Removing use of -retain (incompatible with ARC). (#243)

Author: nhojb

CMakeLists.txt

@@ -290,6 +290,9 @@ if (APPLE OR CMAKE_SYSTEM MATCHES "Linux")
 endif()
 
 add_definitions(${NANOGUI_EXTRA_DEFS})
+if (APPLE)
+  add_definitions(-fobjc-arc)
+endif()
 
 # Compile main NanoGUI library
 add_library(nanogui-obj OBJECT

src/darwin.mm

@@ -6,7 +6,7 @@
 std::string file_dialog(const std::vector<std::pair<std::string, std::string>> &filetypes, bool save) {
     std::string path = "";
     if (save) {
-        NSSavePanel *saveDlg = [[NSSavePanel savePanel] retain];
+        NSSavePanel *saveDlg = [NSSavePanel savePanel];
 
         NSMutableArray *types = [NSMutableArray new];
         for (size_t idx = 0; idx < filetypes.size(); ++idx)
@@ -17,7 +17,7 @@
         if ([saveDlg runModal] == NSModalResponseOK)
             path = [[[saveDlg URL] path] UTF8String];
     } else {
-        NSOpenPanel *openDlg = [[NSOpenPanel openPanel] retain];
+        NSOpenPanel *openDlg = [NSOpenPanel openPanel];
 
         [openDlg setCanChooseFiles:YES];
         [openDlg setCanChooseDirectories:NO];