Update macOS Installation Instructions for macOS 14+ (Apple Silicon) to Handle PEP 668 "externally-managed-environment" Error

[michaelsmolka]

Issue Description:

The current installation instructions for macOS (using install_osx.py) fail on newer versions like macOS 14.7 due to PEP 668, which marks Homebrew Python as "externally managed" and blocks pip installations without a virtual environment. This results in errors like:

error: externally-managed-environment
...

To fix this, I recommend updating the README with a virtual environment (venv) approach for the Python package installations. Here's a complete, working set of steps for Apple Silicon (M1/M2/M3) Macs:

Prerequisites:

1. Install Homebrew (if not already):
   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
   Restart Terminal or run: eval "$(/opt/homebrew/bin/brew shellenv)".

2. Install dependencies:
   brew install libusb python3 git # (git if not installed)

3. Clone the repository:
   cd ~/Desktop # or desired folder
git clone https://github.com/fablabnbg/inkscape-silhouette.git
cd inkscape-silhouette

Install Python Packages Using venv (to Bypass PEP 668):

1. Create a virtual environment:
   /opt/homebrew/bin/python3 -m venv ~/inkscape-venv

2. Activate it:
   source ~/inkscape-venv/bin/activate

3. Install required packages:
   pip install cssselect lxml tinycss2 matplotlib pyusb wxpython
   (Note: wxpython may take time to compile; if it fails, run brew install wxwidgets first.)

4. Run the installation script (while venv is active):
   chmod +x install_osx.py # if needed
./install_osx.py

5. Deactivate venv:
   deactivate

Configure Inkscape:

1. Edit ~/Library/Application Support/org.inkscape.Inkscape/config/inkscape/preferences.xml (use TextEdit or similar).
   Find <group id="extensions" ... /> and set:
   python-interpreter="/Users/<your-username>/inkscape-venv/bin/python3"
   (Replace <your-username> with your actual username.)

2. Restart Inkscape. The extension should appear under Extensions > Export > Send to Silhouette.

This approach isolates dependencies and avoids system risks. Tested on macOS 14.7.1 (M1). Would be great to incorporate into the README!

[t0b3]

@michaelsmolka thanks for bringing this issue up and proposing this thoroughly tuned solution for macOS. Without featuring a mac myself: I personally like your approach and would like you to open a PR with the necessary changes.

@jnweiger @EtherGraf or other mac users: any input or objection for this approach?

[EtherGraf]

I am not a MAC user but working on (older) debian linux.
venv are known to me, but I am not using them regularly, so I cannot say much in this case.

I support adding this very well written and tested instructions into the README, at least as an working alternative.
The more information the better.

[jnweiger]

Not a Mac user either, but venv is the correct approach in this Case.

It is probanly a good idea also for Linux to use venv for better dependency isolation.

Thanks for taking care!

[mlsteiner]

These instructions worked to get the 'Inkscape-silhouette' plug-in installed and working for me, however wxpython failed to install correct. Installing wxwidgets via homebrew didn't help, although installing wxpython with homebrew (rather than pip) seemed to solve the issue.

Perhaps consider:

3. Install required packages:
   pip install cssselect lxml tinycss2 matplotlib pyusb
   and then brew install wxpython (Note: wxpython may take time to compile; if it fails, run brew install wxwidgets first.)

Tested on Mac mini M2, macOS 26.0.1 (Tahoe), with Inkscape 1.4.2

Thanks @michaelsmolka!