::draw() {pWindowDriver->draw();}
 
 /** Assigns a non-rectangular shape to the window.
  This function gives an arbitrary shape (not just a rectangular region) to an Fl_Window.
diff --git a/src/Fl_cocoa.mm b/src/Fl_cocoa.mm
index 94ade1d9e..821ef57bf 100644
--- a/src/Fl_cocoa.mm
+++ b/src/Fl_cocoa.mm
@@ -84,7 +84,7 @@ static unsigned make_current_counts = 0; // if > 0, then Fl_Window::make_current
 static NSBitmapImageRep* rect_to_NSBitmapImageRep(Fl_Window *win, int x, int y, int w, int h);
 
 // make this available on all platforms to make code maintainability easier
-class Fl_Widget *fl_selection_requestor;
+extern class Fl_Widget *fl_selection_requestor;
 
 int fl_mac_os_version = Fl_X::calc_mac_os_version();		// the version number of the running Mac OS X (e.g., 100604 for 10.6.4)
 
diff --git a/src/Fl_win32.cxx b/src/Fl_win32.cxx
index 0caf501f1..b1715edb2 100644
--- a/src/Fl_win32.cxx
+++ b/src/Fl_win32.cxx
@@ -86,7 +86,7 @@
 */
 
 // make this available on all platforms to make code maintainability easier
-class Fl_Widget *fl_selection_requestor;
+extern class Fl_Widget *fl_selection_requestor;
 
 // Internal functions
 static void fl_clipboard_notify_target(HWND wnd);
diff --git a/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H b/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H
index 419469df7..8a5c8d42e 100644
--- a/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H
+++ b/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.H
@@ -52,11 +52,13 @@ struct Fl_Window_Driver::shape_data_type {
   CGImageRef mask;
 };
 
+
 class FL_EXPORT Fl_Cocoa_Window_Driver : public Fl_Window_Driver
 {
 private:
   void shape_bitmap_(Fl_Image* b);
   void shape_alpha_(Fl_Image* img, int offset);
+
 public:
   Fl_Cocoa_Window_Driver(Fl_Window*);
   ~Fl_Cocoa_Window_Driver();
@@ -65,7 +67,14 @@ public:
   virtual int decorated_w();
   virtual int decorated_h();
 
+  // --- window management
   virtual void take_focus();
+  virtual void flush_single();
+  virtual void flush_double();
+  virtual void flush_overlay();
+  virtual void draw_begin();
+  virtual void draw_end();
+
   virtual void shape(const Fl_Image* img);
   virtual void draw();
   // that one is implemented in Fl_Cocoa.mm because it uses Objective-c
diff --git a/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.cxx b/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.cxx
index 6a4e141d7..0285af9df 100644
--- a/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.cxx
+++ b/src/drivers/Cocoa/Fl_Cocoa_Window_Driver.cxx
@@ -20,25 +20,14 @@
 #include "../../config_lib.h"
 #include "Fl_Cocoa_Window_Driver.h"
 #include <FL/Fl_Double_Window.H>
+#include <FL/Fl_Overlay_Window.H>
 #include <FL/fl_draw.H>
 #include <FL/Fl.H>
 
-// class used for Fl_Double_Window but not for Fl_Overlay_Window
-class Fl_Cocoa_Double_Window_Driver : public Fl_Cocoa_Window_Driver {
-public:
-  Fl_Cocoa_Double_Window_Driver(Fl_Window *w) : Fl_Cocoa_Window_Driver(w) {}
-  int double_flush(int eraseoverlay) {
-    draw();
-    return 0;
-  }
-};
 
 Fl_Window_Driver *Fl_Window_Driver::newWindowDriver(Fl_Window *w)
 {
-  if (w->as_double_window() && !w->as_double_window()->as_overlay_window())
-    return new Fl_Cocoa_Double_Window_Driver(w);
-  else
-    return new Fl_Cocoa_Window_Driver(w);
+  return new Fl_Cocoa_Window_Driver(w);
 }
 
 
@@ -47,6 +36,7 @@ Fl_Cocoa_Window_Driver::Fl_Cocoa_Window_Driver(Fl_Window *win)
 {
 }
 
+
 Fl_Cocoa_Window_Driver::~Fl_Cocoa_Window_Driver()
 {
   if (shape_data_) {
@@ -57,8 +47,6 @@ Fl_Cocoa_Window_Driver::~Fl_Cocoa_Window_Driver()
   }
 }
 
-extern Fl_Window *fl_xfocus;
-
 
 void Fl_Cocoa_Window_Driver::take_focus()
 {
@@ -67,6 +55,108 @@ void Fl_Cocoa_Window_Driver::take_focus()
 }
 
 
+void Fl_Cocoa_Window_Driver::flush_single()
+{
+  if (!pWindow->shown()) return;
+  pWindow->make_current();
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return; // window not yet created
+  fl_clip_region(i->region); i->region = 0;
+  pWindow->draw();
+}
+
+
+void Fl_Cocoa_Window_Driver::flush_double()
+{
+  if (!pWindow->shown()) return;
+  pWindow->make_current();
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return; // window not yet created
+  fl_clip_region(i->region); i->region = 0;
+  pWindow->draw();
+}
+
+
+void Fl_Cocoa_Window_Driver::flush_overlay()
+{
+  Fl_Overlay_Window *oWindow = pWindow->as_overlay_window();
+  if (!oWindow) return flush_single();
+
+  if (!pWindow->shown()) return;
+  pWindow->make_current(); // make sure fl_gc is non-zero
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return; // window not yet created
+
+  int erase_overlay = (pWindow->damage()&FL_DAMAGE_OVERLAY);
+  pWindow->clear_damage((uchar)(pWindow->damage()&~FL_DAMAGE_OVERLAY));
+
+  if (!i->other_xid) {
+      i->other_xid = fl_create_offscreen(pWindow->w(), pWindow->h());
+      pWindow->clear_damage(FL_DAMAGE_ALL);
+  }
+  if (pWindow->damage() & ~FL_DAMAGE_EXPOSE) {
+    fl_clip_region(i->region); i->region = 0;
+    if ( i->other_xid ) {
+      fl_begin_offscreen( i->other_xid );
+      fl_clip_region( 0 );
+      draw();
+      fl_end_offscreen();
+    } else {
+      draw();
+    }
+  }
+  if (erase_overlay) fl_clip_region(0);
+  
+  int X,Y,W,H; fl_clip_box(0,0,pWindow->w(),pWindow->h(),X,Y,W,H);
+  if (i->other_xid) fl_copy_offscreen(X, Y, W, H, i->other_xid, X, Y);
+
+  if (oWindow->overlay_ == oWindow) oWindow->draw_overlay();
+}
+
+
+void Fl_Cocoa_Window_Driver::draw_begin()
+{
+  if (shape_data_) {
+# if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
+    if (shape_data_->mask && (&CGContextClipToMask != NULL)) {
+      CGContextClipToMask(fl_gc, CGRectMake(0,0,pWindow->w(),pWindow->h()), shape_data_->mask); // requires Mac OS 10.4
+    }
+    CGContextSaveGState(fl_gc);
+# endif
+  }
+}
+
+
+void Fl_Cocoa_Window_Driver::draw_end()
+{
+  // on OS X, windows have no frame. Before OS X 10.7, to resize a window, we drag the lower right
+  // corner. This code draws a little ribbed triangle for dragging.
+  if (fl_mac_os_version < 100700 && fl_gc && !pWindow->parent() && pWindow->resizable() &&
+      (!pWindow->size_range_set || pWindow->minh!=pWindow->maxh || pWindow->minw!=pWindow->maxw)) {
+    int dx = Fl::box_dw(pWindow->box())-Fl::box_dx(pWindow->box());
+    int dy = Fl::box_dh(pWindow->box())-Fl::box_dy(pWindow->box());
+    if (dx<=0) dx = 1;
+    if (dy<=0) dy = 1;
+    int x1 = pWindow->w()-dx-1, x2 = x1, y1 = pWindow->h()-dx-1, y2 = y1;
+    Fl_Color c[4] = {
+      pWindow->color(),
+      fl_color_average(pWindow->color(), FL_WHITE, 0.7f),
+      fl_color_average(pWindow->color(), FL_BLACK, 0.6f),
+      fl_color_average(pWindow->color(), FL_BLACK, 0.8f),
+    };
+    int i;
+    for (i=dx; i<12; i++) {
+      fl_color(c[i&3]);
+      fl_line(x1--, y1, x2, y2--);
+    }
+  }
+# if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
+  if (shape_data_) CGContextRestoreGState(fl_gc);
+# endif
+}
+
+
+
 static void MyProviderReleaseData (void *info, const void *data, size_t size) {
   delete[] (uchar*)data;
 }
diff --git a/src/drivers/Pico/Fl_Pico_Graphics_Driver.cxx b/src/drivers/Pico/Fl_Pico_Graphics_Driver.cxx
index 914fdafd3..3968ea756 100644
--- a/src/drivers/Pico/Fl_Pico_Graphics_Driver.cxx
+++ b/src/drivers/Pico/Fl_Pico_Graphics_Driver.cxx
@@ -35,10 +35,10 @@ void Fl_Pico_Graphics_Driver::point(int x, int y)
 
 void Fl_Pico_Graphics_Driver::rect(int x, int y, int w, int h)
 {
-  line(x, y, x+w, y);
-  line(x+w, y, x+w, y+h);
-  line(x+w, y+h, x, y+h);
-  line(x, y+h, x, y);
+  line(x, y, x+w-1, y);
+  line(x+w-1, y, x+w-1, y+h-1);
+  line(x+w-1, y+h-1, x, y+h-1);
+  line(x, y+h-1, x, y);
 }
 
 void Fl_Pico_Graphics_Driver::rectf(int x, int y, int w, int h)
@@ -231,10 +231,20 @@ static const char *font_data[128] = {
   0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
 
   /* */0, /*!*/"\31\34\100\35\36", 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
-
-  0, 0, /*B*/"\43\54\45\15\11\41\52\43\13", 0, 0, /*E*/"\51\11\15\55\100\13\43", 0, 0,
-  /*H*/"\11\15\100\61\65\100\13\63", 0, 0, 0, 0, 0, 0, 0,
+  /*0*/"\62\51\21\12\14\25\55\64\62\100\52\61",
+  /*1*/"\22\31\35\100\25\45",
+  0, 0, 0, 0, 0, 0,  0, 0, 0, 0, 0, 0, 0, 0,
+
+  0,
+  /*A*/"\15\31\55\100\23\43",
+  /*B*/"\43\54\45\15\11\41\52\43\13",
+  /*C*/"\62\51\21\12\14\25\55\64",
+  /*D*/"\11\51\62\64\55\15\11",
+  /*E*/"\61\11\15\65\100\13\43",
+  /*F*/"\61\11\15\100\13\43",
+  /*G*/"\62\51\21\12\14\25\55\64\100\65\63\33",
+  /*H*/"\11\15\100\61\65\100\13\63",
+  /*I*/"\21\41\100\31\35\100\25\45", 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, /*T*/"\11\71\100\41\45", 0, 0, /*W*/"\01\15\33\55\61",
   /*X*/"\15\51\100\11\55", 0, 0, 0, 0, 0, 0, 0,
 
diff --git a/src/drivers/Pico/Fl_Pico_Window_Driver.H b/src/drivers/Pico/Fl_Pico_Window_Driver.H
index 51e9db920..40d6457fa 100644
--- a/src/drivers/Pico/Fl_Pico_Window_Driver.H
+++ b/src/drivers/Pico/Fl_Pico_Window_Driver.H
@@ -37,6 +37,13 @@ public:
   // --- window data
   virtual int decorated_w();
   virtual int decorated_h();
+
+  // --- window management
+  virtual void flush_single();
+  virtual void flush_double();
+  virtual void flush_overlay();
+  virtual void draw_begin();
+  virtual void draw_end();
 };
 
 
diff --git a/src/drivers/Pico/Fl_Pico_Window_Driver.cxx b/src/drivers/Pico/Fl_Pico_Window_Driver.cxx
index b14696d6f..bb5b4e612 100644
--- a/src/drivers/Pico/Fl_Pico_Window_Driver.cxx
+++ b/src/drivers/Pico/Fl_Pico_Window_Driver.cxx
@@ -25,14 +25,6 @@
 
 
 
-// TODO: move this to Fl_Window_Driver
-void Fl_X::flush()
-{
-  w->driver()->flush();
-}
-
-
-
 Fl_Pico_Window_Driver::Fl_Pico_Window_Driver(Fl_Window *win)
 : Fl_Window_Driver(win)
 {
@@ -58,6 +50,43 @@ int Fl_Pico_Window_Driver::decorated_h()
 }
 
 
+// --- window management
+void Fl_Pico_Window_Driver::flush_single()
+{
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return;
+  fl_clip_region(i->region);
+  i->region = 0;
+  pWindow->draw();
+}
+
+
+void Fl_Pico_Window_Driver::flush_double()
+{
+  flush_single();
+}
+
+
+void Fl_Pico_Window_Driver::flush_overlay()
+{
+  flush_single();
+}
+
+
+
+
+void Fl_Pico_Window_Driver::draw_begin()
+{
+  // nothing to do
+}
+
+
+void Fl_Pico_Window_Driver::draw_end()
+{
+  // nothing to do
+}
+
+
 //
 // End of "$Id: Fl_Pico_Window_Driver.cxx 11253 2016-03-01 00:54:21Z matt $".
 //
\ No newline at end of file
diff --git a/src/drivers/PicoAndroid/Fl_PicoAndroid_Window_Driver.cxx b/src/drivers/PicoAndroid/Fl_PicoAndroid_Window_Driver.cxx
index 6e06c85ab..17957312e 100644
--- a/src/drivers/PicoAndroid/Fl_PicoAndroid_Window_Driver.cxx
+++ b/src/drivers/PicoAndroid/Fl_PicoAndroid_Window_Driver.cxx
@@ -95,6 +95,17 @@ Fl_X *Fl_PicoAndroid_Window_Driver::makeWindow()
 
 #include <FL/fl_draw.h>
 
+
+void Fl_Window_Driver::draw_begin()
+{
+}
+
+
+void Fl_Window_Driver::draw_end()
+{
+}
+
+
 void Fl_PicoAndroid_Window_Driver::flush()
 {
   Fl_PicoAndroid_Screen_Driver *scr = (Fl_PicoAndroid_Screen_Driver*)Fl::screen_driver();
diff --git a/src/drivers/PicoSDL/Fl_PicoSDL_Screen_Driver.cxx b/src/drivers/PicoSDL/Fl_PicoSDL_Screen_Driver.cxx
index 82d94dcd5..942c5a523 100644
--- a/src/drivers/PicoSDL/Fl_PicoSDL_Screen_Driver.cxx
+++ b/src/drivers/PicoSDL/Fl_PicoSDL_Screen_Driver.cxx
@@ -52,24 +52,27 @@ double Fl_PicoSDL_Screen_Driver::wait(double time_to_wait)
     switch (e.type) {
       case SDL_QUIT:
         exit(0);
-      case SDL_WINDOWEVENT_EXPOSED:
-      case SDL_WINDOWEVENT_SHOWN:
-      { // not happening!
-        //event->window.windowID
-        if ( !window ) break;;
-        Fl_X *i = Fl_X::i(Fl::first_window());
-        i->wait_for_expose = 0;
-
-        if ( i->region ) {
-          XDestroyRegion(i->region);
-          i->region = 0;
+      case SDL_WINDOWEVENT:
+        switch (e.window.event) {
+          case SDL_WINDOWEVENT_EXPOSED:
+          case SDL_WINDOWEVENT_SHOWN:
+          {
+            //event->window.windowID
+            if ( !window ) break;;
+            Fl_X *i = Fl_X::i(Fl::first_window());
+            i->wait_for_expose = 0;
+
+            if ( i->region ) {
+              XDestroyRegion(i->region);
+              i->region = 0;
+            }
+            window->clear_damage(FL_DAMAGE_ALL);
+            i->flush();
+            window->clear_damage();
+            Fl_X::first->wait_for_expose = 0;
+          }
+            break;
         }
-        window->clear_damage(FL_DAMAGE_ALL);
-        i->flush();
-        window->clear_damage();
-        Fl_X::first->wait_for_expose = 0;
-      }
-        break;
       case SDL_MOUSEBUTTONDOWN:
         if (!window) break;
         Fl::e_is_click = e.button.clicks;
@@ -204,6 +207,11 @@ void Fl::remove_fd(int)
 {
 }
 
+void Fl_X::flush()
+{
+  w->flush();
+}
+
 
 //
 // End of "$Id: Fl_PicoSDL_Screen_Driver.cxx 11253 2016-03-01 00:54:21Z matt $".
diff --git a/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.H b/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.H
index cc4fb81c4..7cb2e7c43 100644
--- a/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.H
+++ b/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.H
@@ -40,7 +40,11 @@ public:
   virtual ~Fl_PicoSDL_Window_Driver();
 
   virtual Fl_X *makeWindow();
-  virtual void flush();
+  
+  // --- window management
+  virtual void flush_single();
+  virtual void flush_double();
+  virtual void flush_overlay();
 };
 
 
diff --git a/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.cxx b/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.cxx
index a9a7fc95f..346eea241 100644
--- a/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.cxx
+++ b/src/drivers/PicoSDL/Fl_PicoSDL_Window_Driver.cxx
@@ -72,7 +72,7 @@ Fl_X *Fl_PicoSDL_Window_Driver::makeWindow()
 
   pWindow->set_visible();
   pWindow->redraw();
-  flush();
+  pWindow->flush();
   int old_event = Fl::e_number;
   pWindow->handle(Fl::e_number = FL_SHOW);
   Fl::e_number = old_event;
@@ -81,14 +81,34 @@ Fl_X *Fl_PicoSDL_Window_Driver::makeWindow()
 }
 
 
-void Fl_PicoSDL_Window_Driver::flush()
+void Fl_PicoSDL_Window_Driver::flush_single()
 {
-  SDL_RenderClear((SDL_Renderer*)fl_window);
-  pWindow->flush();
-  SDL_RenderPresent((SDL_Renderer*)fl_window);
+  if (!pWindow->shown()) return;
+  pWindow->make_current();
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return;
+  fl_clip_region(i->region);
+  i->region = 0;
+//  SDL_RenderClear((SDL_Renderer*)i->xid);
+  pWindow->draw();
+  SDL_RenderPresent((SDL_Renderer*)i->xid);
+}
+
+
+void Fl_PicoSDL_Window_Driver::flush_double()
+{
+  flush_single();
 }
 
 
+void Fl_PicoSDL_Window_Driver::flush_overlay()
+{
+  flush_single();
+  // draw_overlay();
+}
+
+
+
 //
 // End of "$Id: Fl_PicoSDL_Window_Driver.cxx 11253 2016-03-01 00:54:21Z matt $".
 //
\ No newline at end of file
diff --git a/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.H b/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.H
index f4521b5e7..ebcf72440 100644
--- a/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.H
+++ b/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.H
@@ -72,8 +72,14 @@ public:
   virtual int decorated_w();
   virtual int decorated_h();
 
+  // --- window management
+  virtual void flush_single();
+  virtual void flush_double();
+  virtual void flush_overlay();
+  virtual void draw_begin();
+  virtual void draw_end();
+
   virtual void shape(const Fl_Image* img);
-  virtual void draw();
   virtual void icons(const Fl_RGB_Image *icons[], int count);
   virtual const void *icon() const;
   virtual void icon(const void * ic);
diff --git a/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.cxx b/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.cxx
index 6e7d546da..c1893b841 100644
--- a/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.cxx
+++ b/src/drivers/WinAPI/Fl_WinAPI_Window_Driver.cxx
@@ -18,11 +18,13 @@
 
 
 #include "../../config_lib.h"
+#include <FL/fl_draw.H>
 #include <FL/Fl.H>
 #include <FL/Fl_Window.H>
 #include <FL/Fl_Image.H>
 #include <FL/Fl_Bitmap.H>
 #include <FL/Fl_Window.H>
+#include <FL/Fl_Overlay_Window.H>
 #include <FL/x.H>
 #include "Fl_WinAPI_Window_Driver.H"
 #include <windows.h>
@@ -40,6 +42,7 @@ Fl_WinAPI_Window_Driver::Fl_WinAPI_Window_Driver(Fl_Window *win)
   memset(icon_, 0, sizeof(Fl_Window_Driver::icon_data));
 }
 
+
 Fl_WinAPI_Window_Driver::~Fl_WinAPI_Window_Driver()
 {
   if (shape_data_) {
@@ -96,6 +99,7 @@ int Fl_WinAPI_Window_Driver::decorated_h()
 }
 
 
+// --- window management
 
 
 
@@ -235,7 +239,8 @@ static HRGN bitmap2region(Fl_Image* image) {
 }
 
 
-void Fl_WinAPI_Window_Driver::draw() {
+void Fl_WinAPI_Window_Driver::draw_begin()
+{
   if (shape_data_) {
     if ((shape_data_->lw_ != pWindow->w() || shape_data_->lh_ != pWindow->h()) && shape_data_->shape_) {
       // size of window has changed since last time
@@ -246,9 +251,84 @@ void Fl_WinAPI_Window_Driver::draw() {
       SetWindowRgn(fl_xid(pWindow), region, TRUE); // the system deletes the region when it's no longer needed
       delete temp;
     }
-  }  Fl_Window_Driver::draw();
+  }
+}
+
+
+void Fl_WinAPI_Window_Driver::draw_end()
+{
 }
 
+
+void Fl_WinAPI_Window_Driver::flush_single()
+{
+  if (!pWindow->shown()) return;
+  pWindow->make_current(); // make sure fl_gc is non-zero
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return;
+  fl_clip_region(i->region);
+  i->region = 0;
+  pWindow->draw();
+}
+
+
+void Fl_WinAPI_Window_Driver::flush_double()
+{
+  if (!pWindow->shown()) return;
+  pWindow->make_current(); // make sure fl_gc is non-zero
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return; // window not yet created
+
+  if (!i->other_xid) {
+    i->other_xid = fl_create_offscreen(pWindow->w(), pWindow->h());
+    pWindow->clear_damage(FL_DAMAGE_ALL);
+  }
+  if (pWindow->damage() & ~FL_DAMAGE_EXPOSE) {
+    fl_clip_region(i->region); i->region = 0;
+    fl_begin_offscreen(i->other_xid);
+    fl_graphics_driver->clip_region( 0 );
+    draw();
+    fl_end_offscreen();
+  }
+
+  int X,Y,W,H; fl_clip_box(0,0,pWindow->w(),pWindow->h(),X,Y,W,H);
+  if (i->other_xid) fl_copy_offscreen(X, Y, W, H, i->other_xid, X, Y);
+}
+
+
+void Fl_WinAPI_Window_Driver::flush_overlay()
+{
+  Fl_Overlay_Window *oWindow = pWindow->as_overlay_window();
+  if (!oWindow) return flush_single();
+
+  if (!pWindow->shown()) return;
+  pWindow->make_current(); // make sure fl_gc is non-zero
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return; // window not yet created
+
+  int eraseoverlay = (pWindow->damage()&FL_DAMAGE_OVERLAY);
+  pWindow->clear_damage((uchar)(pWindow->damage()&~FL_DAMAGE_OVERLAY));
+
+  if (!i->other_xid) {
+    i->other_xid = fl_create_offscreen(pWindow->w(), pWindow->h());
+    pWindow->clear_damage(FL_DAMAGE_ALL);
+  }
+  if (pWindow->damage() & ~FL_DAMAGE_EXPOSE) {
+    fl_clip_region(i->region); i->region = 0;
+    fl_begin_offscreen(i->other_xid);
+    fl_graphics_driver->clip_region(0);
+    draw();
+    fl_end_offscreen();
+  }
+
+  if (eraseoverlay) fl_clip_region(0);
+  int X, Y, W, H; fl_clip_box(0, 0, pWindow->w(), pWindow->h(), X, Y, W, H);
+  if (i->other_xid) fl_copy_offscreen(X, Y, W, H, i->other_xid, X, Y);
+
+  if (oWindow->overlay_ == oWindow) oWindow->draw_overlay();
+}
+
+
 void Fl_WinAPI_Window_Driver::icons(const Fl_RGB_Image *icons[], int count) {
   free_icons();
   
diff --git a/src/drivers/X11/Fl_X11_Window_Driver.H b/src/drivers/X11/Fl_X11_Window_Driver.H
index 02c0de989..126f4b103 100644
--- a/src/drivers/X11/Fl_X11_Window_Driver.H
+++ b/src/drivers/X11/Fl_X11_Window_Driver.H
@@ -75,7 +75,14 @@ public:
   virtual int decorated_w();
   virtual int decorated_h();
 
+  // --- window management
   virtual void take_focus();
+  virtual void flush_single();
+  virtual void flush_double();
+  virtual void flush_overlay();
+  virtual void draw_begin();
+  virtual void draw_end();
+
   virtual void shape(const Fl_Image* img);
   virtual void draw();
   virtual void icons(const Fl_RGB_Image *icons[], int count);
diff --git a/src/drivers/X11/Fl_X11_Window_Driver.cxx b/src/drivers/X11/Fl_X11_Window_Driver.cxx
index 6ff2158c2..b8ca36480 100644
--- a/src/drivers/X11/Fl_X11_Window_Driver.cxx
+++ b/src/drivers/X11/Fl_X11_Window_Driver.cxx
@@ -19,7 +19,9 @@
 
 #include "../../config_lib.h"
 #include "Fl_X11_Window_Driver.H"
+
 #include <FL/Fl_Shared_Image.H>
+#include <FL/Fl_Overlay_Window.H>
 #include <FL/fl_draw.H>
 #include <FL/Fl.H>
 #include <string.h>
@@ -32,26 +34,37 @@
 #if USE_XDBE
 #include <X11/extensions/Xdbe.h>
 
-static int can_xdbe(); // forward
+// whether the Xdbe extension is usable
+// DO NOT call this if the window is not mapped!
+static int can_xdbe()
+{
+  static int tried = 0;
+  static int use_xdbe = 0;
+  if (!tried) {
+    tried = 1;
+    int event_base, error_base;
+    fl_open_display();
+    if (!XdbeQueryExtension(fl_display, &event_base, &error_base)) return 0;
+    Drawable root = RootWindow(fl_display,fl_screen);
+    int numscreens = 1;
+    XdbeScreenVisualInfo *a = XdbeGetVisualInfo(fl_display,&root,&numscreens);
+    if (!a) return 0;
+    for (int j = 0; j < a->count; j++) {
+      if (a->visinfo[j].visual == fl_visual->visualid) {
+        use_xdbe = 1; break;
+      }
+    }
+    XdbeFreeVisualInfo(a);
+  }
+  return use_xdbe;
+}
 
-// class to be used only if Xdbe is used
-class Fl_X11_Dbe_Window_Driver : public Fl_X11_Window_Driver {
-public:
-  Fl_X11_Dbe_Window_Driver(Fl_Window *w) : Fl_X11_Window_Driver(w) {}
-  virtual int double_flush(int eraseoverlay);
-  virtual void destroy_double_buffer();
-};
 #endif // USE_XDBE
 
 
 Fl_Window_Driver *Fl_Window_Driver::newWindowDriver(Fl_Window *w)
 {
-#if USE_XDBE
-  if (w->as_double_window() && can_xdbe())
-    return new Fl_X11_Dbe_Window_Driver(w);
-  else
-#endif
-    return new Fl_X11_Window_Driver(w);
+  return new Fl_X11_Window_Driver(w);
 }
 
 
@@ -123,63 +136,172 @@ void Fl_X11_Window_Driver::take_focus()
       Fl_X::activate_window(i->xid);
 }
 
-#if USE_XDBE
 
-static int can_xdbe() { // whether the Xdbe extension is usable
-  static int tried;
-  static int use_xdbe = 0;
-  if (!tried) {
-    tried = 1;
-    int event_base, error_base;
-    fl_open_display();
-    if (!XdbeQueryExtension(fl_display, &event_base, &error_base)) return 0;
-    Drawable root = RootWindow(fl_display,fl_screen);
-    int numscreens = 1;
-    XdbeScreenVisualInfo *a = XdbeGetVisualInfo(fl_display,&root,&numscreens);
-    if (!a) return 0;
-    for (int j = 0; j < a->count; j++) {
-      if (a->visinfo[j].visual == fl_visual->visualid) {
-        use_xdbe = 1; break;
-      }
+void Fl_X11_Window_Driver::draw_begin()
+{
+  if (shape_data_) {
+    if (( shape_data_->lw_ != pWindow->w() || shape_data_->lh_ != pWindow->h() ) && shape_data_->shape_) {
+      // size of window has changed since last time
+      combine_mask();
     }
-    XdbeFreeVisualInfo(a);
   }
-  return use_xdbe;
 }
 
-int Fl_X11_Dbe_Window_Driver::double_flush(int eraseoverlay) {
+
+void Fl_X11_Window_Driver::draw_end()
+{
+}
+
+
+void Fl_X11_Window_Driver::flush_single()
+{
+  if (!pWindow->shown()) return;
+  pWindow->make_current(); // make sure fl_gc is non-zero
+  Fl_X *i = Fl_X::i(pWindow);
+  if (!i) return;
+  fl_clip_region(i->region);
+  i->region = 0;
+  pWindow->draw();
+}
+
+
+void Fl_X11_Window_Driver::flush_double()
+{
+  if (!pWindow->shown()) return;
+  pWindow->make_current(); // make sure fl_gc is non-zero
   Fl_X *i = Fl_X::i(pWindow);
-    if (!i->other_xid) {
-      i->other_xid = XdbeAllocateBackBufferName(fl_display, i->xid, XdbeCopied);
+  if (!i) return; // window not yet created
+  if (!i->other_xid) {
+#if USE_XDBE
+    if (can_xdbe()) {
+      i->other_xid = XdbeAllocateBackBufferName(fl_display, fl_xid(pWindow), XdbeCopied);
       i->backbuffer_bad = 1;
-      pWindow->clear_damage(FL_DAMAGE_ALL);
-    }
-    if (i->backbuffer_bad || eraseoverlay) {
+    } else
+#endif
+      i->other_xid = fl_create_offscreen(pWindow->w(), pWindow->h());
+    pWindow->clear_damage(FL_DAMAGE_ALL);
+  }
+#if USE_XDBE
+  if (can_xdbe()) {
+    if (i->backbuffer_bad) {
       // Make sure we do a complete redraw...
       if (i->region) {XDestroyRegion(i->region); i->region = 0;}
       pWindow->clear_damage(FL_DAMAGE_ALL);
       i->backbuffer_bad = 0;
     }
+
     // Redraw as needed...
     if (pWindow->damage()) {
       fl_clip_region(i->region); i->region = 0;
       fl_window = i->other_xid;
-      draw();
+      pWindow->draw();
       fl_window = i->xid;
     }
+
     // Copy contents of back buffer to window...
     XdbeSwapInfo s;
-    s.swap_window = i->xid;
+    s.swap_window = fl_xid(pWindow);
     s.swap_action = XdbeCopied;
     XdbeSwapBuffers(fl_display, &s, 1);
-    return 1;
+    return;
+  } else
+#endif
+    if (pWindow->damage() & ~FL_DAMAGE_EXPOSE) {
+      fl_clip_region(i->region); i->region = 0;
+      fl_window = i->other_xid;
+      pWindow->draw();
+      fl_window = i->xid;
+    }
+  int X,Y,W,H; fl_clip_box(0,0,pWindow->w(),pWindow->h(),X,Y,W,H);
+  if (i->other_xid) fl_copy_offscreen(X, Y, W, H, i->other_xid, X, Y);
 }
 
-void Fl_X11_Dbe_Window_Driver::destroy_double_buffer() {
+
+void Fl_X11_Window_Driver::flush_overlay()
+{
+  Fl_Overlay_Window *oWindow = pWindow->as_overlay_window();
+  if (!oWindow) return flush_single();
+
+  if (!pWindow->shown()) return;
+  pWindow->make_current(); // make sure fl_gc is non-zero
   Fl_X *i = Fl_X::i(pWindow);
-  XdbeDeallocateBackBufferName(fl_display, i->other_xid);
-  i->other_xid = 0;
+  if (!i) return; // window not yet created
+
+#ifdef BOXX_BUGS
+  if (oWindow->overlay_ && oWindow->overlay_ != oWindow && oWindow->overlay_->shown()) {
+    // all drawing to windows hidden by overlay windows is ignored, fix this
+    XUnmapWindow(fl_display, fl_xid(oWindow->overlay_));
+    flush_double();
+    XMapWindow(fl_display, fl_xid(oWindow->overlay_));
+    return;
+  }
+#endif
+
+  int erase_overlay = (pWindow->damage()&FL_DAMAGE_OVERLAY);
+  pWindow->clear_damage((uchar)(pWindow->damage()&~FL_DAMAGE_OVERLAY));
+
+  if (!i->other_xid) {
+#if USE_XDBE
+    if (can_xdbe()) {
+      i->other_xid = XdbeAllocateBackBufferName(fl_display, fl_xid(pWindow), XdbeCopied);
+      i->backbuffer_bad = 1;
+    } else
+#endif
+      i->other_xid = fl_create_offscreen(pWindow->w(), pWindow->h());
+    pWindow->clear_damage(FL_DAMAGE_ALL);
+  }
+#if USE_XDBE
+  if (can_xdbe()) {
+    if (i->backbuffer_bad || erase_overlay) {
+      // Make sure we do a complete redraw...
+      if (i->region) {XDestroyRegion(i->region); i->region = 0;}
+      pWindow->clear_damage(FL_DAMAGE_ALL);
+      i->backbuffer_bad = 0;
+    }
+
+    // Redraw as needed...
+    if (pWindow->damage()) {
+      fl_clip_region(i->region); i->region = 0;
+      fl_window = i->other_xid;
+      pWindow->draw();
+      fl_window = i->xid;
+    }
+
+    // Copy contents of back buffer to window...
+    XdbeSwapInfo s;
+    s.swap_window = fl_xid(pWindow);
+    s.swap_action = XdbeCopied;
+    XdbeSwapBuffers(fl_display, &s, 1);
+
+    pWindow->make_current();
+    if (erase_overlay) fl_clip_region(0);
+    if (oWindow->overlay_ == oWindow) oWindow->draw_overlay();
+
+    return;
+  } else
+#endif
+    if (pWindow->damage() & ~FL_DAMAGE_EXPOSE) {
+      fl_clip_region(i->region); i->region = 0;
+      fl_window = i->other_xid;
+      pWindow->draw();
+      fl_window = i->xid;
+    }
+  if (erase_overlay) fl_clip_region(0);
+  int X,Y,W,H; fl_clip_box(0,0,pWindow->w(),pWindow->h(),X,Y,W,H);
+  if (i->other_xid) fl_copy_offscreen(X, Y, W, H, i->other_xid, X, Y);
+
+  if (oWindow->overlay_ == oWindow) oWindow->draw_overlay();
 }
+
+
+
+#if USE_XDBE
+
+//void Fl_X11_Dbe_Window_Driver::destroy_double_buffer() {
+//  Fl_X *i = Fl_X::i(pWindow);
+//  XdbeDeallocateBackBufferName(fl_display, i->other_xid);
+//  i->other_xid = 0;
+//}
 #endif // USE_XDBE