From 8a2b7c043fe86916d56044d7489f8dce6ed2d479 Mon Sep 17 00:00:00 2001
From: James Le Cuirot <chewi@gentoo.org>
Date: Sun, 27 Feb 2022 14:01:33 +0000
Subject: [PATCH 3/3] Allow building against the system FLTK library

`USE_INTERNAL_FLTK` defaults to true and ignores `USE_INTERNAL_LIBS`
because users are unlikely to have it installed.

Odamex makes of use screen scaling features in FLTK that have not yet
been released. This change therefore checks for the Fl::screen_scale
symbol and skips the associated code if it is absent. In practise, this
only affects the size of the dialog window on HiDPI screens. The game
window is unaffected.

Tested against FLTK 1.3.5 on Gentoo Linux.

--- a/CMakeLists.txt	2022-11-24 21:02:08.000000000 -0600
+++ b/CMakeLists.txt	2023-05-12 14:08:26.838832213 -0500
@@ -43,6 +43,7 @@
 cmake_dependent_option( USE_INTERNAL_ZLIB "Use internal zlib" ${USE_INTERNAL_LIBS} BUILD_CLIENT 0 )
 cmake_dependent_option( USE_INTERNAL_PNG "Use internal libpng" ${USE_INTERNAL_LIBS} BUILD_CLIENT 0 )
 cmake_dependent_option( USE_INTERNAL_CURL "Use internal libcurl" ${USE_INTERNAL_LIBS} BUILD_CLIENT 0 )
+cmake_dependent_option( USE_INTERNAL_FLTK "Use internal FLTK" 1 BUILD_CLIENT 0 )
 cmake_dependent_option( USE_INTERNAL_JSONCPP "Use internal JsonCpp" 1 BUILD_SERVER 0 )
 cmake_dependent_option( USE_INTERNAL_WXWIDGETS "Use internal wxWidgets" ${USE_INTERNAL_LIBS} BUILD_LAUNCHER 0 )
 cmake_dependent_option( ENABLE_PORTMIDI "Enable portmidi support" 1 BUILD_CLIENT 0 )
--- a/client/CMakeLists.txt	2022-11-24 21:02:08.000000000 -0600
+++ b/client/CMakeLists.txt	2023-05-12 14:10:01.895750073 -0500
@@ -206,8 +206,28 @@
   target_link_libraries(odamex ${PNG_LIBRARY} ${ZLIB_LIBRARY} CURL::libcurl)
   if(NOT GCONSOLE)
     target_include_directories(odamex PRIVATE gui)
-    target_link_libraries(odamex fltk fltk_images)
-  endif()
+    if(USE_INTERNAL_FLTK)
+      set(FLTK_LIBRARIES fltk fltk_images)
+      set(HAVE_FLTK_SCREEN_SCALE TRUE)
+    else()
+      set(FLTK_SKIP_OPENGL 1)
+      set(FLTK_SKIP_FORMS 1)
+      set(FLTK_SKIP_FLUID 1)
+      find_package(FLTK REQUIRED)
+      target_include_directories(odamex SYSTEM PRIVATE ${FLTK_INCLUDE_DIR})
+
+      include(CheckCXXSymbolExists)
+      set(CMAKE_REQUIRED_INCLUDES ${FLTK_INCLUDE_DIR})
+      set(CMAKE_REQUIRED_LIBRARIES ${FLTK_LIBRARIES})
+      check_cxx_symbol_exists(Fl::screen_scale "FL/Fl.H" HAVE_FLTK_SCREEN_SCALE)
+    endif()
+
+    if(HAVE_FLTK_SCREEN_SCALE)
+      target_compile_definitions(odamex PRIVATE HAVE_FLTK_SCREEN_SCALE)
+    endif()
+
+    target_link_libraries(odamex ${FLTK_LIBRARIES})
+   endif()
 
   if(ENABLE_PORTMIDI)
     target_link_libraries(odamex ${PORTMIDI_LIBRARY})
--- a/client/gui/gui_boot.cpp	2022-11-24 21:02:08.000000000 -0600
+++ b/client/gui/gui_boot.cpp	2023-05-12 14:11:19.362517260 -0500
@@ -537,12 +537,14 @@
  */
 scannedWADs_t GUI_BootWindow()
 {
+#ifdef HAVE_FLTK_SCREEN_SCALE
 	// Scale according to 1600x900.
 	Fl::screen_scale(0, MAX(Fl::h() / 900.0f, 1.0f));
 
 	// This feature is too clever by half, and in my experience just
 	// deforms the window.
 	Fl::keyboard_screen_scaling(0);
+#endif
 
 	BootWindow* win = MakeBootWindow();
 	win->initWADDirs();
--- a/libraries/CMakeLists.txt	2022-11-24 21:02:08.000000000 -0600
+++ b/libraries/CMakeLists.txt	2023-05-12 14:11:46.463789831 -0500
@@ -264,7 +264,7 @@
 
 ### FLTK (dep: libpng) ###
 
-if(BUILD_CLIENT)
+if(BUILD_CLIENT AND USE_INTERNAL_FLTK)
   set(_FLTK_BUILDGEN_PARAMS
     "-DOPTION_USE_SYSTEM_LIBJPEG=OFF"
     "-DOPTION_PRINT_SUPPORT=OFF"