Add CMake option FLTK_OPTION_PEN_SUPPORT (default: ON)

This option can be used to disable pen/tablet support if there are
build problems on a particular platform or build system (e.g. MinGW)
so users can continue to build FLTK 1.5.

Users can also choose to disable pen support if they don't need it.

11 files changed, 88 insertions, 18 deletions

diff --git a/CMake/options.cmake b/CMake/options.cmake
index 937bc29f9..27cffd038 100644
--- a/CMake/options.cmake
+++ b/CMake/options.cmake
@@ -468,6 +468,7 @@ option(FLTK_BUILD_SHARED_LIBS
 
 option(FLTK_OPTION_PRINT_SUPPORT      "allow print support"          ON)
 option(FLTK_OPTION_FILESYSTEM_SUPPORT "allow file system support"    ON)
+option(FLTK_OPTION_PEN_SUPPORT        "include Pen/Tablet support"   ON)
 
 option(FLTK_BUILD_FORMS        "Build forms compatibility library"   OFF)
 option(FLTK_BUILD_FLUID        "Build FLUID"                         ON)
@@ -481,12 +482,21 @@ else()
   option(FLTK_BUILD_TEST       "Build test/demo programs"            OFF)
 endif()
 
+
+# set variables to generate config.h or fl_config.h
+
 if(FLTK_BUILD_FORMS)
   set(FLTK_HAVE_FORMS 1)
 else()
   set(FLTK_HAVE_FORMS 0)
 endif()
 
+if(FLTK_OPTION_PEN_SUPPORT)
+  set(FLTK_HAVE_PEN_SUPPORT 1)
+else()
+  set(FLTK_HAVE_PEN_SUPPORT 0)
+endif()
+
 #######################################################################
 if(DOXYGEN_FOUND)
   option(FLTK_BUILD_HTML_DOCS "build html docs" ON)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d3ccbc6fc..2f41e5db8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -397,9 +397,12 @@ fl_summary_build("Static libraries"    lib    TRUE                      "n/a")
 fl_summary_build("Shared libraries"    lib    FLTK_BUILD_SHARED_LIBS    FLTK_BUILD_SHARED_LIBS)
 fl_summary_build("The forms library"   lib    FLTK_BUILD_FORMS          FLTK_BUILD_FORMS)
 fl_summary_build("The OpenGL library"  lib    FLTK_USE_GL               FLTK_BUILD_GL)
+fl_summary_build("Pen/tablet support"  lib    FLTK_OPTION_PEN_SUPPORT   FLTK_OPTION_PEN_SUPPORT)
+
+message(STATUS "")
+
 fl_summary_build("fluid"               bin    FLTK_BUILD_FLUID          FLTK_BUILD_FLUID)
 fl_summary_build("fltk-options"        bin    FLTK_BUILD_FLTK_OPTIONS   FLTK_BUILD_FLTK_OPTIONS)
-
 fl_summary_build("Test programs"       bin/test        FLTK_BUILD_TEST        FLTK_BUILD_TEST)
 fl_summary_build("Example programs"    bin/examples    FLTK_BUILD_EXAMPLES    FLTK_BUILD_EXAMPLES)
 fl_summary_build("Screenshot programs" bin/screenshots FLTK_BUILD_SCREENSHOTS FLTK_BUILD_SCREENSHOTS)
diff --git a/README.CMake.txt b/README.CMake.txt
index 77a404482..7043b13de 100644
--- a/README.CMake.txt
+++ b/README.CMake.txt
@@ -285,6 +285,16 @@ FLTK_OPTION_OPTIM - default EMPTY
     "-Wall -Wno-deprecated-declarations". Example:
     cmake -D FLTK_BUILD_EXAMPLES=on -D FLTK_OPTION_OPTIM="-Wall -Wextra -pedantic" ..
 
+FLTK_OPTION_PEN_SUPPORT - default ON
+    Pen support is relatively small and should be included by default, but
+    this option allows to switch it off if not needed.
+    Note: on some older systems or build platforms (notably "classic" MinGW)
+    compiling and building pen support may not be possible. As of this writing
+    (Jan. 2026) we don't use dynamic (CMake) tests to find out whether building
+    is possible or not. Instead users are encouraged to report build errors and
+    switch this option off to allow to proceed building FLTK 1.5.0.
+    Note: this option is WIP and may be removed later w/o further notice.
+
 FLTK_OPTION_PRINT_SUPPORT - default ON
     When turned off, the Fl_Printer class does nothing and the
     Fl_PostScript_File_Device class cannot be used, but the FLTK library
diff --git a/config.h.in b/config.h.in
index 8eebd16ea..9f235f7d1 100644
--- a/config.h.in
+++ b/config.h.in
@@ -356,3 +356,17 @@
  */
 
 #cmakedefine01 HAVE_CURSOR_SHAPE
+
+
+/*
+ * FLTK_HAVE_PEN_SUPPORT
+ *
+ * Do we have pen/tablet support for the current platform?
+ * See CMake option FLTK_OPTION_PEN_SUPPORT
+ *
+ * Note: this option is "hidden" in 'config.h', i.e. it's not (yet)
+ * publicly accessibe. Move this to 'fl_config.h' to make it public.
+ *
+ */
+
+#cmakedefine FLTK_HAVE_PEN_SUPPORT 1
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 55f5166b2..bae8d0e81 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -241,7 +241,6 @@ 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/Base/Fl_Base_Pen_Events.cxx
     Fl_x.cxx
     fl_dnd_x.cxx
     Fl_Native_File_Chooser_FLTK.cxx
@@ -249,9 +248,9 @@ if(FLTK_USE_X11 AND NOT FLTK_USE_WAYLAND)
     Fl_get_key.cxx
   )
 
-    list(APPEND DRIVER_FILES
-      Fl_Native_File_Chooser_Kdialog.cxx
-      Fl_Native_File_Chooser_Zenity.cxx)
+  list(APPEND DRIVER_FILES
+    Fl_Native_File_Chooser_Kdialog.cxx
+    Fl_Native_File_Chooser_Zenity.cxx)
 
   if(FLTK_USE_CAIRO)
     list(APPEND DRIVER_FILES
@@ -291,7 +290,6 @@ if(FLTK_USE_X11 AND NOT FLTK_USE_WAYLAND)
     drivers/Xlib/Fl_Xlib_Copy_Surface_Driver.H
     drivers/Xlib/Fl_Xlib_Image_Surface_Driver.H
     drivers/Unix/Fl_Unix_System_Driver.H
-    drivers/Base/Fl_Base_Pen_Events.H
  )
  if(FLTK_USE_CAIRO)
    set(DRIVER_HEADER_FILES ${DRIVER_HEADER_FILES}
@@ -319,7 +317,6 @@ 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/Base/Fl_Base_Pen_Events.cxx
     Fl_Native_File_Chooser_FLTK.cxx
     Fl_Native_File_Chooser_GTK.cxx
   )
@@ -351,7 +348,6 @@ elseif(FLTK_USE_WAYLAND)
     drivers/Wayland/Fl_Wayland_Copy_Surface_Driver.H
     drivers/Wayland/Fl_Wayland_Image_Surface_Driver.H
     drivers/Unix/Fl_Unix_System_Driver.H
-    drivers/Base/Fl_Base_Pen_Events.H
   )
 
 elseif(APPLE)
@@ -373,7 +369,6 @@ elseif(APPLE)
     drivers/Cocoa/Fl_Cocoa_Screen_Driver.cxx
     drivers/Posix/Fl_Posix_System_Driver.cxx
     drivers/Darwin/Fl_Darwin_System_Driver.cxx
-    drivers/Base/Fl_Base_Pen_Events.cxx
     Fl_get_key_mac.cxx
     drivers/Darwin/fl_macOS_platform_init.cxx
   )
@@ -387,7 +382,6 @@ elseif(APPLE)
     drivers/Quartz/Fl_Quartz_Copy_Surface_Driver.H
     drivers/Quartz/Fl_Font.H
     drivers/Quartz/Fl_Quartz_Image_Surface_Driver.H
-    drivers/Base/Fl_Base_Pen_Events.H
   )
 
 else()
@@ -399,7 +393,6 @@ else()
     drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx
     drivers/WinAPI/Fl_WinAPI_Window_Driver.cxx
     drivers/WinAPI/Fl_WinAPI_Printer_Driver.cxx
-    drivers/WinAPI/Fl_WinAPI_Pen_Driver.cxx
     drivers/GDI/Fl_GDI_Graphics_Driver.cxx
     drivers/GDI/Fl_GDI_Graphics_Driver_arci.cxx
     drivers/GDI/Fl_GDI_Graphics_Driver_color.cxx
@@ -410,7 +403,6 @@ 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/Base/Fl_Base_Pen_Events.cxx
     Fl_win32.cxx
     fl_dnd_win32.cxx
     Fl_Native_File_Chooser_WIN32.cxx
@@ -425,11 +417,29 @@ else()
     drivers/GDI/Fl_Font.H
     drivers/GDI/Fl_GDI_Copy_Surface_Driver.H
     drivers/GDI/Fl_GDI_Image_Surface_Driver.H
-    drivers/Base/Fl_Base_Pen_Events.H
   )
 
+  # Optional Pen/Tablet Support
+
+  if(FLTK_OPTION_PEN_SUPPORT)
+    list(APPEND DRIVER_FILES
+      drivers/WinAPI/Fl_WinAPI_Pen_Driver.cxx
+    )
+  endif(FLTK_OPTION_PEN_SUPPORT)
+
 endif(FLTK_USE_X11 AND NOT FLTK_USE_WAYLAND)
 
+# Common Pen/Tablet Support Files
+
+if(FLTK_OPTION_PEN_SUPPORT)
+  list(APPEND DRIVER_FILES
+    drivers/Base/Fl_Base_Pen_Events.cxx
+  )
+  list(APPEND DRIVER_HEADER_FILES
+    drivers/Base/Fl_Base_Pen_Events.H
+  )
+endif(FLTK_OPTION_PEN_SUPPORT)
+
 source_group("Header Files" FILES ${HEADER_FILES})
 source_group("Private Header Files" FILES ${PRIVATE_HEADER_FILES})
 source_group("Driver Source Files" FILES ${DRIVER_FILES})
@@ -632,10 +642,14 @@ if(APPLE AND NOT FLTK_BACKEND_X11)
   set(MMFILES
     Fl_cocoa.mm
     drivers/Cocoa/Fl_Cocoa_Printer_Driver.mm
-    drivers/Cocoa/Fl_Cocoa_Pen_Events.mm
     Fl_Native_File_Chooser_MAC.mm
     Fl_MacOS_Sys_Menu_Bar.mm
   )
+  if(FLTK_OPTION_PEN_SUPPORT)
+    list(APPEND MMFILES
+      drivers/Cocoa/Fl_Cocoa_Pen_Events.mm
+    )
+  endif()
   source_group("ObjC Source Files" FILES ${MMFILES})
 else()
   set(MMFILES)
diff --git a/src/Fl_cocoa.mm b/src/Fl_cocoa.mm
index 32abcbc88..2a90f5bf1 100644
--- a/src/Fl_cocoa.mm
+++ b/src/Fl_cocoa.mm
@@ -72,7 +72,7 @@ extern int fl_send_system_handlers(void *e);
 // converting cr lf converter function
 static void createAppleMenu(void);
 static void cocoaMouseHandler(NSEvent *theEvent);
-#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_9
+#if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_9) && defined(FLTK_HAVE_PEN_SUPPORT)
 static bool cocoaTabletHandler(NSEvent *theEvent, bool lock);
 extern bool fl_cocoa_tablet_handler(NSEvent*, Fl_Window*);
 #endif
@@ -631,7 +631,7 @@ void Fl_Cocoa_Screen_Driver::breakMacEventLoop()
            endedAtPoint:(NSPoint)screenPoint operation:(NSDragOperation)operation;
 #endif
 - (BOOL)did_view_resolution_change;
-#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_9
+#if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_9) && defined(FLTK_HAVE_PEN_SUPPORT)
 - (void)tabletProximity:(NSEvent *)theEvent;
 - (void)tabletPoint:(NSEvent *)theEvent;
 #endif
@@ -1057,6 +1057,7 @@ static void cocoaMagnifyHandler(NSEvent *theEvent)
 #endif
 }
 
+#if defined(FLTK_HAVE_PEN_SUPPORT)
 
 static bool cocoaTabletHandler(NSEvent *theEvent, bool lock)
 {
@@ -1067,6 +1068,8 @@ static bool cocoaTabletHandler(NSEvent *theEvent, bool lock)
   return ret;
 }
 
+#endif // FLTK_HAVE_PEN_SUPPORT
+
 namespace Fl {
 namespace Private {
 // Global mouse position at mouse down event
@@ -1084,6 +1087,7 @@ static void cocoaMouseHandler(NSEvent *theEvent)
 
   fl_lock_function();
 
+#if defined(FLTK_HAVE_PEN_SUPPORT)
   // Handle tablet proximity and point subevents
   if (   ([theEvent type] != NSEventTypeMouseEntered)  // does not have a subtype
       && ([theEvent type] != NSEventTypeMouseExited) ) // does not have a subtype
@@ -1098,6 +1102,7 @@ static void cocoaMouseHandler(NSEvent *theEvent)
       // else fall through into mouse event handling
     }
   }
+#endif // FLTK_HAVE_PEN_SUPPORT
 
   Fl_Window *window = (Fl_Window*)[(FLWindow*)[theEvent window] getFl_Window];
   if (!window || !window->shown() ) {
@@ -2635,7 +2640,7 @@ static FLTextInputContext* fltextinputcontext_instance = nil;
 - (void)mouseExited:(NSEvent *)theEvent {
   cocoaMouseHandler(theEvent);
 }
-#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_9
+#if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_9) && defined(FLTK_HAVE_PEN_SUPPORT)
 - (void)tabletProximity:(NSEvent *)theEvent {
   cocoaTabletHandler(theEvent, true);
 }
diff --git a/src/Fl_grab.cxx b/src/Fl_grab.cxx
index d9f47c445..9def8ee4f 100644
--- a/src/Fl_grab.cxx
+++ b/src/Fl_grab.cxx
@@ -14,6 +14,7 @@
 //     https://www.fltk.org/bugs.php
 //
 
+#include <config.h>
 #include <FL/Fl.H>
 #include "Fl_Screen_Driver.H"
 
@@ -27,6 +28,8 @@
 
 void Fl::grab(Fl_Window *win)
 {
+#if defined(FLTK_HAVE_PEN_SUPPORT)
   Fl::Pen::release();
+#endif
   screen_driver()->grab(win);
 }
diff --git a/src/Fl_win32.cxx b/src/Fl_win32.cxx
index abb875be7..cbc5fbd83 100644
--- a/src/Fl_win32.cxx
+++ b/src/Fl_win32.cxx
@@ -1837,9 +1837,11 @@ content  key    keyboard layout
         return 0;
 
       default: {
+#if defined(FLTK_HAVE_PEN_SUPPORT)
         LRESULT ret = fl_win32_tablet_handler(fl_msg);
         if (ret != -1)
           return ret;
+#endif
         if (Fl::handle(0, 0))
           return 0;
         break; }
diff --git a/src/drivers/Wayland/fl_wayland_platform_init.cxx b/src/drivers/Wayland/fl_wayland_platform_init.cxx
index a97e3846b..4c4477740 100644
--- a/src/drivers/Wayland/fl_wayland_platform_init.cxx
+++ b/src/drivers/Wayland/fl_wayland_platform_init.cxx
@@ -145,6 +145,8 @@ Fl_Image_Surface_Driver *Fl_Image_Surface_Driver::newImageSurfaceDriver(int w, i
   return new Fl_Wayland_Image_Surface_Driver(w, h, high_res, off);
 }
 
+#if defined(FLTK_HAVE_PEN_SUPPORT)
+
 namespace Fl {
 namespace Pen {
 Driver default_driver;
@@ -152,3 +154,4 @@ Driver& driver = default_driver;
 } // namespace Pen
 } // namespace Fl
 
+#endif // FLTK_HAVE_PEN_SUPPORT
diff --git a/src/drivers/X11/fl_X11_platform_init.cxx b/src/drivers/X11/fl_X11_platform_init.cxx
index 022513d5a..6a2851900 100644
--- a/src/drivers/X11/fl_X11_platform_init.cxx
+++ b/src/drivers/X11/fl_X11_platform_init.cxx
@@ -75,9 +75,11 @@ Fl_Image_Surface_Driver *Fl_Image_Surface_Driver::newImageSurfaceDriver(int w, i
   return new Fl_Xlib_Image_Surface_Driver(w, h, high_res, off);
 }
 
+#if defined(FLTK_HAVE_PEN_SUPPORT)
 namespace Fl {
 namespace Pen {
 Driver default_driver;
 Driver& driver = default_driver;
 } // namespace Pen
 } // namespace Fl
+#endif // FLTK_HAVE_PEN_SUPPORT
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 81d0c42fb..4522c99bc 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -183,7 +183,11 @@ fl_create_example(navigation navigation.cxx fltk::fltk)
 fl_create_example(output output.cxx fltk::fltk)
 fl_create_example(overlay overlay.cxx fltk::fltk)
 fl_create_example(pack pack.cxx fltk::fltk)
-fl_create_example(penpal penpal.cxx fltk::fltk)
+
+if(FLTK_OPTION_PEN_SUPPORT)
+  fl_create_example(penpal penpal.cxx fltk::fltk)
+endif()
+
 fl_create_example(pixmap pixmap.cxx fltk::images)
 fl_create_example(pixmap_browser pixmap_browser.cxx fltk::images)
 fl_create_example(preferences preferences.fl fltk::fltk)