Update freedesktop README and snappy.desktop.

freedesktop/README

@@ -1,46 +1,22 @@
 To make the SnapPy application launchable from a Linux desktop, the
-files in the share directory can be installed either in $HOME/.local/share
-or in /usr/share.
+files in the share directory can be installed either in $HOME/.local/share.
+For example, you could do this by running the command:
+
+cp -rp share/* ~/.local/share
+
+You should then be able to search for and launch the snappy application
+and pin the SnapPy application icon to your gnome Dock or KDE Application
+launcher.
 
 The files consist of a .desktop file and icon files of various sizes in
 .png format.  The .desktop file is used by the window manager uses to
 recognize SnapPy as an application, and to know how to launch it.
 Usually you have to logout and log back in before the application icon
 will be recognized.
 
-In the old days of setuptools, the snappy.desktop file needed to be
-adjusted for different Linux distributions, according to where python
-setuptools installs the SnapPy script.  So far I have observed:
-
-Ubuntu 13.04     /usr/local/bin
-Mandriva 2010    /usr/bin
-Fedora 18        /usr/bin
-
-Now we should install python packages with pip instead of setuptools
-(and the setup.py file in SnapPy supports this with the the target:
-"python setup.py pip_install").  However, as of 2018 a number of
-distros, e.g. Ubuntu 18.04, have implemented a new policy for
-installing packages with pip.  By default the system version of pip
-assumes the --user option, which means that packages are installed in
-$HOME/.local/lib/pythonX.Y/site-packages and executables such as the
-SnapPy script will be installed in $HOME/.local/bin.  This is a big
-improvement in many ways, but there are two gotchas:
-
-1) The application launcher (as far as I can tell by experiment since
-none of this is documented) does not have $HOME/.local/bin in its path.
-So when editing your .desktop file be sure to use full paths in both the
-Exec and the TryExec lines.  If either file is not found, your application
-will be silently ignored by the application launcher.  (It is not necessary
-to use a full path for the Icon line.)
-
-2) If you run pip install --upgrade pip, as you will be instructed to do,
-you will no longer have a pip which assumes --user as a default option.
-A good way to deal with this is to create a file $HOME/.config/pip/pip.conf
-containing these lines:
-
-[install]
-user = yes
-
-Then you can use a new version of pip without creating the conflicts with
-the linux package manager that the default --user option was designed to
-avoid.
+Modern linux systems, such as Ubuntu 24.04, no longer support installing
+python packages with pip unless they are being installed in a venv.
+The .desktop file assumes that you are using $HOME/venv as the name
+of the venv that you used to install the snappy package with pip.
+If that is incorrect then you will need to edit the Exec line in
+snappy.desktop appropriately.

freedesktop/share/applications/snappy.desktop

@@ -1,11 +1,10 @@
 [Desktop Entry]
-Version=1.0
+Version=3.1
 Name=SnapPy
 GenericName=Manifold browser
 Comment=Study hyperbolic 3-manifolds.
 MimeType=;
-Exec=/usr/local/bin/SnapPy
-TryExec=SnapPy
+Exec=/home/culler/venv/bin/python3 -m snappy.app
 Icon=SnapPy
 Type=Application
 Terminal=false