Add pen/stylus/tablet API and driver for macOS (#1326)

* define the pen/tablet support API
* add pen event handler stub as a fallback
* add pen device test "penpal".
* Add macOS pen/stylus/tablet driver.
* Add Oxygen documentation.

1 files changed, 73 insertions, 0 deletions

diff --git a/src/drivers/Stubs/Fl_Stubs_Pen_Events.cxx b/src/drivers/Stubs/Fl_Stubs_Pen_Events.cxx
new file mode 100644
index 000000000..6b3512023
--- /dev/null
+++ b/src/drivers/Stubs/Fl_Stubs_Pen_Events.cxx
@@ -0,0 +1,73 @@
+//
+// Definition of default Pen/Tablet event driver.
+//
+// Copyright 2025 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>
+#include <FL/platform.H>
+#include <FL/core/pen_events.H>
+#include <FL/Fl.H>
+
+class Fl_Widget;
+
+namespace Fl {
+
+namespace Pen {
+
+// double e_pressure_;
+
+} // namespace Pen
+
+} // namespace Fl
+
+
+using namespace Fl::Pen;
+
+
+Trait Fl::Pen::driver_traits() { return Trait::NONE; }
+
+Trait Fl::Pen::pen_traits(int pen_id) { return Trait::NONE; }
+
+void Fl::Pen::subscribe(Fl_Widget* widget) { }
+
+void Fl::Pen::unsubscribe(Fl_Widget* widget) { }
+
+void Fl::Pen::release() { }
+
+double Fl::Pen::event_x() { return 0.0; }
+
+double Fl::Pen::event_y() { return 0.0; }
+
+double Fl::Pen::event_x_root() { return 0.0; }
+
+double Fl::Pen::event_y_root() { return 0.0; }
+
+int Fl::Pen::event_pen_id() { return 0; }
+
+double Fl::Pen::event_pressure() { return 1.0; }
+
+double Fl::Pen::event_barrel_pressure() { return 0.0; }
+
+double Fl::Pen::event_tilt_x() { return 0.0; }
+
+double Fl::Pen::event_tilt_y() { return 0.0; }
+
+double Fl::Pen::event_twist() { return 0.0; }
+
+double Fl::Pen::event_proximity() { return 0.0; }
+
+State Fl::Pen::event_state() { return Fl::Pen::State::NONE; }
+
+State Fl::Pen::event_trigger() { return Fl::Pen::State::NONE; }