Background

PR #240 fixed the drag & drop functionality by correctly delegating to super when the operation wasn't handled. However, as noted in the TODO comments added by @wltb, there are several remaining issues with the image inlining feature that should be addressed.

Issues Identified

1. draggingEntered: filtering is ineffective (NOOP)

Location: MacDown/Code/View/MPEditorView.m:58-65

The method checks for public.jpeg UTI but performDragOperation: doesn't respect this filter - it processes any file with NSFilenamesPboardType. This means the filter is essentially a no-op.

Recommended fix: Either remove the filter entirely or make performDragOperation: respect it by checking the UTI of dropped files.

2. All file types are inlined as JPEG

Location: MacDown/Code/View/MPEditorView.m:77-95

Currently, any file dragged into the editor is inlined with a hardcoded data:image/jpeg MIME type, even if it's a PNG, GIF, PDF, or non-image file. This produces invalid/broken image references.

Recommended fix:

• Detect the actual file type using UTI or file extension
• Only allow supported image types (JPEG, PNG, GIF, etc.)
• Use the correct MIME type in the data URL (image/png, image/gif, etc.)
• Reject non-image files or fall back to default behavior

3. Drag operation is not undoable

Location: MacDown/Code/View/MPEditorView.m:93-95

The code uses setString: directly, which bypasses the undo manager. Users cannot undo an accidental image drop.

Recommended fix: Use insertText:replacementRange: or register the change with the undo manager properly, similar to how paste: handles text insertion (line 259).

4. Deprecated API usage

• NSFilenamesPboardType is deprecated - should use NSPasteboardTypeFileURL
• base64Encoding is deprecated - should use base64EncodedStringWithOptions:

5. Only first file is processed

Location: MacDown/Code/View/MPEditorView.m:84

When multiple files are dropped, only files[0] is processed. The rest are silently ignored.

Recommended fix: Either process all dropped files or provide user feedback that only single-file drops are supported.

Suggested Implementation Approach

1. Create a helper method to detect image type from file path/UTI
2. Update draggingEntered: to properly filter for supported image types
3. Update performDragOperation: to:
   • Validate the file is a supported image type
   • Determine the correct MIME type
   • Use insertText:replacementRange: for undo support
4. Replace deprecated APIs with modern equivalents

Related

• PR Fix drag & drop #240 - Fix drag & drop
• Issue Drag and drop text #11 (referenced in PR Fix drag & drop #240)