Add Pen event handler stub.

This is a fallback for platforms that don't
support pens and tablets yet.

FL/core/pen_events.H

@@ -59,6 +59,8 @@ namespace Pen {
  If a bit is clear, the corresponding event value will not be set.
  */
 enum Features : uint32_t {
+  /// Return this if this implementation of FLTK does not support pens and tablets.
+  NONE             = 0x0000,
   /// Set if FLTK supports tablets and pens on this platform
   SUPPORTED        = 0x0001,
   /// Set if the system found a pen and/or tablet device
@@ -362,43 +364,65 @@ FL_EXPORT extern State event_trigger();
 } // namespace Fl
 
 /**
- * \brief Bitwise OR operator for Features enum.
- * \param lhs Left-hand side feature flags
- * \param rhs Right-hand side feature flags
- * \return Combined feature flags
+ \brief Bitwise OR operator for Features enum.
+ \param lhs Left-hand side feature flags
+ \param rhs Right-hand side feature flags
+ \return Combined feature flags
  */
 inline constexpr Fl::Pen::Features operator|(Fl::Pen::Features lhs, Fl::Pen::Features rhs) {
   return static_cast<Fl::Pen::Features>(static_cast<uint32_t>(lhs) | static_cast<uint32_t>(rhs));
 }
 
 /**
- * \brief Bitwise AND operator for Features enum.
- * \param lhs Left-hand side feature flags
- * \param rhs Right-hand side feature flags
- * \return Intersection of feature flags
+ \brief Bitwise AND operator for Features enum.
+ \param lhs Left-hand side feature flags
+ \param rhs Right-hand side feature flags
+ \return Intersection of feature flags
  */
 inline constexpr Fl::Pen::Features operator&(Fl::Pen::Features lhs, Fl::Pen::Features rhs) {
   return static_cast<Fl::Pen::Features>(static_cast<uint32_t>(lhs) & static_cast<uint32_t>(rhs));
 }
 
 /**
- * \brief Bitwise OR operator for State enum.
- * \param lhs Left-hand side state flags
- * \param rhs Right-hand side state flags
- * \return Combined state flags
+ \brief Bitwise OR assignment operator for Features enum.
+ \param lhs Left-hand side feature flags (modified in place)
+ \param rhs Right-hand side feature flags
+ \return Reference to modified lhs
+ */
+inline Fl::Pen::Features& operator|=(Fl::Pen::Features& lhs, Fl::Pen::Features rhs) {
+  lhs = lhs | rhs;
+  return lhs;
+}
+
+/**
+ \brief Bitwise OR operator for State enum.
+ \param lhs Left-hand side state flags
+ \param rhs Right-hand side state flags
+ \return Combined state flags
  */
 inline constexpr Fl::Pen::State operator|(Fl::Pen::State lhs, Fl::Pen::State rhs) {
   return static_cast<Fl::Pen::State>(static_cast<uint32_t>(lhs) | static_cast<uint32_t>(rhs));
 }
 
 /**
- * \brief Bitwise AND operator for State enum.
- * \param lhs Left-hand side state flags
- * \param rhs Right-hand side state flags
- * \return Intersection of state flags
+ \brief Bitwise AND operator for State enum.
+ \param lhs Left-hand side state flags
+ \param rhs Right-hand side state flags
+ \return Intersection of state flags
  */
 inline constexpr Fl::Pen::State operator&(Fl::Pen::State lhs, Fl::Pen::State rhs) {
   return static_cast<Fl::Pen::State>(static_cast<uint32_t>(lhs) & static_cast<uint32_t>(rhs));
 }
 
+/**
+ \brief Bitwise OR assignment operator for State enum.
+ \param lhs Left-hand side state flags (modified in place)
+ \param rhs Right-hand side state flags
+ \return Reference to modified lhs
+ */
+inline Fl::Pen::State& operator|=(Fl::Pen::State& lhs, Fl::Pen::State rhs) {
+  lhs = lhs | rhs;
+  return lhs;
+}
+
 #endif // !Fl_core_pen_events_H

src/CMakeLists.txt

@@ -241,6 +241,7 @@ if(FLTK_USE_X11 AND NOT FLTK_USE_WAYLAND)
     drivers/Xlib/Fl_Xlib_Copy_Surface_Driver.cxx
     drivers/Xlib/Fl_Xlib_Image_Surface_Driver.cxx
     drivers/X11/fl_X11_platform_init.cxx
+    drivers/Stubs/Fl_Stubs_Pen_Events.cxx
     Fl_x.cxx
     fl_dnd_x.cxx
     Fl_Native_File_Chooser_FLTK.cxx
@@ -317,6 +318,7 @@ elseif(FLTK_USE_WAYLAND)
     drivers/Wayland/fl_wayland_clipboard_dnd.cxx
     drivers/Wayland/fl_wayland_platform_init.cxx
     drivers/Cairo/Fl_Cairo_Graphics_Driver.cxx
+    drivers/Stubs/Fl_Stubs_Pen_Events.cxx
     Fl_Native_File_Chooser_FLTK.cxx
     Fl_Native_File_Chooser_GTK.cxx
   )
@@ -369,6 +371,7 @@ elseif(APPLE)
     drivers/Cocoa/Fl_Cocoa_Screen_Driver.cxx
     drivers/Posix/Fl_Posix_System_Driver.cxx
     drivers/Darwin/Fl_Darwin_System_Driver.cxx
+    drivers/Stubs/Fl_Stubs_Pen_Events.cxx
     Fl_get_key_mac.cxx
     drivers/Darwin/fl_macOS_platform_init.cxx
   )
@@ -403,6 +406,7 @@ else()
     drivers/GDI/Fl_GDI_Graphics_Driver_vertex.cxx
     drivers/GDI/Fl_GDI_Copy_Surface_Driver.cxx
     drivers/GDI/Fl_GDI_Image_Surface_Driver.cxx
+    drivers/Stubs/Fl_Stubs_Pen_Events.cxx
     Fl_win32.cxx
     fl_dnd_win32.cxx
     Fl_Native_File_Chooser_WIN32.cxx

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;
+
+Features Fl::Pen::features() { return NONE; }
+
+void Fl::Pen::subscribe(Fl_Widget*, bool) { }
+
+void Fl::Pen::unsubscribe(Fl_Widget*) { }
+
+void Fl::Pen::grab(Fl_Widget*) { }
+
+void Fl::Pen::release() { }
+
+double Fl::Pen::event_x() { return static_cast<double>(Fl::event_x()); }
+
+double Fl::Pen::event_y() { return static_cast<double>(Fl::event_y()); }
+
+double Fl::Pen::event_x_root() { return static_cast<double>(Fl::event_x_root()); }
+
+double Fl::Pen::event_y_root() { return static_cast<double>(Fl::event_y_root()); }
+
+int Fl::Pen::event_id() { return -1; }
+
+double Fl::Pen::event_pressure() { return 0.0; }
+
+double Fl::Pen::event_tangential_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 static_cast<State>(0); }
+
+State Fl::Pen::event_trigger() { return static_cast<State>(0); }
+