README: icon caches, sandbox installs

Several users creating packages and local installs have been bitten by
icon trouble recently. Include some instructions about how to rebuild
the icon cache for the hicolor theme after a standard install, and a
note on sandbox installs since that's a standard thing even if we don't
require it.

diff --git a/README b/README
index db787b9..9896852 100644 (file)
--- a/README
+++ b/README
@@ -8,16 +8,38 @@ A list of contributors can be found in the about dialog.
 Building on Linux:
 
     Compile and run:
-    scons && ./mypaint
+
+        $ scons && ./mypaint
 
     Install:
-    scons prefix=/usr/local install
+
+        # scons prefix=/usr/local install
+
+    Install (for packagers)
+
+        $ scons prefix=/usr --install-sandbox=path/to/sandbox
 
     Required: pygtk, python, swig, gtk, numpy, pycairo(>=1.4), libpng
-    Debian users: apt-get install g++ python-dev libglib2.0-dev python-numpy swig scons gettext libpng12-dev
+
+    Debian users can fetch these dependencies by running:
+
+        # apt-get install g++ python-dev libglib2.0-dev python-numpy \
+                          swig scons gettext libpng12-dev
 
     Recommended: a pressure sensitive input device (graphic tablet)
 
+    Take care to update the central icon theme cache if you're installing
+    mypaint to a standard system prefix. If you install new icons, the icon
+    cache must be updated too if it exists. For example for an install into
+    /usr, you should run
+
+        $ gtk-update-icon-cache /usr/share/icons/hicolor
+        $ chmod a+r /usr/share/icons/hicolor/icon-theme.cache
+
+    after installation to ensure that the cache is up to date. Scons won't
+    do this for you because the cache file is optional.
+
+
 Building on Windows:
 
     NOTE: This is still very experimental.