Fix file drag sources in the Cocoa backend (PR #27047)

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exkrexpexfex

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Sep 21, 2026, 4:23:34 PM (yesterday) Sep 21
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Problem

Dragging a wxFileDataObject to an external macOS application does not
provide valid file URLs. Cocoa recipients expect public.file-url pasteboard
data, but wx currently exposes the internal newline-separated filename data.

Changes

  • Convert filename drag data to CFURL-backed public.file-url payloads.
  • Create an NSDraggingItem for every dragged file.
  • Preserve the existing generic pasteboard writer for non-file data.
  • Restrict advertised drag operations to copy and, when allowed, move.

Result

External Cocoa targets, such as Finder, receive valid file URLs for single-
and multi-file drags.

You can view, comment on, or merge this pull request online at:

  https://github.com/wxWidgets/wxWidgets/pull/27047

Commit Summary

  • 84c80a2 Cocoa: export wxFileDataObject drags as file URLs

File Changes

(1 file)

Patch Links:

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VZ

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Sep 21, 2026, 4:43:03 PM (yesterday) Sep 21
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@vadz commented on this pull request.

Thanks, I didn't test this but if it solves the problem with dragging files (does this work when dragging them from the dnd sample now?), it should be merged, of course, but I'm not sure about the NSDragOperationDelete removal.

@csomor Do you see anything wrong here?

In src/osx/cocoa/dnd.mm:

>          size_t size = m_data->GetDataSize(format);
-        CFMutableDataRef data = CFDataCreateMutable(kCFAllocatorDefault,size );
+        CFMutableDataRef data = CFDataCreateMutable(kCFAllocatorDefault, size);

Minor, but please try to avoid making whitespace-only changes in the same commits as the actual changes, this is distracting and results in wrong results from git-blame later.

In src/osx/cocoa/dnd.mm:

>          wxCFMutableArrayRef<NSDraggingItem*> items;
-        NSDraggingItem* item = [[NSDraggingItem alloc] initWithPasteboardWriter:writer];
-        [item setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
-        items.push_back(item);
+        wxPasteBoardWriter* writer = nil;
+
+        wxArrayString files = GetFilenamesFromDataObject(m_data);
+        if ( files.GetCount() > 1 )
+        {
+            for ( size_t i = 0; i < files.GetCount(); ++i )
+            {
+                wxCFRef<CFURLRef> url(wxOSXCreateURLFromFileSystemPath(files[i]));
+                if ( !url )
+                    continue;
+
+                CFDataRef data = CFURLCreateData(nullptr, url, kCFStringEncodingUTF8, true);

Should also use wxCFRef<CFDataRef> here (and remove the explicit CFRelease() below).

In src/osx/cocoa/dnd.mm:

>          wxCFMutableArrayRef<NSDraggingItem*> items;
-        NSDraggingItem* item = [[NSDraggingItem alloc] initWithPasteboardWriter:writer];
-        [item setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
-        items.push_back(item);
+        wxPasteBoardWriter* writer = nil;
+
+        wxArrayString files = GetFilenamesFromDataObject(m_data);
+        if ( files.GetCount() > 1 )

Why do we have to handle the case of a single file differently from multiple ones?

In src/osx/cocoa/dnd.mm:

> +
+        if ( items.empty() )

This could/should be just

⬇️ Suggested change 
-
-        if ( items.empty() )
+        else

, right?

In src/osx/cocoa/dnd.mm:

> @@ -555,8 +623,11 @@ - (nullable id)pasteboardPropertyListForType:(nonnull NSPasteboardType)type
         result = NSDragOperationToWxDragResult([delegate code]);
         [delegate release];
         [image release];
-        [writer clearDataObject];
-        [writer release];
+        if ( writer )

AFAIK this is not really needed, sending events to a nil object doesn't do anything anyhow.

In src/osx/cocoa/dnd.mm:

>  
-    // NSDragOperationGeneric also makes a drag to the trash possible
-    // resulting in something we don't support (NSDragOperationDelete)

I don't quite understand why is this code not correct any more, I think we still don't support NSDragOperationDelete and so dragging to the trash should remain forbidden.

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exkrexpexfex

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Sep 21, 2026, 5:07:32 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

>          wxCFMutableArrayRef<NSDraggingItem*> items;
-        NSDraggingItem* item = [[NSDraggingItem alloc] initWithPasteboardWriter:writer];
-        [item setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
-        items.push_back(item);
+        wxPasteBoardWriter* writer = nil;
+
+        wxArrayString files = GetFilenamesFromDataObject(m_data);
+        if ( files.GetCount() > 1 )

It turns out the single-file case is not equivalent in practice. Using an explicit NSPasteboardItem containing only public.file-url makes Finder create an alias, while the existing wxPasteBoardWriter path preserves the additional pasteboard representations Finder needs to accept it as the actual file.

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VZ

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Sep 21, 2026, 5:13:40 PM (yesterday) Sep 21
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@vadz commented on this pull request.

In src/osx/cocoa/dnd.mm:

>          wxCFMutableArrayRef<NSDraggingItem*> items;
-        NSDraggingItem* item = [[NSDraggingItem alloc] initWithPasteboardWriter:writer];
-        [item setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
-        items.push_back(item);
+        wxPasteBoardWriter* writer = nil;
+
+        wxArrayString files = GetFilenamesFromDataObject(m_data);
+        if ( files.GetCount() > 1 )

Thanks, but it would be nice to explain this in a comment as it certainly doesn't seem obvious (at least to me).

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exkrexpexfex

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Sep 21, 2026, 5:50:42 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

>          wxCFMutableArrayRef<NSDraggingItem*> items;
-        NSDraggingItem* item = [[NSDraggingItem alloc] initWithPasteboardWriter:writer];
-        [item setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
-        items.push_back(item);
+        wxPasteBoardWriter* writer = nil;
+
+        wxArrayString files = GetFilenamesFromDataObject(m_data);
+        if ( files.GetCount() > 1 )

Checked again, it's fine here to handle both single and multiple files same way, the issue with links is due to the other suggestion, see answer on Trash denial thread

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exkrexpexfex

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Sep 21, 2026, 5:51:43 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

>  
-    // NSDragOperationGeneric also makes a drag to the trash possible
-    // resulting in something we don't support (NSDragOperationDelete)

The problem I observed was Finder creating an alias instead of copying the file. The old NSDragOperationEvery mask still advertised NSDragOperationLink, although wxDropSource::DoDragDrop() has no flag for allowing link operations: its contract is Copy only, or Copy and Move when wxDrag_AllowMove/wxDrag_DefaultMove is supplied. Finder can select Link and create an alias.

The new code is therefore an explicit whitelist of the operations wx actually supports: Copy always, plus Move when requested. It still forbids Delete and Generic, and no longer offers unsupported Link.

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exkrexpexfex

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Sep 21, 2026, 5:57:13 PM (yesterday) Sep 21
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@exkrexpexfex pushed 1 commit.

  • 67f71a3 Cocoa: export wxFileDataObject drags as file URLs

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exkrexpexfex

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Sep 21, 2026, 5:57:44 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

>          size_t size = m_data->GetDataSize(format);
-        CFMutableDataRef data = CFDataCreateMutable(kCFAllocatorDefault,size );
+        CFMutableDataRef data = CFDataCreateMutable(kCFAllocatorDefault, size);

ok

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exkrexpexfex

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Sep 21, 2026, 5:57:51 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

>          wxCFMutableArrayRef<NSDraggingItem*> items;
-        NSDraggingItem* item = [[NSDraggingItem alloc] initWithPasteboardWriter:writer];
-        [item setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
-        items.push_back(item);
+        wxPasteBoardWriter* writer = nil;
+
+        wxArrayString files = GetFilenamesFromDataObject(m_data);
+        if ( files.GetCount() > 1 )
+        {
+            for ( size_t i = 0; i < files.GetCount(); ++i )
+            {
+                wxCFRef<CFURLRef> url(wxOSXCreateURLFromFileSystemPath(files[i]));
+                if ( !url )
+                    continue;
+
+                CFDataRef data = CFURLCreateData(nullptr, url, kCFStringEncodingUTF8, true);

done

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exkrexpexfex

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Sep 21, 2026, 5:58:07 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

>          wxCFMutableArrayRef<NSDraggingItem*> items;
-        NSDraggingItem* item = [[NSDraggingItem alloc] initWithPasteboardWriter:writer];
-        [item setDraggingFrame:NSMakeRect(p.x, p.y, 16, 16) contents:image];
-        items.push_back(item);
+        wxPasteBoardWriter* writer = nil;
+
+        wxArrayString files = GetFilenamesFromDataObject(m_data);
+        if ( files.GetCount() > 1 )

so, done as suggested

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exkrexpexfex

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Sep 21, 2026, 5:58:26 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

> +
+        if ( items.empty() )

Yes, that's better, done

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exkrexpexfex

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Sep 21, 2026, 5:58:44 PM (yesterday) Sep 21
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@exkrexpexfex commented on this pull request.

In src/osx/cocoa/dnd.mm:

> @@ -555,8 +623,11 @@ - (nullable id)pasteboardPropertyListForType:(nonnull NSPasteboardType)type
         result = NSDragOperationToWxDragResult([delegate code]);
         [delegate release];
         [image release];
-        [writer clearDataObject];
-        [writer release];
+        if ( writer )

ok

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exkrexpexfex

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Sep 21, 2026, 6:01:22 PM (yesterday) Sep 21
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exkrexpexfex left a comment (wxWidgets/wxWidgets#27047)

@vadz thanks for review! Files are dragging out of WX with these changes for me. NSDragOperationDelete is still denied, I have switched from blacklisting to whitelisting to explicitly allow Copy and Move while denying not only Delete but also Link

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Stefan Csomor

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csomor left a comment (wxWidgets/wxWidgets#27047)

Thanks, I didn't test this but if it solves the problem with dragging files (does this work when dragging them from the dnd sample now?), it should be merged, of course, but I'm not sure about the NSDragOperationDelete removal.

@csomor Do you see anything wrong here?

thanks @exkrexpexfex

I have to go through the changes, as I wasn't even aware this was not working properly under Cocoa (anymore ?), as I've been separating the Windows inspired files-data for decades before ...

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