7 files changed, 319 insertions, 218 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; }
diff --git a/src/drivers/Cocoa/Fl_Cocoa_Pen_Events.mm b/src/drivers/Cocoa/Fl_Cocoa_Pen_Events.mm
index c2840a41e..1ebbd11eb 100644
--- a/src/drivers/Cocoa/Fl_Cocoa_Pen_Events.mm
+++ b/src/drivers/Cocoa/Fl_Cocoa_Pen_Events.mm
@@ -14,81 +14,17 @@
 //     https://www.fltk.org/bugs.php
 //
 
+#include "src/drivers/Base/Fl_Base_Pen_Events.H"
 
-#include <config.h>
-#include <FL/platform.H>
-#include <FL/core/pen_events.H>
 #include <FL/Fl.H>
 #include <FL/Fl_Window.H>
-#include <FL/Fl_Tooltip.H>
-#include <FL/Fl_Widget_Tracker.H>
 #include "../../Fl_Screen_Driver.H"
 
 #import <Cocoa/Cocoa.h>
 
-#include <map>
-#include <memory>
 
 extern Fl_Window *fl_xmousewin;
 
-/*
- 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;
-  /* Remove subscribers that have a nullptr as a widget */
-  void 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> 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 remove(Fl_Widget *w) {
-    auto it = find(w);
-    if (it != end()) {
-      it->second->clear();
-      erase(it);
-    }
-  }
-};
-
-static SubscriberList subscriber_list_;
-static std::shared_ptr<Subscriber> pushed_;
-static std::shared_ptr<Subscriber> below_pen_;
 static NSPointingDeviceType device_type_ { NSPointingDeviceTypePen };
 
 // The trait list keeps track of traits for every pen ID that appears while
@@ -109,103 +45,53 @@ static Fl::Pen::Trait driver_traits_ {
   // Notably missing: PROXIMITY
 };
 
-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 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 };
-};
-
 // Temporary storage of event data for the driver;
-static struct EventData ev;
+static Fl::Pen::EventData ev;
 
 
 namespace Fl {
 
 namespace Private {
+
 // Global mouse position at mouse down event
 extern int e_x_down;
 extern int e_y_down;
+
 }; // namespace Private
 
 namespace Pen {
-// The event data that is made available to the user during event handling
-struct EventData e;
-} // namespace Pen
-
-} // namespace Fl
-
 
-using namespace Fl::Pen;
-
-
-// Return a bit for everything that AppKit could return.
-Trait Fl::Pen::driver_traits() {
-  return driver_traits_;
-}
-
-Trait Fl::Pen::pen_traits(int pen_id) {
-  auto it = trait_list_.find(pen_id);
-  if (pen_id == 0)
-    return current_pen_trait_;
-  if (it == trait_list_.end()) {
-    return Trait::DRIVER_AVAILABLE;
-  } else {
-    return it->second;
+class Cocoa_Driver : public Driver {
+public:
+  Cocoa_Driver() = default;
+  //virtual void subscribe(Fl_Widget* widget) override;
+  //virtual void unsubscribe(Fl_Widget* widget) override;
+  //virtual void release() override;
+  virtual Trait traits() override { return driver_traits_; }
+  virtual Trait pen_traits(int pen_id) override {
+    auto it = trait_list_.find(pen_id);
+    if (pen_id == 0)
+      return current_pen_trait_;
+    if (it == trait_list_.end()) {
+      return Trait::DRIVER_AVAILABLE;
+    } else {
+      return it->second;
+    }
   }
-}
-
-void Fl::Pen::subscribe(Fl_Widget* widget) {
-  if (widget == nullptr) return;
-  subscriber_list_.add(widget);
-}
-
-void Fl::Pen::unsubscribe(Fl_Widget* widget) {
-  if (widget == nullptr) return;
-  subscriber_list_.remove(widget);
-}
-
-void Fl::Pen::release() {
-  pushed_ = nullptr;
-  below_pen_ = nullptr;
-}
-
-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; }
+Cocoa_Driver cocoa_driver;
+Driver& driver { cocoa_driver };
 
-double Fl::Pen::event_tilt_y() { return e.tilt_y; }
+} // namespace Pen
 
-double Fl::Pen::event_twist() { return e.twist; }
+} // namespace Fl
 
-// Not supported in AppKit NSEvent
-double Fl::Pen::event_proximity() { return 0.0; }
 
-State Fl::Pen::event_state() { return e.state; }
+using namespace Fl::Pen;
 
-State Fl::Pen::event_trigger() { return e.trigger; }
 
-/**
+/*
  Copy the event state.
  */
 static void copy_state() {
@@ -218,7 +104,7 @@ static void copy_state() {
   Fl::e_y_root = (int)ev.ry;
 }
 
-/**
+/*
  Offset coordinates for subwindows and subsubwindows.
  */
 static void offset_subwindow_event(Fl_Widget *w, double &x, double &y) {
@@ -321,8 +207,7 @@ static State button_to_trigger(NSInteger button, bool down) {
 
 /*
  Handle events coming from Cocoa.
- TODO: clickCount: store in Fl::event_clicks()
- capabilityMask is useless, because it is vendor defined
+ `capabilityMask` is useless, because it is vendor defined
  If a modal window is open, AppKit will send window specific events only there.
  */
 bool fl_cocoa_tablet_handler(NSEvent *event, Fl_Window *eventWindow) {
@@ -477,7 +362,7 @@ bool fl_cocoa_tablet_handler(NSEvent *event, Fl_Window *eventWindow) {
         return 0;
     }
   } else {
-    // Anything to do here?
+    // Proximity events were handled earlier.
   }
 
   if (!receiver)
diff --git a/src/drivers/Stubs/Fl_Stubs_Pen_Events.cxx b/src/drivers/Stubs/Fl_Stubs_Pen_Events.cxx
deleted file mode 100644
index 6b3512023..000000000
--- a/src/drivers/Stubs/Fl_Stubs_Pen_Events.cxx
+++ /dev/null
@@ -1,73 +0,0 @@
-//
-// 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; }
diff --git a/src/drivers/Wayland/fl_wayland_platform_init.cxx b/src/drivers/Wayland/fl_wayland_platform_init.cxx
index bd6089f96..70c44348e 100644
--- a/src/drivers/Wayland/fl_wayland_platform_init.cxx
+++ b/src/drivers/Wayland/fl_wayland_platform_init.cxx
@@ -21,6 +21,7 @@
 #include "../Unix/Fl_Unix_System_Driver.H"
 #include "Fl_Wayland_Window_Driver.H"
 #include "Fl_Wayland_Image_Surface_Driver.H"
+#include "../Base/Fl_Base_Pen_Events.H"
 #ifdef FLTK_USE_X11
 #  include "../Xlib/Fl_Xlib_Copy_Surface_Driver.H"
 #  include "../Cairo/Fl_X11_Cairo_Graphics_Driver.H"
@@ -143,3 +144,11 @@ Fl_Image_Surface_Driver *Fl_Image_Surface_Driver::newImageSurfaceDriver(int w, i
 #endif
   return new Fl_Wayland_Image_Surface_Driver(w, h, high_res, off);
 }
+
+namespace FL {
+namespace Pen{
+Driver default_driver;
+Driver& driver { default_driver };
+} // namespace Pen
+} // namespace FL
+
diff --git a/src/drivers/WinAPI/fl_WinAPI_platform_init.cxx b/src/drivers/WinAPI/fl_WinAPI_platform_init.cxx
index fa6b41d24..49c7436c3 100644
--- a/src/drivers/WinAPI/fl_WinAPI_platform_init.cxx
+++ b/src/drivers/WinAPI/fl_WinAPI_platform_init.cxx
@@ -21,6 +21,7 @@
 #include "Fl_WinAPI_System_Driver.H"
 #include "Fl_WinAPI_Window_Driver.H"
 #include "../GDI/Fl_GDI_Image_Surface_Driver.H"
+#include "../Base/Fl_Base_Pen_Events.H"
 
 
 Fl_Copy_Surface_Driver *Fl_Copy_Surface_Driver::newCopySurfaceDriver(int w, int h)
@@ -81,3 +82,10 @@ Fl_Image_Surface_Driver *Fl_Image_Surface_Driver::newImageSurfaceDriver(int w, i
 {
   return new Fl_GDI_Image_Surface_Driver(w, h, high_res, off);
 }
+
+namespace FL {
+namespace Pen{
+Driver default_driver;
+Driver& driver { default_driver };
+} // namespace Pen
+} // namespace FL
diff --git a/src/drivers/X11/fl_X11_platform_init.cxx b/src/drivers/X11/fl_X11_platform_init.cxx
index e9d40dbc3..a6b0ad82b 100644
--- a/src/drivers/X11/fl_X11_platform_init.cxx
+++ b/src/drivers/X11/fl_X11_platform_init.cxx
@@ -26,6 +26,7 @@
 #include "../Unix/Fl_Unix_System_Driver.H"
 #include "Fl_X11_Window_Driver.H"
 #include "../Xlib/Fl_Xlib_Image_Surface_Driver.H"
+#include "../Base/Fl_Base_Pen_Events.H"
 
 
 Fl_Copy_Surface_Driver *Fl_Copy_Surface_Driver::newCopySurfaceDriver(int w, int h)
@@ -73,3 +74,10 @@ Fl_Image_Surface_Driver *Fl_Image_Surface_Driver::newImageSurfaceDriver(int w, i
 {
   return new Fl_Xlib_Image_Surface_Driver(w, h, high_res, off);
 }
+
+namespace FL {
+namespace Pen{
+Driver default_driver;
+Driver& driver { default_driver };
+} // namespace Pen
+} // namespace FL