OK, so up through the last post, we’d figured out how to use Squirrel for Windows to install stuff. In that simple configuration, Squirrel creates an icon on the desktop and in the start menu for every .exe it finds in the package.
No auto-update yet, and the diffs that it generated are going to waste. And also, I didn’t actually want a shortcut for all of the .exe’s.
Telling Squirrel which shortcuts to make
So first we want to figure out how to install only the shortcuts we want. In my case, I have a backround .exe that can be used from the command line, but is entirely useless when launched from a shortcut, so how do we supress the shortcut for it?
It’s worth repeating here that the goal is to use Squirrel for Windows without using .Net ourselves, so we need to call back and forth from Squirrel without using those assembly calls. The answer is launching with command line parameters. In this case, we want to use command line arguments both directions.
We want to call Update.exe with “–createShortcut=our.exe” and we need to handle “our.exe –install x.y.z.m” after Update.exe installs us so we know when to call back with createShortcut. Also we need to let Update.exe know that’s what we’re doing somehow so it calls us and doesn’t create the shortcuts itself.
This first bit on handling events is covered in Handling Squirrel Events
The way Squirrel knows we’re an enlightened application and want to handle the events is by including a VERSIONINFO block in the executable with a special VALUE in it “SquirrelAwareVersion” that is set to “1”. You add this to your exe resources via the rc compiler. Mine looks like this:
There are a few gotchas here. One is that Squirrel looks specifically for the English US unicode StringInfoBlock, so if you don’t have 0x40904b0 there, Squirrel will miss it. Also, if you don’t have the required fields before the BEGIN block it won’t end up in the .exe (and it seemed to me that windres failed silently).
Incoming command line
With that SquirrelAwareVersion, now the automatic creating of shortcuts doesn’t happen any more. So we need to do it. Actually, we should handle all of the command line arguments that squirrel will send and do the necessary and exit quickly with a success. Squirrel events that we could see on the command line are:
That x.y.z.m as the argument parameter is the version number that squirrel is acting upon.
Now, when squirrel calls us with –squirrel-install we want to turn around and launch Update.exe with –createShortcut=our.exe. And likewise when we get –squirrel-uninstall we want to turn around and call Update.exe with –removeShortcut=our.exe
Outgoing command line
We also want to add auto updating to our application, so we need to call
Update.exe for that too. We’ll do
Update.exe --download=url to check for
available updates occasionally and
Update.exe --upgrade=url to upgrade us to
the latest version. Squirrel will put the new version of our application in a
new folder so it takes effect after the user quits the old one and starts the
When called this way Update.exe outputs the percentage completed to stdout so if your app can read that it can show the user progress as squirrel does its work. Also when –download is complete it returns some json describing the current version and the most recent available version. You can see it your self by calling Update.exe from the command line by hand.
Files in the url location
When you upload your release you need a place to put setup.exe, RELEASES and the nupkg’s. Squirrel builds RELEASES but only puts local paths in it. You can have them be full urls, so, for example, you could put each releases’ packages in separate folders as long as the path in RELEASES is correct.