Separate libslic3r code from slic3r application code

xs/src/slic3r/GUI/GUI.cpp

@@ -0,0 +1,39 @@
+#include "GUI.hpp"
+
+#if __APPLE__
+#import <IOKit/pwr_mgt/IOPMLib.h>
+#elif _WIN32
+#include <Windows.h>
+#pragma comment(lib, "user32.lib")
+#endif
+
+namespace Slic3r { namespace GUI {
+
+#if __APPLE__
+IOPMAssertionID assertionID;
+#endif
+
+void
+disable_screensaver()
+{
+    #if __APPLE__
+    CFStringRef reasonForActivity = CFSTR("Slic3r");
+    IOReturn success = IOPMAssertionCreateWithName(kIOPMAssertionTypeNoDisplaySleep, 
+        kIOPMAssertionLevelOn, reasonForActivity, &assertionID); 
+    // ignore result: success == kIOReturnSuccess
+    #elif _WIN32
+    SetThreadExecutionState(ES_DISPLAY_REQUIRED | ES_CONTINUOUS);
+    #endif
+}
+
+void
+enable_screensaver()
+{
+    #if __APPLE__
+    IOReturn success = IOPMAssertionRelease(assertionID);
+    #elif _WIN32
+    SetThreadExecutionState(ES_CONTINUOUS);
+    #endif
+}
+
+} }