Refactor and improve "Print front window" dialog

src/print_button.cxx: "Print front window" implementation (new file)

This is compiled and activated if USE_PRINT_BUTTON is defined.

The feature can be fine controlled by environment variable
  'FLTK_PRINT_BUTTON' (see docs in source file).

6 files changed, 208 insertions, 170 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0efbfede4..8b64485a6 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -133,6 +133,8 @@ set (CPPFILES
   fl_diamond_box.cxx
   fl_draw.cxx
   fl_draw_pixmap.cxx
+  fl_encoding_latin1.cxx
+  fl_encoding_mac_roman.cxx
   fl_engraved_label.cxx
   fl_file_dir.cxx
   fl_font.cxx
@@ -153,13 +155,12 @@ set (CPPFILES
   fl_shadow_box.cxx
   fl_shortcut.cxx
   fl_show_colormap.cxx
+  fl_string.cxx
   fl_symbols.cxx
+  fl_utf8.cxx
   fl_vertex.cxx
+  print_button.cxx
   screen_xywh.cxx
-  fl_utf8.cxx
-  fl_string.cxx
-  fl_encoding_latin1.cxx
-  fl_encoding_mac_roman.cxx
 )
 
 # find all header files in source directory <FL/...>
diff --git a/src/Fl_Window_Driver.H b/src/Fl_Window_Driver.H
index 6d740892c..aa1a62b9a 100644
--- a/src/Fl_Window_Driver.H
+++ b/src/Fl_Window_Driver.H
@@ -38,6 +38,9 @@ class Fl_X;
 class Fl_Image;
 class Fl_RGB_Image;
 
+// not directly window driver related, but ...
+int fl_create_print_window(); // used internally on some platforms
+
 /**
  \brief A base class for platform specific window handling code.
 
diff --git a/src/Fl_win32.cxx b/src/Fl_win32.cxx
index 3ca0744cc..9abbb5d58 100644
--- a/src/Fl_win32.cxx
+++ b/src/Fl_win32.cxx
@@ -1,7 +1,7 @@
 //
 // Windows-specific code for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2018 by Bill Spitzak and others.
+// Copyright 1998-2021 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
@@ -105,7 +105,6 @@ extern void fl_cleanup_pens(void);
 #define round(A) int((A) + 0.5)
 #endif // _MSC_VER <= 1600
 
-//
 // USE_ASYNC_SELECT - define it if you have WSAAsyncSelect()...
 // USE_ASYNC_SELECT is OBSOLETED in 1.3 for the following reasons:
 /*
@@ -568,8 +567,8 @@ void Fl_WinAPI_Screen_Driver::open_display_platform() {
     }
   }
   OleInitialize(0L);
-
   get_imm_module();
+  fl_create_print_window();
 }
 
 
@@ -594,7 +593,7 @@ void Fl_WinAPI_Screen_Driver::desktop_scale_factor() {
     dpi[ns][0] = float(dpiX);
     dpi[ns][1] = float(dpiY);
     scale(ns, dpiX / 96.f);
-  //fprintf(LOG, "desktop_scale_factor ns=%d factor=%.2f dpi=%.1f\n", ns, scale(ns), dpi[ns][0]);
+    // fprintf(LOG, "desktop_scale_factor ns=%d factor=%.2f dpi=%.1f\n", ns, scale(ns), dpi[ns][0]);
   }
 }
 
@@ -2631,10 +2630,6 @@ void Fl_WinAPI_Window_Driver::show() {
       BringWindowToTop(i->xid);
     // ShowWindow(i->xid,fl_capture?SW_SHOWNOACTIVATE:SW_RESTORE);
   }
-#ifdef USE_PRINT_BUTTON
-  void preparePrintFront(void);
-  preparePrintFront();
-#endif
 }
 
 // the current context
@@ -2807,82 +2802,4 @@ void Fl_WinAPI_Window_Driver::capture_titlebar_and_borders(Fl_RGB_Image *&top, F
   Fl_Surface_Device::pop_current();
 }
 
-
-#ifdef USE_PRINT_BUTTON
-// to test the Fl_Printer class creating a "Print front window" button in a separate window
-// contains also preparePrintFront call above
-#include <FL/Fl_Printer.H>
-#include <FL/Fl_Button.H>
-void printFront(Fl_Widget *o, void *data) {
-  Fl_Printer printer;
-  o->window()->hide();
-  Fl_Window *win = Fl::first_window();
-  if (!win)
-    return;
-  int w, h;
-  if (printer.begin_job(1)) {
-    o->window()->show();
-    return;
-  }
-  if (printer.begin_page()) {
-    o->window()->show();
-    return;
-  }
-  printer.printable_rect(&w, &h);
-  int wh, ww;
-  wh = win->decorated_h();
-  ww = win->decorated_w();
-  // scale the printer device so that the window fits on the page
-  float scale = 1;
-  if (ww > w || wh > h) {
-    scale = (float)w / ww;
-    if ((float)h / wh < scale)
-      scale = (float)h / wh;
-    printer.scale(scale, scale);
-  }
-// #define ROTATE 20.0
-#ifdef ROTATE
-  printer.scale(scale * 0.8, scale * 0.8);
-  printer.printable_rect(&w, &h);
-  printer.origin(w / 2, h / 2);
-  printer.rotate(ROTATE);
-  printer.print_widget(win, -win->w() / 2, -win->h() / 2);
-  // printer.print_window_part(win, 0, 0, win->w(), win->h(), -win->w() / 2, -win->h() / 2);
-#else
-  printer.print_window(win);
-#endif
-  printer.end_page();
-  printer.end_job();
-  o->window()->show();
-}
-
-#include <FL/Fl_Copy_Surface.H>
-void copyFront(Fl_Widget *o, void *data) {
-  o->window()->hide();
-  Fl_Window *win = Fl::first_window();
-  if (!win)
-    return;
-  Fl_Copy_Surface *surf = new Fl_Copy_Surface(win->decorated_w(), win->decorated_h());
-  surf->set_current();
-  surf->draw_decorated_window(win); // draw the window content
-  delete surf;                      // put the window on the clipboard
-  Fl_Display_Device::display_device()->set_current();
-  o->window()->show();
-}
-
-void preparePrintFront(void) {
-  static BOOL first = TRUE;
-  if (!first)
-    return;
-  first = FALSE;
-  static Fl_Window w(0, 0, 120, 60);
-  static Fl_Button bp(0, 0, w.w(), 30, "Print front window");
-  bp.callback(printFront);
-  static Fl_Button bc(0, 30, w.w(), 30, "Copy front window");
-  bc.callback(copyFront);
-  w.end();
-  w.show();
-}
-#endif // USE_PRINT_BUTTON
-
 #endif // defined(_WIN32) and !defined(FL_DOXYGEN)
diff --git a/src/Fl_x.cxx b/src/Fl_x.cxx
index 0a81f5a66..4d30cc2e3 100644
--- a/src/Fl_x.cxx
+++ b/src/Fl_x.cxx
@@ -716,6 +716,7 @@ void Fl_X11_Screen_Driver::open_display_platform() {
   // the unique GC used by all X windows
   GC gc = XCreateGC(fl_display, RootWindow(fl_display, fl_screen), 0, 0);
   Fl_Graphics_Driver::default_driver().gc(gc);
+  fl_create_print_window();
 }
 
 
@@ -3216,81 +3217,4 @@ void Fl_X11_Window_Driver::show() {
   }
 }
 
-
-//#define USE_PRINT_BUTTON 1
-#ifdef USE_PRINT_BUTTON
-
-// to test the Fl_Printer class creating a "Print front window" button in a separate window
-#include <FL/Fl_Printer.H>
-#include <FL/Fl_Button.H>
-
-void printFront(Fl_Widget *o, void *data)
-{
-  Fl_Printer printer;
-  o->window()->hide();
-  Fl_Window *win = Fl::first_window();
-  if(!win) return;
-  int w, h;
-  if( printer.begin_job(1) ) { o->window()->show(); return; }
-  if( printer.begin_page() ) { o->window()->show(); return; }
-  printer.printable_rect(&w,&h);
-  // scale the printer device so that the window fits on the page
-  float scale = 1;
-  int ww = win->decorated_w();
-  int wh = win->decorated_h();
-  if (ww > w || wh > h) {
-    scale = (float)w/ww;
-    if ((float)h/wh < scale) scale = (float)h/wh;
-    printer.scale(scale, scale);
-    printer.printable_rect(&w, &h);
-  }
-
-// #define ROTATE 20.0
-#ifdef ROTATE
-  printer.scale(scale * 0.8, scale * 0.8);
-  printer.printable_rect(&w, &h);
-  printer.origin(w/2, h/2 );
-  printer.rotate(ROTATE);
-  printer.print_window( win, - win->w()/2, - win->h()/2);
-  //printer.print_window_part( win, 0,0, win->w(), win->h(), - win->w()/2, - win->h()/2 );
-#else
-  printer.origin(w/2, h/2 );
-  printer.print_window(win, -ww/2, -wh/2);
-  //printer.print_window_part( win, 0,0, win->w(), win->h(), -ww/2, -wh/2 );
-#endif
-
-  printer.end_page();
-  printer.end_job();
-  o->window()->show();
-}
-
-#include <FL/Fl_Copy_Surface.H>
-void copyFront(Fl_Widget *o, void *data)
-{
-  o->window()->hide();
-  Fl_Window *win = Fl::first_window();
-  if (!win) return;
-  Fl_Copy_Surface *surf = new Fl_Copy_Surface(win->decorated_w(), win->decorated_h());
-  Fl_Surface_Device::push_current(surf);
-  surf->draw_decorated_window(win); // draw the window content
-  Fl_Surface_Device::pop_current();
-  delete surf; // put the window on the clipboard
-  o->window()->show();
-}
-
-static int prepare_print_button() {
-  static Fl_Window w(0,0,140,60);
-  static Fl_Button bp(0,0,w.w(),30, "Print front window");
-  bp.callback(printFront);
-  static Fl_Button bc(0,30,w.w(),30, "Copy front window");
-  bc.callback(copyFront);
-  w.end();
-  w.show();
-  return 0;
-}
-
-static int unused = prepare_print_button();
-
-#endif // USE_PRINT_BUTTON
-
 #endif // !defined(FL_DOXYGEN)
diff --git a/src/Makefile b/src/Makefile
index 0b7b89a92..e38040332 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -157,11 +157,12 @@ CPPFILES = \
 	fl_shadow_box.cxx \
 	fl_shortcut.cxx \
 	fl_show_colormap.cxx \
+	fl_string.cxx \
 	fl_symbols.cxx \
-	fl_vertex.cxx \
-	screen_xywh.cxx \
 	fl_utf8.cxx \
-	fl_string.cxx
+	fl_vertex.cxx \
+	print_button.cxx \
+	screen_xywh.cxx
 
 OBJCPPFILES = \
 	Fl_cocoa.mm \
diff --git a/src/print_button.cxx b/src/print_button.cxx
new file mode 100644
index 000000000..35c7d1063
--- /dev/null
+++ b/src/print_button.cxx
@@ -0,0 +1,192 @@
+//
+// "Print Window" functions for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 1998-2021 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
+//
+
+// Notes: This function must be activated by defining the preprocessor macro
+// USE_PRINT_BUTTON on the commandline.
+//
+// Although this function is compiled on all platforms it is only used by
+// platform specific code of fl_open_display() on Linux (X11) and Windows.
+// macOS uses the "Print front window" menu in the application menu.
+//
+// The environment variable FLTK_PRINT_BUTTON can be defined to control the
+// creation of the sometimes annoying print button feature at runtime if it
+// has been compiled in (see above):
+//
+//  - FLTK_PRINT_BUTTON undefined: like 1 below (default)
+//
+//  - FLTK_PRINT_BUTTON = 0 : print front window disabled for this program
+//  - FLTK_PRINT_BUTTON = 1 : window shown at startup
+//  - FLTK_PRINT_BUTTON = 2 : window not shown, shortcut available to show
+//  - FLTK_PRINT_BUTTON = 3 : window shown at startup, shortcut available
+//
+// If options 2 or 3 are used the shortcut can be used to show the window
+// if it was not shown (2) or accidentally closed (3).
+//
+// Currently the shortcut can't be configured and is always ALT+SHIFT+'s'.
+// Todo: make the shortcut configurable.
+
+#ifdef USE_PRINT_BUTTON
+
+#include <FL/Fl_Printer.H>
+#include <FL/Fl_Button.H>
+#include <FL/Fl_Check_Button.H>
+#include <FL/Fl_Copy_Surface.H>
+#include <FL/Fl_Image_Surface.H>
+#include <FL/Fl_RGB_Image.H>
+#include <FL/fl_draw.H>
+#include <FL/fl_ask.H>
+
+#include <stdlib.h>
+#include <stdio.h>
+
+// define the optional rotation of print output in degrees to test it
+// #define ROTATE 20.0
+
+// Global variables to simplify and clarify the code:
+
+static Fl_Window *print_window = 0;       // "print front window" dialog window
+static Fl_Check_Button *deco_button = 0;  // window decoration button
+
+// The button callback does the job for both printing and copying to the
+// clipboard. The callback is called with 'mode' == (int)(data).
+//  1: print window
+//  2: copy window to clipboard
+// else: see 2.
+
+static void output_cb(Fl_Widget *o, void *data) {
+
+  print_window->hide();
+  Fl_Window *win = Fl::first_window();
+
+  // if no (other) window exists we return silently w/o showing the
+  // print window again (which ends the program)
+
+  if (!win) return;
+
+  int mode = fl_int(data);
+  int deco = deco_button->value();
+  int ww = deco ? win->decorated_w() : win->w();
+  int wh = deco ? win->decorated_h() : win->h();
+
+  if (mode == 1) { // print window
+
+    Fl_Printer printer;
+    int w, h;
+    if (printer.begin_job(1)) { // fail or cancel
+      print_window->show();
+      return;
+    }
+    if (printer.begin_page()) { // fail or cancel
+      print_window->show();
+      return;
+    }
+    printer.printable_rect(&w, &h);
+    // scale the printer device so that the window fits on the page
+    float scale = 1;
+    if (ww > w || wh > h) {
+      scale = (float)w / ww;
+      if ((float)h / wh < scale)
+        scale = (float)h / wh;
+      printer.scale(scale, scale);
+      printer.printable_rect(&w, &h);
+    }
+#ifdef ROTATE
+    printer.scale(scale * 0.8, scale * 0.8);
+    printer.printable_rect(&w, &h);
+    printer.origin(w / 2, h / 2);
+    printer.rotate(ROTATE);
+    printer.print_widget(win, -win->w() / 2, -win->h() / 2);
+#else
+    printer.origin(w / 2, h / 2);
+    printer.print_window(win, -ww / 2, -wh / 2);
+#endif
+    printer.end_page();
+    printer.end_job();
+
+  } else { // copy window to clipboard
+
+    Fl_Copy_Surface *surf = new Fl_Copy_Surface(ww, wh);
+    if (deco)
+      surf->draw_decorated_window(win); // draw the window content
+    else
+      surf->draw(win); // draw the window content
+    delete surf;       // put the window on the clipboard
+
+  } // print | copy
+
+  print_window->show();
+}
+
+// Global event handler for screenshot (ctrl/alt/command + s)
+// This pops up the "Print front window" dialog if it had been closed
+
+static int shortcut_handler(int event) { // global shortcut handler
+
+  // required key and keyboard states for shortcut
+  // (should be configurable)
+
+  const int key = 's';                 // global shortcut key
+  const int state = FL_ALT | FL_SHIFT; //  | FL_CTRL | FL_COMMAND;
+
+  if (print_window &&
+      (event == FL_SHORTCUT || event == FL_KEYBOARD) &&
+      ((Fl::event_state() & state) == state) &&
+      (Fl::event_key() == key)) {
+    print_window->show();
+    return 1;
+  }
+  return 0;
+}
+
+// create and initialize the "Print/copy front window" dialog window
+
+int fl_create_print_window() {
+  static int first = 1;
+  if (!first)
+    return 0;
+  first = 0;
+  int val = 1;
+  const char *print_button = fl_getenv("FLTK_PRINT_BUTTON");
+  if (print_button)
+    val = atoi(print_button);
+  if (val) {
+    // prevent becoming a subwindow
+    Fl_Group *cg = Fl_Group::current();
+    Fl_Group::current(0);
+    print_window  =     new Fl_Window( 0,  0, 200, 110, "FLTK screenshot");
+    Fl_Button *bp =     new Fl_Button(10, 10, 180,  30, "Print front window");
+    Fl_Button *bc =     new Fl_Button(10, 40, 180,  30, "Copy front window");
+    deco_button = new Fl_Check_Button(10, 70, 180,  30, "Window decoration");
+    bp->callback(output_cb, (void *)1);
+    bc->callback(output_cb, (void *)2);
+    print_window->end();
+    if (val & 1)
+      print_window->show();
+    // reset saved current group
+    Fl_Group::current(cg);
+    if (val & 2)
+      Fl::add_handler(shortcut_handler);
+  }
+  return 1;
+}
+
+#else // USE_PRINT_BUTTON not defined
+
+int fl_create_print_window() {
+  return 0;
+}
+
+#endif // USE_PRINT_BUTTON