add file picker to osx

PanoPainter-OSX/main.cpp

@@ -97,6 +97,32 @@
     }
     return ret;
 }
+- (std::string)pick_file_save:(NSArray<NSString*>*)types
+{
+    NSSavePanel *panel = [NSSavePanel savePanel];
+    [panel setCanCreateDirectories:YES];
+    
+    [panel setAllowedFileTypes:types];
+
+    [self removeTrackingArea:trackingArea];
+    if (!cursor_visible)
+        [NSCursor unhide];
+
+    NSInteger clicked = [panel runModal];
+    
+    [self addTrackingArea:trackingArea];
+    if (!cursor_visible)
+        [NSCursor hide];
+
+    std::string ret;
+    if (clicked == NSFileHandlingPanelOKButton)
+    {
+        NSURL *url = [panel URL];
+        LOG("selected file: %s", [[url path] cStringUsingEncoding:NSUTF8StringEncoding]);
+        ret = [[url path] cStringUsingEncoding:NSUTF8StringEncoding];
+    }
+    return ret;
+}
 - (std::string)pick_dir
 {
     NSOpenPanel *panel = [NSOpenPanel openPanel];