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Dang Marc, have you been reading my hard drive again?
Nagy Vilmos wrote:
I need to work out an article for just this
That would be great. The impetus, partly, for my survey'ish question is because I've been adding state/configuration persistence to an app, and I was wondering what sort of "best practices" there might be out there. The .NET class seems not configurable enough - I'd like to leave it open to the developer as to how to persist the state information. On the other hand, it also seems to closely coupled to "the Microsoft way", what with all the binding support, not that one needs to use it.
At the moment, I've decided to go for an interface-less, more functional approach, resulting in this raw usage example:
Program.AppState.Register("Form", () =>
new State("X", View.Location.X),
new State("Y", View.Location.Y),
new State("W", View.Size.Width),
new State("H", View.Size.Height),
new State("WindowState", View.WindowState.ToString()),
// Silently handle exceptions for when we add state items that are part of the state file until we
// save the state. This allows me to add new state information without crashing the app on startup.
Program.Try(() => View.Location = new Point(state.Single(t => t.Key == "X").Value.to_i(), state.Single(t => t.Key == "Y").Value.to_i()));
Program.Try(() => View.Size = new Size(state.Single(t => t.Key == "W").Value.to_i(), state.Single(t => t.Key == "H").Value.to_i()));
Program.Try(() => View.WindowState = state.Single(t => t.Key == "WindowState").Value.ToEnum<FormWindowState>());
App option specific stuff locally on the machine of the client. If there is a server everything else goes there into a database. Else I use depending on the amount of data a SQLite DB or XML/CSV files located in the AppData for everything.
For more complex data I try to stick to DB-like data, with SqlCE files or XML if I want human readable.
I also have a encryption class which has a file option for more secure data - but the data I serialise to that is normally XML.
If you get an email telling you that you can catch Swine Flu from tinned pork then just delete it. It's Spam.
Back when I was a teenager, I thought saving UI State was all the rage but I soon gave it up. The massive amount of code required to store and manage it and make it all perfect just wasn't worth it. Heck, even today, I have a problem when I load firefox at home. You see I have a laptop hooked up to another monitor. However, that monitor is also wired to another machine. When the other machine is on, Windows on the laptop works fine but when I open something that was previously opened on the second monitor guess where it opens?
If Windows and Firefox can't manage to get UI saving settings right why even bother? Plus, if you make an infinitely configurable UI, power users will complain that they can't configure X and that is so obvious or worse an upgrade will wipe their settings and lose you a customer.
So, long story short, only save the bare essentials that make the app usable. The rest, don't make configurable unless they ask.
IMHO, this is a generic problem: i.e. restoring potentially invalid state. Whenever I restore state (almost always from an editable XML file), my code validates and auto-corrects the data being read. Other examples of this are selecting a tree node that may no longer exist, etc. The bottom line is, it's the developer's responsibility to handle all possible use cases.
All this takes additional work and time. And your users will love you for it.
I have been a developer for many years now,
and I support this message to the fullest.
So should YOU!
Seriously, settings are such a hassle.
The 'Appconfig' likes to forget them.
If you roll your own you have to be backward compatible.
Even VS has a 'reset to defaults button' for the interface because
it can get stuck in a bad layout you can not manually correct anymore.
If you provide too many options your application becomes 'too difficult'
Fortunately I was able to convince my coworkers of this.
Our application remembers the sizes of the screens,
when a screen is shown, it checks if the position is a valid
desktop position (making multi-monitor compatible even if you remove a monitor).
Whenever a customer ask for more setting, we say:
Tell us exactly what settings you want.
For which screens?
How should remember them?
Is it ok to break it with future changes.
But before you do this, remember that each setting cost 1 hour to develop,
1 hour to deploy, 1 hour to test.
Plus the square root (in hours) of all settings combined for additional testing where settings may interfere with each other.
Then multiply that with out hourly wage and ask yourself this question:
"Do you really want that setting?"
Maybe, one day, one of our clients will say yes...
Then we'll slap them with a 200% 'we really do not want to do this' bonus fee.
Yes, get's used from time to time; there's a wizard integrated into the IDE to manipulate the settings-file, it's defaults, and one can very easily bind to a property and forget about it.
Marc Clifton wrote:
if you develop client/server apps, if you store your app's state information locally or in a database so that your user can use any client machine and the UI is configured to their preferences ?
The apps state-information is not stored; only preferences, on user and application-scope (local and global). I've tried to save the complete state once (including undo/redo stack) and have the app restore to that state - it just confuses the users.
Marc Clifton wrote:
And yes, I'm talking about UI things, such as last window size and location
Hence the difference between "local" and "global" user-settings. Some things roam, others don't. The form-size doesn't roam, since my monitors have different sizes at different work-locations.
Marc Clifton wrote:
Same with, say, a tree control - what nodes were expanded and what nodes weren't?
No, not ever. How often do you need to be at that exact place in the tree? If very often, make a shortcut for the user. The reasoning is simlpe; you don't want to wait until the "Windows Explorer" loaded the entire tree, if you can simply click a hyperlink.
Marc Clifton wrote:
Plus things like "exit without asking" info, and so forth.
The question does not even exist. There's only a warning if something is dirty, but I'm not going to ask the user whether he knows what he/she is doing on every action.
Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
I typically save a file in the working directory, which allows the user to set up different shortcuts with different preferences if they want, and it makes the app portable as nothing is stored in system folders (or the registry etc) so you can put it on a USB stick. I put default configuration settings into the app as a resource so I can use the same reader to load it.
My application is a bit different. We run a printing press and related equipment. In that case, there aren't any 'user-specific' data to be persisted. At one time we would have used HKEY_LOCAL_MACHINE in the registry and called it a day, or stored a file with our application. Under Win7, none of that works. Our current solution is a group of XML files stored in the folder returned by SHGetKnownFolderPath(FOLDERID_ProgramData)[^].
I keep waiting for some moron to suggest we store settings data in the 'cloud' even though our machines never have an Internet connection...