2 files changed, 264 insertions, 0 deletions
diff --git a/src/drivers/Base/Fl_Base_Pen_Events.H b/src/drivers/Base/Fl_Base_Pen_Events.H
new file mode 100644
index 000000000..ba4882d0b
--- /dev/null
+++ b/src/drivers/Base/Fl_Base_Pen_Events.H
@@ -0,0 +1,116 @@
+//
+// 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
+//
+
+
+#ifndef FL_BASE_PEN_EVENTS_H
+#define FL_BASE_PEN_EVENTS_H
+
+#include <config.h>
+#include <FL/core/pen_events.H>
+#include <FL/Fl.H>
+
+#include <map>
+#include <memory>
+
+
+class Fl_Widget;
+
+namespace Fl {
+
+namespace Pen {
+
+/* Pen event data storage.
+  A second storage may be useful if the driver needs to collect pen data
+  from multiple events, or if one system event can send multiple FLTK events.
+*/
+typedef struct EventData {
+  double x { 0.0 };
+  double y { 0.0 };
+  double rx { 0.0 };
+  double ry { 0.0 };
+  double tilt_x { 0.0 };
+  double tilt_y { 0.0 };
+  double pressure { 1.0 };
+  double proximity { 0.0 };
+  double barrel_pressure { 0.0 };
+  double twist { 0.0 };
+  int pen_id { 0 };
+  Fl::Pen::State state { (Fl::Pen::State)0 };
+  Fl::Pen::State trigger { (Fl::Pen::State)0 };
+} EventData;
+
+extern EventData e;
+
+
+/*
+  Widgets and windows must subscribe to pen events. This is to reduce the amount
+  of events sent into the widget hierarchy.
+
+  Usually there is a pretty small number of subscribers, so looping through the
+  subscriber list should not be an issue.
+
+  All subscribers track their widget. If a widget is deleted while subscribed,
+  including during event handling, the driver will remove the subscription.
+  There is no need to explicitly unsubscribe.
+ */
+class Subscriber : public Fl_Widget_Tracker {
+public:
+  Subscriber(Fl_Widget *w) : Fl_Widget_Tracker(w) { }
+};
+
+
+/*
+ Manage a list of subscribers.
+ */
+class SubscriberList : public std::map<Fl_Widget*, std::shared_ptr<Subscriber>> {
+public:
+  SubscriberList() = default;
+  void cleanup();
+  std::shared_ptr<Subscriber> add(Fl_Widget *w);
+  void remove(Fl_Widget *w);
+};
+
+extern SubscriberList subscriber_list_;
+extern std::shared_ptr<Subscriber> pushed_;
+extern std::shared_ptr<Subscriber> below_pen_;
+
+/* The base driver for calls by apps into the pen system.
+
+  Most traffic is generated by system events. The data is then converted
+  for the FLTK API and stored in Fl::Pen::e. The Pen interface then sends
+  the appropriate FLTK events to the subscribers.
+
+  This driver class manages calls from the app into FLTK, including subscriber
+  management and queries for driver an pen abilities.
+*/
+class Driver {
+public:
+  Driver() = default;
+  virtual void subscribe(Fl_Widget* widget);
+  virtual void unsubscribe(Fl_Widget* widget);
+  virtual void release();
+  virtual Trait traits();
+  virtual Trait pen_traits(int pen_id);
+};
+
+extern Driver& driver;
+
+} // namespace Pen
+
+} // namespace Fl
+
+
+#endif // FL_BASE_PEN_EVENTS_H
diff --git a/src/drivers/Base/Fl_Base_Pen_Events.cxx b/src/drivers/Base/Fl_Base_Pen_Events.cxx
new file mode 100644
index 000000000..f4ebbd8ad
--- /dev/null
+++ b/src/drivers/Base/Fl_Base_Pen_Events.cxx
@@ -0,0 +1,148 @@
+//
+// Implementation 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 "src/drivers/Base/Fl_Base_Pen_Events.H"
+
+
+class Fl_Widget;
+
+
+namespace Fl {
+
+namespace Pen {
+
+EventData e;
+SubscriberList subscriber_list_;
+std::shared_ptr<Subscriber> pushed_;
+std::shared_ptr<Subscriber> below_pen_;
+
+} // namespace Pen
+
+} // namespace Fl
+
+
+using namespace Fl::Pen;
+
+
+// ---- SubscriberList implementation ------------------------------------------
+
+/* Remove subscribers that have a nullptr as a widget */
+void Fl::Pen::SubscriberList::cleanup() {
+  for (auto it = begin(); it != end(); ) {
+    if (!it->second->widget()) {
+      it = erase(it);
+    } else {
+      ++it;
+    }
+  }
+}
+
+/* Add a new subscriber, or return an existing one. */
+std::shared_ptr<Subscriber> Fl::Pen::SubscriberList::add(Fl_Widget *w) {
+  cleanup();
+  auto it = find(w);
+  if (it == end()) {
+    auto sub = std::make_shared<Subscriber>(w);
+    insert(std::make_pair(w, sub));
+    return sub;
+  } else {
+    return it->second;
+  }
+}
+
+/* Remove a subscriber from the list. */
+void Fl::Pen::SubscriberList::remove(Fl_Widget *w) {
+  auto it = find(w);
+  if (it != end()) {
+    it->second->clear();
+    erase(it);
+  }
+}
+
+// ---- Driver implementation --------------------------------------------------
+// Override the methods below to handle subscriptions and queries by user apps.
+
+void Fl::Pen::Driver::subscribe(Fl_Widget* widget) {
+  if (widget == nullptr) return;
+  subscriber_list_.add(widget);
+}
+
+void Fl::Pen::Driver::unsubscribe(Fl_Widget* widget) {
+  if (widget == nullptr) return;
+  subscriber_list_.remove(widget);
+}
+
+void Fl::Pen::Driver::release() {
+  pushed_ = nullptr;
+  below_pen_ = nullptr;
+}
+
+Trait Fl::Pen::Driver::traits() {
+  return Trait::NONE;
+}
+
+Trait Fl::Pen::Driver::pen_traits(int pen_id) {
+  (void)pen_id;
+  return Trait::NONE;
+}
+
+// ---- Fl::Pen API ------------------------------------------------------------
+
+void Fl::Pen::subscribe(Fl_Widget* widget) {
+  driver.subscribe(widget);
+}
+
+void Fl::Pen::unsubscribe(Fl_Widget* widget) {
+  driver.unsubscribe(widget);
+}
+
+void Fl::Pen::release() {
+  driver.release();
+}
+
+Trait Fl::Pen::driver_traits() {
+  return driver.traits();
+}
+
+Trait Fl::Pen::pen_traits(int pen_id) {
+  return driver.pen_traits(pen_id);
+}
+
+double Fl::Pen::event_x() { return e.x; }
+
+double Fl::Pen::event_y() { return e.y; }
+
+double Fl::Pen::event_x_root() { return e.rx; }
+
+double Fl::Pen::event_y_root() { return e.ry; }
+
+int Fl::Pen::event_pen_id() { return e.pen_id; }
+
+double Fl::Pen::event_pressure() { return e.pressure; }
+
+double Fl::Pen::event_barrel_pressure() { return e.barrel_pressure; }
+
+double Fl::Pen::event_tilt_x() { return e.tilt_x; }
+
+double Fl::Pen::event_tilt_y() { return e.tilt_y; }
+
+double Fl::Pen::event_twist() { return e.twist; }
+
+double Fl::Pen::event_proximity() { return e.proximity; }
+
+State Fl::Pen::event_state() { return e.state; }
+
+State Fl::Pen::event_trigger() { return e.trigger; }