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).

1 files changed, 192 insertions, 0 deletions

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