Fix compilation with older CMake/GCC and link in tinfow

The 'if (NCURSESW)' has been removed because ncurses is already compulsory. The REQUIRED option of find_library is not available in older CMake versions, so the only way to trigger an error is to dereference NCURSESW unconditionally.

tinfow has to be linked in systems where both tinfo and tinfow are available. See #11.

CMakeLists.txt

@@ -1,5 +1,7 @@
 cmake_minimum_required (VERSION 3.5)
-cmake_policy(SET CMP0091 NEW)
+if (${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.15.0")
+    cmake_policy(SET CMP0091 NEW)
+endif()
 
 project(tvision)
 
@@ -15,7 +17,7 @@ else()
 endif()
 
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
-    # Static RTL linkage for MSVC.
+    # Static RTL linkage for MSVC (requires CMake >= 3.15).
 #     set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
 
     add_compile_options(
@@ -67,11 +69,22 @@ add_executable(palette ${PALETTESRC})
 set(LIBS tvision)
 
 if (TV_PLATF EQUAL TV_PLATF_UNIX)
-    find_library(NCURSESW ncursesw REQUIRED)
-    if (NCURSESW)
-        list(APPEND LIBS ${NCURSESW})
-        target_compile_definitions(tvision PRIVATE HAVE_NCURSES)
+    # ncursesw
+    find_library(NCURSESW ncursesw)
+    list(APPEND LIBS ${NCURSESW})
+    target_compile_definitions(tvision PRIVATE HAVE_NCURSES)
+
+    # tinfow (comes with ncurses and is often provided as 'tinfo',
+    # but we need to link the 'w' version when both are available)
+    find_library(TINFOW tinfow)
+    if (TINFOW)
+        list(APPEND LIBS ${TINFOW})
     endif()
+
+    if (CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9)
+        list(APPEND LIBS "stdc++fs")
+    endif()
+
     # Optional dependencies
     find_library(GPM gpm)
     if (GPM)

include/tvision/internal/platform.h

@@ -1,6 +1,7 @@
 #ifndef PLATFORM_H
 #define PLATFORM_H
 
+#include <tvision/tv.h>
 #include <memory>
 #include <functional>
 #include <queue>