Check that the C++11 future feature is supported

The mingw cross compiler for windows can be built with either a
posix thread model or a win32 thread model. The win32 thread model does
not fully support future. So we detect if future compilation works and
disable multithreading if not.

Fixes issue #178

src/filter/kaleid0sc0pe/CMakeLists.txt

@@ -1,5 +1,6 @@
 include(CheckIncludeFileCXX)
 include(CheckCSourceCompiles)
+include(CheckCXXSourceCompiles)
 
 cmake_policy(SET CMP0056 NEW)
 cmake_policy(SET CMP0066 NEW)
@@ -59,4 +60,10 @@ else()
     endif()
 endif()
 
+check_cxx_source_compiles("
+			    #include <future>
+			    int main(){ std::future<void> f; return 0;}" HAS_WORKING_FUTURE)
+if (NOT HAS_WORKING_FUTURE)
+	add_definitions(-DNO_FUTURE)
+endif()
 install (TARGETS ${TARGET} LIBRARY DESTINATION ${LIBDIR})

src/filter/kaleid0sc0pe/kaleid0sc0pe.cpp

@@ -25,7 +25,9 @@
 #include "kaleid0sc0pe.h"
 #include <memory>
 #include <cstring>
+#ifndef NO_FUTURE
 #include <future>
+#endif
 
 #ifdef __SSE2__
 #define USE_SSE2
@@ -612,6 +614,21 @@ std::int32_t Kaleid0sc0pe::process(const void* in_frame, void* out_frame)
     if (m_n_segments == 0) {
         init();
     }
+#ifdef NO_FUTURE
+    Block block(reinterpret_cast<const std::uint8_t*>(in_frame),
+        reinterpret_cast<std::uint8_t*>(out_frame),
+        0, 0,
+        m_width - 1, m_height - 1);
+#ifdef __SSE2__
+    if (m_edge_reflect) {
+        process_block(&block);
+    } else {
+        process_block_bg(&block);
+    }
+#else
+    process_block(&block);
+#endif
+#else
     if (m_n_threads == 1) {
         Block block(reinterpret_cast<const std::uint8_t*>(in_frame),
             reinterpret_cast<std::uint8_t*>(out_frame),
@@ -655,6 +672,7 @@ std::int32_t Kaleid0sc0pe::process(const void* in_frame, void* out_frame)
             f.wait();
         }
     }
+#endif
 
     return 0;
 }