[dolphin] [Bug 498577] New: [Feature request] Make Preview File Size Limit Smarter Based on File Type and Embedded Data

[bugzilla_noreply at kde.org]

https://bugs.kde.org/show_bug.cgi?id=498577

            Bug ID: 498577
           Summary: [Feature request] Make Preview File Size Limit Smarter
                    Based on File Type and Embedded Data
    Classification: Applications
           Product: dolphin
           Version: 24.08.3
          Platform: Fedora RPMs
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: view-engine: icons mode
          Assignee: dolphin-bugs-null at kde.org
          Reporter: phirestalker at gmail.com
                CC: kfm-devel at kde.org
  Target Milestone: ---

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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

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