PLT Thumbnail (HP-GL) Generator for GNOME

Thumbnailer for the GNOME desktop environment that displays thumbnails for PLT (.plt) and HP-GL (.hpgl) files in the file manager (Nautilus/Files).

This tool uses plotconvert to rasterize vector plot files into PNG thumbnails, with stroke scaling optimized for small preview sizes.

Features

• Converts .plt and .hpgl files to PNG thumbnails via plotconvert.
• Uses --png-max-size to limit the longest side to the size requested by GNOME.
• Uses --png-stroke-scale 10 for visible outlines in small thumbnails.
• Registers a custom MIME type (application/x-plt) for .plt files.
• Also supports the standard MIME type application/vnd.hp-hpgl for .hpgl files.
• Downloads the latest plotconvert binary automatically during installation.

Dependencies

• curl or wget: To download plotconvert from GitHub Releases. Install with sudo apt install curl if needed.
• GNOME Desktop Environment: Required for thumbnailer integration (Nautilus/Files).
• sudo: Required to install plotconvert and the thumbnailer script in /usr/bin/.

Installation

First, make the scripts executable:

chmod +x install.sh install-and-update.sh uninstall.sh

Then run the installer:

./install.sh

To install (if needed) and update plotconvert when a newer release is available:

./install-and-update.sh

This script checks the latest version on GitHub, compares it with the installed plotconvert, downloads and installs the update when a newer version exists, and refreshes the thumbnailer files.

The script will:

1. Fetch the latest plotconvert release from GitHub Releases.
2. Download and install the plotconvert-linux-x86_64 binary to /usr/bin/plotconvert (requires sudo).
3. Register a custom MIME type (application/x-plt) for .plt files at ~/.local/share/mime/packages/.
4. Copy plt-thumbnailer.sh to /usr/bin/ and make it executable (requires sudo).
5. Copy plt.thumbnailer to ~/.local/share/thumbnailers/.
6. Update the paths in the .thumbnailer file.

Note: The thumbnailer script and plotconvert binary must be installed in /usr/bin/ because GNOME 43+ runs thumbnailers inside a bubblewrap (bwrap) sandbox that only has access to /usr, /lib, and /lib64. Scripts in ~/.local/bin/ are not accessible inside the sandbox.

After installation, clear the thumbnail cache and restart Nautilus:

rm -rf ~/.cache/thumbnails/*
nautilus -q

Updating plotconvert

If the thumbnailer is already installed, run:

./install-and-update.sh

The script will:

1. Fetch the latest plotconvert release from GitHub.
2. Compare it with the installed version (plotconvert --version).
3. Download and install the new binary when a newer version is available.
4. Refresh plt-thumbnailer.sh and plt.thumbnailer.

If the thumbnailer is not installed yet, it runs ./install.sh automatically.

Uninstallation

./uninstall.sh

After uninstalling, clear the cache and restart Nautilus:

rm -rf ~/.cache/thumbnails/*
nautilus -q

Manual Installation

If you prefer to install manually:

1. Download the latest plotconvert binary:

TAG=$(curl -fsSL https://api.github.com/repos/rhafaelcm/plotconvert/releases/latest \
  | grep -o '"tag_name"[[:space:]]*:[[:space:]]*"[^"]*"' \
  | sed -E 's/.*"([^"]*)".*/\1/')
curl -fsSL "https://github.com/rhafaelcm/plotconvert/releases/download/${TAG}/plotconvert-linux-x86_64" \
  -o /tmp/plotconvert
sudo install -m 755 /tmp/plotconvert /usr/bin/plotconvert

2. Register the custom MIME type:

mkdir -p ~/.local/share/mime/packages
cat > ~/.local/share/mime/packages/application-x-plt.xml << 'EOF'
<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
  <mime-type type="application/x-plt">
    <comment>HP-GL Plot File</comment>
    <glob pattern="*.plt"/>
  </mime-type>
</mime-info>
EOF
update-mime-database ~/.local/share/mime

3. Copy the script to /usr/bin/ and make it executable:

sudo cp plt-thumbnailer.sh /usr/bin/
sudo chmod +x /usr/bin/plt-thumbnailer.sh

4. Create the thumbnailers directory (if it doesn't exist) and copy the configuration file:

mkdir -p ~/.local/share/thumbnailers
cp plt.thumbnailer ~/.local/share/thumbnailers/

5. Update the paths in the .thumbnailer file:

sed -i "s|^TryExec=.*|TryExec=/usr/bin/plt-thumbnailer.sh|" ~/.local/share/thumbnailers/plt.thumbnailer
sed -i "s|^Exec=.*|Exec=/usr/bin/plt-thumbnailer.sh %i %o %s|" ~/.local/share/thumbnailers/plt.thumbnailer

6. Clear the cache and restart Nautilus:

rm -rf ~/.cache/thumbnails/*
nautilus -q

How It Works

GNOME uses .thumbnailer files in ~/.local/share/thumbnailers/ (user-level) or /usr/share/thumbnailers/ (system-level) to generate thumbnails.

The plt.thumbnailer file specifies:

• MimeType: application/x-plt for .plt files and application/vnd.hp-hpgl for .hpgl files.
• TryExec: Path to the script. The system checks if it exists before using it.
• Exec: Command executed by GNOME. %i = input file, %o = output file, %s = requested size.

The plt-thumbnailer.sh script receives these arguments and calls plotconvert:

plotconvert --to png --png-stroke-scale 10 --png-max-size <SIZE> --output <output> <input>

The --png-max-size parameter receives the size requested by GNOME (%s), limiting the longest side of the PNG. The default is 256 pixels if no size is provided.

GNOME 43+ runs external thumbnailers inside a bubblewrap (bwrap) sandbox for security. The sandbox only mounts /usr, /lib, and /lib64 as read-only, which is why both plotconvert and the script must be installed in /usr/bin/.

Troubleshooting

• Thumbnails not showing:

  • Check that plotconvert is installed: which plotconvert && plotconvert --version
  • Verify the MIME type is registered: xdg-mime query filetype yourfile.plt (should return application/x-plt)
  • Verify the paths in ~/.local/share/thumbnailers/plt.thumbnailer are correct.
  • Check that plt-thumbnailer.sh is executable: ls -la /usr/bin/plt-thumbnailer.sh
  • Clear the cache: rm -rf ~/.cache/thumbnails/* and restart: nautilus -q
  • Check logs: journalctl --user -b | grep -i thumb

• Manual script test:

/usr/bin/plt-thumbnailer.sh /path/to/file.plt /tmp/test.png 256

• Unsupported architecture:
  • Currently only x86_64 is supported. The installer downloads plotconvert-linux-x86_64 from GitHub Releases.

Contributing

Feel free to open issues or pull requests if you find problems or have suggestions.