Bug 498577

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SUMMARY
The current "Generate previews for files smaller than" setting in Dolphin applies an absolute file size limit to all file types, which unnecessarily restricts previews for files where only a small part of the file needs to be read (e.g., audio tags, embedded image thumbnails in JPEGs). I propose making the file size limit smarter by applying it only to file types that require reading the entire file for generating a preview, while always allowing previews for files with embedded metadata or thumbnails.

Description:
Dolphin's preview functionality is an excellent feature, allowing users to quickly identify files based on their content. However, the existing file size limit setting prevents previews for large files, even when only a small portion of the file (such as metadata or embedded thumbnails) is required to generate the preview.

For example:

Audio Files: Album art stored in metadata can be displayed without loading the entire file.
Images: Many image formats, such as JPEG, contain embedded thumbnails that can be extracted without reading the entire file.
Videos: Some video formats include a small embedded thumbnail in the file header.
Currently, the file size limit is applied indiscriminately, causing these previews to be skipped unnecessarily for large files. This behavior can negatively impact usability, especially for users managing large multimedia collections.

Proposed Solution:

Modify the preview system to differentiate between file types that:

Require reading the entire file (e.g., text files, RAW image formats, videos without embedded thumbnails).
Can generate previews from small portions of the file (e.g., embedded thumbnails, metadata, or headers).
Apply the file size limit only to file types in the first category, while always allowing previews for files in the second category, regardless of size.

Extend the preview configuration options to let users control this behavior for specific file types, allowing further customization.

Benefits:

Improved usability for managing large multimedia files.
Better performance by avoiding unnecessary file reads.
More consistent and predictable previews for files with embedded metadata or thumbnails.
Example Use Cases:

An audio file with embedded album art should display the album art even if the file is 500 MB.
A large JPEG image should show its embedded thumbnail regardless of file size.
A video file with a header-based thumbnail should display the thumbnail even if the video file exceeds the size limit.
Additional Notes:
This change would align Dolphin's behavior with user expectations and make file previews more efficient and helpful without compromising performance or resource usage.




SOFTWARE/OS VERSIONS
Operating System: Aurora-DX 41
KDE Plasma Version: 6.2.4
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0
Kernel Version: 6.11.10-304.bazzite.fc41.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × AMD Ryzen 5 7600 6-Core Processor
Memory: 15.3 GiB of RAM
Graphics Processor: AMD Radeon RX 7600