thumbnail_provider.mm

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/* SPDX-FileCopyrightText: 2025 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#import <AppKit/NSImage.h>
 
#include "BLI_fileops.h"
#include "BLI_filereader.h"
#include "BLI_utility_mixins.hh"
#include "blendthumb.hh"
 
#include "thumbnail_provider.h"
 
class FileDescriptorRAII : blender::NonCopyable, blender::NonMovable {
 private:
  int src_fd = -1;
 
 public:
  explicit FileDescriptorRAII(const char *file_path)
  {
    src_fd = BLI_open(file_path, O_BINARY | O_RDONLY, 0);
  }
 
  ~FileDescriptorRAII()
  {
    if (good()) {
      int ok = close(src_fd);
      if (!ok) {
        NSLog(@"Blender Thumbnailer Error: Failed to close the blend file.");
      }
    }
  }
 
  bool good()
  {
    return src_fd > 0;
  }
 
  int get()
  {
    return src_fd;
  }
};
 
static NSError *create_nserror_from_string(NSString *errorStr)
{
  NSLog(@"Blender Thumbnailer Error: %@", errorStr);
  return [NSError errorWithDomain:@"org.blenderfoundation.blender.thumbnailer"
                             code:-1
                         userInfo:@{NSLocalizedDescriptionKey : errorStr}];
}
 
static NSImage *generate_nsimage_for_file(const char *src_blend_path, NSError *error)
{
  /* Open source file `src_blend`. */
  FileDescriptorRAII src_file_fd = FileDescriptorRAII(src_blend_path);
  if (!src_file_fd.good()) {
    error = create_nserror_from_string(@"Failed to open blend");
    return nil;
  }
 
  FileReader *file_content = BLI_filereader_new_file(src_file_fd.get());
  if (file_content == nullptr) {
    error = create_nserror_from_string(@"Failed to read from blend");
    return nil;
  }
 
  /* Extract thumbnail from file. */
  Thumbnail thumb;
  eThumbStatus err = blendthumb_create_thumb_from_file(file_content, &thumb);
  if (err != BT_OK) {
    error = create_nserror_from_string(@"Failed to create thumbnail from file");
    return nil;
  }
 
  std::optional<blender::Vector<uint8_t>> png_buf_opt = blendthumb_create_png_data_from_thumb(
      &thumb);
  if (!png_buf_opt) {
    error = create_nserror_from_string(@"Failed to create png data from thumbnail");
    return nil;
  }
 
  NSData *ns_data = [NSData dataWithBytes:png_buf_opt->data() length:png_buf_opt->size()];
  NSImage *ns_image = [[NSImage alloc] initWithData:ns_data];
  return ns_image;
}
 
@implementation ThumbnailProvider
 
- (void)provideThumbnailForFileRequest:(QLFileThumbnailRequest *)request
                     completionHandler:(void (^)(QLThumbnailReply *_Nullable reply,
                                                 NSError *_Nullable error))handler
{
 
  NSLog(@"Generating thumbnail for %@", request.fileURL.path);
  @autoreleasepool {
    NSError *error = nil;
    NSImage *image = generate_nsimage_for_file(request.fileURL.path.fileSystemRepresentation,
                                               error);
    if (image == nil || image.size.width <= 0 || image.size.height <= 0) {
      handler(nil, error);
      return;
    }
 
    const CGFloat width_ratio = request.maximumSize.width / image.size.width;
    const CGFloat height_ratio = request.maximumSize.height / image.size.height;
    const CGFloat scale_factor = MIN(width_ratio, height_ratio);
 
    const NSSize context_size = NSMakeSize(image.size.width * scale_factor,
                                           image.size.height * scale_factor);
 
    const NSRect context_rect = NSMakeRect(0, 0, context_size.width, context_size.height);
 
    QLThumbnailReply *thumbnailReply = [QLThumbnailReply replyWithContextSize:context_size
                                                   currentContextDrawingBlock:^BOOL {
                                                     [image drawInRect:context_rect];
                                                     /* Release the image that was strongly
                                                      * captured by this block. */
                                                     [image release];
                                                     return YES;
                                                   }];
 
    /* Return the thumbnail reply. */
    handler(thumbnailReply, nil);
  }
  NSLog(@"Thumbnail generation successfully completed");
}
 
@end