Cocoa: support drag-and-drop of multiple objects.

src/video/cocoa/SDL_cocoawindow.m

@@ -106,18 +106,35 @@
 
 - (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender
 {
+    if (([sender draggingSourceOperationMask] & NSDragOperationGeneric) == NSDragOperationGeneric) {
         return NSDragOperationGeneric;
     }
 
-- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender
-{
-    NSURL *fileURL = [NSURL URLFromPasteboard:[sender draggingPasteboard]];
-    NSNumber *isAlias = nil;
+    return NSDragOperationNone; /* no idea what to do with this, reject it. */
+}
 
-    if (fileURL == nil) {
+- (BOOL)performDragOperation:(id <NSDraggingInfo>)sender
+{ @autoreleasepool
+{
+    NSPasteboard *pasteboard = [sender draggingPasteboard];
+    NSArray *types = [NSArray arrayWithObject:NSFilenamesPboardType];
+    NSString *desiredType = [pasteboard availableTypeFromArray:types];
+    if (desiredType == nil) {
+        return NO;  /* can't accept anything that's being dropped here. */
+    }
+
+    NSData *data = [pasteboard dataForType:desiredType];
+    if (data == nil) {
         return NO;
     }
 
+    SDL_assert([desiredType isEqualToString:NSFilenamesPboardType]);
+    NSArray *array = [pasteboard propertyListForType:@"NSFilenamesPboardType"];
+
+    for (NSString *path in array) {
+        NSURL *fileURL = [[NSURL fileURLWithPath:path] autorelease];
+        NSNumber *isAlias = nil;
+
         /* Functionality for resolving URL aliases was added with OS X 10.6. */
         if ([fileURL respondsToSelector:@selector(getResourceValue:forKey:error:)]) {
             [fileURL getResourceValue:&isAlias forKey:NSURLIsAliasFileKey error:nil];
@@ -140,8 +157,13 @@
             }
         }
 
-    return (BOOL) SDL_SendDropFile([[fileURL path] UTF8String]);
+        if (!SDL_SendDropFile([[fileURL path] UTF8String])) {
+            return NO;
         }
+    }
+
+    return YES;
+}}
 
 - (BOOL)wantsPeriodicDraggingUpdates
 {